Vitamin D

Last week, a scientific panel from the National Academies' Institute of Medicine suggested increasing the RDA for vitamin D. They made recommendations based on all age groups, including bumping up the adult dosage to 4,000 IU daily. You can read the article here:

http://www.usnews.com/science/articles/2010/11/30/vitamin-d-targets-increased.html?s_cid=rss:vtripling itamin-d-targets-increased

However, many scientists have immediately countered and rejected these suggestions. Dr. Clifford Rosen, in this interview with NPR, suggested that actually we need very little vitamin D levels to maintain health, and that intaking too much (thousands of IU's daily) could really be harmful (increased risk of certain diseases and fractures).

http://www.npr.org/2010/11/30/131704380/panel-clarifies-vitamin-d-intake

So, what to do?

According to Patrick Holford, in The Optimum Nutrition Bible, optimal daily intake is 400 IU (this includes food and sunshine as sources). So, one only needs to supplement 120 to 200 IU.

Signs of vitamin D deficiency include soft bones and teeth, fractures, and bone curvature.

I believe it is important to consider that the average person does not get exposed to adequate sunlight each day. I also believe that most of the fortified food sources of vitamin D (dairy, etc.) are not ideal. Dairy also includes saturated fats, and often growth hormones and antibiotics. Often fortified milk contains vitamin A, which in certain forms, can actually weaken bones.

I wonder about the studies that brought about these new suggestions (and rejections) about vitamin D levels. Each person is different, and many factors could contribute to vitamin D needs. Darkness of skin, climate/latitude, sun exposure, diet (Vit D works together with calcium to strengthen bones, so if you aren't getting enough of either, you could have problems), other health concerns, etc.

In regards to vitamin D toxicity, I've found 50,000 IU to be the going number for upper intake that can cause negative affects in most adults. Signs of toxicity:

"Anorexia, nausea, and vomiting can develop, often followed by polyuria, polydipsia, weakness, nervousness, pruritus, and eventually renal failure. Proteinuria, urinary casts, azotemia, and metastatic calcifications (particularly in the kidneys) can develop."

source: Merck Manual http://www.merckmanuals.com/professional/sec01/ch004/ch004k.html

Vitamin D plays a vital role in bone health, immune activity, absorption in the intestines, kidney function, parathyroid hormone secretion, and insulin secretion. So, I think it is necessary to supplement. But how much?

It is important to thoroughly consider your physical makeup and lifestyle when deciding on a recommended dose. Do your research, talk to your nutritional consultant, and consider getting your vitamin D levels tested.