Believe It or Not: 10 Popular Claims About Vitamin D

As my last post about sunscreen noted, the quality of the anti-aging and wellness advice you consume is  a lot more important than the quantity. The recent buzz about the "sunshine vitamin" is a case in point. Test Your Vitamin D Knowledge Quotient The more you hear and read about vitamin D in the media, the less sure you may be about its relationship to your dietary choices, sun protection practices, and overall health. The following quiz is designed to help you check some popular claims and assumptions about vitamin D against the scientific evidence to date. TRUE OR FALSE? 1. A lack of vitamin D is associated with serious health problems. 2. More than 75% of Americans don't get enough vitamin D to protect their bones. 3. Lab tests are a highly accurate and reliable way of diagnosing vitamin D deficiency. 4. Scientists have confirmed that high vitamin D levels help prevent non-Hodgkin lymphomas and stomach cancer. 5. Increased vitamin D intake reduces the symptoms of psoriasis. 6. Significantly overweight individuals have a higher risk of vitamin D deficiency. 7. Dark-skinned individuals may need more sun exposure to maintain adequate vitamin D levels. 8. To be on the safe side, we should all take high-dose vitamin D supplements. 9. Getting enough vitamin D from natural food sources can be difficult. 10. Scientists keep changing the rules of sun safety and good nutrition. ANSWERS1. True: Vitamin D deficiency causes rickets and osteomalacia, a painful disease that softens bones and diminishes muscle strength. Low vitamin D levels are also a contributing factor in osteoporosis. Studies also suggest that treatment with vitamin D in conjunction with calcium increases bone density and reduces the incidence of fractures in postmenopausal women. (The treatment has shown no significant effect on pre- and peri-menopausal women, however.) 2. False: An in-depth study by the National Academies of Science's Institute of Medicine (IOM) found that despite vitamin D intakes that fall somewhat below minimum recommended levels, most of us have high enough blood levels of vitamin D to maintain healthy bones. 3. False: According to an American Association for Clinical Chemistry (AACC) news magazine article, the current lack of standardized procedures and objective measures for diagnosing vitamin D deficiency has undermined the value of routine vitamin D testing. The article also notes that many physicians remain unclear about which blood test to order and what the results mean. IOM researchers believe this problem has led to the false impression that an epidemic of vitamin D deficiencies is sweeping North America. Their reassessment of the data indicates the proportion of Americans at risk is approximately 10%. 4. False: While a number of studies have suggested vitamin D may help prevent stomach malignancies and non-Hodgkin lymphomas, as well as colo-rectal, ovarian, esophageal, kidney, and pancreatic cancers, a recent National Cancer Institute (NCI) report based on an extensive review of existing data revealed no clear or consistent link between cancer risk and vitamin D intake. Nevertheless, the jury is still out on the role potential role of vitamin D in treating a variety of medical conditions, including depression, heart disease, diabetes, and autoimmune disorders, as well as some cancers. 5. False: The latest studies showed no relationship between higher blood levels of vitamin D and improvement in the symptoms of psoriasis. Topical vitamin D ointments and creams, however, are effective psoriasis treatments. 6. True: Thick layers of subcutaneous fat interfere with the release of vitamin D into the bloodstream. Many other health and lifestyle factors can also increase the risk of vitamin D deficiency, including lactose intolerance, impaired fat absorption, vegetarian gastric bypass surgery, and restricted sun exposure. Breast-fed infants may also be a higher risk for vitamin D deficiency. 7. True: Higher levels of melanin (brown pigment) in the skin limit the amount of UV radiation the body can absorb.

8. False: When it comes to vitamin D, you can get too much of a good thing. In doses higher than 4,000 IUs daily, vitamin D can lead to heart damage and arrhythmias, as well blood vessel and kidney damage. How much vitamin D is enough? As general guidelines, the NIH suggests between 400 and 600 IUs daily for adults under the age of 70 and 800 IUs for older people. 9. True: Unless you happen to be a big fan of cod liver oil or fatty fish, your dietary sources of vitamin D can be pretty limited.  If  your palate favors neither sardines, salmon, nor mackerel as menu options, try adding a daily mealtime serving of a vitamin D-fortified dairy product or cereal. The following table provides some useful guidelines.

Food Sources of Vitamin D: IUs* per serving

Cod liver oil, 1 tablespoon: 1,360

Salmon (sockeye), cooked, 3 oz.: 447

Mackerel, cooked, 3 oz.:  388

Tuna fish, canned in water, 3 oz.: 154

Milk (fortified**), 1 cup:  115-124

Orange juice (fortified**), 1 cup: 100

Yogurt (fortified), 6 oz.: 80

Beef Liver, cooked, 3.5 oz.: 49

Sardines, canned in oil, 2: 46

Egg, 1 large: 41

Fortified** cereal, 1 cup: 40

Swiss Cheese, 1 oz.: 6

* IUs = International unit* *Amounts may vary.Source: National Institute of Health Office of Dietary Supplements: http://ods.od.nih.gov/factsheets/vitamind/ 10. False: The widespread impression that yesterday's recommended skincare habits are today's risky behaviors and vice-versa doesn't really stand up under scrutiny. While "scientific "truth" will always remain subject to revision, advertising claims and sensational headlines In fact, the weight reliable scientific evidence still stands firmly on the side time-tested skincare do's and don'ts. That's why it's so important to consider the source of your information before you decide to act on it.   Natural Wisdom: The Beauty of the Middle Path Until science provides more definitive answers on vitamin D, my advice is to take the long view and use common sense. Instead of rushing to adopt radical nutritional theories or throw sun safety precautions to the wind, consider the big picture. Although our lifestyles continue to change as civilization progresses, our basic nutritional needs and physical vulnerabilities remain the same. It's wise to remember that fact before rushing to extremes. ON BALANCE: If one way be better than another, then you may be sure it's Nature's way. - Aristotle