Vitamin D for bone health: a quick guide for athletes
Vitamin D (also called calciferol) is essential for bone health, mainly because your body needs it to actually absorb calcium — without enough vitamin D, extra calcium in your diet doesn’t help much. It’s unusual among nutrients in that your skin can make it directly from sunlight, on top of getting it from food or a supplement.
Where it comes from
- Sunlight: roughly 5–30 minutes of midday sun exposure is enough for many people, though this varies a lot by skin tone, latitude, season, and age — darker skin needs more sun exposure to make the same amount.
- Food: fatty fish (salmon, tuna), egg yolks, mushrooms, and fortified foods like milk, yogurt, and some cereals and juices.
- Supplements: either D2 (a manufactured form) or D3 (the form your body makes naturally); unlike calcium, vitamin D supplements can be taken with or without food. See our supplements guide for more on quality and safety.
Who’s more likely to be low
Deficiency is more common in people who are lactose intolerant, follow a dairy-free or vegan diet, or simply get limited sun exposure — relevant for indoor-sport athletes or anyone training mostly early morning or evening. Left unaddressed, deficiency can lead to osteomalacia (softening of the bone), and is a factor worth checking in athletes dealing with recurrent bone stress injuries — see our RED-S and bone stress injuries guides.
How much do you need?
General guidelines suggest about 600 IU/day for most children, teens, and adults up to 70. Some bone health specialists recommend a higher daily target — around 800–1,000 IU — to maintain optimal blood levels, particularly for athletes with limited sun exposure or other risk factors. If you’re concerned about your levels, a simple blood test can confirm where you stand rather than guessing.
This page is educational and general in nature and does not replace individualized nutrition advice — see our medical disclaimer.