Does weight loss influence vitamin D levels?

Vitamins!

Travis’ Note:  Today’s guest post comes from our friend and colleague Dr Caitlin Mason.  More details on Caitlin and her work can be found at the bottom of this post.

In most places, the arrival of summer brings with it more opportunities to be outside, fewer clothes and more vitamin D.  And, vitamin D is a hot topic these days.

It has long been known that vitamin D is important for bone health, but vitamin D receptors are found in more than 30 cell types & it has diverse non-skeletal roles as well.  Some, albeit certainly not conclusive, evidence suggests it could have a protective role against heart disease, cancer, and a variety of autoimmune diseases.

Blood vitamin D concentrations are consistently lower in persons with obesity and it has been hypothesized that these low levels could be one factor that helps account for increased risk of heart disease, cancer, and other chronic conditions associated with overweight and obesity.

The prevailing hypothesis is that vitamin D (a fat-soluble compound) is taken up and stored in the body’s fat depots, making it physiologically unavailable to circulate in blood and be transformed via the liver and kidneys into its biologically active form.

If true, then weight loss could theoretically increase the amount of vitamin D circulating in the blood. But, whether this occurs and how much weight loss actually affects blood levels of vitamin D has not been widely examined.

Thus, as part of a team of researchers that is interested in how obesity influences breast cancer risk, we recently conducted a study to measure the impact of weight loss on blood levels of vitamin D.  If interested, the full paper was recently published in the American Journal of Clinical Nutrition.

What did we find?…in short , that losing 5-15% of body weight through diet and/or exercise (an amount that is usually accompanied by fairly significant metabolic improvements ) only raised blood vitamin D levels by a very modest 2-3 ng/mL, an amount equivalent to what could be expected from taking a standard multivitamin.  However, the rise in blood concentrations was much greater (more than double) in women who lost more than 15% of their starting weight.  This seems to indicate that the body doesn’t  ‘release’ vitamin D into the bloodstream in an amount that is directly proportional to weight loss; rather, there may be a threshold effect .  And, understanding this threshold may lead to a clearer understanding of how reduced body weight influences disease risk.

The implications for this are probably more important to helping understand vitamin D metabolism than they are for weight loss recommendations or for guiding nutritional intake.  Vitamin D metabolism in the body is a particularly complex process and currently the ‘optimal’ level of blood vitamin D for maintaining health is hotly debated.

Sadly, most nutritional research seems to become considerably less useful by our propensity to focus on single nutrients rather than more holistic dietary and behaviour patterns (Read more about  Dr. David Katz’s take on the ONAAT (One Nutrient At  A Time) fallacy here.  You probably remember when Vitamin E was thought to be the answer to all our woes, or fiber? Anti-oxidants?

Understanding the interrelationships between vitamin D, obesity, and disease risk certainly could uncover new avenues for disease prevention, but I’m betting it’s not a panacea.

So, until we have a better understanding of how vitamin D influences body fat and disease risk,  I personally take a multivitamin, a little extra vitamin D in the winter, wear sunscreen, &  try to get outside for at least half an hour of daylight exercise every day.

Dr Caitlin Mason

Caitlin Mason is a postdoctoral fellow at the Fred Hutchinson Cancer Research Center in Seattle, Washington.  Her research focuses primarily on understanding the relationships between physical activity, obesity, and cancer risk, including breast cancer.

ResearchBlogging.orgCaitlin Mason, Liren Xiao, Ikuyo Imayama, & et al. (2011). Effects of weight loss on serum vitamin D in postmenopausal women American Journal of Clinical Nutrition : ajcn.111.015552v194/1/95

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15 Responses to Does weight loss influence vitamin D levels?

  1. mgeek says:

    Thanks for sharing this very interesting study. There are many variables indeed and the inclusion / exclusion criteria select a very specific population.

    I would be glad if you could comment on three aspects:

    1. – is there specific data that supports the request not to exercise for 24 h before the post intervention blood sample?

    2. – The diet group has lost more weight then the excercise only group: did you find a statistical significance in this difference? Could you please analyze this aspect for the blog readers?

    3. – The recent Endocrine Society Clinical Practice Guidelines (June 2011) on Evaluation, Treatment, and Prevention of Vitamin D Deficiency insert among candidates for screening obese children and adults (BMI > 30). This study selected postmenopausal women population and included also overweight individuals.
    The same guidelines highlight, as an increased risk population, African-American and Hispanic children and adults. This study has given particular attention to Asian-American (including BMI betweeb 23 and 25, whereas BMI >25 was the parameter for other ethnic groups).
    Do this study’s specific criteria make the results distant from the current clinical practice?

    Thanks for your attention

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    • Travis Saunders, MSc, CEP says:

      I can only personally speak to question 1 – exercise has a number of effects on circulating factors (insulin, glucose, HDL & TG especially) that can last 24-48 hours, so it’s common to require that participants avoid exercise in the 24 hours prior to a blood draw. Whether or not it would impact vitamin D levels I’m not sure, but it’s a pretty common step taken to ensure that exercise isn’t influencing things.

