Calcium connection

Food rich in the nutrient might help people shed pounds but more reserach is needed

Food rich in the nutrient might help people shed pounds but more reserach is neededWith recent trends toward low-fat, then low-carb diets, Americans have come to view dairy products as high-fat, calorie-rich foods that have no place in a dieter’s kitchen. After all, whole milk, cheese, yogurt and similar products are naturally packed with fat, and even some nonfat dairy products, like milk, are high in carbohydrates.It’s best to leave such products for children who need calcium to build bones, many shoppers and dieters believe. Now a new diet book, a television advertising campaign endorsed by dietitians and a growing body of research suggests the opposite: Calcium products, specifically those found in dairy foods, could help people lose weight.The claim may not be as far-fetched as it seems: Calcium is a critical nutrient in cell functions throughout the body. Diets low in the mineral appear to set off a chain reaction that prompts the body to metabolize fat less efficiently.The sooner the public knows about calcium’s effect on weight, the better, says one national expert in calcium metabolism.Although he acknowledges that the science supporting the theory is incomplete, Dr. Robert P. Heaney, a professor of medicine at Creighton University in Omaha, says that if everyone consumed adequate dietary calcium – three to four servings a day – while controlling their calories, Americans could lose an average of 15 pounds.”It could have profound effects, population-wide, by lowering the number of people who are overweight,” he says.The theory is so promising that the federal government is funding a study on the approach, and calcium is on the agenda of almost every nutrition or obesity conference this year. At Purdue University in West Lafayette, Ind., a kids’ summer camp is focusing on whether a diet rich in calcium can help adolescents lose weight. Milk, yogurt and cheese pizza are all on the menu.The camp began in 1990 to study calcium metabolism in teenagers, particularly with regard to bone health. But the recent research led Purdue researchers to shift their attention this summer to weight.Of course, not all nutrition experts are convinced that increasing calcium intake is a panacea for people wanting to shed pounds. The connection between dietary calcium and weight loss is debatable, they say, and needs more study before milk and dairy diets are dangled before a vulnerable, overweight American public.”I’m not totally sold on the theory,” says Berdine Martin, a nutrition researcher and director of Purdue’s Camp Calcium. “But the earlier studies have been convincing enough for us to want to look at it.”Calcium’s surprise resultThe idea that dietary calcium could trigger weight loss was dismissed when it was first raised in the early 1990s. At the time, scientists believed that adding calcium to the diet could simply help lower blood pressure. Then researchers found that prescribing two cups of low-fat yogurt a day to a small group of hypertensive men led to lower blood pressure and an average weight loss of 11 pounds in one year.The author of that study, Michael Zemel – now the leading proponent of calcium and weight loss and the author of “The Calcium Key” – couldn’t explain the result and didn’t bother to publish his findings.”People said it didn’t make sense and they sat on their data,” Heaney says, noting that researchers had never suspected that calcium could play a role in weight loss and had no explanation for it.Zemel, however, believed he was onto something, and the University of Tennessee researcher eventually discovered a plausible explanation for why his hypertension patients lost weight.Low levels of dietary calcium prompt the body to increase production of a hormone called calcitriol, Zemel suggests. This hormone causes the body to hoard its calcium stores by sending more calcium into fat cells. More calcium in fat cells signals those cells to store more fat and burn less. The calcium tells the fat cells to become more efficient – which may be an evolutionary trait to protect the primitive human body.But, Zemel says, the reverse also seems to be true. In a calcium-rich diet, calcitriol production decreases and less calcium is shuttled to fat cells. Consequently, less fat is stored and more is burned.In Zemel’s most recent study, published in the April issue of Obesity Research, 32 overweight adults were put on modest, calorie-restricted diets that included varying amounts of dietary calcium. The high-dairy diet patients lost the most weight, an average of 24 pounds after 24 weeks, compared with individuals who also cut calories but consumed few or no dairy products. The study was funded by the National Dairy Council.”This is getting much more acceptable,” says Zemel, a professor in the department of nutrition and medicine. “When we first introduced these concepts, there was understandable skepticism. I was skeptical myself. It took time to make sure this was real. It’s still a work in progress.”Although some experts think that calcium could play a role in weight loss, they aren’t all sold on Zemel’s explanation. Others suggest calcium somehow binds with fat in the body to inhibit absorption. Still others say that adding dairy products to one’s daily diet could make people feel full so that they eat less.Other studies, in groups as varied as teenage girls, post-menopausal women and middle-aged men, support the connection. In a study presented at an