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Dietary supplements · Vitamin D
Sunlight: most vitamin D is made by the skin

Sunlight: most vitamin D is made by the skin

James Day · Unsplash

Strong evidence20 studies
How we rate

“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.

Vitamin D

The vitamin the body manufactures in the sun — often deficient in winter, with a key role for bones, muscles, and immunity.

Immunity

Benefits

  • Slightly reduces the risk of acute respiratory infections, especially with daily or weekly intake and in severely deficient individuals (meta-analyses)
  • At 700-800 IU per day, reduces the risk of hip fracture and non-vertebral fracture in the elderly; 400 IU is not enough (meta-analysis)
  • In schoolchildren, 1,200 IU per day during the winter reduced seasonal influenza A
  • Ordinary doses, 528 IU per day on average, are associated with lower all-cause mortality (meta-analysis of 18 trials, over 57,000 participants)

Precautions

Fat-soluble vitamin: prolonged excess can become toxic. Do not exceed recommended doses without a blood test or medical advice.

Recommended dosage

400 to 1,000 IU per day in trials on infections; at least 700 to 800 IU for bones.

How to take it

  • Every day rather than a large dose: against respiratory infections, daily or weekly intakes protect better than massive single doses.
  • Dose: 400 to 1,000 IU per day in trials protecting against infections. For bones, at least 700 to 800 IU per day: 400 IU were not enough against fractures.
  • In winter: in schoolchildren, 1,200 IU per day during the winter reduced seasonal influenza A.
  • Especially if you are deficient: individuals with a very low baseline level (less than 25 nmol/L) derived the most benefit.
  • Safety margin: known cases of poisoning, with too much calcium in the blood, correspond to 40,000 IU per day or more.

Did you know?

Routine vitamin D supplementation, either on its own or in combination with calcium, does not reduce the risk of fractures in older adults living at home.

What the studies say

  • This updated meta-analysis confirmed that vitamin D supplementation was safe and generally reduced the risk of acute respiratory tract infections (ARIs), although the risk reduction was modest. Protective effects were associated with daily administration of 400-1000 IU for a duration of up to 12 months. These benefits were mainly observed in participants aged 1 to 15 years.

    Jolliffe DA, Camargo CA, Sluyter JD, Aglipay M, Aloia JF, Ganmaa D, Bergman P, Bischoff-Ferrari HA, Borzutzky A, Damsgaard CT, Dubnov-Raz G, Esposito S, Gilham C, Ginde AA, Golan-Tripto I, Goodall EC, Grant CC, Griffiths CJ, Hibbs AM, Janssens W, Khadilkar AV, Laaksi I, Lee MT, Loeb M, Maguire JL, Majak P, Mauger DT, Manaseki-Holland S, Murdoch DR, Nakashima A, Neale RE, Pham H, Rake C, Rees JR, Rosendahl J, Scragg R, Shah D, Shimizu Y, Simpson-Yap S, Trilok-Kumar G, Urashima M, Martineau AR. — The lancet. Diabetes & endocrinology (2021) — View the source study

For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more