Vitamin D And Insulin Resistance

Last modified on October 3rd, 2013

The more research that’s published, the more evidence I seem to run into that indicates insulin resistance (and consequently obesity) seems to be related to oxidative stress and/or nutritional deficiencies. As I’ve pointed out before, one of the strange paradoxes that most theories generally can’t explain is why obesity often goes hand in hand with poor nutrition. That is, if obesity is caused solely by overeating, then we should see the lack of obesity in populations where food is scarce or nutrient poor. As several populations have shown us (most notably the Pima Indians), that isn’t always the case.

Several current theories say that obesity is actually caused by nutritional deficiencies, which would jive with the observations above. Several vitamins/minerals that have been implicated in insulin control include chromium, vitamin C, calcium, and more recently vitamin D.

The research around vitamin D and insulin resistance is actually fairly interesting. As most people are aware, vitamin D is primarily produced by the body as a response to sun exposure. Several working theories are implicating vitamin D deficiency as a central or possibly even primarily role in the development of type-II diabetes.

This theory actually makes a lot of sense to me. First, we know that many animals hibernate in the winter. Prior to hibernation, most animals gain weight (in fact, human weight’s vary as well, generally being higher in the winter and lower in the summer). If you believe that excess insulin causes the accumulation of fat (which most research supports), and that vitamin D has a role in controlling insulin production (which current research seems to indicate), then you can hypothesize that vitamin D levels directly influence weight storage by their affects on insulin levels.

One crucial logic point involves causality. Most of the current research tends to show that exercise, while it obviously makes you healthier, often doesn’t lead to any noticeable or long term weight loss — it generally leads to hunger. Diets can help you lower weight, but the reasons behind the loss aren’t entirely understood. If you’re a low-carb (i.e. low insulin) proponent, then reducing your food intake naturally lowers the insulin levels in your blood, which generally causes you to lose weight. If you’re a low-fat proponent, you’ll probably argue that the weight loss is directly related to a reduction in calories.

If you believe the low-carb camp (which a lot of the research supports), then people are not getting fat because they are eating too much, they are eating too much because they are getting fat (the casualty is reversed). That is, because obese people generally have hyperinsulinemia (high levels of insulin in the blood) and insulin causes fat to be stored in fat cells, obese people generally display a level of internal starvation (their muscle cells are literally starved for food because their fat cells are hoarding nutrients) and generally can’t satisfy their body’s demands for energy by eating. In this scenario, lethargy isn’t a cause of obesity, it’s an effect of it (due to the internal starvation).

With regards to vitamin D, the same can be said. Since most people have an increased exposure to sunshine in the summer months, the internal levels of vitamin D would go up. In that case, insulin levels would drop, and weight would naturally decrease. In the winter, when exposure to sunshine is reduced, vitamin D levels would drop, insulin would rise, and fat would be stored. So that bear who is stocking up on food for the winter — he’s not gaining weight because he’s eating more, he’s eating more because he’s gaining weight.

Obviously it’s just a hypothesis, but it jives with most of the current observations. Additional support to the theory can be found in several research reports, one of which reported “heart attacks peak in winter and decline in summer in temperate but not tropical latitudes,” which also lends credit to the idea that exposure to sunshine may ultimately influence insulin production.

Here’s one of the recent studies I was reading tonight:

Common obesity is associated with the metabolic syndrome and can be distinguished from secondary obesity and from rare forms of monogenic and polygenic obesity. The prevalence of common obesity has become a public health concern in many countries as phenomenological approaches to the understanding of obesity have failed to achieve any long term effect on prevention or treatment. There is evidence for a central control mechanism which maintains body-weight to a set-point by the regulation of energy intake and energy expenditure through homeostatic pathways. It is suggested in this paper that common obesity occurs when the set-point is raised and that accumulation of fat mass functions to increase body size. Larger body size confers a survival advantage in the cold ambient temperatures and food scarcity of the winter climate by reducing surface area to volume ratio and by providing an energy store in the form of fat mass. In addition, it is suggested that the phenotypic metabolic and physiological changes observed as the metabolic syndrome, including hypertension and insulin resistance, could result from a winter metabolism which increases thermogenic capacity. Common obesity and the metabolic syndrome may therefore result from an anomalous adaptive winter response. The stimulus for the winter response is proposed to be a fall in vitamin D. The synthesis of vitamin D is dependent upon the absorption of radiation in the ultraviolet-B range of sunlight. At ground level at mid-latitudes, UV-B radiation falls in the autumn and becomes negligible in winter. It has previously been proposed that vitamin D evolved in primitive organisms as a UV-B sensitive photoreceptor with the function of signaling changes in sunlight intensity. It is here proposed that a fall in vitamin D in the form of circulating calcidiol is the stimulus for the winter response, which consists of an accumulation of fat mass (obesity) and the induction of a winter metabolism (the metabolic syndrome). Vitamin D deficiency can account for the secular trends in the prevalence of obesity and for individual differences in its onset and severity. It may be possible to reverse the increasing prevalence of obesity by improving vitamin D status.

