Ever quench your thirst with vitamin water then pat yourself on the back for your healthful drink choices? You can stop congratulating yourself, because your “healthful” vitamin drink may be starting you on the road to type-2 diabetes. Findings released in the November 1 issue of the journal Diabetes Care suggest that there’s a strong link between drinking even one to two sugar-sweetened beverages per day – including soda, vitamin water, energy drinks, iced tea, and fruit drinks – and type-2 diabetes. People who drank one sugary beverage per day were 25 percent more likely to develop type-2 diabetes, and 20 percent more likely to develop metabolic syndrome – a precursor to diabetes – than were to people who drank one or fewer beverages per month.
The research team, led by Vasanti Malik, a research fellow in the Harvard School of Public Health Department of Nutrition, performed a “study of studies,” called a meta-analysis. They probed the available literature and found eleven studies that were adequately designed and contained enough data for analysis. Of the 11 studies, eight focused on a possible link between sugar-sweetened beverages and type 2 diabetes, and three focused on to metabolic syndrome.
All told, the studies included data from 310,819 patients. In most of the studies, dietary intake was assessed through questionnaires. The strongest link was found in the largest diabetes study, which followed more than 91,000 American women ages 24 to 44 for eight years. Even after researchers adjusted for weight gain, the link between diabetes and sugary drinks persisted.
Diabetes and Consumption of Sugary Drinks: Growing in Tandem
Diabetes is a chronic disease that develops when problems occur with the body’s ability to use and/or produce insulin.Type-2 diabetes, the most common form of the disease, usually develops gradually, partly as a result of cells’ gradual decrease in the ability to use insulin, called insulin resistance. Metabolic syndrome, sometimes called “pre-diabetes,” is a group of indicators, such as slightly-above normal blood glucose levels, that serve as warning signs of impending diabetes. There is no cure for diabetes, although the disease can be managed. But people with diabetes are likely to develop a host of other health problems, including heart and blood vessel disease, kidney failure, slow wound healing (which can lead to amputations), loss of vision, and more.
Diabetes is reaching epidemic proportions around the world. According to the International Diabetes Federation, 285 million adults, or 6.6 percent of the world’s 4.3 billion people, are living with diabetes. By the year 2030, that figure is expected to reach 438 million, with a prevalence rate of 7.8 percent. The United States currently has one of the highest rates of diabetes, with about one in 10 people living with diabetes. By the year 2050, that ratio will grow to 1 in 3, according to recent projections from the Centers for Disease Control (CDC).
As diabetes prevalence has expanded, so has the consumption of sugar-sweetened beverages. Drinks that fall under this classification contain caloric sweeteners such as sucrose, high-fructose corn syrup, or fruit juice concentrates. Beverages that are 100 percent fruit juice are not considered sugar-sweetened beverages, nor are drinks that contain nonnutritive sweeteners such as Aspartame, saccharin, or Splenda.
Consumption of sugar-sweetened beverages in the United States more than doubled between the late 1970s and 2006, reaching an average of 141.7 calories – the equivalent of one soda – per day. That average includes many people who avoid sugar-sweetened beverages entirely, and many people who consume as many as six to eight sodas per day. Teens are commonly on the high end of the scale: The average teenage boy consumes about 32 ounces of soda per day, equivalent to 26 teaspoons of sugar. Sugar-sweetened beverages are the primary source of added sugars in the American diet. In Mexico, more than 12 percent of daily calories come from added sugars, mostly beverages; likewise, consumption is rapidly increasing in countries such as India and China, where Coca-Cola reported growth of 14 and 17 percent, respectively, in 2007.
More than Weight
Many studies have shown that people who regularly drink sodas and other sugar-sweetened beverages are more likely to gain weight and to be overweight or obese. In turn, people who are overweight or obese are more likely to develop type 2 diabetes. But Malik’s team found the increased risk of diabetes was present whether or not people were overweight.
Their findings confirm a growing body of research that suggests that weight gain is not the only reason sugar-sweetened beverages increase the risk of diabetes. One factor may be the manner in which they are consumed. A single can of soda contains the equivalent of 15 teaspoons of sugar, and it can be consumed in a matter of minutes. The quick overload of sugar causes blood glucose to rise quickly, and the pancreas responds by producing insulin. This pattern of a quick spike in blood glucose, followed by the pancreas going into overdrive, can lead to insulin resistance, high blood pressure, and inflammation—three markers of metabolic syndrome. In addition, high-fructose corn syrup, the most common beverage sweetener, has been linked to high blood pressure.
More Research Needed
Malik’s team called for additional studies to probe the link between sugar-sweetened beverages and diabetes and noted that their study had several limitations of the study. People who drink more sugar-sweetened beverages may also be more likely to consume an overall less-healthful diet with too many trans-fats and not enough fiber. Nor were the results stratified to discern whether there was a difference between people who drink six to eight Cokes in each day and one-a-day users. The risk could be significantly higher for these extremely high consumers. Finally, since the original studies didn’t set out to answer the same question, the researchers cautioned that their findings should be interpreted with care.
Limitations aside, this study adds to a growing body of evidence that excessive consumption of sugar-sweetened beverages contributes to both obesity and diabetes.