A recent study in Archives of Internal Medicine shows that you are more than twice as likely to die from heart disease or attack if you have sub-optimal vitamin D levels. According to the authors, this deficiency is due to a decrease in outdoor activity. So, yes, it is important to get outside when the sun is shining.
Unfortunately, it's not always shining. In the winter in Chicago, it is not possible to produce vitamin D from the sun because the it never gets high enough in the sky for its ultraviolet B rays to penetrate the atmosphere. Luckily, summer - and let's be honest, especially summer in Chicago - is a great time to stock up on the nutrient. When the summer sun's UV-B rays hit the skin, it generates a reaction that enables skin cells to make vitamin D. It is estimated that if you're fair skinned, you only need about 10 minutes in the midday sun (shorts and T-shirt, no sunscreen) to give you enough radiation to produce about 10,000 international units (IUs) of the vitamin. Dark-skinned and elderly individuals also produce less vitamin D, and many people don't get enough of the nutrient from dietary sources like fatty fish - more of this to come in a future blog post.
The FDA's recommendations for vitamin D intake are 200 IUs a day up to age 50, 400 IUs up to 70, and 600 IUs over 70. Unfortunately, the consensus among most experts is that these recommendations are far too low to maintain healthful vitamin D levels. They advocate for supplementation in the winter of about 2,000 IUs per day (whether through supplement or food source) and a dose of daily sunshine in the summer.
The sunshine vitamin may protect against a wide array of diseases including osteoporosis, heart disease, and cancers of the breast, prostate, and colon. Furthermore, sunlight has additional fringe benefits such as protecting against depression, insomnia, and an overactive immune system (think allergies and asthma).
As with most everything, direct sun bathing is best done in moderation. If you are going to be out in the sun for a prolonged period of time, it is still advisable to apply sunscreen at regular intervals and stay well hydrated. So get out there and enjoy our early summer sun in the greatest summer city of all!