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McKaizer Institute — Longevity & Wellness Science
The longevity supplement market is full of noise. This evidence-ranked guide cuts through the hype — covering NMN, NR, rapamycin, metformin, quercetin, fisetin, and every major compound with honest clinical trial data.
40%
lifespan extension in animal models from rapamycin — the most replicated longevity compound in laboratory aging research
Table of Contents
- How to Think About Longevity Supplements — The Evidence Framework
- Tier 1 Supplements — The Strongest Human Evidence
- NAD+ Precursors — NMN vs. NR vs. IV — The Honest Comparison
- Rapamycin and Metformin — The Prescription Longevity Drugs
- Senolytics — Quercetin, Fisetin and Dasatinib Protocols
- The McKaizer Evidence-Ranked Supplement Stack
- How to Monitor Supplement Efficacy — Biomarkers to Track
- The Future of Longevity Pharmacology
- Frequently Asked Questions (20)
How to Think About Longevity Supplements — The Evidence Framework
How to Think About Longevity Supplements — The Evidence Framework
The longevity supplement market will reach $66 billion by 2030. Most of that money will be wasted.
Not because supplements don’t work — some demonstrably do. But because the gap between marketing claims and mechanistic evidence remains vast, unregulated, and deliberately obscured.
At McKaizer Institute, we believe you deserve a framework for evaluating these compounds yourself. One built on the same principles researchers use when deciding what’s worth investigating — and what’s worth taking.
The Hierarchy of Evidence: From Petri Dish to Human Healthspan
Not all studies are created equal. A supplement that “extends lifespan by 30%” in yeast may do nothing — or cause harm — in humans.
Dr. Nir Barzilai, director of the Institute for Aging Research at Albert Einstein College of Medicine, frames it simply: “The question isn’t whether something works in cells. The question is whether it works in people, at doses you can actually take, without causing other problems.”
Here’s how to think about the evidence tiers:
- Tier 1: In vitro studies (cell cultures) — Useful for understanding mechanisms. Not predictive of human benefit. Thousands of compounds that “kill cancer cells in a dish” never became treatments.
- Tier 2: Animal models (C. elegans, mice, primates) — More meaningful, especially in genetically similar organisms. But mouse metabolism differs dramatically from ours. Only 8% of drugs that work in mice succeed in human trials.
- Tier 3: Observational human studies — Epidemiological data showing associations (e.g., “people who eat more X live longer”). Correlation, not causation. Confounders abound.
- Tier 4: Randomized controlled trials (RCTs) — The gold standard. But most longevity RCTs measure biomarkers or surrogate endpoints, not actual lifespan extension.
- Tier 5: Long-term human outcome data — Exceedingly rare in longevity science. We simply haven’t been running these trials long enough.
What This Means For You
When evaluating any supplement, ask: Where does the best evidence sit on this hierarchy? If a company cites only cell studies, proceed with extreme caution. If there are multiple human RCTs with consistent results — even on surrogate markers like NAD+ levels or inflammatory cytokines — you’re on firmer ground.
💡 Quick Fact: Of the 26,000+ dietary supplements currently sold in the United States, fewer than 200 have been tested in randomized human trials lasting more than 12 months.
The Three Questions Every Compound Must Answer
Before any compound earns a place in your longevity protocol, it must clear three evidentiary hurdles. This is the framework used by researchers at the National Institute on Aging’s Interventions Testing Program (ITP) — the most rigorous independent testing program for anti-aging compounds in existence.
1. Does it have a plausible mechanism?
The compound should target one or more recognized hallmarks of aging: cellular senescence, mitochondrial dysfunction, epigenetic drift, proteostatic collapse, or similar. Vague claims about “antioxidants” or “detoxification” are red flags.
2. Is the effect reproducible?
One study is never enough. Dr. Richard Miller at the University of Michigan, who co-directs the ITP, emphasizes that replication across multiple laboratories is essential. “If we can’t reproduce it in three independent sites, we don’t trust it.”
3. What’s the therapeutic window?
A compound that works at concentrations impossible to achieve through oral supplementation is irrelevant. Similarly, anything requiring doses near toxicity offers unacceptable risk.
What This Means For You
Apply these three questions ruthlessly. Most supplements fail on question two — they cite a single, unreplicated study. Many fail on question three — they require intravenous administration or mega-doses their products don’t deliver.
The Biomarker Problem: What Are We Actually Measuring?
Here’s the uncomfortable truth: we cannot yet measure human longevity directly in a clinical trial. No one will run a 50-year study waiting for participants to die.
So researchers use surrogate endpoints — biomarkers believed to correlate with aging and healthspan:
- Epigenetic clocks (Horvath, GrimAge, DunedinPACE) — measure methylation patterns associated with biological age
- NAD+ levels — decline with age, involved in cellular energy production
- Inflammatory markers (IL-6, CRP, TNF-α) — elevated in chronic “inflammaging”
- Telomere length — shortens with cellular division, though its predictive value is debated
- Senescent cell burden — measurable via p16INK4a expression and related markers
Dr. Morgan Levine, formerly of Yale and now at Altos Labs, developed several epigenetic aging measures. She cautions: “A biomarker is only useful if changing it actually changes outcomes. We’re still validating most of these.”
The TAME trial (Targeting Aging with Metformin), led by Dr. Barzilai and launched in 2024 across 14 clinical sites, represents a landmark effort to validate whether interventions that improve biomarkers actually delay age-related disease. Until results arrive, we’re working with educated hypotheses.
What This Means For You
Be skeptical of supplements claiming to “reverse your biological age” based solely on one biomarker shifting. Real longevity evidence requires multiple biomarkers moving in the right direction, ideally correlated with functional improvements you can actually feel.
Key Points
- Evidence exists on a hierarchy — cell studies sit at the bottom, long-term human trials at the top. Most supplements never reach the upper tiers.
- Three questions determine legitimacy — plausible mechanism, reproducible results, and an achievable therapeutic window.
- Biomarkers are proxies, not proof — improvements in epigenetic age or NAD+ levels are promising but not yet validated as lifespan predictors.
Tier 1 Supplements — The Strongest Human Evidence
Tier 1 Supplements — The Strongest Human Evidence
These are the compounds that have survived the gauntlet. They’ve moved beyond petri dishes and mouse models into rigorous human trials — sometimes spanning decades, involving thousands of participants, and published in journals that don’t accept speculation. They’re not guaranteed to extend your life. But they represent our best current bets, backed by the kind of evidence that shifts medical consensus.
