Vitamin D is an essential nutrient with important roles in bone health, muscle function, nerve signaling, and immune function. Your body can make vitamin D when skin is exposed to sunlight, and you can also obtain it from certain foods, fortified foods, and dietary supplements.
Why Vitamin D Matters for Your Bones
One of vitamin D’s best-established jobs is helping the body absorb calcium. Adequate vitamin D and calcium help support normal bone mineralization and strong bones. Too little vitamin D can contribute to soft or weakened bones.
Vitamin D and Muscle Function
Your muscles need vitamin D for normal movement and function. Maintaining adequate vitamin D status is part of supporting overall musculoskeletal health. Taking extra vitamin D beyond your needs, however, has not consistently been shown to improve muscle strength or athletic performance.
Immune and Nerve Function
Vitamin D contributes to normal immune function, and the body also needs it for nerve-related functions.
How Much Vitamin D Do Adults Need?
The NIH Office of Dietary Supplements lists 15 micrograms (600 IU) per day for adults ages 19–70 and 20 micrograms (800 IU) per day for adults age 71 and older. Individual needs can differ, particularly when a healthcare professional is treating a diagnosed deficiency.
Where Can You Get Vitamin D?
Fatty fish such as salmon and trout are natural sources. Fortified milk and some plant beverages and cereals can provide vitamin D, while egg yolks contain smaller amounts. Skin can also produce vitamin D after UV exposure. Vitamin D2 and D3 are both used in supplements.
More Is Not Always Better
Vitamin D is fat-soluble, so excessive supplemental intake can be harmful. For adults, the tolerable upper intake level is generally 100 micrograms (4,000 IU) per day unless a healthcare professional recommends otherwise. If you are concerned about deficiency or high-dose supplementation, discuss testing and appropriate intake with a qualified healthcare professional.
The CIWO Takeaway
Vitamin D contributes to several systems that help keep you active: bones, muscles, nerves, and immune function. A balanced diet, appropriate outdoor activity, and professional guidance when supplementation is needed can help support adequate vitamin D as part of an overall healthy lifestyle.
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