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.
There is conflicting evidence about the amount of vitamin D that is safe and effective, or even necessary, to use as a supplement. 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).
People with low levels of vitamin D seem to have an increased risk of dying from all causes, according to population studies.
Analysis of 18 vitamin D studies suggests that people taking vitamin D supplements at an average dose of 528 IU/day have a 7% lower risk of dying from any cause than people who do not supplement with vitamin D.
Why do people take vitamin D?
Vitamin D is quite 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 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 ages 70 or over
Some experts think that these recommendations are too low, especially for people at risk of osteoporosis. Ask your doctor how much vitamin D you need.
Recently the Institute of Medicine (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.
