Much has been written about the benefits of vitamin D, but how much do you really know? And could you determine for yourself just how much vitamin D you should take for good health? Or how your body produces vitamin D?
Few people can, but vitamin D is a critical part of child development and adult bone health. It was first identified when scientists discovered that giving it as a supplement could prevent rickets in children, particularly dark-skinned children, in dark northern inner-city neighborhoods.
That specific fact is a clue as to how vitamin D is formed. Unlike most vitamins, your body can manufacture vitamin D from a cholesterol precursor when you expose your skin to sunlight. If your skin is dark or you wear sunscreen, you need more sunlight. Those black children in northern city neighborhoods were severely sunlight starved, robbing them of the benefits of vitamin D.
Lately, scientists have found other benefits of vitamin D: energy metabolism, boosting the immune system, and prevention of a particular type of thigh muscle weakness that contributes heavily to falls as we age. MS and other similar autoimmune diseases like lupus and type 1 diabetes are rare at the equator, but more common the further north you go – indicating that vitamin D has something to do with how these diseases are initiated. Children who get a lot of sunlight don’t develop these diseases at the same rate as children who don’t.
And it must be sunlight. While you can take vitamin D supplements, and are almost certainly taking vitamin D in your milk, oral vitamin D does not absorb into the body as well as vitamin D produced by your skin, so cannot give you the full benefits of vitamin D. (And besides, studies have shown that milk does not contain a reliable level of vitamin D, often containing higher or lower levels than stated on the label.) A scant half-hour of sunlight outside, not through a window, is generally enough to create all the vitamin D you need in a day – and the half hour can be spread apart throughout the day. Other sources of vitamin D include fish and fish oil, but few foods overall contain this vitamin.
It is possible to take too much vitamin D. Toxicity, however, only occurs if you’re taking a supplement; no matter how much sunlight you get, you can never overdose on skin-synthesized vitamin D. Symptoms of toxicity are vague and include nausea, vomiting, weight loss, irritability, fatigue, dehydration, and constipation, and toxicity can cause kidney stones and overcalcification of the bones. Detoxing vitamin D is fairly easy; just eat a low-calcium diet for about a month, which is how long vitamin D stays in your system.
The most important sign of inadequate vitamin D intake is osteomalacia, where your bones do not get enough calcium and therefore start to weaken. This is almost impossible to detect before serious damage has been done. It’s wiser, and won’t hurt anything, to just start getting more sunlight just in case so that you will be certain to profit from the benefits of vitamin D. A few minutes’ exposure daily is enough for vitamin D production, but not enough to put you at any serious risk of skin cancer.
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