by Craig Weatherby
No evidence supports the efficacy of drastic calorie-cutting, which is proven unhealthful and rarely yields lasting results.
Nor do studies suggest there are any advantages to diets weighted heavily toward carbohydrates, protein, or fat.
That said, everyone is interested in gaining every edge they can in the battle of the bulge!
So we noted with interest a study suggesting that higher blood levels of vitamin D may improve weight loss among folks on very-low-calorie diets.
And when we found that some evidence links low vitamin D levels to increased risk of obesity, we though it was worth another look at the hypothesis that vitamin D might influence weight loss or gain.
Report links vitamin D to greater dieting success
The findings that caught our attention were presented last week at the Endocrine Society Meeting in Washington, D.C. by Shalamar Sibley, M.D., Ph.D., of the University of Minnesota.
Vitamin D shares many properties with hormones, so it made sense that there were many presentations regarding the “sunshine-and-seafood” vitamin at a conference where hormone-science researchers gather to share their results.
Dr. Sibley's Minnesota team recruited 38 overweight men and women and assigned them to restricted diets that provided 750 calories a day fewer than their estimated total needs.
The study lasted for 11 weeks, and the participants' blood levels of vitamin D were measured at its start and finish.
Dr. Sibley told meeting attendees that many of the subjects were vitamin D deficient or had insufficient levels of vitamin D at the outset of the trial.
Significantly, the participants' blood levels of vitamin D at the beginning of the study accurately predicted their success in losing weight, with vitamin D levels linked to weight loss in a linear relationship.
Better yet, having higher vitamin D levels at the beginning of the trial predicted increased loss of abdominal fat: a particularly heart-unhealthful kind.
|The skinny on vitamin D|
When it comes to foods and supplements, the term “vitamin D” refers to two inactive precursors to this hormone-like nutrient, called D3 (cholecalciferol, obtainable only from animal foods) and D2 (ergocalciferol, made from yeast).
The D3 form—which is produced in the skin on exposure to UV sunrays and is abundant only in fatty fish—appears to be more effective at raising body levels of vitamin D.
Winter sunrays in northern latitudes are so weak that many people make no vitamin D at all during these short, dim days. And darker-skinned people are the least able to make vitamin D when sunrays are weak.
This means that dietary supplements, fatty fish, and tanning lamps are the only ways to boost vitamin D levels.
Vitamin D deficiency can cause or exacerbate osteoporosis and fractures and appears to promote common cancers, autoimmune diseases, infectious diseases, type 1 diabetes, and cardiovascular disease.
(For more reports on vitamin D science, search our newsletter archive for “vitamin d”)
Most experts have urged the Institute of Medicine to quickly raise the adult RDA from 200 IU (birth to age 50) or 400 IU (aged 51-plus) to at least 1,000 IU... preferably to 2,000 IU or more.
The current officially recommended upper daily limit is 2,000 IU... a level vitamin D researchers decry as wholly unfounded and misleading, since all the published evidence shows that adults can very safely consume at least 10,000 IU per day.
Due to their low body weight, children should not exceed 2,000 IU of supplemental vitamin D per day, unless approved by a doctor.
Fatty fish are the only rich food sources of vitamin D3, and tuna and wild salmon top that list, providing about 200 IU (king salmon) to 600 IU (albacore tuna and sockeye salmon) per 3.5 oz (100 gram) serving.
The National Institutes of Health (NIH) defines vitamin D deficiency as having blood levels below 15 nanograms per liter (ng/mL) and states that anything less than 20 ng/mL is inadequate for bone and overall health. NIH sets 30 ng/mL as the minimum needed for good overall health.
According to NIH, up to 45 percent of Americans fall below the sufficiency level (20 ng/mL), and 50-78 percent have blood levels that fall below the recommended sufficiency level (30 ng/mL or more).
Vitamin D experts recommend a target of 30 to 100 ng/mL based on good evidence that rates of major diseases drop when blood levels rise into this range (Klein GL et al 2009).
Only blood levels that consistently test higher than 200 ng/mL (i.e., 500 nanomoles per liter) are considered potentially toxic.
- Take 20,000 IU of vitamin D3 twice a week (i.e., the equivalent of taking 5,714 IU daily)
- Take 20,000 IU of vitamin D3 once a week (i.e., the equivalent of taking 2,857 IU daily)
- Take placebo (inactive) pills twice a week
As the Norwegians wrote, “Significant weight reduction in overweight and obese subjects is unlikely to occur with cholecalciferol [vitamin D3] supplementation” (Sneve M et al. 2008).
This finding comes as no surprise, since no prior evidence suggested that taking vitamin D supplements would, by itself, cause weight loss.
The study was funded by the National Institutes of Health, the University of Minnesota, and the Pennock Family Endowment at the University of Minnesota.
Vitamin D lowered key heart-risk factors in overweight people
A study published earlier this year suggests that supplemental vitamin D reduces markers of inflammation associated with cardiovascular disease (Zittermann A et al 2009).
The positive outcomes of this study fit with prior indications that vitamin D can enhance heart health: see “Vitamin D May Reduce Heart Attack Risk” and “Vitamin D Linked to Better Heart Health... Again.”
German researchers recruited 200 healthy overweight people with average vitamin D (25[OH]D) levels of 30 nmol/L (12 ng/mL)—levels considered insufficient or deficient—for a randomized, double-blind clinical trial.
The volunteers were divided into two groups, with some assigned to take 83 micrograms (3,320 IU) of vitamin D daily and the remainder given placebo pills, while all participated in a low-calorie weight-reduction program.
At the end of the one-year study, the results showed no greater weight loss in the vitamin D group.
However, compared with the placebo-pill group, the vitamin D group showed pronounced decreases in blood levels of two risk factors for cardiovascular disease: triglycerides and the inflammation marker TNF-alpha.
Importantly, these two beneficial effects were independent of any loss in body weight or fat mass.
Conversely, LDL cholesterol levels increased in the vitamin D group by about seven percent … a pretty insignificant effect given the amount of the increase and the oft-overstated importance of LDL levels as an indicator of heart risks.
- Sibley SD. Presentation #OR14-5. Plasma Vitamin D: A Predictor of Subsequent Weight Loss Success. Thursday, June 11, 2009. Endocrine Society 91st Annual Meeting. Washington, DC. http://www.abstracts2view.com/endo/view.php?nu=ENDO09L_OR14-5
- Sneve M, Figenschau Y, Jorde R. Supplementation with cholecalciferol does not result in weight reduction in overweight and obese subjects. Eur J Endocrinol. 2008 Dec;159(6):675-84.
- Zittermann A et al. Vitamin D supplementation enhances the beneficial effects of weight loss on cardiovascular disease risk markers. Am J Clin Nutr. 2009 May;89(5):1321-7. Epub 2009 Mar 25.