Most people understand the importance of calcium to build strong bones and prevent osteoporosis, but the role of vitamin D is less understood. Calcium needs vitamin D to help it absorb into the intestines; when vitamin D levels drop, so does calcium absorption. Vitamin D comes from sunlight and dietary intake. Because vitamin D is not found in large quantities in many foods, and because increasing numbers of people spend little time outside, vitamin D supplements are often necessary.
Sunshine and Vitamin D
The sun shining on bare skin for as little as five to 30 minutes twice a week would manufacture enough D3, one of several types of vitamin D, to supply your needs. Since vitamin D can be stored in the liver and in fat, adequate spring, summer and fall sunlight exposure would boost your vitamin D stores to last through the winter months. Tanning beds also supply UV rays needed to synthesize vitamin D. A number of factors affect the amount of sun time you need. Skin color affects the amount of time needed, since people with darker skin need longer exposure. Cloud cover can reduce the UV rays needed to synthesize vitamin D by 50 percent. Sunscreen and window glass both block UV rays as well.
Types of Supplements
Vitamin D supplements are available both in food and as separate supplements often combined with calcium to decrease the risk of osteoporosis. Vitamin D-fortified milk, cereals and orange juice all serve as good sources of dietary vitamin D. Vitamin D supplements are also available as separate supplements or as part of a calcium or multivitamin supplement. Both D-2, synthesized by plants and D-3, synthesized in the skin by the sun and also found in some foods are available as supplements. Most supplements contain vitamin D3.
Doses
New research appears to be indicating that Americans need more vitamin D than previously thought to prevent diseases such as osteoporosis, according to the Vitamin D Council. Current recommendations for vitamin D supplementation are a recommended dietary intake of 600 International Units for men and women between the ages of 1 and 70, including pregnant and breast-feeding women and 400 IU for infants under 1 year. Both men and women over age 70 need 800 IU daily.
Risks
While too little vitamin D can lead to osteoporosis, too much vitamin D also has risks. There are no risks from getting too much vitamin D from food or sunlight, but sunlight exposure does have other risks. Too much sun exposure can cause sunburn or increase your risk of developing skin cancer. Taking too much vitamin D in the form of supplements could cause kidney stones and calcification in major organs, such as the heart, kidneys and blood vessels caused by too much calcium absorption. Nausea, vomiting, loss of appetite, weakness, dizziness, unsteadiness and excessive thirst are symptoms of hypercalcemia.