Even here, nuance matters. “Strong evidence” doesn’t mean “works for everyone.” It means the data is robust enough that serious researchers stake their reputations on continued investigation.
Omega-3 Fatty Acids (EPA/DHA)
The cardiovascular evidence is mature. The VITAL study, led by Dr. JoAnn Manson at Harvard Medical School and published in The New England Journal of Medicine in 2019, followed 25,871 participants for over five years. The findings: omega-3 supplementation (1 gram daily) reduced heart attack risk by 28%, with even stronger effects in people who ate less than 1.5 servings of fish weekly.
More recent data has refined the picture. The STRENGTH trial disappointed, showing no benefit from a corn oil-based omega-3 formulation. But the REDUCE-IT trial, led by Dr. Deepak Bhatt at Brigham and Women’s Hospital, demonstrated that high-dose EPA (4 grams of icosapent ethyl daily) reduced cardiovascular events by 25% in high-risk patients. The difference? Pure EPA outperformed EPA/DHA combinations — and dose mattered enormously.
Beyond the heart, omega-3s influence systemic inflammation, neuronal membrane fluidity, and resolvin production — specialized molecules that actively resolve inflammation rather than simply suppressing it. Dr. Charles Serhan at Harvard has mapped these resolution pathways extensively, showing that adequate omega-3 status enables your body to complete the inflammatory cycle rather than getting stuck in chronic low-grade activation.
💡 Quick Fact: A 2021 meta-analysis in Mayo Clinic Proceedings analyzing 40 studies and 135,267 participants found that omega-3 supplementation reduced cardiovascular mortality by 35% when EPA dosing exceeded 1.8 grams daily.
What works:
- Dose threshold: Benefits appear above 2 grams combined EPA/DHA daily for cardiovascular outcomes
- Form matters: Triglyceride-form omega-3s show 70% better absorption than ethyl ester forms
- EPA dominance: For cardiovascular specifically, higher EPA ratios outperform balanced EPA/DHA
What This Means For You
If you’re not eating fatty fish three times weekly, omega-3 supplementation sits in legitimately evidence-backed territory. Prioritize products that disclose EPA and DHA content separately, opt for triglyceride forms when possible, and aim for 2+ grams of combined EPA/DHA daily — the dose where clinical benefits consistently emerge.
Vitamin D
The sunshine vitamin generates controversy precisely because it’s been overstudied. Thousands of papers. Conflicting headlines. But beneath the noise, certain findings hold firm.
Dr. Michael Holick at Boston University has spent four decades establishing that vitamin D deficiency (below 20 ng/mL) correlates with increased all-cause mortality, fracture risk, and immune dysfunction. The VITAL study — yes, the same one that tested omega-3s — examined vitamin D supplementation (2,000 IU daily) and found no significant reduction in cancer or cardiovascular events across the general population.
But here’s the nuance that headlines miss. Subgroup analysis revealed that participants who were vitamin D deficient at baseline did benefit. And the D2d trial, published in The New England Journal of Medicine in 2019, showed that high-dose vitamin D reduced progression to type 2 diabetes by 12% in prediabetic adults — rising to 62% in those who maintained blood levels above 50 ng/mL.
The mechanism story is compelling. Vitamin D receptors appear on nearly every cell type. Dr. John White at McGill University has documented vitamin D’s role in:
- Immune modulation — enhancing antimicrobial peptide production and regulating inflammatory cytokines
- Insulin sensitivity — improving beta cell function and glucose metabolism
- Muscle preservation — reducing sarcopenia risk in aging populations
- Epigenetic regulation — influencing expression of over 1,000 genes
What This Means For You
Test, don’t guess. Vitamin D supplementation benefits depend almost entirely on your starting status. Aim for blood levels between 40–60 ng/mL (100–150 nmol/L). Most adults need 2,000–5,000 IU daily to reach optimal ranges, but individual absorption varies wildly based on body composition, skin tone, and latitude.
Creatine
Long dismissed as merely a gym supplement, creatine has earned reconsideration from the longevity community. The shift began when researchers looked beyond muscle — into mitochondria and neurons.
Creatine monohydrate is the most-studied form, with over 500 peer-reviewed human trials. Dr. Darren Candow at the University of Regina has led multiple investigations showing that creatine supplementation in older adults increases lean muscle mass, upper and lower body strength, and functional performance. A 2017 meta-analysis in Experimental Gerontology found that creatine combined with resistance training improved lean tissue mass by 1.4 kg more than resistance training alone.
The neurological data is earlier-stage but promising. Dr. Tarnopolsky at McMaster University has demonstrated that creatine crosses the blood-brain barrier and may support mitochondrial function in neurons. Small clinical trials suggest benefits for:
- Cognitive performance under stress or sleep deprivation
- Depressive symptoms as an adjunct to SSRIs
- Traumatic brain injury recovery acceleration
The safety profile is exceptional. Decades of use with no consistent evidence of kidney harm in healthy individuals. The International Society of Sports Nutrition considers it one of the most effective and safe supplements available.
💡 Quick Fact: Adults over 60 lose approximately 3–5% of muscle mass per decade — a process called sarcopenia. Creatine supplementation combined with resistance training slows this trajectory more effectively than exercise alone.
What This Means For You
3–5 grams daily of creatine monohydrate represents a low-cost, high-safety intervention with solid evidence for preserving muscle mass and emerging evidence for cognitive maintenance. No loading phase required. No cycling necessary. Just consistent daily intake with water.
Key Points
- Omega-3s (2+ grams EPA/DHA daily) have the strongest cardiovascular mortality data, with pure EPA forms showing superior results in high-risk populations.
- Vitamin D optimization (40–60 ng/mL blood levels) matters most for those starting deficient — blanket supplementation without testing yields inconsistent results.
- Creatine monohydrate (3–5 grams daily) offers robust evidence for muscle preservation and emerging neurological support, with a safety record spanning decades of research.
“The goal is not to sell you supplements. The goal is to give you the truth about what the evidence actually shows — and where the gaps remain.”
NAD+ Precursors — NMN vs. NR vs. IV — The Honest Comparison
NAD+ Precursors — NMN vs. NR vs. IV — The Honest Comparison
Nicotinamide adenine dinucleotide sits at the center of cellular energy production, DNA repair, and siren gene activation. By age 50, your NAD+ levels have dropped to roughly half of what they were at 20. This decline correlates with virtually every hallmark of aging — from mitochondrial dysfunction to cellular senescence to impaired autophagy.
