GradedHealth

Vitamins & Minerals

Vitamins & Minerals: what peer-reviewed studies say each one helps with, and how strong the evidence is.

  • Folate (folic acid) — Taken before and during early pregnancy, folic acid prevents neural tube birth defects such as spina bifida, cutting the risk by roughly 70% in pooled randomis…
  • Iodine — Where diets lack iodine, iodine prevents goitre and hypothyroidism: salt iodisation roughly halved goitre prevalence in China, and supplements cut hypothyroidi…
  • Iron — Oral iron corrects iron-deficiency anaemia, and in people who are iron-deficient but not anaemic it eases fatigue.
  • Magnesium — Magnesium supplements modestly lower blood pressure, mainly in people with high blood pressure or low magnesium levels, and may slightly improve blood sugar in…
  • Multivitamins — A daily multivitamin may slightly improve memory in older adults and slowed two DNA-based aging clocks in one trial, but the evidence for both is limited and m…
  • Riboflavin (vitamin B2) — Riboflavin (vitamin B2) may reduce how often adults get migraines: 400 mg a day cut attacks in a small placebo-controlled trial.
  • Selenium — In trials, selenium improved eye signs and quality of life in people with mild Graves' eye disease, and in selenium-poor parts of China supplements cut the rat…
  • Vitamin A — Vitamin A supplements prevent night blindness and other eye problems in people who are vitamin A deficient, and in low-income countries they cut child deaths b…
  • Vitamin B12 — Vitamin B12 supplements treat and prevent B12 deficiency: tablets work about as well as injections for most people, and supplementation keeps levels up in vega…
  • Vitamin C — Taken every day, vitamin C shortens colds by about 8% in adults and 14% in children and makes them less severe - a 2023 meta-analysis found severity fell 15%.
  • Vitamin D — In people with prediabetes, vitamin D supplements lower the chance of developing type 2 diabetes.
  • Vitamin E — Vitamin E supplements have one place where the evidence clearly supports them: in fatty liver disease (NASH/MASH), 800 IU a day improved liver histology in the…
  • Vitamin K2 — Vitamin K2 may help keep spine bone density up in postmenopausal women, but fracture results are mixed and the artery studies are small and do not agree.
  • Zinc — Zinc lozenges taken at the start of a cold shorten the illness by roughly two to three days in randomised trials.