The 10 Safest Supplements on Earth

Out of 733 supplements in our database, exactly one earns a perfect 100/100 — and the WHO calls it the most cost-effective intervention in modern medicine. Here are the 10 you could hand a stranger on the street without flinching: wide therapeutic windows, decades of human data, and toxicity profiles so clean they're boring.

1. Oral rehydration salts (WHO formula) — Score 100/100. The only perfect score in the database. Cents per serving.
2. Electrolyte replacement (clinical) — Same evidence base as ORS, formulated for adults rather than pediatric dehydration.
3. Creatine monohydrate — 500+ trials. ISSN's 2017 position stand: safe at 3–5 g/day in healthy adults; 2024–25 reviews extend to older adults and teen athletes.
4. Psyllium husk — Cochrane review of 28 RCTs and an FDA-authorized coronary heart disease claim at 7 g/day.
5. Oat beta-glucan — 58 RCTs, N=3,974, LDL down 5–10% at 3 g/day. Also FDA-approved cholesterol claim.
6. Protein supplementation (sarcopenia) — PROT-AGE consensus: 1.2–1.6 g/kg/day to preserve muscle in older adults.
7. Lactase enzyme — Cochrane-confirmed for lactose intolerance. Acts only in the gut, never enters the bloodstream.
8. Vitamin B1 (Thiamine, clinical) — Life-saving in alcohol-use disorder and refeeding syndrome. No documented chronic toxicity.
9. L-Leucine (standalone) — 2.5–3 g triggers muscle protein synthesis via mTOR. The "leucine threshold" matters more than total protein per meal.
10. Melatonin (0.1–0.5 mg, physiological) — Matches natural nighttime peaks without next-day grogginess. Most retail products are 10–30× higher than they need to be.

Bottom line

The safest supplements aren't the trendiest. They're cheap, off-patent, and supported by hundreds of trials each. None of them have an Instagram presence — and that's a feature, not a bug.

See the full breakdown with composite scores and study citations on Discover →