Supplements are heavily marketed, but evidence exists primarily for specific ones. Quality issues may also arise. Small changes in the chemical structure of supplements can significantly reduce bioavailability — e.g., ferrous (Fe²⁺) vs. ferric (Fe³⁺) iron, ubiquinone vs. ubiquinol, magnesium oxide vs. glycinate or citrate.

The following supplements are backed by high-quality evidence, and a favorable benefit-risk profile.

For everyone

Vitamin D3 — year-round supplementation is reasonable, though excess intake is also harmful. Fracture risk management; evidence also in the longevity context.

Magnesium — in citrate or glycinate form. Blood pressure, insulin sensitivity, migraine prevention.

Creatine monohydrate — cognitive enhancement, resistance training performance improvement.

Conditional

Iron (Fe²⁺) — if ferritin < 30. Higher targets if trying to conceive, restless legs, competitive athletics, or functional optimization goals. For fatigue symptoms, exercise performance improvement.

Melatonin — for jet lag and certain fertility indications.

Vitamin B12 — for older adults, vegetarians, and PPI users.

Folate — for women of reproductive age. Also in the context of certain diseases and medications.

Saccharomyces boulardii CNCM I-745 — during and after antibiotic courses. Not for immunosuppressed individuals.

Iodine — if you don't consume dairy products or use salt in cooking.

Ubiquinone — for statin users, in IVF treatments, for heart failure patients, possibly in migraine.

Zinc acetate — in high doses as lozenges or spray during common cold symptoms.

Plant stanols — taken with meals. LDL cholesterol reduction.

Psyllium fiber — LDL cholesterol reduction.

Choline — If dietary intake of eggs is low. During and when planning for pregnancy.