You might hear the phrase "getting my dose of vitamin D" associated with someone taking a walk outdoors. That's because your body makes vitamin D when exposed to sunlight. There are other sources of vitamin D, too, including supplements and some foods. Recommended levels of vitamin D for good health are often tempered by warnings not to take too much.
Role of Vitamin D
Good bone health is the main role of vitamin D, which facilitates calcium absorption in the body, and calcium is necessary for strong bones and teeth. Bones become brittle and more prone to injury when you don't have enough vitamin D in your system. Preventing health conditions associated with weak bones, such as osteoporosis and rickets, requires adequate levels of vitamin D. It also plays a role in reducing inflammation, aiding cell growth and helping immune and neuromuscular function. Research into vitamin D's role in prevention and treatment of conditions such as cancer, diabetes, high blood pressure and multiple sclerosis is growing and ongoing.
Sources of Vitamin D
Vitamin D is found naturally in foods such as egg yolks, cheese and beef liver, but at very low levels. It's more abundant in fish liver oil and the flesh of fatty fish, such as salmon and tuna. Getting your dose of vitamin D through diet often comes from foods that have been fortified with vitamin D. Milk, cereal, yogurt, orange juice and infant formula are often vitamin-D fortified. Sunshine is the ultimate natural source of vitamin D. With skin exposure to UV B rays, your body creates vitamin D naturally in the body. If you're not getting enough sun or consuming enough in foods, vitamin D supplements are readily available.
Recommended Vitamin D Dosage
The Food and Nutrition Board establishes the recommended dietary allowances for vitamin D. The numbers were determined with consideration for maintaining bone health for someone with normal calcium metabolism and limited sun exposure. For babies under 1 year old, 400 international units, or IU, per day are recommended; 600 IUs for children over 1 and adults up to 70 years old; and 800 IUs for those 71 years and older. You can drink about five to six cups of fortified, reduced-fat milk to give you 600 IUs for the day. Vitamin D excess must be considered when determining adequate levels of vitamin D. The Food and Nutrition Board established a daily upper limit of vitamin D for this reason. For infants up to 6 months old, 1,000 IU is the upper limit; 1,500 IU for babies 6 months to 12 months; 2,500 IU for 1 to 3 years old; 3,000 IU for those 4 to 8 years old; and 4,000 IU for anyone over 9 years old.
Considerations
Vitamin D toxicity is rare and usually occurs from taking too many supplements. Vitamin D generated from consuming foods and from sun exposure isn't likely to cause toxicity. The body has the ability to regulate levels of vitamin D generated from sun exposure, and foods with vitamin D don't contain enough to cause toxicity, notes the Office of Dietary Supplements. Toxicity of vitamin D rarely even occurs with vitamin D supplements, but vitamin D deficiency is a more pressing health concern in America, given its role in bone health. Symptoms of toxicity include nausea, vomiting, constipation, kidney stones and weakness. Your doctor can check levels of vitamin D with a blood test. Vitamin D supplements interact with medications such as corticosteroids, medications for epilepsy, some weight-loss drugs and some cholesterol-lowering medications.
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