Vitamin D plays several key roles in your body. Most importantly, vitamin D helps your body absorb the minerals calcium and phosphorus from the food you eat, which is important for bone health.
Many Americans have been found to have low levels of vitamin D. The reasons for this include low availability of vitamin D in food sources, increased time working indoors, and possibly increased use of sunscreens (since sunlight helps the body produce vitamin D).
Certain people may benefit from vitamin D supplementation. However, there is conflicting evidence about the amount of vitamin D that is safe and effective, or even necessary, to use as a supplement.
Why do people take vitamin D?
Vitamin D is important for people with osteoporosis. Studies show that calcium and vitamin D together can increase bone density in postmenopausal women. Vitamin D also helps with other disorders associated with weak bones, like rickets.
People who have low levels of vitamin D may need supplements. Vitamin D deficiencies are more common in those who:
- Are over 50
- Get very little sun exposure
- Have kidney disease or diseases that affect the absorption of minerals
- Have darker skin
- Are lactose intolerant
- Are vegan
- Are infants who are fed only breast milk
Vitamin D deficiency is commonly seen in people living in the Northern parts of the U.S.
Vitamin D deficiency may cause hormone problems, muscle weakness and pain, and other symptoms.
Studies have found prescription-strength vitamin D lotions helpful in treating psoriasis. Vitamin D has also been studied for other conditions ranging from cancer prevention to high blood pressure, but the evidence is unclear.
How much vitamin D should you take?
The Institute of Medicine (IOM) has set a recommended dietary allowance for vitamin D. Getting this amount of vitamin D from diet, with or without supplements, should be enough to keep you healthy.
- 600 IU (international units) a day for anyone aged 1-70
- 800 IU/day for anyone over 70
Some experts think that these recommendations are too low, especially for people at risk of osteoporosis. Ask your health care provider how much vitamin D you need.
Recently the IOM reviewed more than 1,000 research papers on vitamin D and concluded that high levels of the supplement are unnecessary and could be harmful.
The IOM warned that doses above 4,000 units a day were potentially harmful and that doses above 10,000 IU per day are associated with kidney and tissue damage.
Can you get vitamin D naturally from foods?
The best source of natural vitamin D is sunlight. Just 10 to 15 minutes of exposure without sunscreen a couple of times a week usually gives you enough vitamin D.
Vitamin D is also naturally found in butter, eggs, and fish such as salmon, tuna and mackerel. Vitamin D is often added to fortified foods, too, such as milk and cereal.
What are the risks of taking vitamin D?
- Side effects. At normal doses, vitamin D seems to have few side effects.
- Interactions. Vitamin D can interact with many medicines, such as drugs for high blood pressure and heart problems. If you take daily medicine, ask your health care provider if it's safe for you to take vitamin D supplements.
- Risks. Too much vitamin D can cause loss of appetite, frequent urination, and weight loss. High doses of vitamin D can also lead to disorientation and kidney and heart problems.