Vitamin D is both a nutrient we eat and a hormone our bodies make. Few, so the biggest dietary sources of vitamin D are fortified foods and .
Good sources include dairy products and breakfast cereals (both of which are fortified with vitamin D), and fatty fish such as salmon and tuna.
For most people, the best way to get enough vitamin D is taking a supplement, but the level in most multivitamins (400 IU) is too low.
Encouragingly, some manufacturers have begun adding 800 or 1,000 IU of vitamin D to their standard multivitamin preparations.
If the multivitamin you take does not have adequate level of vitamin D, you may want to consider adding a separate vitamin D supplement, especially if you don’t spend much time in the sun. Talk to your healthcare provider.
Two forms of vitamin D are used in supplements: vitamin D2 (“ergocalciferol,” or pre-vitamin D) and vitamin D3 (“cholecalciferol”). Vitamin D3 is chemically indistinguishable from the form of vitamin D produced in the body.
The body also manufactures vitamin D from cholesterol, through a process triggered by the action of sunlight on skin, hence its nickname, “the sunshine vitamin.”
Vitamin D helps ensure that the body absorbs and retains calcium and phosphorus, both critical for building bone.
Laboratory studies show that vitamin D can reduce cancer cell growth and plays a critical role in controlling infections. Many of the body’s organs and tissues have receptors for vitamin D.
Several studies link low vitamin D levels with an increased risk of fractures in older adults, and they suggest that vitamin D supplementation may prevent such fractures—as long as it is taken in a high enough dose.
Vitamin D may also help increase muscle strength, which in turn helps to prevent falls, a common problem that leads to substantial disability and death in older people.
Studies are finding vitamin D deficiency may be linked to heart disease.There’s evidence that vitamin D plays a role in controlling blood pressure and preventing artery damage, and this may explain these findings.
Dozens of studies suggest an association between low vitamin D levels and increased risks of colon and other cancers. The evidence is strongest for colorectal cancer, with most (but not all) observational studies finding that the lower the vitamin D levels, the higher the risk of these diseases.
Most experts recommend a daily intake of at least 600 International Units. You won’t find many foods that are high in vitamin D, but there are some.
Beef liver, cheese, egg yolks and fatty fish, which contain small amounts of D3, are the best dietary sources of D3.
Cod liver oil provide a time-honored potent source of D3, although the taste might be a turnoff.
Fortified milk and orange juice also contain vitamin D; manufacturers can choose to add either either D2 or D3.
Mushrooms supply D2 to your diet.
Over-the-counter and prescription supplements can increase your vitamin D3 intake.
The amount of vitamin D necessary for good health is a matter of sharp debate.
The Food and Nutrition Board’s adequate intake amount is 600 IUs per day between the ages of 1 and 70 and 800 IUs per day for adults over age 70.
Don’t take doses higher than this without talking to your doctor first.
Some organizations,, recommend at least 5,000 IU per day for healthy adults, while some experts suggest a tolerable upper intake of 10,000 IUs per day.
The Food and Nutrition Board’s tolerable upper intake limit is much less — 4,000 IUs per day.
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