Nutrition ABCs: Vitamin D

Many moons ago, I thought it would be cool to start a little encyclopedia of nutrition terms I wanted you all to know more about. I made it to the letter C. Ahem...onward and upward! I think it is time to pick up this little theme once again. Nutrition is getting no less confusing...and we are still a wee bit unhealthy as a society. Just sayin'.

I started the Nutrition ABCs in 2010. A was for anti-oxidants; b was for broccoli and c was for calories...so now we are on to d. Which, of course, means we must chat about vitamin D!

The news on vitamin D seems to have cooled off as of late; just a few years ago you could hardly pick up a magazine or turn on the news without seeing a story on vitamin D. And rightly so: long dismissed as simply the ugly best friend of calcium in the quest for bone health, vitamin D finally got to stand out in the spotlight. What has changed since my last post on vitamin D? Well, the Institute of Medicine and Health Canada did indeed change their recommendations on vitamin D. What was the cutting edge of the research is becoming accepted nutritional fact: we need more vitamin D. Health Canada now recommends 600IU for those aged 7 - 70. The upper limit, or amount at which there is no foreseen risk of daily use, has been doubled to 4000IU. Again, most vitamin D experts would consider this conservative. 

So what will vitamin D actually do for you? Research is growing in the areas of heart health, cancer prevention, prevention of type 2 diabetes and auto-immune diseases and even weight loss. However, some of the challenges with this research (especially in the initial stages) include ineffective dosing and lack of placebo-controlled, double blind trials. However, the evidence is considered substantial enough for many in the world of health and research to call for a widespread increase in intake. 

While called a vitamin, vitamin D is actually more biologically similar to a steroid hormone once activated by the kidneys. It has an effect on almost every organ and tissue in the body and helps to modulate the immune system. This is one of the most interesting outcomes of vitamin D intake to me; considering all of the attention on chronic inflammation in the progressive health literature, keeping the immune system tuned is important. And most of us have not been getting enough vitamin D. Ideally, your physician would assess your blood levels of vitamin D so you can be dosed accordingly. In the absence of that knowledge, a safe bet for almost all adults would be 2000-3000 IU of vitamin D3 a day. As mentioned in my previous post, you can't really rely on most food sources (except for fatty fish like salmon) for an effective dose. As a dietitian, I don't like people to pop pills unnecessarily; however, I routinely recommend vitamin D to my clients. 

PS. Read my opinion...and then discuss it with your health professional. This post is offered as information only; this article can't take the place of in person consultation with a qualified health professional. And no, I don't have a financial stake in any supplement company. I just want you to be healthier!

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. http://www.iom.edu/?ID=61170