Overweight women with low Vitamin D levels who lose more than 15% of their body weight experience a significant increase in levels of this nutrient, according to a new study by researchers at Fred Hutchinson Cancer Center. "Since vitamin D is generally lower in persons with obesity, it is possible that low vitamin D could account, in part, for the link between obesity and diseases such as cancer, heart disease and diabetes," said Caitlin Mason, PhD, lead author of the study published in the American Journal of Clinical Nutrition.

Vitamin D promotes calcium absorption and is needed for bone growth and bone healing.   Along with calcium, vitamin D helps protect older adults from osteoporosis.  This nutrient also influences cell growth, neuromuscular and immune function and reduces inflammation.

The study involved 439 overweight-to-obese, sedentary, postmenopausal Seattle-area women, ages 50 to 75 who were randomized into four groups:   exercise only, diet only, exercise plus diet and no intervention.  Those who lost between 5-10% of their weight saw some moderate increase in vitamin D levels, but women who lost more than 15% of their weight experienced a nearly threefold increase in vitamin D, independent of dietary intake of the nutrient.   Optimal levels of vitamin D are between 20 and 50 ng/mL.  Levels below 20 ng/mL are inadequate for bone health and levels above 5o ng/mL can have adverse side effects such as an increased risk of kidney stones.