The Need for Calcium

Cynthia Buffington, Ph.D.

Beyond Change, September 2001

Dairy products with their high content of calcium help to build strong bones and teeth and prevent or reduce the risk of high blood pressure, heart disease, osteoporosis (bone loss) and colon cancer.  For these reasons alone, we should pay close attention to our intake of dietary calcium, attempting to meet on a daily basis the RDA of 1000 to 1300 mg.

But, there is another important reason for sufficient intake of dairy products and other foods high in calcium.  Dietary calcium helps to reduce body fat!

Studies by Dr. Michael Zemel, Dr. Hang Shi, and their colleagues at The Department of Nutrition and Medicine, The University of Tennessee, Knoxville, found that dietary calcium reduces body weight and fat in mice bred to overexpress a protein, agouti, that causes obesity.

In one series of experiments, investigators determined if dietary calcium supplementation could slow the progression of diet-induced obesity in agouti mice.  All animals were placed on a high fat/ high sugar diet containing a low amount of calcium (an amount that in humans would be equivalent to about 500 mg per day or that amount the majority of American women consume). 

One group of mice, the controls, remained on the low calcium diet throughout the study period.  The diets of three other groups of mice were supplemented with additional calcium.   One group of animals were fed calcium carbonate (the ingredient in ‘Tums’) at an amount roughly equivalent to 1600 mg in humans (which is close to the RDA).  Non-fat dry milk was used to supply medium and high amounts of dietary calcium to the other two groups of animals at amounts that in humans, would be equivalent to approximately 1600 and 3200 mg per day.

The high calorie diet caused a 29% weight gain and a nearly 2-fold increase in fat mass in those animals on low calcium.  Diet-induced weight and fat gains were markedly reduced in the animals on the three high calcium diets.  Furthermore, reductions in weight gain with added calcium altered fat cell metabolism, causing a reduction in fat synthesis and storage and an increase in fat breakdown.

Dr. Zemel and associates further examined the influence of dietary calcium on diet-induced weight loss.  In these studies, agouti mice were fed a high calorie diet to induce weight gain.   The animals were then switched to a low calcium, low calorie diet (low fat/low sugar) and dietary calcium was supplemented with calcium carbonate or non-fat dry milk, as described above.

At the end of the 6-week study period, the control (or low dietary calcium) animals had lost 11% of their body weight and had an 8% decrease in body fat.  Those on the calcium carbonate supplements had a 19% decrease in body weight and a 42% reduction in fat.  And, animals on the medium and high calcium milk diets had a respective 25% and 29% decrease in body weight and a 60% and 69% loss of body fat.

The reductions in body fat in the high dietary calcium groups were accompanied by a decrease in synthesis of fat in fat cells and a substantial increase in fat breakdown.  Furthermore, the high calcium diets increased core temperatures, indicating an increase in calories burned.  These findings demonstrate that, at least in agouti mice, high dietary calcium not only prevents diet-induced weight gain but also facilitates the weight loss of a low calorie diet and does so by reducing fat storage and by enhancing fat breakdown and energy utilization.

The above findings regarding dietary calcium and obesity in agouti mice are quite impressive.   But, is there any evidence that dietary calcium can prevent obesity or facilitate weight loss in humans?

Dr. Zemel and associates found, in humans, that increasing the dietary calcium of obese patients for one year resulted in a 4.9 kg or a nearly 11 pound loss of body fat.  In another study by Dr. Robert Hearney and associates at Creighton University, Omaha, Nebraska, women who took calcium supplements exhibited significant weight loss across nearly four years of observation.

Dr. Hearney and associates also found, upon revaluation of 5 studies originally performed to examine relationships between dietary calcium and bone in women, an inverse relationship between calcium intake and body weight. In other words, the more dietary calcium the women consumed, the less likely they were to be obese. Women who were in the lower, as compared to upper half, of their group’s calcium intake were 2.25 times more likely be overweight, i.e. have a body mass index of 25 or greater. 

Other investigators have, likewise, found that obesity is more prevalent in men and women with low intakes of dairy products and dietary calcium.   A recent study by Dr. Jennifer Lovejoy and associates from the Pennington Biomedical Research Center in Barton Rouge, Louisiana, noted that African American females are more obese and consume less dietary calcium than do their Caucasian counterparts and that for both races, low dietary calcium intake is associated with a greater percentage body fat.

NHANES III is a large epidemiological study conducted between 1988 and 1994.  Analysis of this data showed that women who consumed high amounts of dietary calcium, i.e. those in the upper quartile or 25% of dietary calcium intakes for their respective group, were 6.25 times less likely to be obese than those whose dietary intakes were in the lower quartile.   An inverse relationship between dietary calcium intake and obesity was also noted among men.

In another longitudinal study, University of Tennessee scientists, Drs. Caruth and Skinner, assess preschool children’s food consumption over a period of 24 to 60 months and related these findings to their body composition measured at 70 months. The study found that higher longitudinal intakes of calcium and servings of dairy products are associated with lower body fat in children.