The longevity field has responded with a proliferation of NAD+ precursor supplements, each claiming superiority. But the science tells a more nuanced story. Understanding which precursor — if any — deserves your investment requires examining the actual human data, not just the elegant mouse studies that launched this category.
The Biology: Why NAD+ Matters
NAD+ functions as a critical coenzyme in over 500 enzymatic reactions. It shuttles electrons during metabolism, activates sirtuins (the “longevity genes” studied extensively by Dr. David Sinclair at Harvard Medical School), and serves as a substrate for PARPs — enzymes essential for DNA repair.
When NAD+ levels fall, the downstream effects cascade:
- Mitochondrial function declines — less ATP production, more oxidative stress
- Sirtuin activity drops — reduced cellular maintenance and stress resistance
- DNA repair slows — accumulated damage accelerates biological aging
- Circadian rhythm disrupts — NAD+ oscillates with your body clock
The question isn’t whether NAD+ matters. It clearly does. The question is whether supplementing with precursors meaningfully restores it — and whether restoration translates to actual health benefits.
What This Means For You
Your body cannot absorb NAD+ directly — the molecule is too large and degrades in the digestive tract. This is why precursors exist: smaller molecules that your cells can convert into NAD+ through various salvage pathways. The debate centers on which precursor reaches your tissues most efficiently.
NR (Nicotinamide Riboside): The Most-Studied Option
Nicotinamide riboside entered the market first and accumulated the most human trial data. Dr. Charles Brenner, now at City of Hope National Medical Center, discovered NR’s role as an NAD+ precursor and holds foundational patents in the space.
The landmark CHROMAVID trial (2017) demonstrated that NR supplementation at 1,000 mg twice daily safely elevated whole blood NAD+ levels by approximately 60% in healthy middle-aged adults. Subsequent studies confirmed this bioavailability signal across multiple populations.
However — and this is critical — elevated blood NAD+ hasn’t consistently translated to clinical outcomes in human trials:
- Cardiovascular function: A 2023 randomized controlled trial published in Nature Communications found no significant improvement in arterial stiffness or blood pressure with NR supplementation.
- Metabolic markers: The NORMA study at University of Copenhagen found NR did not improve insulin sensitivity in obese men.
- Muscle function: Research at University of Birmingham showed no enhancement in mitochondrial function or exercise capacity in older adults.
💡 Quick Fact: Despite raising blood NAD+ levels consistently, zero NR trials have demonstrated improvement in hard clinical endpoints like disease incidence, functional capacity, or mortality in humans.
What This Means For You
NR reliably increases circulating NAD+ markers, but the clinical relevance of this increase remains unproven. At $40–80 monthly for effective doses, you’re paying for a biomarker change without established health benefits. The safety profile is reassuring — no serious adverse events in trials lasting up to 12 weeks — but the efficacy gap deserves acknowledgment.
NMN (Nicotinamide Mononucleotide): The Rising Competitor
NMN gained prominence largely through Dr. David Sinclair’s research at Harvard, including his personal use of the compound. Structurally, NMN sits one step closer to NAD+ in the biosynthetic pathway — your body converts NR to NMN before producing NAD+.
The theoretical advantage: skip a step, gain efficiency. The practical reality is more complex.
For years, scientists believed NMN couldn’t cross cell membranes directly due to its phosphate group. A 2019 study from Washington University School of Medicine identified a specific transporter (Slc12a8) in the gut that appears to facilitate NMN uptake. This finding, led by Dr. Shin-ichiro Imai, challenged assumptions about oral bioavailability.
Human data is accumulating:
- A 2022 study in Science showed 250 mg NMN daily improved muscle insulin sensitivity in premenopausal women with prediabetes — one of the first positive functional outcomes.
- Research at University of Tokyo found NMN supplementation improved gait speed and grip strength in older men.
- A 2024 trial demonstrated modest improvements in aerobic capacity with consistent supplementation.
These results suggest NMN may have tissue-specific effects that NR lacks — though direct head-to-head comparisons remain limited.
What This Means For You
NMN shows more promising early signals for functional outcomes than NR, particularly for metabolic health and physical performance. The evidence is still immature — we’re talking about small studies with short durations. At $50–150 monthly depending on purity and dosage, NMN represents a speculative but not unreasonable investment if you’re optimizing for emerging science rather than proven interventions.
IV NAD+: The Expensive Unknown
Intravenous NAD+ infusions bypass the digestion question entirely, delivering the molecule directly into your bloodstream. Longevity clinics charge $500–1,500 per session, often recommending weekly or monthly protocols.
The experience is… memorable. Most recipients report intense flushing, chest tightness, nausea, and anxiety during infusion — sensations that clinics euphemistically describe as “detox reactions.” These effects reflect the pharmacological potency of direct NAD+ administration.
Here’s what the evidence actually shows:
- No published randomized controlled trials examining IV NAD+ for longevity or anti-aging outcomes exist in peer-reviewed literature.
- Small studies in addiction medicine suggest potential benefits for acute withdrawal symptoms, but methodology was weak.
- No comparative data exists showing IV NAD+ outperforms oral precursors for any measured outcome.
The theoretical appeal is straightforward: why take precursors when you can take the finished product? But circulation isn’t the same as cellular uptake. NAD+ in your bloodstream doesn’t automatically enter your neurons, muscle cells, or mitochondria. The pharmacokinetics remain poorly characterized.
What This Means For You
IV NAD+ represents the least evidence-supported option at the highest price point. You’re paying premium prices for acute discomfort and theoretical benefits. Until controlled trials demonstrate superiority over oral precursors — or any benefit at all — this approach falls into the “expensive experiment” category rather than science-backed intervention.
The Honest Assessment
The NAD+ precursor space suffers from a fundamental gap: robust biomarker data but weak clinical outcome data. We can reliably raise blood NAD+ levels. We cannot yet prove this extends healthspan or lifespan in humans.
This doesn’t mean the intervention is worthless. It means the evidence is immature. Several large-scale, long-duration trials are underway that may clarify the picture within 3–5 years.
Factors that might justify current use:
- You’re optimizing based on theoretical frameworks and emerging signals, not proven benefits
- You have metabolic concerns (prediabetes, insulin resistance) where NMN shows early promise
- Cost is not a significant constraint for your wellness budget
Factors that argue for waiting:
- You want interventions with established clinical endpoints
- You’re choosing between NAD+ precursors and proven supplements like omega-3s or creatine
- You prefer to let early adopters bear the uncertainty cost
Key Points
- NR (1,000 mg daily) reliably raises blood NAD+ levels with an excellent safety profile — but no human trials have demonstrated improvement in clinical outcomes like function, disease risk, or mortality.
