Why do we need vitamin D?
Vitamin D is needed for the absorption of calcium and phosphorus, required for strong bones and teeth, and it helps with bone formation. Vitamin D also helps keep the immune system functioning normally, so our bodies can resist disease.
What happens if we do not get enough vitamin D?
Lack of vitamin D affects bones and many other parts of the body. Growing children who do not get enough vitamin D may have bones that are too soft and unable to support their weight, a disease known as rickets. Adults deficient in vitamin D can develop soft bones (osteomalacia). They can also lose bone mass, which leads to fragile bones that are at risk of fracturing (osteoporosis).
How much vitamin D do we need?
We need to get enough vitamin D from all sources to have adequate levels of it in our blood. Current vitamin D intake recommendations for healthy people are shown in Table 1. Some people may need more vitamin D. For example, persons with certain diseases and conditions may be at higher risk of having low levels of vitamin D in their blood. Your physician may suggest a higher intake than current recommendations.
Recommended Dietary Allowances for Vitamin D (Institute of Medicine, 2011).
How can we get enough vitamin D?
We get vitamin D from three sources—food, supplements, and sunlight.
Eggs, sardines, and salmon contain vitamin D. Most fluid milk and some brands of yogurt are fortified with vitamin D as well. Fortified breakfast cereals, breads, and orange juice may also contain vitamin D. Table 2 lists some foods and the amount of vitamin D they typically contain.
Typical vitamin D content in food (US Department of Agriculture, 2019).
If you cannot get enough vitamin D from your diet and you don't get out in the sun much, you may need to take a vitamin D supplement. It is recommended that older adults and persons with darker skin get extra vitamin D from fortified foods or supplements.
When exposed to sunlight, the skin makes a form of vitamin D, which is then activated in the body. Most people get some vitamin D from sunlight. However, several factors affect how well the body makes vitamin D after the skin is exposed to sunlight. For example, people in the northern United States make less vitamin D than those in the South, because of the winter months.
In general, the following people may be at risk for vitamin D deficiency (NIH, 2021):
- Older people
- Persons with darker skin
- People who are obese or have kidney or liver disease
- People who do not get direct sun exposure
How much is too much?
Vitamin D toxicity is very rare, but it can cause nausea, constipation, weakness, and kidney damage. It is recommended to get no more than 4,000 IU (less for children younger than nine) of vitamin D each day from food and supplements (Institute of Medicine, 2011). Sun exposure will not cause vitamin D toxicity.
Where can I get more information?
Your local UF/IFAS Extension Family and Consumer Sciences (FCS) agent may have written information and nutrition classes for you to attend. In Florida, find your local UF/IFAS Extension office at https://sfyl.ifas.ufl.edu/find-your-local-office/. Also, a registered dietitian (RD or RDN) or physician can provide reliable information on vitamin D.
Reliable nutrition information may be found online at these sites:
National Institutes of Health: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
US Department of Health and Human Services:
US Department of Agriculture: https://www.nutrition.gov
Institute of Medicine. 2011. “Dietary Reference Intakes for Calcium and Vitamin D.” Washington (DC). https://www.ncbi.nlm.nih.gov/books/NBK56070/
National Institutes of Health. "Fact Sheet for Professionals", 2021. Accessed May 4, 2022. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
U.S. Department of Agriculture and U.S. Agricultural Research Service. FoodData Central, 2019. Accessed May 13, 2021. https://fdc.nal.usda.gov/index.html