Thursday, January 7, 2010

Vitamin D Deficiency, Obesity and Cardiometabolic Risk: Is there any Relationship?

Until now we have been talking about several different risk conditions like adiposity, cardiovascular disease, diabetes, osteoporosis, hormone imbalance, vitamin D deficiency and other related disorders. After spending billions of dollars in medical research, we have collected huge amount of data and a wealth of information. It is time to get serious and make use of this information. Let me put it this way, we have collected most of the pieces of a big puzzle and now it is time to put together these pieces and complete the puzzle. We all recognize that our bodies do not work in isolation and so we need to look at all the body systems together as one system, which controls how we live our lives. I believe we may already have answers to so many questions. We may not have to spend more money into research to collect more data, which might create more confusion for us and more challenge to analyze all that new data. We could keep debating over what we should or should not do, but for now, since I titled this piece with a focus on role of vitamin D in obesity and cardiometabolic risk, let me discuss how vitamin D is emerging as a strong candidate to consider when we accumulate few extra pounds in our bodies, especially around our abdomen.

Now that holidays are over and New Year has begun, many of us are busy exercising and trying to shed those extra pounds we gained enjoying cookies and treats. Most of us have been indoors by the fireplace, especially in the Northwest where I live and where sun is known to be a luxury. Of course I do not have any reason to envy those who are in Midwest, especially after reading the newspaper this morning to see how most of the country is under the grip of winter chills with temperatures as low as 52 below zero in the Midwest. My point is that we have not had a chance to get out and get some sunlight so we could make some vitamin D. We all know how important is, sun exposure for endogenous production of vitamin D in the skin. There is evidence now that vitamin D is implicated in the cardiovascular morbidity and mortality, in addition to its role in musculoskeletal health. There is also some evidence that vitamin D deficiency is associated with obesity. We could argue that this association is indirect because obese individuals are less active and thus they get less sunlight exposure. However, some studies have shown that since vitamin D is fat soluble and therefore stored in fat tissue, which makes it less bio-available when there is more fat tissue. Obesity has been shown to have connection with insulin resistance and metabolic syndrome. Does that mean there is a link between insulin resistance, metabolic syndrome and vitamin D deficiency? The answer is yes, because some computed tomography imaging studies combined with measurements like BMI and waist circumference have suggested that vitamin D may be related to variation in regional adiposity and thus could be implicated in insulin resistance and metabolic syndrome, thereby connected indirectly with all biochemical mechanisms including inflammatory pathways leading to conditions like diabetes, atherosclerosis and coronary heart disease.

A recent study by Susan et al. that appeared in the January 2010 issue of Diabetes journal has shown that vitamin D deficiency is related with increased BMI; there is an inverse relation of 25-hydroxyvitamin D [25(OH)D] with subcutaneous and abdominal fat even in individuals who are lean with low BMI; and finally there is strong correlation between 25(OH)D and markers of insulin resistance, especially connected with abdominal adiposity. One could argue that some other factors like limited physical activity or low vitamin D intake may have caused the observed correlations, but the good thing is that this study took into consideration those confounders too as their subjects were all young to middle aged, with little comorbidities and low medication use. The study showed independent association between subcutaneous fat or visceral fat with 25(OH)D. It is also discussed that only differences in sunlight exposure are not enough to account for vitamin D concentration differences between obese and non-obese individuals. I will not go into too many details here about biochemical mechanisms that have been discussed to explain possible association of vitamin D with adiposity. Several findings have suggested multiple mechanisms involved with good evidence that vitamin D deficiency is implicated in obese individuals and thus connected with insulin resistance and related disorders.

So, for now the message is, let us watch out for those extra calories that we throw into our bellies. I am not asking you to stop enjoying cookies and left over treats from holidays, but what I am saying is that it is time we pay more attention to what we eat, how much we eat and what we do to metabolize all the extra calories we consume. Let us take good care of our waistline and if we see someone with a big waist, let us help them by making them aware of how vitamin D deficiency could be something to look for. How do we know we are vitamin D deficient? Well- there are tests available that can help us determine the vitamin D levels in our body and how much supplement do we need to replenish healthy levels. To make our life easy, there is a dried blood spot test available, which involves convenient home collection of sample, which is simply mailed to the laboratory and analyzed. You do not have to get out of home, get an appointment with a lab or phlebotomist, drive across town or take off from work. Does that not sound good? Feel free to email me ( if you wish to share some thoughts or need more information. Let us continue this discussion.