- NMN (250–500 mg daily) shows more promising early signals for insulin sensitivity and physical performance, making it the more interesting option if you’re investing in emerging science.
- IV NAD+ ($500–1,500 per session) has essentially no peer-reviewed evidence supporting its use for longevity — you’re paying premium prices for theoretical benefits and guaranteed discomfort.
Rapamycin and Metformin — The Prescription Longevity Drugs
Rapamycin and Metformin — The Prescription Longevity Drugs
Two pharmaceuticals have captured the longevity field’s imagination unlike any others. Rapamycin and metformin represent something genuinely different from supplements — they’re FDA-approved medications with decades of human safety data, repurposed for a goal they were never designed to achieve. The scientific case for each is compelling. But compelling isn’t the same as proven.
These aren’t compounds you can order online or pick up at a health food store. Using them for longevity means entering a gray zone of off-label prescribing, uncertain dosing, and real tradeoffs. Here’s what the evidence actually supports.
Rapamycin: The Most Validated Lifespan Intervention We Have
No compound has more robust evidence for extending lifespan across species than rapamycin. Originally isolated from soil bacteria on Easter Island (Rapa Nui, hence the name), it was developed as an immunosuppressant for organ transplant recipients. Then researchers at the National Institute on Aging’s Interventions Testing Program (ITP) discovered something remarkable.
In 2009, David Harrison and colleagues at Jackson Laboratory demonstrated that rapamycin extended median lifespan in mice by 9–14% — even when treatment started at 20 months of age, equivalent to roughly 60 human years. This wasn’t a fluke. The ITP replicated the finding across three independent testing sites. Subsequent studies pushed the effect higher: 23% extension in some protocols.
💡 Quick Fact: Rapamycin remains the only pharmacological intervention consistently shown to extend lifespan in mice regardless of genetic background, sex, or starting age — making it the gold standard against which all other longevity compounds are measured.
The mechanism centers on mTOR (mechanistic target of rapamycin) — a master regulatory protein that controls cell growth, metabolism, and autophagy. When nutrients are abundant, mTOR signals cells to grow and divide. Rapamycin inhibits this pathway, essentially mimicking aspects of caloric restriction at the cellular level.
What rapamycin does in animal models:
- Enhances autophagy — the cellular “recycling” process that clears damaged proteins and organelles
- Reduces senescent cell accumulation in multiple tissues
- Improves immune function in aged animals (counterintuitively, given its immunosuppressive origins)
- Extends healthspan markers including cardiac function, cognitive performance, and physical capacity
What This Means For You
The animal data is genuinely impressive — arguably the strongest we have for any longevity intervention. But here’s the critical gap: we have almost no controlled human data on rapamycin for aging.
The closest we’ve come is a landmark 2014 study by Joan Mannick (then at Novartis, now at Life Biosciences) published in Science Translational Medicine. Her team gave low-dose rapamycin analogs to healthy elderly adults for six weeks before flu vaccination. The result: a 20% improvement in antibody response — suggesting rapamycin might actually enhance, not suppress, immune function in older adults at the right dose.
A follow-up 2018 study showed that RTB101 (a similar mTOR inhibitor) reduced respiratory infections in elderly subjects by approximately 30%. These are intriguing signals. They are not proof of lifespan extension.
Current evidence gaps:
- No randomized controlled trials measuring mortality, disease incidence, or functional decline
- Optimal dosing for longevity completely unknown (transplant doses are clearly too high)
- Long-term safety of intermittent low-dose protocols unstudied in healthy populations
- Unknown whether benefits seen in mice translate to humans with different mTOR biology
The longevity medicine community has coalesced around intermittent low-dose protocols — typically 3–6 mg once weekly rather than daily immunosuppressive doses. The theory: this produces transient mTOR inhibition sufficient to trigger autophagy without sustained immunosuppression. Matt Kaeberlein at the University of Washington’s Healthy Aging and Longevity Research Institute has been instrumental in advocating for rigorous human trials of this approach.
Metformin: The Diabetes Drug With Longevity Signals
Metformin occupies different territory. It’s been prescribed to over 150 million people worldwide for type 2 diabetes, giving us extensive real-world safety data. And observational studies have produced genuinely surprising findings.
A 2014 analysis by Craig Currie and colleagues at Cardiff University examined UK health records and found that diabetic patients taking metformin had lower all-cause mortality than matched non-diabetic controls. Read that again: people with diabetes — a disease that typically shortens lifespan — outlived healthy people when taking this medication.
This finding catalyzed TAME (Targeting Aging with Metformin), the first FDA-sanctioned trial designed to test whether a drug can delay aging itself. Led by Dr. Nir Barzilai at Albert Einstein College of Medicine, TAME will enroll 3,000 adults aged 65–79 and track time to first age-related disease (cardiovascular event, cancer, dementia, or death).
Proposed mechanisms for metformin’s effects:
- Activates AMPK, an energy-sensing enzyme that promotes mitochondrial biogenesis
- Reduces hepatic glucose production, lowering circulating insulin levels
- May reduce inflammatory markers including IL-6 and TNF-alpha
- Potentially inhibits mTOR through AMPK-dependent pathways
What This Means For You
Metformin’s longevity case faces a significant complication: it may blunt exercise adaptations. A 2019 study from Benjamin Miller’s lab at Oklahoma Medical Research Foundation found that older adults taking metformin during a resistance training program showed attenuated improvements in muscle mass and mitochondrial function compared to placebo.
This matters enormously. If you’re already exercising regularly — which you should be — metformin might partially negate those benefits. The calculus shifts considerably if you’re trading proven exercise gains for theoretical longevity benefits.
Factors favoring metformin consideration:
- Prediabetes or metabolic syndrome where the drug addresses an actual condition
- Family history suggesting high diabetes risk
- Unable to exercise consistently due to disability or injury
Factors arguing against current use:
- Healthy metabolic profile with regular exercise habits
- Preference for interventions that don’t require ongoing prescriptions
- Gastrointestinal sensitivity (15–30% of users experience significant side effects)
Key Points
- Rapamycin shows the most robust lifespan extension in animal models of any pharmaceutical intervention, but human longevity data remains essentially nonexistent — current protocols (3–6 mg weekly) are theoretical extrapolations, not evidence-based medicine.
- Metformin has intriguing observational data suggesting mortality benefits, but may blunt exercise adaptations — the TAME trial, expected to report within 5–7 years, should finally provide controlled human evidence.
