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

Doses, forms, timing, interactions, and how to test before supplementing are covered under The core stack. Creatine warrants its own treatment — the most-evidenced and safest of the five, with a growing brain-bioenergetics literature on top of the muscle data; see Creatine. For supplements that target sleep and anxiety specifically — magnesium glycinate, L-theanine, melatonin, ashwagandha, glycine, valerian, CBD, including the tolerance question — see Sleep & anxiety supplements.

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. See Geroprotectors for the full landscape and the gap between mechanistic promise and clinical translation. And a handful of supplements have documented harm at common doses — high-dose vitamin E, beta-carotene in smokers, retinol overload, calcium megadosing, chronic high-dose B6, selenium above 200 µg in already-replete people — collected under Supplements to avoid.

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Prescription pharmacology — including GLP-1 receptor agonists (Ozempic-class drugs) and testosterone therapy — lives under the Clinical Care pillar. This section is for over-the-counter, food-derived, and nutritionally-bounded interventions.

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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