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      • Travis Saunders, MSc, CEP says:

        Here’s the response from Caitlin:

        1.- is there specific data that supports the request not to exercise for 24 h before the post intervention blood sample?

        This study was performed using data from a larger randomized controlled trial that measured a variety of other hormones in the blood – some of which are sensitive to the acute effects of exercise. For this reason, women were asked not to exercise for 48 prior to blood collection.

        2. – The diet group has lost more weight then the excercise only group: did you find a statistical significance in this difference? Could you please analyze this aspect for the blog readers?

        The main findings related to weight loss and body composition changes from the larger trial were recently published by Foster-Schubert et al. in Obesity and can be accessed at PMID:21494229.

        3. – The recent Endocrine Society Clinical Practice Guidelines (June 2011) on Evaluation, Treatment, and Prevention of Vitamin D Deficiency insert among candidates for screening obese children and adults. This study selected postmenopausal women population and included also overweight individuals. The same guidelines highlight, as an increased risk population, African-American and Hispanic children and adults. This study has given particular attention to Asian-American (including BMI between 23 and 25, whereas BMI >25 was the parameter for other ethnic groups).
        Do this study’s specific criteria make the results distant from the current clinical practice?

        The data used for this study were collected as part of a larger clinical trial whose aim was to test the separate and combined effects of dietary weight loss and aerobic exercise on blood levels of sex hormones and other variables. The BMI inclusion criteria reflected international guidelines for the classification of overweight and obesity which recommend a lower BMI threshold for Asian women. However, the study participants were predominantly non-Hispanic White.
        It has been well documented that blood levels of vitamin D tend to be lower in persons with obesity and in individuals with darker skin pigmentation (including African Americans) which is reflected in the current guidelines mentioned above. However, as mentioned in this post, the rise in blood vitamin D associated with weight loss was quite small in our study and prescribing weight loss for persons at risk of vitamin D deficiency is likely not the most effective means of treating them.

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    • CLS says:

      The Endocrine Society made their recs to groups “at risk” of vitamin D deficiency.

      In reality nearly the entire 1st world is at risk.

      Regarding vitamin D and weight loss during dieting there were recent abstracts posted on Pubmed…

      The essence of one abstract was this: People with higher levels of circulating vitamin D were “more gregarious, outgoing, and willing to undertake new challenges vs those with lower levels”

      The moral here/there is vitamin D imporves mental outlook, perhaps the MOST important component of weight loss regimens.

      In those deficient/insufficient higher levels of vitamin D metabolites result in denser muscle, more fast twitch/response enhancement, and significant elevations in relevant strength.

      Further, recent research has shown that eating a breakfast meal with decent amounts of calcium and vitamin D “significantly reduced food cravings and prolonged the period for later day meal(s).

      It’s all there in Pubmed- if you look. I check the vitamin D news- daily- for the last 4 years. I have read almost everything printed and listened to the same re: spoken in regards to this most potent of steroid hormones.

      NOTHING in medical history has prepared us for what lies ahead when considering vitamin D.

      This UV derived miracle holds more promise for improved human health than all drug company R & D, factored by a hundred.

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  2. Kevan Gelling says:

    Is it known what causes vitamin D to be released from fat cells? Is it released as a fat is metabolised, or only when the whole of the cell is consumed or is another mechanism at play?

    It has been hypothesised that exercise itself causes vitamin D to be released. Do you know of any scientific evidence that could back this up?

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    • Travis says:

      I can’t really speak to your final question, but I would imagine that Vitamin D is released when fat droplets leave the cell, since healthy weight loss doesn’t destroy the fat cells themselves – it just drains them of fat. I’m not sure of the exact process, but since Vitamin D is fat soluble I’m assuming that as fat exits the cell the Vitamin D goes with it. Anyone more knowledgeable about this feel free to jump in.

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  3. Count Iblis says:

    On the issue of “optimal levels”, why not look at healthy people and put them through some vigorous exercise program? If you give half of the people high dose vitamin D supplements while monitoring the calcidiol levels of everyone, you can see how vitamin D levels correlate with improvement in athletic performance.

    For healthy people such results results would be more relevant, because there is more to being in optimal health than disease prevention. E.g., the amount of vegetables you need to eat to not get scurvy is not a good measure to the amount you need to be in optimal health (say 300 grams per day). If you eat 150 grams per day instead of 300 grams per day, you may not have a significantly higher risk of getting some serious illness, but you may notice a diffference when doing hard exercise.

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  4. Pingback: Healthy Eating Site » Blog Archive Sun, bones and Vitamin D

  5. Pingback: Vitamin D and Obesity | Clinically Proven Weight Loss

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