Concerns noted on study of soft drinks and metabolic syndrome

A recent observational study reported in the journal Circulation ("Soft Drink Consumption and Risk of Developing Cardiometabolic Risk Factors and the Metabolic Syndrome in Middle-Aged Adults") needs to be considered in the proper scientific context, especially in relation to other previously published research that has reached the opposite conclusion.

The study in Circulation alleges an increased risk of metabolic syndrome (which can lead to an increased risk of heart disease and diabetes) for those who consume diet soda. However, this conclusion does not reflect the extensive scientific literature confirming the safety and benefits of low-calorie sweeteners and the products that contain them. The following outlines significant concerns with the study.

• This study is observational and does not show cause and effect. The study authors note in the paper, "Individuals with greater intake of soft drinks also have a dietary pattern characterized by greater intake of calories and saturated and trans fats, lower consumption of fiber and dairy products and a sedentary life." Experts agree that factors such as caloric imbalance and sedentary lifestyle are related to weight gain, heart disease and metabolic syndrome. Further the researchers note, "Given the observational nature of the present study, we cannot infer that the observed associations are causal. As noted above, it is conceivable that residual confounding by lifestyle/dietary factors not adjusted for may have contributed to the metabolic risks associated with soft drink intake."
• Leading health groups agree that low-calorie sweeteners and the products that contain them can help people manage their weight as part of an overall healthy diet. Even the American Heart Association recommends, "Substitute lower-calorie foods for high-calorie foods. You can subtract calories by making small but effective changes in your daily eating patterns." Further, according to the American Dietetic Association, "Non-nutritive sweeteners added to the diet have been shown to promote modest loss of weight and, within a multi-disciplinary weight-control program, may facilitate long term maintenance or reduction in body weight." No major health group is making a change to its dietary recommendations based on this observational study.
• The authors offer no definitive conclusions – only possible explanations or "theories" – as to why use of diet soft drinks might be related to an increased risk of developing metabolic syndrome.
• The American Heart Association, in its July 23, 2007 press release on the study, states: "Since this is an observational study, it is important to note that the study does not show that soft drinks cause risk factors for heart disease." AHA adds: "Diet soda can be a good option to replace caloric beverages that do not contain important vitamins and minerals. The American Heart Association supports dietary patterns that include low-calorie beverages like water, diet soft drinks, and fat-free or low-fat milk as better choices than full calorie soft drinks."
• Previous research has shown that consuming low-calorie foods and beverages not only aids in facilitating weight loss, but also weight control. Experts agree that achieving and maintaining a healthy weight can help reduce the risk of heart diabetes, diabetes, and other risks associated with obesity.
• Specifically, the observational study published in Circulation is contradicted by these other recent studies (references follow):
• A 2007 study by Bellisle and Drewnowski, published in the European Journal of Clinical Nutrition , evaluated a variety of laboratory, clinical and epidemiological studies regarding low-calorie sweeteners, energy density and satiety. Dr. Adam Drewnowski, Director, Center for Public Health Nutrition at the University of Washington and co-author of the study, noted, "This review of a variety of studies indicates that low-calorie sweeteners and the products that contain them may assist in weight loss efforts."
• Blackburn and his Harvard colleagues investigated whether the addition of aspartame to a multidisciplinary weight control program would improve weight loss and long-term control of body weight in obese women. One hundred sixty-eight obese women aged 20 to 60 years were studied over a two-year period. The researchers found that participation in this multidisciplinary weight control program including the use of aspartame-sweetened foods and beverages not only facilitated weight loss, but long-term maintenance of a reduced body weight.
• Raben and colleagues found that using low-calorie sweeteners aided in the prevention of weight gain. Participants (a total of 41) followed a regular diet supplemented with food and drinks containing either sucrose or low-calorie sweeteners for two and a half months. The researchers found that participants consuming the sucrose sweetened foods and beverages had an increase in caloric energy, while those consuming the low-calorie sweetened foods and beverages showed a statistically significant decrease. Additionally, those in the sucrose group experienced an increase in weight while the low-calorie sweetener group experienced a decrease in weight.
• Ludwig and colleagues enrolled 548 ethnically diverse children (ages 7-11 years) and studied them prospectively for 19 months. They found that diet soft drink consumption was not related to obesity incidence.
• A 2006 study presented at the Pediatric Academic Societies' Meeting found that using sucralose or sucralose-sweetened beverages as well as increasing activity helped maintain and lower body mass index for children participating in the Families on the Move Program.
• A study published in the Journal of Food Science found that people who use reduced-calorie products not only had a better quality diet but also were more likely to consume fewer calories than those who did not use reduced-calorie products.

References:

American Dietetic Association (2004). Position of the American Dietetic Association: Use of Nutritive and Nonnutritive Sweeteners. Journal of the American Dietetic Association . 104(2), 255-275.

Bellisle, F. and Drewnowski, A. (2007). Intense sweeteners, energy intake and the control of body weight. European Journal of Clinical Nutrition . 61, 691-700.

Blackburn, G. L., et al. The effect of aspartame as part of a multidisciplinary weight-control program on short- and long-term control of body weight. American Journal of Clinical Nutrition . 1997. Vol. 65. 409-418.

Ludwig, D. S. et el. Relation between consumption of sugar-sweetened drinks and childhood obesity: a prospective, observational analysis. 2001. Vol. 357. 505-508.

Raben, A., et. al. Sucrose Compared with Artificial Sweeteners: Different Effects on Ad Libitum Food Intake and Body Weight After 10 Weeks of Supplementation in Overweight Subjects. American Journal of Clinical Nutrition . October 2002. Vol. 76. No. 4. 721-729.

Rodearmel, S.J., et al. Effectiveness of Families on the Move! A Family Based Approach for Preventing Excessive Weight Gain in Children. 2006. Pediatric Academic Societies' Annual Meeting.

Sigman-Grant, M., and Hsieh, G. (2005) Reported use of reduced sugars foods and beverages reflect high quality diets. Journal of Food Science . 70(1), S42-S46.