Altogether the animal and human studies discussed above support a role for dietary calcium in the regulation of body fat and obesity.  Is it possible that low dietary intake of calcium and dairy products have contributed to the more recent and very serious increase in obesity prevalence in this country and throughout the industrialized world?

According to various epidemiological studies, American, Canadian and Western and Southern European diets are low in dietary calcium.   And, studies have noted a significant decline in dairy food servings and dietary calcium intakes over the course of only one generation.  One study, for instance, found that U.S. adolescents in 1996 consumed 36% less milk than did adolescents in 1965.   And, a Canadian study noted a significant decline in the intake of dairy products and dietary calcium between 1970 and 1997-98. 

Why are individuals consuming fewer dairy products and other high calcium-containing foods?  For adolescents, milk has been replaced by sodas and juice.  And, most American children and adults do not eat enough vegetables, many of which are also high in calcium.

The campaign against fat and cholesterol has also taken its toll on dietary calcium. Ironically, people who are overweight or obese often avoid dairy products (even low fat or non-fat items) in an attempt to lose weight, having no idea that by doing so, they may be moving farther from their weight loss goal.

Some ethnic populations, such as African Americans and American Indians, have difficulty digesting milk due to an intolerance to lactose, the primary sugar found in milk. Aging and weight gain may also cause changes in lactose tolerance.  In fact, it is believed that as many as 1 out of 5 Americans are lactose intolerant.

For individuals who have difficulty digesting lactose, there is lactose-free milk or across- the-counter tablets that can be taken that break down lactose and assist in the digestion of foods.   In addition, there are numerous other foods high in calcium that have little, if any, lactose.  Such foods include cooked broccoli, Collard greens, Chinese cabbage, kale, turnip greens, salmon, shrimp, sardines, oysters, molasses, tofu, and various other foods which can be found listed, along with their calcium and lactose contents, at: http://www.niddnih.gov/health/digest/pubs/lactose/lactose.htm).

For some individuals, calcium supplements may be necessary to guarantee adequate amounts of dietary calcium.  Individuals on low calorie diets or those whose calorie intakes have been restricted by obesity surgical intervention may have an insufficient intake of dietary calcium and need to take calcium supplements to avoid bone loss associated with weight reduction and, possibly, as discussed above, to achieve greater weight loss. 

There is also concern that without calcium supplementation individuals with poor absorption, i.e. the elderly, those with malabsorptive disease, or those who have had malabsorptive obesity surgery may be at risk of dietary calcium deficiencies. 

As discussed in the November 2000 issue of Beyond Change by the highly prestigious and knowledgeable obesity surgeon, Dr. Edward Mason, patients who have had certain malabsorptive surgeries for weight loss, including the gastric bypass, may not only be at risk of dietary calcium deficiencies because of their reduced calorie intakes but also because food no longer passes through the portion of the gut where calcium is most readily absorbed.   Furthermore, many individuals who have had obesity surgery can no longer tolerate dairy foods, causing even greater risk of calcium deficiency.

Individuals who are able to obtain much of their calcium from milk or milk products may have an advantage over those who take supplements alone with regard to weight loss.   As discussed earlier, the agouti mice on the dairy diet (those whose calcium was supplemented by dry milk) were less likely to gain weight and had far greater weight loss with calorie restriction than did those animals who were taking an equal amount of supplemental calcium.  The reason for these differences are unknown but suggest that milk may contain ingredient(s), in addition to calcium, that promote weigh loss.

Conjugated linoleic acid (CLA) is a fatty acid in milk believed to have anti-obesity actions.  A number of studies have found that CLA reduces body fat and prevents obesity in animals. Recent studies suggest that CLA also has anti-obesity effects in humans.   One controlled trial demonstrated a significant decrease in body weight in healthy normal weight men and women taking CLA.  And, in a recent study of middle-aged males, short-term use of CLA caused a preferential loss of abdominal fat.   A reduction in abdominal obesity may have a powerful influence on overall health as this type of obesity carries the highest risk for co-morbid disease, i.e. diabetes, hypertension, heart disease, arthritis, others.

In summary, animal and human studies have found evidence that dietary calcium protects against obesity and reduces body fat.  Milk and other dairy products are an excellent source of dietary calcium and, in addition, contain other substances that promote weight loss. Lactose-free milk and lactose-digesting tablets are available for the individual with lactose intolerance, as are a variety of nondairy foods high in calcium.  Individuals whose calorie intakes are low, i.e. those on diets on who have had gastric restrictive surgery, and those who have had malabsorptive surgery may need calcium supplements not only to prevent bone loss but, as the above studies suggest, to enhance weight loss and prevent weight regain, as well. 

Next month, we will continue to discuss changes that have occurred in the American diet over the last several decades that may be contributing to our nation’s high prevalence of obesity.