In this society of sedentary desk jobs and fast-food drive-through windows, obesity has become an epidemic. It has been reported that in the United States for the years 2003 to 2004, about 17% of children and adolescents were overweight, and about 32% of adults were obese (note that the term overweight, when used for children or adolescents, refers to being at or above the 95th percentile of the sex-specific body mass index [BMI] for age growth charts) (1). For many people already stressed by the demands of a hectic lifestyle, the thought of improving their health through dieting or exercise seems like too much of a burden. People want a quick fix to their health problems, and as such, there has been a rise in the popularity of dietary supplements in recent years. For example, in 1998, Americans spent an estimated $13.9 billion on dietary supplements compared with $8.6 billion in 1994 (2).
Chromium and calcium are two popular mineral supplements that are purported to improve body weight and body composition, but do they really? As greater numbers of people turn to these supplements in an attempt to better their health, we recognize the importance of disclosing the positives and negatives of chromium and calcium (via supplements or milk products) supplementation. This article will explore the latest research on these two minerals to ascertain what effects, if any, they have on body weight and body composition.
Chromium is a required trace mineral best known for its function in potentiating the effects of insulin. The Dietary Reference Intake for chromium was established as an "adequate intake" (AI) at 25 and 35 μg/day for adult women and men, respectively (3). Good food sources of chromium include unrefined grains, meat, and oils.
The use of chromium as a dietary supplement came into vogue in the 1990s. After calcium, it is the second best-selling mineral supplement on the market, and in 1999, 10 million Americans spent a total of $150 million on chromium supplementation (4). The mineral has been purported to improve body composition, glucose tolerance, blood lipid levels, and decrease body fat and body weight, and increase lean body mass. Because picolinate, a natural derivative of the amino acid tryptophan, is believed to enhance the absorption of chromium into the body, chromium supplements are often sold in the form of chromium picolinate; however, other forms, such as chromium nicotinate, also have become popular.
The question is whether chromium supplementation performs as advertised; various studies have arrived at differing answers. Researchers at Georgetown University, for example, investigated the effects 600 μg (200 μg three times/day) of niacin-bound chromium (e.g., chromium nicotinate) on the body composition of 20 overweight African American women and concluded that the supplement caused the subjects to lose significantly more fat although conserving lean body mass (5). The subjects were divided into two groups, one of which received a placebo for 2 months before receiving chromium for an additional 2 months. The other group received chromium first and then the placebo. Although the former group did lose more body fat and retain more lean body mass while taking the chromium supplement versus the placebo, the group that took the chromium supplement first followed by the placebo lost more body fat and retained more lean body mass while on the placebo versus the chromium. All study participants were on diet and exercise programs during the study, with the aim of improving their health. Given that the subjects, as a whole, showed improvements in body weight, fat loss, and lean body mass during the latter part of the study than during the first phase suggests that these improvements could have stemmed from their dietary and exercise programs rather than the chromium supplementation. While it is a positive development to see a study conducted with African American female subjects, often an understudied population, it is difficult to reach widespread conclusions about the effects of chromium supplementation based on the study of only 20 subjects from a specific ethnic group in a specific geographic area.
In a larger study of 158 moderately obese subjects, the addition of a multimineral supplement, including chromium picolinate, significantly accelerated the rate of fat loss although maintaining lean body mass, compared with a placebo (6). Nevertheless, this study also failed to demonstrate any specific effects of chromium picolinate because the supplement contained several other minerals that could have been responsible for the significant difference. Therefore, although the sample size was fairly large, it is difficult to draw solid conclusions from this study regarding the contribution that chromium picolinate made to the results.
Whereas the previously mentioned studies argue that chromium supplementation does yield positive effects, one double-blind study assessed the impact of chromium picolinate supplementation in moderately obese women on body composition and resting metabolic rate. The authors found that the supplementation did not have a significant impact on either measure (7). This study was conducted in 44 women who had BMIs (kg/m2) ranging from 27 to 41, and ranged in age from 27 to 51 years. Participants in this study received either 400 μg/day of chromium picolinate or an identical-looking placebo. This is in contrast to other studies in which the subjects received both a placebo and supplement at differing time points. Doing so can introduce a wide variety of biases because a given subject's health profile can be influenced by other factors over time. Furthermore, the only supplement the subjects received was chromium picolinate, as opposed to other studies that have investigated many different supplements at once. Despite the positive aspects of this study, the experimental design was such that the results cannot be applied to the general population. For example, the sample size was small and exclusively composed of moderately obese white females. Because of its subject pool composition, this study does not answer questions about the effects of chromium supplementation on males, females with lower BMIs, or other populations. Other researchers, however, also reported no effect of chromium supplementation on body weight (8, 9).