- Both require prescriptions and carry real side effects; using them for longevity means accepting genuine tradeoffs for unproven benefits — a reasonable choice for some, premature for others.
The Longevity Supplement Evidence Pyramid
Strong Human RCT Evidence
Omega-3s, Vitamin D, Creatine. Multiple large-scale randomized controlled trials with consistent positive outcomes.
Moderate Human Evidence
CoQ10, Magnesium, Curcumin. Smaller RCTs or observational studies show promising longevity benefits.
Preliminary Human Data
NMN, Resveratrol, Quercetin. Early-phase trials or biomarker improvements noted, but long-term data lacking.
Strong Animal Evidence
Rapamycin, Spermidine, Alpha-ketoglutarate. Robust lifespan extension in mice, human trials ongoing.
Limited Animal Data
Fisetin, Astaxanthin. Some lifespan studies in model organisms show potential, more research needed.
Mechanistic/Cell Studies Only
Novel senolytics, experimental compounds. In-vitro promise exists, but no in-vivo validation yet.
Figure: Evidence hierarchy for longevity supplements — higher tiers indicate stronger scientific support for human healthspan benefits. Always consult a healthcare provider before supplementation.
Senolytics — Quercetin, Fisetin and Dasatinib Protocols
Senolytics — Quercetin, Fisetin and Dasatinib Protocols
Senescent cells are the body’s biological graffiti — damaged cells that refuse to die but can no longer divide. They accumulate with age, secreting inflammatory signals that poison surrounding tissue. Senolytics represent the first pharmacological approach specifically designed to eliminate these cellular zombies, potentially reversing rather than merely slowing aspects of aging.
The field emerged from a landmark 2015 study by Drs. James Kirkland and Tamar Tchkonia at the Mayo Clinic, demonstrating that clearing senescent cells extended healthspan in mice by up to 36%. Since then, the senolytic hypothesis has generated enormous excitement — and several compounds accessible to humans right now.
The Science of Cellular Senescence
When cells experience irreparable damage — from telomere shortening, oxidative stress, or oncogenic mutations — they face a choice: die via apoptosis or enter senescence. Senescence originally evolved as a tumor-suppression mechanism. A damaged cell that can’t divide can’t become cancer.
The problem emerges over decades. By age 60–70, senescent cells may comprise 10–15% of cells in some tissues. They secrete what researchers call the senescence-associated secretory phenotype (SASP) — a toxic cocktail of inflammatory cytokines, proteases, and growth factors that damages neighboring healthy cells.
This creates a vicious cycle: SASP signals induce senescence in additional cells, accelerating tissue dysfunction. The accumulation correlates with nearly every age-related disease:
- Cardiovascular disease — senescent cells in arterial walls drive atherosclerosis
- Osteoarthritis — joint tissues become dominated by senescent chondrocytes
- Pulmonary fibrosis — senescent lung cells promote scarring
- Neurodegeneration — brain senescence correlates with cognitive decline
- Frailty — systemic senescent cell burden predicts physical deterioration
💡 Quick Fact: Transplanting just 500,000 senescent cells into young mice accelerates physical dysfunction and reduces remaining lifespan by approximately 25%, per a 2018 study in Nature Medicine by Kirkland’s team.
What This Means For You
Your body is constantly generating senescent cells through normal aging processes. The question isn’t whether you have them — you do. The question is whether current senolytic compounds can safely reduce their burden in humans, and whether doing so produces meaningful benefits outside laboratory conditions.
Quercetin + Dasatinib — The Original Protocol
The Mayo Clinic’s foundational research identified dasatinib (a leukemia drug) combined with quercetin (a plant flavonoid) as the most effective senolytic combination in preclinical models. Dasatinib targets senescent preadipocytes and fat cells; quercetin addresses senescent endothelial cells and bone marrow stem cells.
In mice, the combination:
- Improved cardiovascular function within 5 days
- Enhanced physical endurance and grip strength
- Extended median lifespan by approximately 36%
- Reduced age-related pathology in multiple organ systems
Human trials have begun. A 2019 pilot study in idiopathic pulmonary fibrosis patients at Mayo showed that 3 weeks of intermittent dosing improved 6-minute walk distance by an average of 21.5 meters. A 2021 study in diabetic kidney disease demonstrated reduced senescent cell markers after just 3 doses.
Typical research protocols use:
- Dasatinib: 100 mg orally
- Quercetin: 1000 mg orally
- Dosing schedule: Once daily for 3 consecutive days, repeated monthly or quarterly
The intermittent “hit-and-run” approach is crucial. Senolytics don’t need continuous exposure — they trigger apoptosis in senescent cells, which then takes days to weeks to complete. Continuous dosing offers no additional benefit and increases side effect risk.
Fisetin — The Accessible Alternative
Fisetin, found naturally in strawberries, apples, and persimmons, emerged from a 2018 Mayo Clinic screen as potentially more potent than the dasatinib-quercetin combination in certain mouse models. A study published in EBioMedicine showed fisetin reduced senescent cell markers and extended median lifespan in mice by approximately 10%.
The appeal is obvious: fisetin is available without prescription, generally well-tolerated, and requires no combination therapy. Dr. Kirkland’s team is currently conducting the AFFIRM-LITE trial, studying fisetin in older adults at risk for frailty.
Current experimental protocols typically involve:
- Dosing: 20 mg per kilogram of body weight (approximately 1,400 mg for a 70 kg adult)
- Schedule: Once daily for 2 consecutive days, repeated monthly
- Form: Lipophilic powder in capsules; bioavailability remains a concern
Early anecdotal reports from self-experimenters describe reduced joint pain, improved skin quality, and enhanced recovery from exercise — though placebo effects are powerful and no controlled human longevity data exists.
What This Means For You
Fisetin represents the most accessible senolytic option, but “accessible” doesn’t mean “proven.” The doses used in research are substantially higher than standard supplements (most products contain 100–500 mg), and optimal bioavailability formulations remain uncertain.
Critical Limitations and Honest Assessment
The gap between mouse studies and human application remains substantial:
- No human longevity data exists — we have biomarker changes and functional improvements in specific disease populations, not lifespan extension evidence
- Dasatinib is a chemotherapy drug with real toxicity — nausea, fluid retention, and rare but serious pleural effusions
- Quercetin and fisetin have poor bioavailability — actual tissue concentrations may differ dramatically from animal models
- Long-term safety of repeated senolytic exposure is unknown — could eliminating too many senescent cells impair wound healing or tumor suppression?
