Study unravels health impact, interplay of diet soft drinks and overall diet

Are diet sodas good or bad for you? The jury is still out, but a new study sheds light on the impact that zero-calorie beverages may have on health, especially in the context of a person’s overall dietary habits.

For the average person, the scientific evidence can seem confusing. A number of studies have implicated diet beverage consumption as a cause of cardiovascular disease. However, others have suggested such drinks may be a viable tactic for people who are trying to lose or control their weight.

Either way, most previous research has tended to focus either on people’s drinking patterns and preferences, or their overall dietary habits – in other words, most studies have failed to tease apart how those two aspects interact to affect people’s health.

To address this problem, a new study from the University of North Carolina at Chapel Hill examined not only people’s beverage consumption patterns but also the diets of those who consume diet and sugar-sweetened beverages. The findings appear in the April issue of the American Journal of Clinical Nutrition.

Kiyah Duffey, Ph.D., study author and research assistant professor of nutrition at the UNC Gillings School of Global Public Health, said that similar to previous studies, the new analysis found that people who consumed diet beverages tended to be less healthy than people who did not consume them.

The Centers for Disease Control and Prevention (CDC) reports that heart disease is the No. 1 cause of death in the United States in both men and women; in 2008, at least 25 percent of adults in most states were obese. In a society of plentiful food and obesity on the rise, the fight on heart disease flourishes. The prudent diet is necessary to dampen this artery-clogging disease.

MedlinePlus reports heart disease includes coronary artery disease, which may occur from the accumulation of a fatty substance in the artery wall, causing a blockage. All individuals with a diagnosis of heart disease or who have a family history of heart disease should follow a prudent diet. The diet is low in total fat, saturated fat, trans fat, cholesterol and sodium. These dietary modifications assist in lowering cholesterol and triglyceride blood levels and blood pressure.

The U.S. Food and Drug Administration reports that a food item is considered low-fat when there is it contains 3 g or less of total fat per serving. A meal is low-fat when there are 3 g or less total fat per 100 g serving and 30 percent or less fewer calories are from fat. Low saturated fat guidelines allow for 1 g or less per serving and no more than 15 percent of calories. Low cholesterol signifies 20 mg or less cholesterol and 2 g or less saturated fat per serving. Low sodium is recognized as 140 mg or less per serving.

Food Items
Plain fruits, vegetables, legumes and whole intact grains, including oats, couscous, barley and quinoa, are generally low in fat, cholesterol and sodium. All animal products contain saturated fat and cholesterol. Animal products include red meat, poultry, pork, fish, eggs and dairy. Choose the lower fat and cholesterol options. Cheese is high in sodium. Prepackaged foods tend to be higher in trans fats and sodium. Read food labels carefully, and remember variety and moderation of foods.

Sodium reduction as been shown to lower blood pressure and the risk for heart disease. According to a study in the May 2009 issue of the “American Journal of Clinical Nutrition,” reducing saturated fat and replacing it with polyunsaturated fats found in some vegetable oils, fatty fish, nuts and seeds prevents coronary heart disease in middle aged and older adults. Soluble fiber in fruits, vegetables, legumes, oats and barley decrease cholesterol in the blood.

“However, there was an important interplay between overall diet and what people drink,” Duffey said. “It is important that people consider the entirety of their diet before they consider switching to or adding diet beverages, because without doing so they may not realize the health benefits they were hoping to see.”

Researchers studied data collected over 20 years from more than 4,000 young adults who participated in the Coronary Artery Risk Development in Young Adults (CARDIA) study.

In terms of eating habits, participants fell into two groups: people who ate what researchers dubbed a “prudent” diet (one with more fruit, fish, whole grains, nuts and milk) and individuals who consumed a “western” diet (which had higher amounts of fast food, meat and poultry, pizza and snacks).

People who were healthiest tended to be those who ate a prudent diet and did not consume diet beverages. They had a lower risk of high waist circumference, high triglyceride levels and metabolic syndrome (22 percent, 28 percent and 36 percent lower, respectively, than people who ate a western diet and did not drink diet beverages). But the second healthiest group was individuals with a prudent diet who also consumed diet beverages.

In contrast, individuals who consumed the western diet had increased risk of heart disease, regardless of whether or not they drank diet beverages.

The UNC researchers found that many dietary factors contributed to a person’s overall health. Without taking diet beverage consumption into account, people who ate the prudent diet had significantly better cholesterol and triglyceride profiles and significantly lower risks of hypertension and metabolic syndrome than those who ate the western diet.

Duffey added: “Our study confirms the recommendations of the American Diabetes Association and many weight-loss programs, which suggest people drink these beverages as a way to cut calories and lose or control weight, but only in the context of the whole diet.”

The new study is titled “Dietary patterns matter: diet beverages and cardiometabolic risks in the longitudinal Coronary Artery Risk Development in Young Adults (CARDIA) Study.”

Other authors were Barry M. Popkin, Ph.D., W. R. Kenan Jr. Distinguished Professor of Nutrition at UNC and a member of the Carolina Population Center; Linda Van Horn, Ph.D., professor of preventive medicine at the Northwestern University Feinberg School of Medicine; and David R. Jacobs Jr., Ph.D., Mayo Professor of Public Health at the University of Minnesota’s School of Public Health.


Gillings School of Global Public Health contact: Chris Perry, (919) 966-4555, .(JavaScript must be enabled to view this email address)
News Services contact: Patric Lane, (919) 962-8596, .(JavaScript must be enabled to view this email address)


The University of North Carolina at Chapel Hill

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