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Drinking at least one sugar-sweetened soft drink or fruit punch daily nearly doubles the risk of diabetes, according to the first large study to examine the suggested link.
Women who drank fewer than one of the beverages a month had half the risk of developing diabetes than those who drank one a day, according to the study of 91,000 nurses. The results are published in today's issue of The Journal of the American Medical Association.
Women who increased the amount of sugar-sweetened drinks they consumed from one or less a week to one or more daily also were most likely to gain weight, picking up 17 pounds in eight years. The study provides more grist for a long-standing debate among nutritionists, government panels and the food and beverage industry about whether added sugars contribute to obesity and chronic diet-related diseases.
The American Beverage Association, formerly the National Soft Drink Association, criticized the study's focus on a single food as a cause of diabetes, saying many factors contribute to the disease.
"Soft drinks are a good subject to attack right now," said Richard Adamson, the beverage group's vice president for scientific and technical affairs.
The research published today is part of a long-running Harvard University-based study of diet, health and disease in 300,000 people. The research has produced influential findings on the dangers of trans-fatty acids and on the links between obesity and chronic disease and between consumption of red meat and colon cancer. 'Directly contributing'
The latest study adjusted for potential risk factors for diabetes, such as physical activity, family history and body mass index, a measure of whether someone is overweight.
During the research period, there were 741 new cases of diabetes among the nurses, who ranged in age from the 20s to the 40s.
An editorial accompanying the study endorsed its conclusions.
The study "provides strong, scientifically sound evidence that excess calories from soft drinks are directly contributing to the epidemics of obesity and type 2 diabetes, at least in the United States, and should help convince the U.S. government that further changes in health policy are needed," wrote Dr. Caroline M. Apovian, a physician and director of the Nutrition and Weight Management Center at Boston Medical Center.
The National Institutes of Health funded the study, which was conducted by researchers with the Harvard School of Public Health, Brigham and Women's Hospital and Boston Children's Hospital. 'Scientifically unsound'
Lobbyists for beverage manufacturers assailed the study's conclusions. A spokeswoman for Coca-Cola referred questions to the American Beverage Association.
"The conclusions are scientifically unsound," said Adamson. "It's a totally unhealthy lifestyle that increased the risk. These women smoked more, they ate more, they had less protein intake, they had less cereal fiber intake, they exercised less. Give me a break, no wonder they had increased risk of type 2 diabetes."
The American Diabetes Association does not single out any food or beverage as causing the disease, said Dr. Nathaniel Clark, a physician who is the group's national vice president for clinical affairs. He said he believes extra pounds, rather than high sugar consumption, triggered diabetes in the women, but added, "It is true [researchers] could not account for the increase in diabetes solely on weight gain."
The extra pounds accounted for only half the increased risk of diabetes, said Dr. JoAnn E. Manson, chief of preventive medicine at Brigham and Women's Hospital and one of the study's authors.
Researchers theorized that the risk of diabetes may increase because the sugars in sweetened drinks are rapidly absorbed in the body, raising blood sugar levels quickly and eventually leading to insulin resistance. U.S. market shifts
Consumers already have started to move away from sweetened soft drinks and toward diet sodas and bottled water. The sales volume of Coke Classic shrank 3 percent last year, according to Beverage Digest, and Pepsi-Cola was down 4.5 percent.
The American Academy of Pediatrics recommended this year that schools eliminate sales of sweetened drinks. Some school districts have moved to restrict sales in recent years.
The study's authors called for public health strategies that would decrease consumption of sugar-sweetened beverages. Manson said that in the last 20 years, soft drink consumption has increased more than 60 percent in adults and has more than doubled in children.
"These trends do parallel the increased epidemic of obesity and type 2 diabetes, in both children and adults," she said. "There is an association."
The study also looked for a link between diet soda and diabetes, because of the caramel coloring that is in both diet and sugar-sweetened beverages. It found a "slight, nonsignificant" increased risk.
The study did not find a link between fruit juice and diabetes. Researchers said that could be because the naturally occurring sugars in fruit juice affect the body differently than the added sugars in sweetened drinks, or because the nutrients, fiber and plant chemicals in fruit juices may counteract the effects of sugar. Low-sugar unpopular
Sweetened soft drinks are the largest single food source of calories for Americans, contributing 7 percent of total calories consumed, according to the accompanying editorial in the medical journal.
To meet federal nutritional guidelines, the U.S. Department of Agriculture says Americans would need to cut in half their consumption of added sugars, found in products like sweetened drinks and many processed foods.
Both Coke and Pepsi have introduced lower-sugar colas this year but consumer response to C2 and Pepsi Edge has been modest, analysts say.
The medical journal's editorial calls for the government to redefine guidelines for sugar consumption, especially in soft drinks, and to support efforts to remove soda machines from schools or replace the products with healthier options.
An independent scientific panel studying federal nutrition guidelines disagreed this summer on the role of sugar on weight gain or body mass index, but concluded that individuals who consumed foods or beverages high in added sugar took in more calories than those who consumed low amounts of added sugar. They also noted that it's more difficult to regulate calories in sugar-sweetened drinks than in solid food.
--- Staff writer Scott Leith contributed to this article.
Copyright 2004 The Atlanta Journal-Constitution