Measuring Up: Vitamin DBy Jennifer Medley
It’s difficult to classify one vitamin as more important than another, but as far as bone development goes, vitamin D definitely tops the list.
This fat-soluble vitamin is necessary for the normal growth and development of a child’s bones and teeth. Late in life, it helps prevent bone fractures. And then there’s the possible cancer-protection benefit. “Vitamin D is used by a lot of the body’s cells to keep the immune system functioning properly,” says Pamela Hops, MD, a family practitioner at New York City’s Continuum Center for Health and Healing.
What Should I Know?
Vitamin D, which helps build bones by regulating calcium and phosphorus, was once used to stave off rickets and other bone diseases. But, Dr. Hops warns, “even though we don’t really see such diseases anymore, deficiencies can still occur.”
Where Can I Find Vitamin D?
The Sun
Vitamin D is unique in that its best source isn’t food, but sunlight—hence its nickname, “the sunshine vitamin.” However, many variables affect vitamin D synthesis (skin color, time of day, time of year, geographical location, etc.), and sunscreen actually blocks synthesis entirely. Many doctors believe that a few minutes of unblocked sunshine a day can be healthy—but even though vitamin D from the sun might help prevent certain cancers, Dr. Hops cautions, “People shouldn’t decrease risk for one type of cancer by increasing the risk of another.”
Note: To forego sunscreen is a personal choice and most experts would advise lathering up. Foods or supplements can also be a viable source of vitamin D, especially during the Northern Hemisphere’s winter months, when sunlight is weaker and isn’t as effective in triggering the skin’s production of vitamin D.
Cereals, Grains, Fruits
Look for fortified grain products such as cereals, cereal bars, breads and crackers; or for fortified orange juice.
Note: Read the nutrition-facts panels of fortified foods to determine vitamin D content—some brands may have 10% of the RDA, while others have none.
Animal Sources
Fatty saltwater fish (salmon, halibut, mackerel, sardines) contain vitamin D naturally, as do egg yolks (especially those from hens fed vitamin D). Milk is a good fortified source (same for nondairy beverages such as rice milk or soymilk).
Note: One cup of vitamin D-fortified milk supplies about one-fourth of the current RDA for this vitamin.
Supplements
Cod liver oil is an age-old source of vitamin D, but Dr. John Cannell, of the Vitamin D Council, urges restraint. “I never recommend cod liver oil—besides its healthy vitamin D and omega-3 fatty acids, it also has a high amount of vitamin A, which is now thought to cause low-grade toxicity.” A basic vitamin D supplement is the safest choice. Look for the ingredient cholecalciferol versus ergocalciferol. For children who find it difficult to swallow a pill, try smashing it up and sneaking it into food.
Note: Mothers who breastfeed should check with their pediatricians to see if their infants would benefit from a vitamin D supplement.
How Much Is Needed?
The Institute of Medicine currently recommends 200 international units (IUs) a day of vitamin D for people who lack adequate sunlight. That number applies to everyone aged 1 to 49, including lactating and pregnant women; adults from 50 to 70 should get 400 IUs a day.
Note: Many doctors feel the current RDA is too low, especially now that sunscreen use is more prevalent. Though too much vitamin D can induce toxicity, 1000-2000 IU of daily supplementation is thought to be perfectly safe.
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