Many people also will experience a decrease in their vitamin D levels, which can play a role in heart disease, according to a new review article in Circulation.

Vitamin D deficiency results in part from reduced exposure to sunlight, which is common during cold weather months when days are shorter and more time is spent indoors.

"Chronic vitamin D deficiency may be a culprit in heart disease, high blood pressure and metabolic syndrome," said Sue Penckofer, PhD, RN, study author and professor, Marcella Niehoff School of Nursing, Loyola University Chicago.

The review article cited a number of studies that linked vitamin D deficiency to heart disease. These studies found rates of severe disease or death may be 30 to 50 percent higher among sun-deprived individuals with heart disease.

Penckofer and colleagues concluded that diet alone is not sufficient to manage vitamin D levels. Treatment options to correct this level, such as vitamin D2 or D3, may decrease the risk of severe disease or death from cardiovascular disorders. The preferred range in the body is 30 - 60 ng/mL of 25(OH) vitamin D.

"Most physicians do not routinely test for vitamin D deficiency," said Penckofer. "However, most experts would agree that adults at risk for heart disease and others who experience fatigue joint pain or depression should have their vitamin D levels measured."

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At the study's end, the mice fed a calorie-restricted diet weighed an average of 19.9 grams “ significantly less than the control mice (average weight 28.8 grams) and the exercised mice (average weight 26 grams). The calorie-restricted mice and the exercised mice showed no significant difference in percentage of body fat, but both groups had significantly less body fat than the sedentary mice that were fed at will.

In addition, blood levels of leptin, a hormone that plays a role in fat metabolism, were significantly reduced in the calorie-restricted and exercised mice compared to the controls. The calorie-restricted mice also displayed increased blood levels of adiponectin, a hormone produced in fat tissue that regulates some metabolic processes, compared to the exercised mice.

Some of the cell signaling pathways regulated by these hormones converge at mTOR, Nogueira explains. She and her colleagues found that the key proteins found downstream of mTOR activation were less active in both the calorie-restricted and exercised mice compared to the controls.

"These data suggest that although exercise can act on similar pathways as caloric restriction, caloric restriction possesses a more global effect on cell signaling and, therefore, may produce a more potent anti-cancer effect," Nogueira said.

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