Vitamin D
Vitamin D is a fat-soluble vitamin that your body mainly makes from sunlight. It helps the body absorb calcium and is important for strong bones, muscles and the immune system.
Vitamin D at a glance
For whom
People at higher risk of deficiency: older adults, people who get little sun, a darker skin or covering clothing, and the winter months.
Not for whom
High doses without a confirmed deficiency add little and can be harmful in excess. Routine high dosing is not needed.
Usual dose
Often 10 to 20 micrograms (400 to 800 IU) per day; with a confirmed deficiency sometimes more on a doctor's advice.
Key caveats
More is not better; very high doses can be harmful. The effect on bones is clearest in people with a deficiency, together with enough calcium.
Known
Not yet
What popular health podcasts claimed about vitamin D, checked against the research.
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