American Heart Association meeting in March, Boston University researchers found that children with the lowest intakes of dairy products gained much more body fat over an eight-year period.”The evidence gets progressively stronger,” says Heaney, whose analysis of nine studies by various researchers found a connection between higher calcium intakes and lower body fat or body weight in children and adults. “It’s a consistent finding. Every time somebody looks for it, they see it. But it’s a small effect, so if you didn’t look for it specifically, you might not notice it.”The theory may be the subject of scientific interest because it’s so attractive, some experts suggest.Adding low-fat milk, yogurt and cheese to the diet while cutting back slightly on calories is a safe way to lose weight that, unlike many fad diets, can be maintained for long periods of time, they say. Moreover, there is widespread agreement that Americans consume too little calcium to foster good bone health. Ten million Americans have osteoporosis.”So many Americans don’t really get enough calcium in their diets. We felt this would be a good opportunity,” Susan Laramee, president of the American Dietetic Association, says of her group’s endorsement of a dairy diet.The ADA, the nation’s largest organization of food and nutrition professionals, began promoting a dairy-based diet called the 24/24 meal plan this year in conjunction with Milk Processor Education Program, an industry group funded by milk processors. The 24/24 meal plan consists of 24 ounces of dairy products, such as three glasses of milk, consumed in 24 hours as part of a 1,600-calories-per-day diet.”It’s a well-balanced diet that provides a relatively moderate amount of calories. For most people, it’s enough to lose weight,” Laramee says. But she acknowledges that the calcium weight-loss theory remains unproven and that more studies free of dairy-industry financial support should be conducted.Although much of Zemel’s work has been funded by the dairy industry, most researchers say the science is solid. And several other studies – some of which have found a connection between weight loss and calcium and others which haven’t – have been performed free of industry support.Not a magic bulletAlthough dairy products can play a role in weight loss, cutting calories is essential, Zemel says.”We still have to worry about calories,” he says. “But within the framework of a calorie-controlled diet, dairy can make your efforts much more effective. It can help prevent weight gain and shift the composition to increase lean body mass. It can double the effectiveness if you are restricting calories. But we’re not dealing with a magic bullet or drug. We’re talking about what happens when you correct an inadequate intake.”The diet won’t help overweight people lose weight if they are already getting adequate dietary calcium. Among people who are not restricting calories, the diet may stabilize weight, he says. And too much dairy, like too much of almost anything, will increase calories to the point of weight gain.Critics of Zemel’s approach and the 24/24 plan, however, suggest that cutting back calories alone can cause a slow, steady weight loss and that calcium may have nothing to do with it. “You would expect a person, on average, to lose about a pound a week on a calorie-restricted diet,” says Dr. Amy Joy Lanou, nutrition director of the Physicians Committee for Responsible Medicine.Another major question surrounding the diet is whether calcium supplements work as well as dairy products. So far, the answer appears to be no, Zemel says.”It’s much less effective,” he says. “Dairy seems to have other components that add synergy.”Some scientists have proposed that certain amino acids in dairy products help preserve muscle mass, thus contributing to the body’s fat-burning process, Heaney says. And some Atkins diet proponents suggest that certain dairy products, such as cheese, trigger weight loss because they are high in protein and low in carbohydrates.In a study published in February in the Journal of Clinical Endocrinology and Metabolism, calcium supplements were found to be useless for weight loss and fat metabolism in adult women. But lead author Sue Shapses says she still believes a dairy-based diet could work.”I wouldn’t dismiss this entirely,” says Shapses, an associate professor of nutrition at Rutgers University in New Jersey. “The bottom line for me is that this diet is not going to do anything bad to people. This diet is at least safe. I’m not worried about this one.”The Los Angeles Times isa Tribune Co. newspaper.Calcium and weight lossAdequate intake of calcium in the diet – suggested as three to four servings of dairy products a day – raises the amount of calcium circulating in the blood. According to one theory, when calcium levels are low, the body’s fat cells store more fat, leading to weight gain or difficulty losing weight. The process begins with the thyroid gland.How it works1. When calcium levles in the blood fall, parathyroid hormone is secreted form the thyroid gland.2. Parathyroid hormone then triggers the release of a hormone called calcitriol, which is made in the kidneys3. Calcitriol increases the absorption of dietary calcum in the intestines so the body can hoard the calcium in fat cells. However, more calcium causes the cells to increase fat storage and to decrease fat burning(Source: Newsday Health, “The Calcium Key,” (Weiley, 2004) Michael Zemel and Bill Gottleib: “Anatomica: The Complete Home Medical Reference”, June 2004)