The more time you spend indoors, the greater the chance you'll need to supplement your diet with vitamin D. Necessary for effective absorption of calcium, vitamin D exists in several forms, two of which are important for the body: vitamin D2, or ergocalciferol, synthesized by plants, and vitamin D3, or cholecalciferol, synthesized in the skin. You can get enough vitamin D3 through regular exposure to sunshine without sunscreen. You can also get it from some foods and via dietary supplements.
Role of Sunshine
Just 20 minutes in the sun three times a week helps ensure you'll get enough vitamin D3. The Vitamin D Council says Caucasian skin can synthesize about 10,000 IU of vitamin D3 through direct exposure to sunlight, which is 50 times the recommended daily requirement. The best times of year to get out in the midday sun are the late spring, summer and early fall. You must also take cloud cover, smog level and skin type into consideration. African-Americans and those with darker skin need more time in the sun due to the higher melanin content of their skin. UVB rays are responsible for vitamin D3 synthesis, so leave off the sunscreen. However, you must take care not to get sunburn.
Appropriate D3 Levels
Currently, the Recommended Dietary Allowance, or RDA, for vitamin D3 is based on the amount needed to maintain normal calcium levels and adequate bone health. Vitamin D3 is measured in mcg, or micrograms, and IU, or International Units; 1 mcg of vitamin D3 equals 40 IU. The daily recommendation for infants is 400 IU, or 10 mcg, and 600 IU, or 15 mcg, for children under 18. Between the ages of 18 and 70, adults of both sexes need 600 IU, or 15 mcg. Over age 70, vitamin D3 needs to increase to 800 IU, or 20 mcg.
Food Sources
There are not many natural food sources of vitamin D3, and it is not found in high amounts in those foods. The foods containing the most vitamin D3 are cod liver oil and fatty fish, such as salmon, tuna and mackerel. Other foods that have some vitamin D3 include beef liver, sardines, egg yolks and cheese. However, it is foods fortified with vitamin D that provide most of the vitamin D3 in the diet. Most commercial milk, of all varieties, is fortified with 100 IU per cup. Other fortified products include breakfast cereals, orange juice, margarine and yogurt.
D3 Deficiency
It has become apparent that vitamin D3 might be an important factor in the development of several diseases, including osteoporosis, cancer, multiple sclerosis and heart disease. A deficiency causes muscle weakness, bone pain and softening of the bones as calcium is pulled out to maintain blood levels. You are at risk if you live in parts of the Northern Hemisphere, have little exposure to sunlight, or are African-American, elderly or obese. Exclusively breast-fed infants need vitamin D supplementation to avoid developing rickets, a bone disease.
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