Most of the research have shown that chromium supplementation is not effective for weight loss. Nonetheless, because of chromium's role in glucose metabolism, it may be promising for individuals with type 2 diabetes mellitus; however, more research is required in this area.
Calcium is mainly known for its role in bone metabolism. It is a major mineral and is a divalent cation. Its Dietary Reference Intake (established as an AI) ranges from 1,000 to 1,300 mg/day, with a tolerable upper intake level set at 2,500 mg/day (10).
Calcium is the best-selling mineral supplement on the market. Although most consumers purchase calcium supplements for their positive effects on bone mineral density, and hence, mitigation of osteoporosis, others hope that it will improve their body composition. The theory is that low calcium intakes inhibit lipolysis, which is the breaking down of body fat, and instead increases lipogenesis, which is the body's mechanism of storing fat (11). Conversely, high calcium intake has been reported to increase lipolysis and decrease lipogenesis (11).
If the theory is correct, calcium supplementation sounds like a good step toward improving body composition. So far, it seems that higher calcium intakes, typically combined with a lower energy diet, can lead to weight loss. For example, in an observational study, 53 children were followed from 2 to 5 years of age while researchers monitored their diet and body composition (12). At 6 years of age, the researchers assessed the children's body composition by dual-energy X-ray absorptiometry and reported that those children with greater intakes of calcium and dairy products had lower body fat than their counterparts. Note that because this was an observational study, interpretation of these results is limited because of potential confounding by other variables.
This same group of children was followed through 8 years of age. The researchers continued to monitor their overall dietary and calcium intake (typically consumed via milk and other dairy products) (13). They also assessed body composition by dual-energy X-ray absorptiometry at 8 years of age. The researchers concluded that calcium intake was inversely related to percent body fat. Those children who consumed more calcium (via food products, not supplements) had a lower percentage of body fat than their peers who consumed less calcium. The study did have drawbacks, however, in that the sample size was relatively small, with 52 children, and they were all white with similar socioeconomic backgrounds.
More recently, C.S. Berkey et al (14) performed a longitudinal study to examine the relationship between milk, calcium from foods and beverages, dairy fat, and weight change in adolescents. These researchers followed more than 12,000 children in the United States for several years. They reported a direct relationship between milk intake and body weight: the more milk the children consumed, the greater their body weight. Nonetheless, this increase in body weight was caused by increased kcal intake. Although this research was conducted on a large sample of children, it must be noted that the children's milk intake and body weight and height were all self-reported, and thus could decrease the accuracy of the results.
What impact does calcium supplementation have on adults? A 2000 study followed 780 women, who were from 30 to 80 years old, on average, to examine if calcium played a role in weight management (15). Researchers found that a 1,000-mg difference in calcium intake was associated with about an 18-lb difference in body weight (that is, the greater the calcium intake, the lower the body weight). Despite the relatively large sample size, some drawbacks to this study were that it was a retrospective study and the subject pool was only composed of females. Furthermore, a number of more recent studies have not shown such dramatic differences in body weight. Although this provided a good starting point for more research, randomized clinical trials, where the specific aim was to assess calcium's impact on body weight, should be more heavily weighted.
