Supplements are the part of health where the most money is spent for the least return. The industry sells hope by the bottle and is regulated more like food than medicine, which means the burden of judgement sits with you.
That said, a small number of things are genuinely worth taking — usually because modern food, modern soil or modern indoor life removed something that used to be there.
Food first, and not as a platitude
Nutrients in food arrive with their cofactors. Vitamin A comes with the fat needed to absorb it; zinc in liver comes alongside copper; magnesium in greens comes with potassium. Isolating one compound and taking it at ten times the dietary dose is a different intervention from eating the food, and it does not always go the way the label implies.
Reading a label properly
- Elemental amount, not compound weight. 500 mg of magnesium glycinate is not 500 mg of magnesium
- The form. Methylfolate not folic acid; MK-7 not K1; bisglycinate not oxide or sulphate. The form usually costs more and usually accounts for whether it works
- Proprietary blends are a warning sign. If the doses are hidden, they are hidden because they are low
- Third-party testing — USP, NSF, Informed Sport — because content and label agree less often than they should
- Compare against the dose used in the research, not against the recommended daily allowance, which is set to prevent deficiency rather than to produce an effect
The short list worth considering
- Vitamin D with K2, at northern latitudes, from autumn to spring — and ideally tested
- Magnesium, because depletion is common and the safety margin is wide
- Omega-3, if oily fish is not on the menu two or three times a week
- Creatine, the best-evidenced performance and cognitive supplement there is, and cheap
- B12, for anyone eating little or no animal food, on metformin, or over sixty
- Iodine and selenium, in regions where the soil is poor in them
Test rather than guess where you can
Vitamin D, ferritin, B12 and thyroid function are all measurable and inexpensive. Taking a supplement to correct a number you have never seen is a strange way to spend money.
A word on interactions
Zinc competes with copper and iron. Calcium blocks iron and zinc. High-dose vitamin C increases iron absorption, which matters in both directions. Vitamin K interacts with anticoagulants. St John's wort induces liver enzymes and interferes with a long list of medications. If you take prescription drugs, tell your doctor what else you are taking — not because supplements are dangerous, but because some of them are, in combination.
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