By Rosemary Barrow, B.S. Exercise Science, NASM Certified Personal Trainer
I think you might dispense with half your doctors if you would only consult Dr. Sun more.
~Henry Ward Beecher
If you've been tuning in at all to the latest buzz in both conventional and alternative medicine, you've probably noticed the newest research involving vitamin D has elevated “the sunshine vitamin” to star status in the health and medical communities. Though technically not a vitamin but a group of five fat-soluble steroid hormones (D1-D5), more specifically hormone precursors known collectively as calciferol, maintenance of an optimal vitamin D level in the body is now more than ever being identified as a cornerstone in the foundations of disease prevention and treatment, as well as in overall well-being. Go figure right? It doesn't take a panel of scientists and doctors or a slew of research to tell us being in the sun makes us feel better. But what these most recent findings reveal are some insight as to why we are so naturally drawn to sunlight; why it fosters a sense of well-being. The fact that there is a vitamin D receptor (VDR) in virtually every cell of our bodies should attest to the integral role this hormone, most readily produced through UVB sunlight exposure, plays in influencing health status.
What does vitamin D do in our bodies?
Adequate vitamin D must be present in order for calcium, the most abundant mineral in the body, to be converted into its ionized (usable) form. It's long been known that its presence is also necessary for the absorption and metabolism of calcium and phosphorus, and for the re-absorption of calcium by the kidneys, all processes that determine proper bone mineralization and muscle contraction. Once bio-available calcium from food enters the small intestine, it interacts with vitamin D and calcium-binding proteins and is then absorbed through the intestine wall for use in the body—99% of which is directed to the bones and the remaining 1% to the blood. It's important to note that this 1% entering the blood is a crucial component in the bio-electric activity of every single cell in the body. Given that we are essentially bio-electromagnetic beings, the significance of 1% is pretty profound! Calcium inside cells determines ideal pH levels that, together with extracellular fluid pH, create a voltage that allows for the appropriate uptake of nutrients and expulsion of waste through cell walls—the most basic operations of our cells.
So, if optimal vitamin D levels are lacking and not enough calcium can be absorbed, the body enters into an increasingly acidic state paving the way for disease to set in. In this way, vitamin D is a key factor in the prevention of certain kinds of cancer, hypertension (high blood pressure), types 1 and 2 diabetes, multiple sclerosis, autoimmune diseases, depression, osteoporosis, and inflammatory diseases such as heart disease and arthritis. It is also fundamental to the regulation of the immune system and gene activity. When calcitriol, the active form of vitamin D in the body, binds to a VDR this pairing determines DNA expression (the turning “on” and “off” of genes) affecting over 2,000 genes, accounting for 10% of the human genome and thus directing the activity of hundreds of enzymes and proteins—and this is just one action involving vitamin D!
How do we get vitamin D?
If this wonder vitamin is so critical to our health and wellness how, you may ask, do we attain optimal levels in our bodies? There are three ways in which we can harness the power of this potent steroid hormone. The first and easiest (and free!) way is by getting adequate sun exposure, more specifically, enough exposure to UVB rays which are required for the formation of cholecalciferol, or vitamin D3 (vitamin D in our skin). In mid-day summer sun exposure for 20-30 minutes (an ideal situation) it is possible to produce approximately 10,000-50,000 IU (international units) of vitamin D3/cholecalciferol in the skin. The minimum amount indicated here is 50 times the U.S. recommended daily allowance (RDA) of 200 IU! Ironically, the very time frame we've been strongly advised to avoid (mid-day 10am-3pm) is the ideal time for maximum UVB exposure and minimal UVA exposure, the type of UV light associated with melanoma (the deadliest skin cancer). It's also been advised that we constantly slather on the sunscreen during this window of mid-day sun but doing so blocks up to 95% of vitamin D-producing UVB rays. This is not to say that sunscreen use should be avoided for prolonged periods of time spent in the sun, but then again prolonged exposure isn't recommended in general. Several factors are key in determining more precisely how much vitamin D each of us requires to reap its health-giving benefits. These include age, body weight, body fat percentage, skin coloration, current season of the year, latitude of where one resides, use of sunscreen, and of course individual sun exposure. This is a topic that will be expounded upon in Part II of this article.
The second way we can get vitamin D is through our diets. Cholecalciferol (D3) and ergocalciferol (D2), to a lesser extent, are the most important forms for humans. As a general rule vitamin D2 is found mainly in plants (i.e., mushrooms) and, as stated, vitamin D3 is made in our skin or obtained through eating certain animal and animal-based foods, such as fatty fish (i.e., salmon, tuna, mackerel), fish liver oils (best sources), and in lesser amounts, beef liver, cheese, and egg yolks. Many foods in our modern diet are fortified with vitamin D but this does not guarantee the proper absorption and assimilation of this precious nutrient when taken out of its natural context. When you consider that a vast majority of calories in the American diet are from processed foods, by which the very nature of their manufacturing implies the depletion of inherent nutritional value, there is cause for question as to the efficacy of fortified foods including those fortified with vitamin D. If it must be synthetically added to a food source not found in nature, to what extent and how well can it be utilized by our bodies?
This leads us to the third and final source of vitamin D: supplementation. For individuals who do not receive adequate sun exposure or regularly consume vitamin D-rich food sources, supplementation is an alternative and often necessary way of obtaining its health and disease-preventing properties. The Vitamin D Council's recommendation states that “healthy children under the age of 1 year should take 1,000 IU per day—over the age of 1, 1,000 IU per every 25 pounds of body weight per day” and “well adults and adolescents should take 5,000 IU per day.”
For now, it's important to remember that the preferred and superior sources for the manufacturing of vitamin D in humans, respectively, are through adequate exposure to UVB rays in sunlight and via the appropriate animal or animal-based food sources previously mentioned. Part II will also highlight how vitamin D in the body contributes to disease prevention, how to test for healthy levels in the blood, as well as some surprising new information about this vital hormone that further validates its significance with regard to human health and survival.