Calcium, Vitamin D, and the Metabolic Syndrome in Middle-Aged and Older Women

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Dietary calcium, vitamin D, and the prevalence of metabolic syndrome in middle-aged and older U.S. women, by S. Liu and colleagues. Diabetes Care 28:2926–2932, 2005.

What is the problem and what is known about it so far?

The metabolic syndrome (a cluster of symptoms that include high blood pressure, large waist size, high levels of fats in the blood, and the body's inability to handle glucose) increases a person's chances of getting cardiovascular disease (disease of the heart and blood vessels) and type 2 diabetes.

Recent studies have shown that dairy can help prevent the metabolic syndrome and type 2 diabetes.

Both calcium and vitamin D are found in dairy products. Calcium helps to prevent becoming overweight, high blood pressure, and heart disease. Vitamin D has been shown to improve the body's ability to use insulin and the function of -cells, which produce insulin; a lack of vitamin D in the body has been shown to lead to higher chances of getting type 2 diabetes. Despite these findings, however, there is not enough evidence to prove that dairy, and calcium and vitamin D in particular, can help prevent the metabolic syndrome.

Why did the researchers do this particular study?

To gather more evidence to see how calcium and vitamin D intake are related to the metabolic syndrome and type 2 diabetes in middle-aged and older women from the U.S.

Who was studied?

The researchers studied 10,066 female health professionals who were at least 45 years old and took part in the Women's Health Study.

How was the study done?

The women in the study were given a survey that asked questions about how often they ate certain foods and how much of those foods they ate. To determine the amount of nutrients each woman got from the foods, the researchers multiplied how often each woman ate the different foods and that food's nutritional content based on the recommended portion size. Dairy products were grouped as low-fat dairy products, including skim or low-fat milk, sherbet, yogurt, and cottage/ricotta cheese; high-fat dairy products, including whole milk, cream, sour cream, ice cream, cream cheese, and other cheese; and total dairy products, including all of the above. The researchers also took into account whether the women were taking calcium or vitamin D supplements, as well as whether they smoked, exercised, drank alcohol, or had a history of heart attack in their family.

The metabolic syndrome was defined from the criteria of the Adult Treatment Panel III of the National Cholesterol Education Program. Women with three or more of the following conditions were said to have the metabolic syndrome: 1) high triglycerides (or fats in the bloodstream), 2) low HDL (“good”) cholesterol, 3) high blood pressure, 4) overweight or obese, and 5) high blood glucose levels.

What did the researchers find?

The researchers found that women who had more calcium in their diets were more likely to not have the metabolic syndrome. These women were also slightly older and thinner and were less likely to smoke, drink alcohol, or have a history of high blood pressure, and they were more likely to exercise and use multivitamins. Calcium was also linked with lower fat and lower cholesterol in these women. These results were similar for vitamin D; however, vitamin D was not related to having lower cholesterol. Overall, the women who had more calcium and vitamin D in their diets had a lower chance of having any one of the five symptoms of the metabolic syndrome. Women with lower amounts of calcium and vitamin D in their diets were more likely to have high glucose levels and diabetes, and lower amounts of vitamin D were shown to affect the body's ability to produce and secrete insulin.

What were the limitations of the study?

There were three main limitations to this study. First, a questionnaire can produce inaccurate results. Second, the design of the study cannot show the long-term effects that calcium has on the symptoms of the metabolic syndrome. Third, the women in this study were mainly white and do not reflect the general U.S. population.

What are the implications of the study?

There is evidence of the positive effects of calcium and vitamin D on preventing the metabolic syndrome and diabetes. However, more studies need to be conducted in order to say for certain that taking more calcium and vitamin D is a good way to prevent diabetes and its complications.

FOR MORE INFORMATION

Is the Metabolic Syndrome Really a Syndrome?

101 Nutrition Tips for People With Diabetes

Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related Complications, by the American Diabetes Association. Diabetes Care 25:202–212, 2002.