If you’re looking for some Vitamin D, you can grab some Vitamin D on Amazon.

10 responses to “Vitamin D And Insulin Resistance”

  1. Beth says:

    This is an interesting hypothesis. I haven’t been keeping as up on the nutrition literature as I would like, but I do believe that there is some good evidence about a role of vitamin D in reducing the risk of some cancers as well – I wonder if insulin is proposed to be involved in that, or if it’s a different proposed mechanism (as I said, haven’t actually read the research on it). Because of all the new research on vitamin D, the recommended intake for vitamin D for Canada & the US is currently under review, with a new recommended level expected to be released in the spring.

    It would also be interesting to see if rising rates of obesity are at all correlated with rising rates of the use of sunscreen, which blocks UV rays and thus, our ability to make our own vitamin D.

  2. I’ve been taking bigger doses of vitamin D as part of my cancer treatment. Not sure if it’s helped, and I already have Type I diabetes (the other kind), so I’m sort of on the wrong side of the prevention curve, but especially in our kind of climate, supplemental vitamin D is probably a good idea for almost anyone.

  3. Duane Storey says:

    True.. Just curious, what else do you take Derek?

  4. Duane Storey says:

    @Beth, that’s true too. I’ve read a lot of research that says sunscreen is ultimately bad for us, especially since most sunscreens only block part of the spectrum (the part that causes the skin to build up resistance to harmful rays). So in those cases, wearing sunscreen is actually worse for you, since the rays that help you adjust to sunshine aren’t getting through, but the UV rays that cause mutations are uninhibited.

    I spend at least two hours a week keeping up to date. Without a doubt, the one term I see with almost all mentions of cancers is insulin.

    Vitamin D probably helps the body with insulin, and it most definitely helps the body absorb more calcium. Intercellular calcium actually causes a lot of cancer sells to self destruct (Apoptosis). In addition, vitamin E and vitamin C also help destroy cancer cells. Alpha lipoic acid (especially the R-enantiomer ) actually helps recycle existing vitamin E and C, so may be the most beneficial supplement you can take.

  5. My list of supplements is pretty long, and I’d have to look up dosages, but there’s nothing too weird.

    Fish oil, garlic, lycopene, thymus, CoQ10, a couple of custom Sisu cancer multivitamin combinations, turmeric, Acidophilus boosters. I have melatonin but generally haven’t needed to take it to get to sleep. The set was recommended by one of the doctors at Inspire Health ( last year, and I can’t be sure how much it’s all helped, but I don’t think it’s made anything worse!

  6. Aita says:

    Fascinating, and just as I suspected given our evolutionary history. It makes sense that since humans lived and worked outdoors in the sun for most of history, the body would have learnt to adapt to this and incorporated sunlight into our fundamental biological processes. I’ve also heard research that suggests lack of sleep can increase the risk of developing Type 2 Diabetes. It would be interesting to see how this all weaves in with sunlight/vitamin D/melatonin balance/insomnia etc.

  7. Duane Storey says:

    Lack of sleep definitely is associated with heart disease and insulin resistance. I’m not entirely sure why. But that’s also why Sleep Apnea is a pretty big risk for both, since fundamentally it results in disrupted sleep.

  8. Beth says:

    Lack of sleep is associated with obesity, which is associated with heart disease and insulin resistance, so it could be linked through obesity.

  9. Jessica says:

    I know this is an old post but thought people may find this helpful.
    I am Insulin Resistant but do not have type 2 Diabetes. I suffer from Insulin Resistance as part of PCOS. I have also had blood tests come back with recently extremely low Vitamin D results which I am about to commence supplements for. In summer I drop anywhere between 10-20 kgs with no effort. This seems impossible to do through winter and I haven’t understood why and simply put it down to the PCOS. I get plenty of sleep (8 hours each night) but am still left feeling extremely tired after meals which have a higher carb content.

  10. Danielle says:

    I stumbled across this for the same exact reasons. I was recently diagnosed with pcos and it seems to have finally tied together years of unexplained symptoms. I have low levels of vitamin d and calcium as well as my white blood cell count. My symptoms seem to get worse as winter sets in I always just called it seasonal depression but summer time comes around and I’m starting to notice the more sun I get the better I feel. I’ve also been taking supplemental vit d. Foggy memory and concentration are definitely improving. I’ve also been prescribed metformin

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