Even a casual glance at health magazines and medical journals reveals widespread interest in vitamin D. A common theme of these articles is that most people are not getting enough of “the sunshine vitamin.” Studies over the last 15 years have consistently demonstrated an epidemic of low vitamin D levels, highest among elderly adults but also seen in up to half of adolescents. Many medical conditions increase a person’s risk for vitamin D deficiency, including osteoporosis, kidney disease, gastrointestinal disorders, and even obesity. It has long been established that adequate amounts of vitamin D support healthy bones; but, can is vitamin D important for your heart as well?
To answer the question, it helps to know just how we get the vitamin D we need. Our bodies produce vitamin D when exposed to the sun and absorb vitamin D when ingested in our diet. Most Americans, though, do not eat the necessary amounts of vitamin D to maintain healthy levels (defined by the Institute of Medicine’s 2010 report as at least 20 ng/ml). Two of the most potent sources of dietary vitamin D, cod liver oil and sun-dried Shitake mushrooms, are not staples in the American diet. Other dietary sources, such as egg yolks and fortified dairy products, provide only modest amounts of vitamin D with each serving. According to the Institute of Medicine, we need between 600 and 1000 units of vitamin D just to maintain our current blood levels. Vitamin D pills can supplement the lack of dietary intake. So can sensible sun exposure.
Our bodies naturally produce vitamin D when exposed to sunlight, and this remains the most efficient way to build up our vitamin D stores. When the body is exposed to natural sunlight for 5 to 15 minutes a day (termed the “minimal erythrodermal dose” since this is the amount of sun most people need to lightly pinken the skin) the amount of vitamin D produced is between 10,000-25,000 units, the equivalent to drinking ¼ cup of cod liver oil or eating 2 pounds of sun-dried Shitake mushrooms.
Which brings us back to questions of the heart. Basic science trials in the lab tell us that vitamin D can reduce blood vessel inflammation, regulate blood pressure, and reinforce blood sugar control. The trouble seems to be translating those mechanisms into meaningful outcomes for patients. Now, that seems to be changing.
In the April 2013 edition of the journal Hypertension, investigators demonstrated that in African American patients with low vitamin D levels and high blood pressure, simply supplementing them with 2000 units of vitamin D can significantly improve their systolic blood pressure. Some have argued that the results were modest and the sample size small, but this trial offers encouragement. Some investigators aim to answer these criticisms. Since 2010, recruitment has been underway to enroll over 20,000 patients in the VITAL Trial, comparing vitamin D and fish oil against placebo to look for beneficial effects on the body, including the heart. Wouldn’t it be great this summer if a little sun could go a long way to improving your health?
To be sure, vitamin D from sun exposure must be measured. Sunburned skin does not produce more vitamin D, and only modest sun exposure is needed to maximize vitamin D production. Even the 2011 Endocrinology Clinical Practice Guidelines on Vitamin D Deficiency acknowledge that while “the major source of vitamin D for children and adults is exposure to natural sunlight,” that exposure must be sensible. Keep sun exposure to the uncovered arms and legs, and limit exposure to no more than 15 minutes a day. Keeping the face covered and applying sunscreen after fifteen minutes (sooner for those prone to sunburn) can balance the body’s needs for vitamin D production while not increasing the risk of skin cancer. Sensible sun exposure is just one more way to stay healthy this summer, and might prove to be a heart healthy habit.