Another group of researchers conducted a study with adult subjects to investigate if calcium supplementation (via supplements or milk) coupled with a reduced-energy (kcal) diet leads to greater weight loss than diet alone (16). The researchers randomly assigned 32 obese adults to one of three diets and followed their progress for 24 weeks (16). The first diet contained 400 to 500 mg of daily dietary calcium (this was the average dietary intake of calcium, so this was the control group). The second was a standard diet (average intake of 400 to 500 mg/day) supplemented with 800 mg/day of calcium as calcium carbonate. The third was a high-dairy diet consisting of 1,200 to 1,300 mg of daily dietary calcium. In addition, all three groups were required to decrease their energy intake 500 kcal/day. Although all three groups lost body weight and reduced their body fat percentages during the study, the results showed that calcium intake had a significantly greater impact on the extent of these changes. For example, subjects in the control group lost an average of 6.4% of their body weight compared with 8.6% and 10.9% for the calcium-supplemented group and dairy-supplemented group, respectively. Another interesting aspect of the results is the influence that calcium intake had on the loss of truncal fat. For the control group, 19% of their total fat loss came from their trunk region. This fraction increased to 50% and 66% for subjects on the calcium supplements and dairy-supplemented diet, respectively. The results of this study suggest that calcium intake combined with a lower kcal intake is important to loss of body weight and body fat, particularly truncal fat. The truncal fat reduction is important because it has been well established that individuals who have android obesity (increased fat deposition in the trunk/waist region) have a greater risk of heart disease and diabetes mellitus.
Despite the fact that some researchers have reported that low-fat dairy has the best impact on weight loss, a 2003 study suggests that the calcium's source is not as important as the quantity of total calcium intake. In a cross-sectional study of 35 men and women, E.L. Melanson et al (17) assessed total calcium intake and intake of calcium from dairy sources on whole-body fat utilization during a 24-hour period. Researchers determined that total calcium intake was a stronger predictor of fat oxidation than the amount of calcium from dairy sources. They also reported that acute calcium intake (the amount of calcium consumed during the 24-hour test period) was correlated to fat oxidation, but habitual calcium intake was not (the amount of calcium consumed in the 4 days before the test). This was especially true during sleep and exercise, where acute calcium intake had a dramatic effect, whereas habitual calcium intake made virtually no difference. Although the researchers acknowledged that lack of effect of habitual calcium intake could simply stem from participants not accurately reporting intake, they suggest that it also is possible that calcium's positive effects work quickly and only for a short time.
E.L. Melanson et al (18) reported similar results in a 2005 publication, where they compared the effects of 24-hour fat oxidation from a low-dairy diet with that of a high-dairy diet. They found that fat oxidation was greater on a high-dairy diet compared with a low-dairy diet during an energy deficit; nonetheless, there was no effect of calcium or dairy intake on macronutrient oxidation during conditions of energy balance.
In a crossover design, N. Boon et al (19) assessed if energy metabolism and adipose tissue enzyme messenger RNA could be changed by dietary calcium intake in healthy nonobese men, who were consuming an isoenergetic diet. In a randomized, crossover design, the men received a high-calcium, high-dairy diet (1,259 mg of calcium), a high-calcium, low-dairy diet (1,259 mg of calcium), and a low-calcium, low-dairy diet (349 mg of calcium). The men were on each diet for 7 days. Despite changes in serum vitamin D concentrations, they did not find significant differences in substrate or energy metabolism among any of the 7-day dietary regimens. Although this was a well-controlled study, it was short-term and was not conducted in individuals who were overweight or obese, which could possibly have resulted in differences in substrate and energy metabolism.
A 2006 meta-analysis by R. Trowman, Ph.D., et al (20) also reported no effects of calcium on weight loss. The objective of their meta-analysis was to examine if there were any relationships between calcium and weight loss by reviewing and conducting a meta-analysis of randomized controlled trials of calcium supplementation in humans who were 18 years or older, and where body weight was the final outcome measure. Based on their criteria, 13 randomized controlled trials were incorporated in the meta-analysis. Dr. Trowman et al (20) reported no relationship between increased intake of calcium, either via supplements or dairy products, and weight loss. In their review of the literature on calcium and weight loss, G. Barba, Ph.D., and P. Russo, Ph.D., (21) stated that available data do not definitively support a relationship between high calcium and/or dairy intake and decreased body weight; however, they indicated the need for more research on the impact dairy foods have on health outside of obesity.
So, based on this short review, what do we conclude about chromium and calcium supplementation and weight loss? Based on most studies conducted on chromium supplementation and weight loss, it seems that chromium is not an effective agent in decreasing body weight in either normal weight or overweight individuals. The good news is that more research is being conducted on chromium supplementation and the impact it may have on individuals with type 2 diabetes mellitus. This has to do with the fact that chromium is required for the protein chromodulin to be active, which in turn, helps to potentiate the effects of insulin. One of the major roles of insulin is to promote glucose uptake into the cells. Thus, those with type 2 diabetes mellitus, who produce insulin but have trouble getting the glucose into their cells, may benefit from supplementation. Keep your eyes open to see what the research being conducted now will find.
