Vitamin D and weight loss

The world of weight-loss is rife with exercise gizmos and magic pills.

But a person’s level of vitamin D may actually be a predictor of his or her ability to lose fat, according to Shalamar Sibley, a researcher in the University of Minnesota Medical School.

In a clinical study of 38 people, Sibley found that higher baseline levels of vitamin D predicted fat loss, especially in the abdominal area.

“What is suggested here is that if you start out with an inadequate vitamin D level, it’s possible that this might inhibit or impede your ability to lose weight on a reduced caloric diet,” she says.

She is quick to point out that hers was an observational study, and there is no definitive causal relationship between vitamin D and weight loss. The next step is to design a follow-up study where vitamin D is administered in a controlled fashion and studied as an addition to standard weight-loss regimens in people who are vitamin D inadequate.
Sibley, who studies metabolic syndrome and obesity, took a special interest in vitamin D about six years ago. The fact that her recent study yielded a potential breakthrough finding on weight loss and vitamin D is a stroke of serendipity.

“One day I ran across a publication by some other researchers showing that a particular hormone pathway—which when overactive can contribute to obesity-related problems such as high blood pressure—was inhibited by the active form of vitamin D,” Sibley says. “Interestingly, this same pathway (the renin-angiotensin system) also affects fat cell development and metabolism. I happened to be doing a weight loss study in which our only intervention was a reduced calorie diet, and came up with the question, 'Is there any possibility that where someone starts with their baseline vitamin D level will predict their ability to lose weight?’

“What’s interesting about our study is we did not recruit people to be vitamin D inadequate; we recruited people who were overweight or obese for our weight-loss study. And they happened, on average, to have inadequate vitamin D levels, so it tells you how prevalent the problem is.”

Indeed, Sibley notes that “vitamin D deficiency is its own epidemic,” and the numbers bear that out. According to one estimate, 36 percent of otherwise healthy young adults in the United States are lacking in vitamin D, and that number jumps to near 57 percent for general medicine inpatients. Increasingly, a deficiency in vitamin D is being linked to a host of health conditions, including higher blood pressure, cardiovascular problems, kidney disease, and a higher risk of certain cancers, including breast and prostate.

More recently, research at the U found that in a group of 150 patients showing chronic musculoskeletal pain, a whopping 93 percent were vitamin D deficient. (Read more about the study here.)

Taking it all in

Vitamin D can be obtained through sources like fatty fish—herring, salmon, catfish, and tuna are examples—as well as fish liver oils and fortified milk, cereal, yogurt, and bread.

In addition, our bodies naturally produce vitamin D through exposure to the sun. Unfortunately, those of us in northern climes can be left out in the cold; vitamin D is only synthesized from UV radiation between April and early autumn, and while it remains in our bodies for a time, there may not be enough to last all winter.

That makes Minnesotans naturally more susceptible to vitamin D deficiency. “But some of it is also modern lifestyle,” Sibley notes. “People work indoors all day. They like to use sunscreen and they should, because they don’t want skin cancer. That’s fine, but we still need to find a way to have adequate vitamin D levels.”

Sibley says that supplements make sense for people who know or suspect that they’re lacking in vitamin D. “In an adult, 1,000-2,000 IUs (international units) as a supplement is a very reasonable thing to do for maintenance,” she says. “If people are vitamin D inadequate, they’re going to need a higher dose for a short period of time to build up their levels.”