Vitamin D found to promote fat loss and muscle gain in women

Higher levels of vitamin D are associated with a reduced risk of a variety of health issues including heart disease, type 2 diabetes and several forms of cancer. This research may be of some interest, but its nature (so-called ‘epidemiological’ studies) can’t tell us whether or not vitamin D actually protects against these conditions. It might be, for example, that healthier people are more likely to go outside and make vitamin D when exposed to sunshine.

Another example concerns the observation that individuals with low levels of vitamin D tend to be more prone to overweight and obesity. However, some have suggested that this might be because vitamin D tends to get sequestered (stored) in fat, removing it from the circulation and the more fat someone has, the more this tends to happen.

Studies that illuminate the role of vitamin D in health are those in which this substance is given to individuals to see what impact it has on them. Recently, a study was published in which vitamin D was given to a group of 77 overweight and obese women [1]. Half of the women were treated with 1,000 IU each day for 12 weeks, while the other half took a placebo. The vitamin D levels in the group taking this nutrients roughly doubled over the course of the study (an average of 38 nmol/l increasing to an average of 75 nmol/l) while the group taking placebo saw no significant increase.

Body weight was static over the course of the study in both groups, but the effects on body composition were not the same. Specifically, the group taking vitamin D ended up losing an average of 2.7 kg (6 lbs) of fat. At the same time, fat free mass (essentially, muscle) increased by an average of 1.8 kg. In those taking placebo, there was no significant change in fat mass or fat free mass.

In the paper, the authors refer to other work in which vitamin D has been mooted to assist in the development of lean body mass and inhibit the development of ‘adipocytes’ (fat cells). The authors also add that it is unclear whether the effect is due to the direct action of vitamin D or the ability of vitamin D to suppress levels of a hormone known as parathyroid hormone.

In the end, it might be hard to unpick the precise mechanisms involved here, What we do have, though, is a study which provides good evidence that maintaining generally higher levels of vitamin D in the body might bring genuine benefits for health.

The study also might remind us that while we can tend to be quite weight-focused, it can be possible to experience improvements in body composition (e.g. muscle gained and fat lost) without that registering on the scales.


1. Salehpour A, et al. A 12-week double-blind randomized clinical trial of vitamin D3 supplementation on body fat mass in healthy overweight and obese women. Nutrition Journal 2012;11:78

10 Responses to Vitamin D found to promote fat loss and muscle gain in women

  1. bert hubert 11 October 2012 at 7:29 pm # has the full text of “A 12-week double-blind randomized clinical trial of vitamin D3 supplementation on body fat mass in healthy overweight and obese women.”!

  2. Ajana 12 October 2012 at 1:59 pm #

    The list of problems from a lack of D3 continues to grow, as does the benefits from taking it. They’ll have to pry my D3 out of my colds dead hands before I’ll ever stop taking it.

  3. Ted Hutchinson 12 October 2012 at 5:14 pm #

    I think if we are to get serious about vitamin D3 we need to use it in amounts closer to the 10,000iu full body non burning UVB exposure would produce and see what happens when we run our body with a 25(OH)D level around 125nmol/l at which level Vit d works most effectively as an anti-inflammatory agent.

    We also have to remember the half-life of 25(OH)D is 3~4 weeks so we need vitamin d3 trials which not only attain 25(OH)D levels @125nmol/l but maintain that level for 2~3 years so we see what happens when human cells are produced in vitamin D enviroments equivalent to those while Human DNA was evolving. This study only achieved 75±22 nmol/l (insufficient even to optimize calcium absorption)

    We can each do our own personal trails using City Assays Vitamin D Blood Spot Tests £25 less if you bulk buy and share and Vitamin D drops from the USA discount providers.
    While there will be a lot of variation MOST of us will require around 5000iu/daily at least to stay above 100nmol/l.
    1000iu/daily for each 25lbs weight is a more appropriate supplementation level.

    We also need to understand that to convert the circulating form of Vitamin D3 (CALCIDIOL) to the active hormonal form (CALCITRIOL) requires the presence of magnesium and is further enhanced by the availability of the omega 3 DHA. Increasing magnesium intake when increasing 25(OH)D levels will counterbalance the actions of increased calcium absorption raising vit d enables.

    We will only see to optimum effect of vitamin D3 in the context of an anti-inflammatory diet and lifestyle, when anti-inflammatory reserves are nearer those paleo humans would have naturally enjoyed living near naked outdoor lives while consuming free range organic foods.
    Unfortunately improving all the anti-inflammatory parameters and building anti-inflammatory reserves is too complex/expensive for current research trials to achieve so we are going to have to rely on individual case studies.

  4. lorraine cleaver 14 October 2012 at 2:17 am #

    This interests me greatly because I lost my parathyroid glands during thyroidectomy operation and must take Calcium and alfacalcidol daily. I struggled to keep calcium in range for years and when I finally asked for my magnesium to be tested , it was below range by quite a way. I now supplement with magnesium chelate and my bloods look good. I did read a study recently which cautioned against too high vit D though.

  5. Ted Hutchinson 14 October 2012 at 5:39 pm #

    Perhaps readers would like to consider Dr Cannell’s comments regarding High and low vitamin D levels cause mortality?
    I keep my 25(OH)D level around 50ng/ml 125nmol/l, at that level Vitamin D3 works most effectively as an anti-inflammatory agent.

    Most chronic conditions involve inflammation and pain. I think enabling your body to optimally control inflammation and the inflammatory response is key to minimising the amount of pain you experience.

    Perhaps if D. Durup et all. are right, and doing shortens my life, then at least I will have enjoyed a life without constant pain or repeat infections.
    What matters ultimately is Quality of Life.

  6. Chloe Brotheridge 15 October 2012 at 7:14 pm #

    Great stuff Dr. B. I’ve just started taking a vitamin d supplement for winter. Hard to balance not wanting to danage your skin with getting enough vit D. I heard that 80% skin damage is environmental :-S

  7. Megan 24 October 2012 at 5:24 pm #

    it is tricky to get enough Vitamin D in the winter. I take around 4,000iu but this means four tablets of high strength option each day. The thought of taking ten each day would have me rattling…however I agree we should top up our levels to where it would be on sunny days when we are outdoors.

  8. Ted Hutchinson 24 October 2012 at 7:53 pm #

    @ Megan You can buy Healthy Origins, Vitamin D3 Drops, 5,000 IU, 377 servings capsules on Amazon UK or from Bigvits for about £13. Or for the same outlay, buy 2 packs from the USA from IHERB or Vitacost and share. If you haven’t bought from abroad before customs add 20% tax to orders at/above £15 + DHL charge £1.25 to collect tax. There are $5 initial discount codes available, mine is WAB666, possibly Dr Briffa has one for himself or site.

    Unfortunately No Vit D3 from sunlight in UK until next March.

    Rule of thumb is that Vit D production is best when shadow length is shorter than height, while shadow length is greater than your height some Vit d production is possible but when shadow length is twice as long as you are tall or greater no vitamin D is produced at all.
    UVA exposure on it’s own, from sunlight filtered though glass, car windsreeen, covered shopping mall) or from tanning tubes with no UVB content processes any vitamin D3 near the surface of skin into suprasterols that the body doesn’t use.
    So people only getting sunlight through a closed office window or while in the car/bus/train will be reducing 25(OH)D levels.
    But please don’t avoid winter sunlight as there is however more to sunlight than just vitamin D3.
    Bright light, through the eyes, helps reset circadian rhythm and improves melatonin secretion during the evening and while asleep. Melatonin like vitamin D is pleiotropic and regulates many different genes apart from simply enabling sleep.


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