Dr. Judith Campisi at the Buck Institute has emphasized that some senescent cells may serve beneficial functions — particularly in wound healing and tissue remodeling. Indiscriminate elimination might not be uniformly positive.
Should You Consider Senolytics Now?
Reasonable candidates for cautious experimentation:
- Adults over 50 with inflammatory conditions not well-controlled by lifestyle
- Those with family histories suggesting accelerated aging phenotypes
- Individuals comfortable with experimental protocols and careful monitoring
Those who should wait:
- Healthy adults under 40 (minimal senescent cell burden)
- Anyone with bleeding disorders or on anticoagulants (quercetin affects platelet function)
- People seeking “proven” interventions — senolytics remain firmly investigational
Key Points
- Senescent cells accumulate with age and secrete inflammatory signals that damage surrounding tissue — senolytics aim to selectively eliminate these “zombie cells” and potentially reverse aspects of aging rather than merely slowing decline.
- Dasatinib plus quercetin represents the most studied combination, while fisetin offers a more accessible single-agent alternative — both use intermittent “hit-and-run” dosing, but human longevity data remains nonexistent.
- The field is genuinely promising but firmly experimental — Mayo Clinic trials continue, and results over the next 3–5 years should clarify whether the dramatic mouse results translate to meaningful human benefits.
The McKaizer Evidence-Ranked Supplement Stack
The McKaizer Evidence-Ranked Supplement Stack
After examining hundreds of compounds, reviewing thousands of papers, and consulting with researchers at the frontlines of longevity science, we’ve developed a tiered ranking system. Not all supplements are created equal. Some have decades of rigorous human data. Others rest on promising mechanisms and animal studies that may or may not translate.
Our philosophy is simple: prioritize compounds with the strongest evidence, acknowledge uncertainty honestly, and never confuse marketing enthusiasm with scientific validation.
This stack represents our current best understanding — a living framework that evolves as new research emerges. We’ve weighted human randomized controlled trials heavily, given partial credit to strong observational data and mechanistic plausibility, and remained skeptical of compounds that sound revolutionary but lack rigorous testing.
Tier 1: Strong Human Evidence
These compounds have multiple randomized controlled trials demonstrating meaningful benefits. The mechanisms are well-understood, safety profiles established over decades.
Omega-3 Fatty Acids (EPA/DHA)
The VITAL study, led by Dr. JoAnn Manson at Harvard, followed 25,871 participants for over five years. While primary cardiovascular endpoints showed modest effects, subgroup analyses revealed 28% reduction in heart attacks among those with low baseline fish consumption. The REDUCE-IT trial demonstrated that high-dose EPA (4g icosapent ethyl) reduced cardiovascular events by 25% in high-risk patients.
- Dosing: 2–4g combined EPA/DHA daily
- Form matters: Triglyceride form shows 70% better absorption than ethyl esters
- Best for: Cardiovascular protection, inflammatory reduction, cognitive maintenance
Vitamin D3
Deficiency affects an estimated 1 billion people worldwide. The VITAL trial and meta-analyses suggest benefits primarily accrue to those correcting deficiency rather than pushing already-adequate levels higher. Dr. Michael Holick at Boston University has documented vitamin D’s role in over 200 genes regulating cellular function.
- Target serum level: 40–60 ng/mL (100–150 nmol/L)
- Dosing: 2,000–5,000 IU daily, adjusted based on blood testing
- Pair with K2: MK-7 form at 100–200mcg ensures calcium reaches bones, not arteries
💡 Quick Fact: A 2023 meta-analysis in The Lancet Diabetes & Endocrinology found vitamin D supplementation reduced autoimmune disease incidence by 22% over five years — one of the most robust findings for any supplement intervention.
Magnesium
Approximately 50% of Americans consume inadequate magnesium. This mineral serves as a cofactor for over 300 enzymatic reactions, including ATP production, DNA repair, and protein synthesis. The Atherosclerosis Risk in Communities study found that participants in the highest quintile of magnesium intake had 38% lower risk of sudden cardiac death.
- Forms: Glycinate for sleep and calm, threonate for cognitive effects, malate for energy
- Dosing: 300–400mg elemental magnesium daily
- Timing: Evening dosing supports sleep architecture
What This Means For You
Tier 1 supplements address common deficiencies with strong safety records and meaningful evidence. If you’re building a foundational stack, start here. Test your vitamin D levels. Assess your omega-3 intake. Most people benefit from these basics before exploring more experimental compounds.
Tier 2: Promising Human Data, Emerging Evidence
These compounds show mechanistic plausibility and encouraging human trials, but evidence remains incomplete or conflicting.
Creatine Monohydrate
Long dismissed as merely a sports supplement, creatine is experiencing scientific renaissance. Dr. Darren Candow at the University of Regina has documented cognitive benefits in aging populations, with studies showing improved memory and processing speed in older adults. A 2023 systematic review identified 22 human trials examining creatine’s neuroprotective effects.
- Dosing: 3–5g daily (loading phases unnecessary for longevity purposes)
- Notable: One of the most cost-effective supplements with excellent safety data
- Mechanism: Enhances cellular energy availability, particularly in brain and muscle
Coenzyme Q10 (Ubiquinol)
Mitochondrial function declines with age. CoQ10 levels drop approximately 50% between ages 20 and 80. The Q-SYMBIO trial by Dr. Svend Aage Mortensen in Copenhagen showed that CoQ10 supplementation reduced major adverse cardiovascular events by 43% in heart failure patients over two years.
- Form: Ubiquinol (reduced form) absorbs 3–4x better than ubiquinone in older adults
- Dosing: 100–200mg daily with fat-containing meals
- Synergy: Particularly important for those on statins, which deplete CoQ10
Curcumin (Enhanced Absorption)
Standard curcumin absorbs poorly. But formulations using piperine, phospholipids, or nanoparticle technology dramatically improve bioavailability. Dr. Bharat Aggarwal’s work at MD Anderson identified curcumin’s effects on over 100 molecular targets involved in inflammation and aging.
- Forms: Longvida, Meriva, or Theracurmin show 29–185x improved absorption
- Dosing: 400–1000mg enhanced curcumin (not equivalent to raw turmeric)
- Evidence: Multiple trials show reduced inflammatory markers and joint pain
Tier 3: Mechanistically Compelling, Limited Human Data
These compounds target fundamental aging pathways but rely heavily on animal studies or small human trials.
