Insulin resistance syndrome (IRS) refers to a combination of conditions: obesity, glucose intolerance, high blood pressure, and dyslipidemia (low blood levels of HDL cholesterol and high blood triglyceride levels). IRS increases your risk of developing type 2 diabetes and heart disease. Diet, physical activity, and smoking are all believed to play roles in the development of IRS. Now, research recently published in the
Journal of the American Medical Association
suggests that overweight people may be able to reduce their risk of IRS by consuming dairy products.
This study was part of the Coronary Artery Risk Development in Young Adults (CARDIA) Study—an ongoing study of risk factors for heart disease among both white and black young adults. The study began in 1985 when the participants were between the ages of 18 and 30. At the start of the study, participants underwent a physical exam and were interviewed about their dietary and lifestyle habits. Physical exams were repeated in 1987, 1990, 1992, and 1995 and the dietary interview was repeated in 1992.
The dietary interview was conducted using a standard dietary history questionnaire that asks participants to recall what they ate and drank over the previous 28 days. Although intake of all food and nutrients was assessed, for this analysis the researchers were particularly interested in dairy products, including:
- Ice cream
- Other dairy-based desserts
Researchers divided participants into two groups based on their body mass index (BMI):
- Normal weight – BMI of less than 25
- Overweight – BMI of 25 or higher
In 1995 after 10 years of follow-up, the researchers compared the dairy consumption of people who developed IRS with those who did not. IRS was defined as having at least two of the four conditions that comprise IRS: obesity, glucose intolerance, high blood pressure, and dyslipidemia.
Among overweight people only, those with the highest dairy consumption (5 or more times per day) were 72% less likely to develop IRS than those with the lowest dairy consumption. Each daily occasion of dairy consumption reduced the odds of developing IRS by 21%. Of note, consumption of both reduced-fat and full-fat dairy products seemed to reduce IRS risk.
In calculating these statistics, the researchers accounted for other factors that might affect the risk of IRS, including physical activity, BMI, smoking, alcohol intake, vitamin supplement intake, and consumption of fruits, vegetables, whole grains, refined grains, meat, fish, and sugared soft drinks. In doing so, they found that fiber also seemed to provide some protection against IRS. People with the highest dairy and fiber consumption combined were 7 times less likely to develop IRS than their counterparts with the lowest consumption of dairy and fiber.
Of note is that these statistics applied only to overweight participants.
Although these results are interesting, there are limitations to this study. As with any study that relies on participants to recall their eating and lifestyle habits, the accuracy of the participants’ recall is unknown. Serving sizes were not clearly defined, so it’s hard to know how much of any given dairy product was actually consumed. In addition, it’s possible that other factors not accounted for in this study—such as genetic and environmental factors—influenced the development of IRS.
These findings provide one more reason to eat and drink dairy products. This study suggests that milk, yogurt and cheese may help overweight people prevent the development of IRS, which in turn reduces their risk of type 2 diabetes and heart disease.
Why is it that consumption of dairy products didn’t produce the same effects on the normal weight people in this study? We don’t know. But it might be that by virtue of their weight, the normal weight people were already at lower risk of IRS, type 2 diabetes, and heart disease. But that doesn’t mean normal weight people have nothing to gain from a diet rich in dairy products. Because they are rich sources of calcium and vitamin D, dairy products are important for strengthening bones and teeth and warding off osteoporosis.
Bottom line? If you are overweight, increasing your intake of low-fat dairy products may help lower your risk of IRS, diabetes, and heart disease. But so will decreasing your overall caloric intake, starting an exercise program, lowering your blood pressure, and quitting smoking. These behaviors work together to promote good heart health.
Pereira MA, et al. Dairy consumption, obesity, and the insulin resistance syndrome in young adults. The CARDIA Study.
Journal of the American Medical Association
. April 25, 2002;287(16):2081-2089.
Last reviewed Apr 25, 2002
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