What You Should Know About Deficiency, Screening and Good Health
How much is enough, and how much is too much? You already know that for good health, you should drink your (low or nonfat) milk, get plenty of rest, and maintain your weight with a healthy diet and physical activity. You may take a multivitamin, plus a calcium supplement, and you wear sunscreen to block out skin-damaging UVA and UVB rays to lower your risk for skin cancer. Is this the best advice?
Since research links the epidemic of deficiency in vitamin D to an increased risk for many chronic diseases, modifications may be in order.
Vitamin D, the “A, B, Cs”
Vitamins are micronutrients found in foods, which work to prevent disease…one great example is vitamin C and scurvy. Although vitamin D2 is available in some foods, the active form that keeps your bones strong is vitamin D3, actually a hormone, made when your skin is exposed to the sun’s UVB rays. Too little D3 is linked to rickets in children, and osteomalacia in adults. Unfortunately, rickets has reemerged as a problem, even in so-called first-world countries including the US and the UK. Scientists theorize that it’s because of maternal deficiency, plus kids are playing outdoors less often…and are wearing…sunscreen.
Dr. Michael F. Holick, director of the Vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center, named vitamin D deficiency “the silent epidemic”, linked to an increased risk of autoimmune diseases including type I and type 2 diabetes, multiple sclerosis, rheumatoid arthritis, and Crohn’s disease; infectious diseases including tuberculosis; psoriasis, hypertension, cardiovascular heart disease, and some cancers including breast, prostate, colon and pancreatic cancer.
Shunning the Sun
We’ve grown fearful of the sun, told to generously apply sunscreen, we protect our children from an early age, and we strive to preserve youthfulness and to fight wrinkles and age spots. But, too little sunlight can have negative effects too. Wearing Sun Protection Factor of 8 or above prevents 95% of your skin's production of vitamin D: at higher SPF (30 and above) production is almost zero. Only few foods naturally contain or are fortified with vitamin D3, and for the most part American’s diets are less likely to include foods that are considered “good” sources of vitamin D2, such fatty fish and cod liver oil. Even foods perceived as good sources are, in light of current recommendations, at any rate just moderately fair, such as milk (less than 100 IU per 8 oz glass): and surveys show that most Americans drink less than one glass per day, and most eat fatty fish only occasionally.
Vitamin D deficiency may be much more common than previously believed. Some studies have shown that as many of 50% of the elderly and women being treated for osteoporosis may be Vitamin D deficient, and some osteoporosis medications now include the recommended Vitamin D dose. The Institute of Medicine recommends 400 IU for adults: experts suggest at least 1,000-2,000 IU daily, especially in the late fall through early spring, when sun exposure is least available. Dr. Holick and colleagues estimate that the body requires daily 3000–5000 IU of vitamin D: every tissue and cell in the body has a vitamin D receptor, which requires vitamin D.
The American Academy of Pediatrics recommends that children and adolescents get at minimum 400 IU of vitamin D daily. Natural sunlight—UVB exposure—initiates the conversion of cholesterol in the skin to vitamin D3. Don’t burn—but sun exposure, depending on skin color, latitude, clouds and pollution, allows the body to make vitamin D3: experts recommend about 5 to 30 minutes of exposure to the skin on face, arms, back or legs (without sunscreen) twice every week. Then cover up, with clothes or sunscreen.
The Screening Test
The 25-hydroxy vitamin D (25(OH) D) test measures vitamin D circulating in your body. Many experts recommend measurement as part of an annual physical examination. Experts say a desirable 25-hydroxy vitamin D concentration is above 75 nmol/L (30 ng/mL).
Best Sources of D
The most potent food sources of vitamin D include: salmon (4 oz Chinook: 411 IU), shrimp (4 oz boiled: 162 IU), sardines (3.25 canned: 250 IU), and fortified milk (2% 8 oz: 98 IU).
Registered and licensed dietitian Susan Burke March, MS, CDE, is the author of "Making Weight Control Second Nature: Living Thin Naturally” – a fun and informative book intended to liberate serial dieters and make healthy living and weight control both possible and instinctual over the long term. Susan consults with individuals and companies to create personalized and practical weight management solutions. She may be reached online at www.SusanBurkeMarch.com