Lynne Kiesling
Over the past year or so I’ve been following the debate and research on Vitamin D intake. Initially Vitamin D supplementation was recommended simply to reduce the incidence of rickets in children, but increasingly Vitamin D is associated with a wide range of health benefits, from reducing fatigue to improving metabolism to improving heart health. Vitamin D has become a particular challenge in the past 30 years, because we’ve gotten out of the stereotypical “spoonful of cod liver oil” that was popular in the early 20th century (fish oils are rich in Vitamin D and in omega-3 and omega-6 fatty acids that are good for metabolism and for the heart). At the same time, we’ve increased our use of sunscreen, and since almost no foods are rich in Vitamin D, the primary way to get it is to expose your skin to sunlight for 10-60 minutes per day, depending on time of year (less in summer, more in winter). Sunscreen blocks Vitamin D absorption while protecting us from skin cancer.
This week a new study was released and presented at the American Heart Association meetings, as reported in this Yahoo/AP story and this longer New York Times story. As the NYT summarized the results:
In the study, researchers looked at tens of thousands of healthy adults 50 and older whose vitamin D levels had been measured during routine checkups. A majority, they found, were deficient in the vitamin. About two-thirds had less vitamin D in their bloodstreams than the authors considered healthy, and many were extremely deficient.
Less than two years later, the researchers found, those who had extremely low levels of the vitamin were almost twice as likely to have died or suffered a stroke than those with adequate amounts. They also had more coronary artery disease and were twice as likely to have developed heart failure.
The findings, which are being presented today at an American Heart Association conference in Orlando, don’t prove that lack of vitamin D causes heart disease; they only suggest a link between the two. But cardiologists are starting to pay increasing attention because of what they’re learning about vitamin D’s roles in regulating blood pressure, inflammation and glucose control — all critical body processes in cardiovascular health.
The article goes into much more detail about the study, and is a very worthy read.
The sports nutrition community have also been paying attention to Vitamin D for a while, and these new results reinforce the idea that Vitamin D levels are an important factor in athletic performance, in addition to overall health. This article from Competitor discusses the role of Vitamin D in fatigue in endurance athletes, something that we frequently attribute to iron deficiency instead (especially in women), but it may be that Vitamin D is a culprit too. The author, a dietitian, summarizes some sports research on Vitamin D levels:
This was my very first experience with vitamin D deficiency and I have since learned that vitamin D deficiency is becoming an epidemic worldwide, not only in geographic regions where sun exposure is limited. And my discussions with fellow dietitians working with college runners and professional athletes in generally sunny states (Texas and Florida) confirmed the alarming prevalence of vitamin D deficiency across ethnicity and gender.
Athletes who live in northern latitudes (north of 35 degrees), or use sunscreen consistently, perform their sport indoors, or keep their skin covered are at the greatest risk. Melanin affects the production of vitamin D. So those with more melanin or darker skin produce less vitamin D. Since vitamin D is a fat-soluble vitamin, athletes with fat malabsorption problems such as cystic fibrosis, Crohn’s disease, and celiac disease are at risk for deficiency. Those who have normal levels typically (around 50 ng/ml) live in sub-equatorial Africa and work outdoors for most of the summer.
Once thought of as being primarily involved in bone development, activated vitamin D (calcitriol), a steroid hormone, is responsible for regulating more than 1000 human genes. Almost every cell in the human body has receptors for vitamin D. Recent research shows that vitamin D deficiency increases the risk of different types of cancer (such as breast cancer and prostate cancer), as well as heart disease, diabetes, depression, autoimmune diseases, hypertension, obesity, gum disease, chronic pain, muscle wasting, inflammation, birth defects, osteoporosis, influenza and colds, etc.
So here’s my public service announcement for the day: at your next annual checkup when you order your blood work, ask to have your Vitamin D levels tested. And think about the sunscreen-Vitamin D tradeoff; getting 30 minutes of unobstructed sun is unlikely to increase skin cancer risk enough to outweigh the Vitamin D benefits from the sun absorption. Vitamin D supplementation is also low-risk; I figure between my multi and my fish oil and my Vitamin D I get about 800 IU, and I have noticed decreases in my fatigue levels.
