Longevity and antioxidant supplements: the evidence

Beta-carotene supplements are one of the clearest cautionary tales in supplement science: two large RCTs found they increased lung cancer and mortality in smokers and asbestos-exposed workers.

Vitamin E deficiency is essentially nonexistent in people who eat food, and as a supplement it has failed nearly every large prevention trial ever run on it — including one that found more prostate cancer.

Astaxanthin is a potent antioxidant in the test tube and it does shift some blood biomarkers, but the changes are small and rarely map onto anything you would notice.

No completed human efficacy trial exists for chaga in any indication, while multiple case reports document kidney failure from oxalate accumulation.

Olive polyphenols demonstrably protect LDL from oxidation — the one claim with regulatory backing.

Pyrroloquinoline quinone is marketed on impressive mitochondrial biology that has not translated into convincing human outcomes.

The famous "red wine molecule" has been studied for 20 years and still has nothing convincing to show in humans: bioavailability is terrible, meta-analyses conflict, and the largest umbrella review found most claimed benefits are unreliable.

A methylated resveratrol analogue with genuinely better bioavailability, but almost no independent human outcome data — and the one clear human finding is that it raises LDL cholesterol.

A senolytic flavonoid with a striking mouse result behind it — and a large, well-controlled replication attempt where fisetin failed to extend lifespan at all.

An autophagy-inducing polyamine backed by strong epidemiology and animal data — and by a well-run randomized trial in older adults with memory complaints that found no cognitive benefit.

NMN reliably raises blood NAD+ levels, but raising a biomarker is not the same as producing a benefit — meta-analyses of the human trials find no meaningful effect on metabolism, muscle or blood pressure.

The best-studied NAD+ precursor, with clean safety data and reliable NAD+ elevation — and a consistent record of failing to improve any functional outcome in well-controlled human trials.

Oral glutathione can raise body glutathione stores — the old claim that it is entirely destroyed in the gut was overstated — but no trial has linked that increase to a clinical benefit, and cheaper precursors like NAC and glycine do the same job.

An unusual amino acid with a dedicated human transporter and a plausible case for being a conditionally essential nutrient — but the clinical evidence is one small pilot trial.

IP-6 is phytic acid — the same compound nutritionists call an antinutrient in beans and grains — repackaged as an anticancer supplement.

He shou wu (Polygonum/Reynoutria multiflora) is sold for hair regrowth and longevity on the strength of a folk legend, not clinical trials.

Cistanche ("desert ginseng") is heavily marketed for testosterone and libido, but the actual human trials tested mobility in older adults and cognition in combination with ginkgo — and found modest effects.

An Amazonian berry with extraordinary vitamin C density, and unusually for this category, two small but real randomized trials — one showing a 15.

Açaí pulp is genuinely rich in anthocyanins, but the "superfood" reputation rests on antioxidant assays rather than outcomes: a 2025 meta-analysis of 8 trials found no effect on cholesterol or triglycerides, with low to very low certainty.

Mangosteen pericarp xanthones are pharmacologically interesting and mangosteen gel has decent data as a local periodontal treatment — but the juice sold through multi-level marketing for "immune and inflammation support" has essentially no oral-supplement evidence behind it.

Purple corn is a legitimately concentrated source of cyanidin-3-glucoside, but almost the entire evidence base is cell culture and rodent work.

This is where almost all commercial resveratrol comes from, so its longevity claims inherit resveratrol's unimpressive human record.

Pycnogenol is a patented French maritime pine bark extract with dozens of small trials spread thinly across a dozen unrelated conditions.

Luteolin is a genuinely interesting anti-inflammatory flavone in cell and animal research with essentially no standalone human efficacy data.

GlyNAC — glycine plus N-acetylcysteine — restores glutathione in older adults, which is not in dispute.

Alpha-ketoglutarate is a real Krebs-cycle metabolite that extended lifespan and compressed morbidity in mice, but the human longevity evidence is one small uncontrolled study of a commercial product using an epigenetic clock.

Plain oral SOD is an enzyme destroyed by stomach acid and digestion, so it does nothing systemically.

An acetylated glutathione claimed to survive digestion better than the plain form.

A Krebs-cycle intermediate sold for fatigue and ageing.

An alkaloid from coffee and fenugreek identified as an NAD+ precursor.

Tablets that release hydrogen gas into water, sold as a selective antioxidant.

A common dietary flavonol from kale, tea and capers with abundant laboratory activity.

A flavonol found in berries, walnuts and tea, studied for glucose control and antioxidant effects.

A pomegranate polyphenol that gut bacteria convert into urolithins.

The blue pigment-protein from spirulina, sold as a concentrated antioxidant.

A fat-soluble ester of vitamin C used mainly as a food and cosmetic antioxidant.

The vitamin E fraction that dominates the Western diet but is left out of most supplements.

Products selling NAD+ itself rather than a precursor.

An enzyme sold on the theory that hair goes grey because hydrogen peroxide builds up in the follicle.

A caffeine-free South African tea rich in aspalathin.

A fullerene dissolved in olive oil, sold on the strength of a single small rat study that reported longer lifespan.

The astragalus compound behind commercial telomerase activators.

A CoQ10 derivative engineered to accumulate inside mitochondria.

A crucifer rich in phenethyl isothiocyanate, sold for detoxification pathways.

Blends of fisetin and quercetin sold to clear "zombie" senescent cells.

Astragalus-derived blends (TA-65, cycloastragenol) sold to lengthen telomeres.

A natural form of vitamin B6 that blocks advanced glycation end-product formation in the laboratory.

A colourless metabolite of curcumin, produced in the gut and sold as a supposedly more bioavailable and more antioxidant alternative.

A histidine dipeptide abundant in fish and poultry, sold with carnosine for brain ageing and fatigue.

The least processed form of Camellia sinensis, marketed as the most antioxidant-rich tea.

Capsules combining CoQ10, PQQ, acetyl-L-carnitine, alpha-lipoic acid and B vitamins for cellular energy.

A glucose disaccharide used as a food sugar and studied as an autophagy activator.