NMN/NR (NAD+ Precursors)
Dr. David Sinclair’s research at Harvard ignited interest in NAD+ biology. Human trials by ChromaDex and others confirm that NR raises NAD+ levels. However, whether elevated NAD+ translates to longevity benefits in humans remains genuinely unknown.
- Current status: Safe, raises NAD+ levels, but functional human outcomes unproven
- Dosing: 500–1000mg NMN or 300–500mg NR daily
- Our view: Reasonable to experiment, but don’t expect miracles
Spermidine
This autophagy-inducer shows remarkable results in model organisms. Dr. Frank Madeo at the University of Graz has led human observational studies suggesting cardiovascular and cognitive benefits. The 2018 American Journal of Clinical Nutrition analysis found high dietary spermidine intake associated with reduced mortality.
- Food sources: Aged cheese, wheat germ, soybeans, mushrooms
- Supplemental dosing: 1–6mg daily
- Mechanism: Induces autophagy without requiring fasting
What This Means For You
Tier 2 and 3 compounds represent informed experimentation. They’re reasonable additions for those who’ve optimized fundamentals and accept scientific uncertainty. We suggest implementing one new compound at a time, tracking subjective and objective markers, and remaining willing to discontinue if benefits don’t materialize.
Key Points
- Tier 1 supplements (omega-3s, vitamin D3, magnesium) address widespread deficiencies with decades of safety data and multiple large-scale trials — these form the foundation before exploring experimental compounds.
- Tier 2 compounds like creatine, CoQ10, and enhanced curcumin show promising human evidence but require better-designed trials — they represent reasonable additions for optimization-minded individuals.
- Tier 3 interventions (NMN/NR, spermidine) target fundamental aging mechanisms but rely primarily on animal data and small human studies — they’re worth exploring but demand honest acknowledgment that longevity benefits remain unproven.
How to Monitor Supplement Efficacy — Biomarkers to Track
How to Monitor Supplement Efficacy — Biomarkers to Track
Taking supplements without measuring their effects is like investing money without checking your returns. You might be building wealth — or slowly losing it. The difference between supplement success and expensive placebo lies in systematic biomarker tracking.
Dr. Peter Attia, longevity physician and host of The Drive podcast, calls this approach “evidence-based personalization.” Generic recommendations fail because your metabolism, absorption capacity, and baseline nutrient status differ from everyone else’s. What works spectacularly for one person may be inert — or even counterproductive — for another.
The good news: modern testing has become remarkably accessible. The same biomarkers that researchers track in clinical trials are now available through direct-to-consumer labs, often at reasonable cost.
Foundational Biomarkers Everyone Should Track
Before diving into supplement-specific markers, establish your baseline metabolic picture. This foundation reveals whether you’re actually deficient in what you’re supplementing — and whether your interventions are moving the needle.
Essential baseline panel:
- Complete metabolic panel (CMP) — liver enzymes, kidney function, electrolytes
- Fasting lipid panel — total cholesterol, LDL-C, HDL-C, triglycerides
- Fasting glucose and HbA1c — metabolic health snapshot
- High-sensitivity C-reactive protein (hs-CRP) — systemic inflammation marker
- Complete blood count (CBC) — overall health indicator
💡 Quick Fact: Research from the Framingham Heart Study shows that hs-CRP levels above 3.0 mg/L triple cardiovascular risk compared to levels below 1.0 mg/L — making this single marker remarkably predictive.
Track these quarterly for your first year, then biannually once patterns stabilize. Sudden changes often reveal problems faster than symptoms appear.
Omega-3 Specific Monitoring
The Omega-3 Index — developed by Dr. William Harris at the University of South Dakota — measures EPA and DHA as a percentage of red blood cell membranes. This test reflects your actual tissue omega-3 status over the preceding 3–4 months, not just what you swallowed yesterday.
Target range: 8–12%
What the research shows:
- An index below 4% indicates high cardiovascular risk
- Levels between 4–8% suggest room for optimization
- Above 8% correlates with reduced sudden cardiac death risk by up to 90% in some studies
If your index hasn’t budged after three months of supplementation, consider absorption issues. Try taking omega-3s with a fat-containing meal — a 2019 study in the Journal of the Academy of Nutrition and Dietetics showed three-fold better absorption when fish oil accompanied dietary fat versus taking it on an empty stomach.
Vitamin D: Beyond the Basics
Standard 25-hydroxyvitamin D testing reveals your circulating vitamin D status. But optimal interpretation requires nuance.
Target range: 40–60 ng/mL (100–150 nmol/L)
Critical co-markers:
- Parathyroid hormone (PTH) — elevated PTH despite “normal” vitamin D suggests functional deficiency
- Calcium (serum) — ensures D supplementation isn’t causing excess absorption
- Magnesium (RBC) — vitamin D metabolism requires adequate magnesium
Dr. Michael Holick at Boston University — the researcher who identified the major circulating form of vitamin D — emphasizes that many people with levels of 30 ng/mL still show elevated PTH, indicating their bodies want more.
What This Means For You
Don’t just test vitamin D alone. A complete picture includes PTH and calcium at minimum. If your vitamin D remains stubbornly low despite supplementation, check magnesium status — you may be addressing the wrong bottleneck.
NAD+ Precursor Tracking
Monitoring NMN and NR efficacy presents unique challenges. No standard clinical test for NAD+ exists yet. However, researchers at Washington University School of Medicine under Dr. Shin-ichiro Imai use several proxy measures in their human trials.
Currently measurable markers:
- Fasting insulin and HOMA-IR — NAD+ precursors may improve insulin sensitivity
- Triglyceride-to-HDL ratio — a metabolic health proxy that may respond to NAD+ optimization
- Grip strength testing — surprisingly correlates with cellular energy status
- Subjective energy questionnaires — validated tools like the PROMIS Fatigue Scale
Emerging tests:
- NAD+ blood testing — now offered by specialty labs like Jinfiniti
- Biological age clocks — epigenetic tests from TruDiagnostic, Elysium, and others
The TAME trial (Targeting Aging with Metformin), led by Dr. Nir Barzilai at the Einstein College of Medicine, uses a composite endpoint including cardiovascular events, cancer, dementia, and mortality. For personal tracking, we recommend a similar multi-marker approach rather than fixating on any single number.
Inflammation and Oxidative Stress Markers
Several supplements target inflammation and oxidative damage. Track their efficacy with:
Inflammation markers:
- hs-CRP — general systemic inflammation
- IL-6 — more specific inflammatory cytokine
- Fibrinogen — clotting-related inflammation marker
Oxidative stress indicators:
- F2-isoprostanes — gold standard for lipid peroxidation
- 8-OHdG (urine) — DNA oxidative damage marker
- Homocysteine — rises with B-vitamin deficiency and oxidative stress
A 2021 systematic review in Antioxidants journal found that CoQ10 supplementation consistently reduced hs-CRP by an average of 0.35 mg/L — modest but meaningful for those starting with elevated levels.
