A deficiency in vitamin D, a common and inexpensive nutrient, may hinder weight loss efforts, a study published in 2014 and recently brought to attention suggests. Vitamin D is synthesized by the body when skin is exposed to sunlight and is also found in foods such as fatty fish, egg yolks, and fortified dairy products.
The nutrient plays a vital role in calcium and phosphorus absorption, essential for bone health. Experts believe a lack of vitamin D could disrupt hormone balances, including leptin, which regulates feelings of fullness. Low levels may also increase parathyroid hormone (PTH) and calcium, potentially promoting fat storage and hindering the body's ability to break down excess fat. Additionally, vitamin D can become trapped in body fat, making it unavailable for use and potentially contributing to chronic inflammation.
Despite recommendations for daily intake of 600 to 800 international units (IUs), the average adult consumes only about 192 IUs from food and beverages, according to National Institutes of Health data. This widespread deficiency leaves many vulnerable to complications like muscle weakness, heart disease, and osteoporosis.
Study Details
The research, conducted at Fred Hutchinson Cancer Center in Seattle, involved 218 overweight or obese women aged 50 to 75 who had gone through menopause. This demographic was chosen because menopause often makes weight loss more challenging due to metabolic and hormonal shifts. All participants had low vitamin D levels, averaging between 10 and 32 ng/mL, a range considered below the healthy level of 30 to 60 ng/mL.
Over one year, the women aimed to lose 10 percent of their body weight and participated in a weight loss program incorporating exercise. They were randomly assigned to receive either a high-dose vitamin D supplement (2,000 IUs daily) or a placebo. The study found that women who took the vitamin D supplement and whose blood levels increased into the normal range experienced greater reductions in weight, body fat, and waist circumference compared to those whose levels did not rise significantly.
Specifically, women whose vitamin D levels rose above 32 ng/mL lost an average of 19 pounds, contrasting with an average of 12 pounds for those who remained below this threshold. Waist circumference decreased by an average of 6.6cm in the higher vitamin D group versus 2.5cm in the low-level group. Furthermore, participants with elevated vitamin D levels lost 4.7 percent of their body fat, compared to 2.6 percent in the control group. Women in the vitamin D group saw their blood levels increase by an average of 13.6 ng/mL, while the placebo group experienced a slight decrease of 1.3 ng/mL.
Implications and Recommendations
Dr. Anne McTiernan, lead author of the study and professor emeritus at Fred Hutchinson Cancer Center, suggested that women trying to lose weight might benefit from having their vitamin D levels checked. She indicated that replenishing vitamin D through supplements, sun exposure, or diet could be beneficial, with rechecking levels after a few months to confirm they have reached a healthy range. Natural ways to increase vitamin D levels include consuming more fatty fish and egg yolks, and spending brief periods in the midday sun. However, the study did not explicitly investigate whether these alternative methods yield the same weight loss results as supplementation.