Vitamin D Functions
Vitamin D is a fat-soluble vitamin that helps control the level of calcium and phosphorus in the blood to help the body build and maintain strong bones and teeth. It also helps increase the body’s absorption of calcium.
Recent research suggest that getting adequate amounts of vitamin D (even more than currently recommended) can help protect against osteoporosis, hypertension, cancer, and autoimmune diseases.
The two main sources of vitamin D include the diet and sunlight.
Vitamin D is found naturally in only a few foods, most notably in fish. Most vitamin D we consume, however, comes from fortified foods including milk, margarine, and ready-to-eat cereal.
Vitamin D (in the form of vitamin D3, the kind found in foods) can be made in the body when the skin is exposed to ultraviolet-B (UVB) rays from sunlight for as little as 10 or 15 minutes.
Deficiencies and Excesses
Some people are at high risk for not getting or making enough vitamin D to meet their daily needs. These include:
• Older people
• People with dark skin
• Obese people
• Infants who are exclusively breastfed
• People who live in environments or climates in which sunlight is limited
• People with certain conditions that limit absorption of fat, such as cystic fibrosis and Crohn’s disease
• People who follow vegetarian or vegan diets and avoid fish, fish oils, and D-fortified dairy and other foods like milk and orange juice.
Without enough vitamin D, blood levels of calcium and phosphate can get too low, which can cause the body to produce hormones that release calcium and phosphate from the bones, causing bones to soften and weaken. In children, a vitamin D deficiency causes rickets. In adults, it causes osteomalacia.
Too much vitamin D from supplements can cause symptoms such as nausea, vomiting, decreased appetite and weight loss, weakness, confusion, altered heart rhythm, and calcium and phosphate deposits in soft tissues. However, D toxicity is now believed to be much less likely than previously believed unless intake routinely exceeds the 1,000 to 2,000 IU a day that experts now recommend.
Cystic fibrosis is an inherited disease that causes endocrine glands (organs that make and secrete hormones into the bloodstream) to malfunction. Mucus becomes thick and sticky and damages other body organs and can lead to serious problems with the lungs, pancreas, and digestive system.
Crohn’s disease is a lifelong inflammatory bowel disease that causes swelling and ulcers (deep sores) in the intestinal tract.
Rickets is a bone disease that occurs in infants and children who have a vitamin D deficiency; symptoms include soft, bendable bones.
Osteomalacia is a bone disease caused by a vitamin D deficiency in adulthood; bones foten and cause bowed legs and curvature of the spine.