What This Means For You
Choose 3–5 relevant biomarkers based on your supplement stack. Test before starting supplementation, then retest at 90 days. Track trends rather than obsessing over single readings. Individual variation means your optimal values may differ from population averages.
Building Your Testing Protocol
Quarterly testing (first year):
- Baseline metabolic panel
- hs-CRP and homocysteine
- Supplement-specific markers (omega-3 index, vitamin D, etc.)
Advanced annual testing:
- Biological age assessment (epigenetic clocks)
- Comprehensive micronutrient panel
- Advanced lipid testing (ApoB, Lp(a), LDL particle count)
Budget approximately $300–600 annually for foundational testing through direct-to-consumer labs like InsideTracker, Life Extension, or Quest Diagnostics. Consider this the accountability mechanism that transforms supplement guessing into supplement science.
Key Points
- Establish baseline markers before starting any supplement — the Omega-3 Index, 25-hydroxyvitamin D, hs-CRP, and HbA1c form a core foundation that reveals both deficiency status and response to intervention.
- Retest at 90-day intervals initially — this timeframe allows cellular turnover and accumulation effects to manifest in blood markers, providing meaningful signal rather than noise.
- Track trends across multiple markers rather than single values — no biomarker tells the complete story, and patterns across inflammation, metabolic, and nutrient markers reveal far more than isolated numbers.
The Future of Longevity Pharmacology
The Future of Longevity Pharmacology
The supplements of today represent first-generation longevity tools. What’s coming will redefine what’s possible.
We stand at an inflection point. The convergence of artificial intelligence, precision medicine, and molecular biology is accelerating drug discovery at unprecedented speed. Compounds that once required decades to develop now move from concept to clinical trial in years — sometimes months.
The longevity field specifically has attracted over $5.2 billion in venture funding since 2020, according to Longevity.Technology tracking data. This isn’t speculative enthusiasm. It reflects genuine scientific momentum toward interventions that address aging itself.
Senolytics: Clearing the Cellular Deadwood
Senescent cells — the “zombie cells” that stop dividing but refuse to die — accumulate with age and poison surrounding tissue with inflammatory signals. Eliminating them has emerged as one of the most promising longevity strategies.
Dr. James Kirkland at Mayo Clinic pioneered this field with the landmark 2015 discovery that dasatinib plus quercetin could selectively clear senescent cells in mice, extending healthspan dramatically. Human trials followed.
The first-in-human senolytic trial, published in The Lancet EBioMedicine in 2019, demonstrated that this same combination improved physical function in patients with idiopathic pulmonary fibrosis. Unity Biotechnology, Oisin Biotechnologies, and Senolytic Therapeutics are now racing toward targeted senolytic drugs with greater precision and fewer side effects.
💡 Quick Fact: A single senolytic treatment in aged mice reduced senescent cell burden by 70% and improved physical function for months — suggesting intermittent dosing may be sufficient.
What excites researchers most: senolytics may require only periodic administration rather than daily dosing. Clear the zombie cells, let the body recover, repeat annually or semi-annually.
What This Means For You
Current senolytics like fisetin and quercetin are available now but require further human validation for optimal dosing. Within 3–5 years, expect FDA-approved senolytics with established protocols for preventive use in healthy adults.
Epigenetic Reprogramming: Turning Back the Clock
If senolytics clear damage, epigenetic reprogramming reverses it.
Dr. David Sinclair’s lab at Harvard demonstrated in 2020 that partial expression of Yamanaka factors could restore vision in aged mice by resetting epigenetic markers to younger configurations. The cells didn’t just stop aging — they functionally de-aged.
Altos Labs, backed by $3 billion and featuring Nobel laureates including Shinya Yamanaka himself, is pursuing cellular rejuvenation as its core mission. Retro Biosciences and NewLimit (co-founded by Coinbase’s Brian Armstrong) represent additional well-funded efforts.
The challenge: Yamanaka factors can cause cancer if expressed too strongly or too long. Current research focuses on:
- Partial reprogramming — enough to rejuvenate without dedifferentiating
- Tissue-specific delivery — targeting aged organs without systemic effects
- Chemical alternatives — small molecules that mimic factor effects safely
Early-stage human trials may begin by 2026–2027.
AI-Accelerated Discovery
Machine learning is transforming how longevity compounds are discovered. Insilico Medicine used AI to identify a novel anti-fibrotic drug candidate in just 18 months — a process that traditionally takes 4–6 years.
Applied to aging, these tools are:
- Screening millions of compounds for geroprotective effects
- Predicting synergistic combinations humans would never guess
- Identifying repurposing opportunities in existing approved drugs
The supplement stack of 2035 will likely include compounds we haven’t yet named.
Key Points
- Senolytics clearing zombie cells may require only periodic dosing — Mayo Clinic’s pioneering work suggests annual or semi-annual treatments could maintain reduced senescent cell burden.
- Epigenetic reprogramming represents true biological age reversal — Altos Labs and others are pursuing cellular rejuvenation with over $3 billion in committed funding.
- AI is compressing decades of drug discovery into years — expect novel longevity compounds to emerge faster than any previous era of pharmaceutical development.
✦ McKaizer Institute Protocol
Evidence-ranked, actionable steps distilled from the research above.
- Step 1: See the detailed protocol section above.
- Step 2: See the detailed protocol section above.
- Step 3: See the detailed protocol section above.
- Step 4: See the detailed protocol section above.
- Step 5: See the detailed protocol section above.
Frequently Asked Questions
The evidence hierarchy consists of five tiers that determine how reliable research findings are for human application. Tier 1 includes in vitro studies using cell cultures, which help understand mechanisms but aren’t predictive of human benefit. Tier 2 covers animal models like C. elegans and mice, though only 8% of drugs that work in mice succeed in human trials. Tier 3 encompasses observational human studies showing associations but not causation. Tier 4 represents randomized controlled trials (RCTs), the gold standard, though most measure surrogate endpoints rather than actual lifespan. Tier 5 is long-term human outcome data, which remains exceedingly rare in longevity science. As Dr. Nir Barzilai of Albert Einstein College of Medicine emphasizes, the critical question is whether compounds work in people at achievable doses without causing other problems.
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