Friday, August 28, 2009

Nutrition Spotlight: Vitamin D

Vitamin D is the current darling of the nutrition world: a PUBMED search for “vitamin D” reveals over 9000 studies just in the last five years. So what is so special about vitamin D?

Dietitians, including myself, believe quite strongly that we can meet our dietary needs with a “food first” approach. Yet vitamin D is unique because there isn’t much of it to be had in our food supply. The only significant source of vitamin D comes from wild caught salmon. Vitamin D is also added to milk at a dose of 100 International Units (IU) per cup; it would take a lot of milk to reach what most experts agree is a physiological daily dose of the vitamin.

For many years, vitamin D has been dismissed as a supporting role to calcium in the story of our bone health: get a bit of vitamin D and you will absorb calcium for strong bones. However, we now know that there are vitamin D receptors all over our body including in the brain, breast, heart and prostate. Where there is a receptor…there is a function. So researchers set out to look for it.

Epidemiological studies, which look at patterns in disease in populations, have found that people living in higher latitudes had a greater risk of dying of certain cancers and a greater risk of certain auto-immune diseases such as Multiple Sclerosis. What is common among people living further away from the equator is that they receive less sunlight – and bright, direct sunlight turns a cholesterol-like molecule in our skin to vitamin D. As a result of this early work, researchers began clinical studies to test for direct relationships to vitamin D.

What they found is that vitamin D is more than just a co-factor in calcium absorption. Vitamin D plays a role in cell cycle regulation and immune function as well. As a result, research is ongoing to look at the role of vitamin D for cancer prevention and treatment, auto-immune diseases, blood sugar regulation, heart health, weight loss and even depression. While future research may moderate some of these early hopes, learning that vitamin D is a far more important player in our overall health is good reason to ensure that we get enough of it.

While current recommendations are 200IU per day, most experts recommend that all school age children and adults take 1000IU of vitamin D3 every single day. It is important not to take more than that, as there is the small chance for over - accumulation because vitamin D is a fat soluble vitamin. Ideally, your physician would do a simple blood test to ensure you are not deficient in vitamin D and that you are taking enough to keep your blood level at a safe and therapeutic level.

The Institute of Medicine, the body that creates the national recommendations for daily intakes of nutrients is currently reviewing their recommendations and it is expected that recommendations for vitamin D will officially increase.

Note: This information is for educational purposes only and is not intended to replace consultation with a qualified health professional. Please speak with your registered dietitian to ensure that vitamin D is right for you.

Reference: Holick, M. and Chen, T. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr 2008;87(suppl):1080S-6S
Institute of Medicine.

No comments: