A few years ago Vitamin D was the “darling” of the nutrition world. Research findings touted its role in preventing and/or even curing almost every chronic disease and then some. I always wondered why all of sudden we discovered these new-found benefits. But now there are some explanations. I guess the bottom line is that we can all thank Dr. Michael Holick, an endocrinologist from Boston University. It also didn’t help when Gywneth Paltrow, Dr. Oz and Oprah added their glowing endorsements.
The actions of Dr. Holick are a blatant example of industry funding on steroids of the medical profession as well as academics. Talk about misleading headlines – they eagerly broadcast the hype of Vitamin D and its alleged health benefits that overtook the nutrition world by storm. As a result, people rushed to their doctors and could not get their blood tested fast enough! Guess what industries were involved – the vitamin D supplement and lab testing industry.
What are the basic facts?
Vitamin D promotes calcium and phosphorus absorption from the intestines and acts with parathyroid hormone to cause the release of calcium from bone and calcium retention by the kidneys. These actions are essential for maintaining proper levels of calcium and phosphorous in the body, necessary for strong bones.
Vitamin D itself is often considered a hormone, since it is made in the skin by exposure to sunlight and then modified in the liver and kidney to its active form. Vitamin D supplements are often recommended for those people at risk for a deficiency, since it not found in many types of foods, except for fish oils, liver, egg yolks and fortified milk.
Back in the day, the roles of vitamin D were not well known and it was quite a surprise for those of us in nutrition science to be made aware (suddenly) of all it could allegedly do for us. Now we’re beginning to rethink this information.
One more thing:
Too much vitamin D in the body can cause high concentrations of calcium in the blood and urine that can result in the deposition of calcium in soft tissues such as blood vessels and kidneys and damage to the cardiovascular system. This does not occur when we make vitamin D from sunlight because this process is highly regulated in the body. Over supplementation and fortification can pose a risk. The Upper Tolerable Limit (UL) for ages 9 or older is 4000 IU (100 ug/day).
Smolin and Grosvenor, Nutrition: Science and Applications, 2013.