Supplements

The honest meta-conclusion of supplement research is sobering: after examining hundreds of thousands of person-years of randomized data, no supplement on the market has been shown to extend life, prevent disease, or slow biological aging in healthy middle-aged adults at the magnitude of basic lifestyle interventions.

That said, a short list has convincing human evidence as gap-fillers, and a few supplements actively cause harm at common doses. This section sorts them.

The evidence-based core

For a generally healthy 35–55-year-old who exercises moderately, the supplements with convincing human evidence and a favorable risk profile are:

1. Vitamin D3 — strong for repletion if deficient; conditional for outcomes
2. EPA/DHA omega-3 — moderate cardiovascular and triglyceride benefit; strong for those who don't eat fish
3. Magnesium — strong for repletion (widespread inadequacy); moderate for sleep and BP
4. Vitamin B12 — strong in specific groups (vegetarians, metformin users, age 50+ with absorption issues)
5. Creatine monohydrate — strong for muscle, moderate for cognition

Almost everything else — including the buzzy "longevity molecules" like NMN, resveratrol, urolithin A, spermidine, lithium orotate — currently rests on animal data, surrogate biomarkers, or industry-funded short-term trials, not on hard outcomes in healthy adults.

Topics covered in depth

The core stack →

The five supplements with convincing human evidence: doses, forms, timing, interactions, who actually needs them, and how to test before supplementing.

Creatine →

The single most-evidenced and safest supplement in the core stack — and the one with the broadest range of benefits. Muscle, strength, and a recent body of brain bioenergetics research showing real effects under sleep deprivation and in older adults. Plus the resolved type-2-diabetes paradox and the kidney-myth debunking.

Sleep & anxiety supplements →

Magnesium glycinate, L-theanine, melatonin, ashwagandha, glycine, valerian, CBD. What works, at what dose, and the addiction/tolerance question explicitly addressed.

Geroprotectors: NMN, resveratrol, rapamycin, metformin, urolithin A, spermidine →

The "longevity molecule" category. Mechanistic promise vs. clinical translation.

GLP-1 receptor agonists: Ozempic, Wegovy, and the longevity question →

Semaglutide and tirzepatide: the only drug class to date that combines double-digit weight loss, a 20% MACE reduction in non-diabetics, and measurable deceleration of validated epigenetic aging clocks. The catch — up to 40% of the weight lost is muscle and bone unless you scaffold with protein and resistance training. Plus: microdosing, food noise, and why you probably can never stop.

Supplements to avoid →

Documented harm at common doses: high-dose vitamin E, beta-carotene in smokers, retinol overload, calcium megadosing, chronic high-dose B6, selenium >200 µg in replete people.

Test before you supplement

For anything fat-soluble, mineral, or chronically dosed, test first. Highest-yield labs in midlife:

• 25-hydroxyvitamin D
• Vitamin B12 with methylmalonic acid (MMA) or holotranscobalamin
• Ferritin and transferrin saturation (especially in premenopausal women)
• RBC magnesium (more sensitive than serum)
• TSH
• Omega-3 index (RBC EPA+DHA percentage; target 8–12%)
• Homocysteine

For Czech residents specifically, vitamin D is the single most cost-effective test — only ~20% of younger adults reach 25(OH)D ≥75 nmol/L.

Quality assurance

Look for USP Verified, NSF Certified for Sport, or Informed Sport marks. ConsumerLab independent testing repeatedly finds 10–30% of products underdosed, contaminated with heavy metals, or mislabeled.

• Fish oil should be third-party tested for oxidation (TOTOX) and rancidity.
• Melatonin OTC in the US varies 83–478% of label dose; EU prolonged-release Circadin 2 mg is more reliable.
• NMN products from Amazon have repeatedly failed label-claim assays.

What's overrated

The novel insight from the most recent five years of evidence is that the gap between mechanistic promise and clinical translation is widening, not narrowing, for the entire emerging-longevity supplement category — while the foundational story for vitamin D in deficient populations, omega-3 for cardiovascular nuance, magnesium for blood pressure and metabolism, and creatine for muscle and cognition has actually become stronger and more practical to act on.

Refuse the cocktail-of-everything approach. Use supplements as targeted gap-fillers where biomarkers, diet, age, or sex create a specific rationale.

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