Information about vitamins D and E
DEAR DR. GOTT: I’ve heard a lot of mixed things about vitamins D and E. Can you tell me the good and the bad about them? Thank you.
DEAR READER: Vitamin D is fat-soluble, meaning that it is stored by the body for future use. It can be produced within the body during exposure to sunlight and is also available in some foods and through supplements. Before the body can use it, however, it must undergo two changes. The first occurs in the liver, the second in the kidneys. At this point, it is now active and ready for use in the body.
Vitamin D is widely known to aid calcium absorption. It also maintains appropriate blood-calcium and phosphate levels, which are necessary for normal bone mineralization. It is necessary for bone growth and remodeling (repair). The body also uses vitamin D for reducing inflammation, modulation of cell growth and normal functioning of the immune and neuromuscular systems.
Because vitamin D is not naturally found in many foods, it is commonly added to cereals, milk and other dairy products. Some foods that naturally contain vitamin D include cod-liver oil, salmon, tuna, mackerel, sardines, liver and eggs.
The recommended dietary allowance (RDA) varies with age. Infants from birth to 12 months should receive 400 IU daily. Children and adults from 1 to 70 years of age should obtain 600 IU daily. For those over 70, the RDA is 800 IU daily.
Deficiency can cause rickets and osteomalacia. Rickets is the softening and weakening of bones in children. It may also cause bone deformities. Osteomalacia is the softening of the bones in adults. It is not the same as osteoporosis. Osteomalacia is the result of an abnormality during the making of bone, whereas osteoporosis occurs in otherwise healthy, normal bone.
Excessive intake (toxicity) can result in loss of appetite, weight loss, heart-rhythm abnormalities and elevated blood-calcium levels with subsequence heart, kidney and blood-vessel damage. Toxicity does not occur from excessive sun exposure. High intake of vitamin D-enriched foods is also unlikely to cause toxicity so the problem lies in the overconsumption of supplements.
Vitamin E is the name given to a group of fat-soluble compounds with distinctive antioxidant activities. There are eight chemical forms but only one (alpha-tocopherol) is recognized to meet human requirements. It is responsible for protecting cells from free-radical damage and is involved in immune function, cell signaling, regulation of gene expression and various other metabolic processes. It also inhibits protein kinase C activity (an enzyme) and indirectly dilates blood vessels and inhibits platelet aggregation (clumping).
Most dietary sources of vitamin E come from nuts and oils. These include wheat-germ oil; almonds and hazelnuts; soybean oil; sunflower seeds and sunflower oil; peanuts, peanut butter and peanut oil; safflower oil; and corn oil. It can also be found in spinach, broccoli, kiwis, tomatoes and mangoes.
The RDA is 6 IU (4 milligrams) for those up to age 6 months, 7.5 IU (5 milligrams) for those from 6 to 12 months, 9 IU (6 milligrams) for ages 1 to 3, 10.4 IU (7 milligrams) for ages 4 to 8, 16.4 IU (11 milligrams) for those 9 to 13, and 22.4 (15 milligrams) for those over age 14. Lactating women should consume 28.4 IU (19 milligrams) daily.
Deficiency is rare, and symptoms have not been found in otherwise healthy people who fail to get adequate amounts from their diets. Deficiency is most common in individuals with an underlying condition that causes fat malabsorption. Symptoms include peripheral neuropathy, immune impairment, retinopathy and more.
Research has not shown that vitamin E obtained from a healthful diet can cause toxicity; however, supplements can cause problems to include poor clotting and hemorrhage.