US researchers are investigating whether calcium intake, previously linked to lower weight in girls, could help prevent women from gaining too much weight when pregnant.
The researchers at Oregon Health & Science University have begun a clinical trial to investigate the effects of a calcium supplement, 1200 milligrams of elemental calcium, on weight gain during pregnancy and weight loss postpartum.
Jane Harrison-Hohner, nurse practitioner and study coordinator, said that pregnancy is a good time to test the effects of calcium on weight regulation.
"There are many positive aspects to increasing calcium consumption during pregnancy," she said. "It would be great if such a simple and safe intervention was able to help women contend with body weight issues as well as provide for the child's needs."
"For many women, excess weight gain during pregnancy and then the failure to lose the additional pounds during the postpartum period marks the beginning of obesity. During this time of rapid weight change, it would be a great benefit if calcium could help curtail excess weight gain and facilitate weight loss following pregnancy," said Dr Daniel Hatton, associate professor of behavioural neuroscience, OHSU School of Medicine and the principal investigator of the study.
Data from the National Health and Nutrition Examination Surveys have consistently shown a relationship between calcium consumption and body weight, noted the researchers. The most recent survey shows that people who consume the lowest range of calcium consumption are six times more likely to be overweight than those in the highest range.
Clinical studies have shown that subjects placed on a weight-loss diet enriched with dietary calcium lose more body weight than those who eat the same amount of calories but with less calcium. Furthermore, the weight loss includes a significantly greater loss of body fat.
The loss of body fat may result from the body burning more fat when there is greater calcium intake. In fact, calcium intake can account for as much as 10 per cent of fat burned in a 24-hour period, according to Hatton.
However scientists still do not understand how calcium promotes fat reduction. Michael Zemel, a nutritionist at the University of Tennessee, suggests that it has to do with the actions of vitamin D. Data appear to show that the active form of vitamin D, called calcitriol, causes fat cells to create more fat. Calcitriol levels are raised with lower intake of calcium. Therefore, fat cells produce more fat on low calcium diets. By contrast, high-calcium diets suppress calcitriol and, as a consequence, promote the burning of fat.