Despite the existence of research that has shown positive effects of increased calcium intake on weight loss in obese or overweight individuals, a number of randomized controlled studies have not. There is no magical formula here; however, there may be individuals who respond better to calcium's effects on fat metabolism during decreased energy intake compared with others. A well-controlled study assessing responders versus nonresponders would be a first step in evaluating if calcium impacts body weight in some individuals more than others.
It also is important to emphasize that a person's source of calcium impacts his or her body composition and weight. One cannot consume gallons of ice cream or nonfat milk, for that matter, and expect to lose body weight. In fact, many of the studies showing calcium's effects on weight loss also included an element of reduced energy intake. Consuming three 8-ounce glasses of skim milk per day (300 mg of calcium per glass) or three containers of yogurt per day (400 mg of calcium per container) would contribute roughly 900 to 1,200 mg of calcium to one's diet. For individuals who are lactose intolerant or experience allergic reactions to dairy products, calcium citrate, coupled with vitamin D, is the best-absorbed calcium supplement. Taking 500 mg of calcium in the morning and then another 500 mg of calcium in the evening yields the best absorption (with about 200 International Units of vitamin D with each supplement). In addition, there are many other sources of calcium, such as calcium-fortified soy milk, calcium-fortified orange juice, almonds, and dark leafy green vegetables, to name a few.
Overweight or obese individuals who are interested in bettering their health should couple an increased calcium intake with an overall healthier lifestyle. Nonetheless, the recommendation to increase calcium intake should not be made until a person's dietary assessment has been made because if he or she is already consuming the AI or above for calcium, then increased levels would not be warranted. Even if a person does increase his or her calcium intake and does not lose more body weight, the increase will still be beneficial to bone health. Regardless of whether an individual increases his or her calcium intake, those who wish to lose weight may want to make the following modifications to their lifestyle:
* Increase intake of fruits and vegetables. The Dietary Approaches to Stop Hypertension (DASH) study reported that eating low-fat dairy plus fruits and vegetables can result in decreased hypertension (22). The U.S. Centers for Disease Control and Prevention recommends that adults consume a minimum of five fruits and vegetables daily (23).Rather than simply adding fruits and vegetables to a diet, which would increase energy (kcal) intake, a better strategy is to use them as substitutes for less nutritious foods. Fruits and vegetables are rich in fiber, vitamins, minerals, and phytochemicals. Moreover, they are filling and yet low in energy, that is, they are known as "high-nutrient-dense, low-energy-dense foods." People can feel good about eating them; they taste great and provide a number of health benefits.
* Establish a pattern of regular physical activity. To lose weight, one needs to expend more energy than he or she consumes. This equation can be manipulated through energy intake, physical activity, or both. The U.S. Centers for Disease Control and Prevention recommends that adults participate in a minimum of 30 minutes of moderate-intensity exercise five times per week, or vigorous-intensity exercise three times a week for 20 minutes at a time (24). Nonetheless, exercising on most days of the week is best because individuals tend to be more consistent if they do so. It is important to remember that exercise does not mean having to run on a treadmill at the local health club. People should select the forms of exercise that they enjoy. Popular choices include hiking, basketball, cross-country skiing, or in-line skating. There also are numerous ways in which to stay active during day-to-day activities, such as taking the stairs instead of the elevator or intentionally parking the car away from the building so the walk is farther. In addition, individuals can change their sedentary behaviors to more active behaviors. For example, individuals can be more physically active during television commercials, by taking quick exercise breaks while at work (especially if an individual sits behind a desk most of the day) and by being a little "inefficient" when it comes to performing chores at home (e.g., take the laundry to the washing machine in two trips rather than one trip).
Consuming the recommended level of calcium intake is a positive step that individuals can make to better their health. Consuming plenty of fruits and vegetables that replace high-energy-dense, low-nutrient-dense foods, and leading an active lifestyle also are facets that can help people lose weight and lead healthier lives. So, there is definitely not a magic bullet with chromium and calcium supplementation and weight loss; however, if a person were to increase his or her calcium intake, the benefits would still outweigh the risks, even if greater weight loss is not achieved.
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