The research is more and more clear that sugar-sweetened beverages (SSBs) cause health problems. When researchers look at this issue they don't include just soft drinks, such as sodas or colas, but they also look at sweetened fruit drinks like punch (not those that are 100 percent juice) as well as energy and vitamin water drinks.
In a recent analysis researchers looked at the health issues caused by SSBs. Their meta-analysis combined the results and data of several studies to yield results for evaluation as if they were all one study. The strength of this method lies in the fact of its aggregate size: The larger and longer a study is, the more reliable are its results. The drawback is that this is a grouping of studies, all performed by different people with different standards and methods.
This particular analysis, reported in Diabetes Care, grouped together 11 prospective studies that included over 310,000 people. The researchers looking at SSBs standardized the serving size of the sugar-sweetened beverage consumption measured in each of the 11 studies. They then standardized the various levels of intake into groups: from none or less than one serving per month up to more than one serving per day. The amount of soft drinks drunk by individuals who developed Type 2 diabetes or metabolic syndrome was then compared to the amount drunk by those who did not develop these conditions. (Metabolic syndrome is defined by those with a grouping of conditions: high blood pressure, central obesity, high blood sugars and cholesterol abnormalities.)
The scientists found that even when they took into account variables such as Body Mass Index or individual caloric intake, those who drank at least one 12-ounce serving of a sugar-sweetened beverage per day were 20 percent more likely to develop metabolic syndrome and 26 percent more likely to develop Type 2 diabetes than those who drank less than one serving per month.
In their report, the researchers note that these results can't be attributed only to soda-drinking people being overweight because of the extra calories they are consuming. Indeed, the sugars (mostly high fructose corn syrup) used in these drinks are thought to contribute to the risk of metabolic syndrome and Type 2 diabetes because they promote fat deposits around the internal organs (contributing to poor cholesterol scores) and contribute to a higher sugar load, which leads to insulin resistance -- one of the symptoms of metabolic syndrome.
Another recent study focusing on the effects of consuming fructose alone (not High Fructose Corn Syrup) versus glucose, was published in The Journal of Clinical Investigation. A multi-university team of researchers recruited 32 men and women between the ages of 40 and 72 to participate in a feeding study. The participants all had a Body Mass Index between 25 and 35 (clinically overweight to clinically obese), and had no history of surgery for weight loss, diabetes, high blood pressure or high triglycerides. Those who already drank one or more sugar-sweetened beverage per day were also excluded from the study.
To set a baseline to compare against, the participants spent two weeks eating nothing but the foods provided to them by the researchers. Each person's diet was specifically designed to maintain their current weight and to provide 15 percent of calories from protein, 30 percent from fat and 55 percent from carbohydrates. During this baseline period the subjects gave blood for cholesterol and other tests, received a glucose tolerance test, and had their abdomens scanned to ascertain how much body fat was deposited around their internal organs versus beneath the skin.
Then for the following eight weeks the participants were randomly assigned to one of two groups: a fructose group and a glucose group. While both groups were given three daily servings of a sweetened beverage to drink with their three daily meals, one group's drink was sweetened with fructose while the other was sweetened with glucose. For those eight weeks the subjects were instructed to follow their usual diets and to avoid drinking other sugar-sweetened beverages or any fruit juices. At the end of the eight weeks the participants again had their cholesterol checked along with a glucose tolerance test and an abdominal scan.
The researchers found that both groups gained weight over the course of the eight weeks: between three and five pounds. However, those who were assigned to the fructose group were at much greater risk of diabetes because the amount of fat around their internal organs increased markedly while they decreased their sensitivity to insulin. Those in the glucose group, on the other hand, deposited most of their fat beneath the skin. Further, both groups' HDL levels (the good cholesterol) stayed the same while the LDL cholesterol (the bad cholesterol) increased significantly for those drinking the fructose-sweetened beverages.
This is a small study, but significant in that it specifically compares glucose with fructose. The results are extremely concerning, but few commercial beverages are sweetened only with fructose; most are sweetened with sucrose, which is half glucose and half fructose. High Fructose Corn Syrup is between 45-58 percent glucose and 42-55 percent fructose. Will HFCS affect your visceral fat, cholesterol levels and insulin sensitivity the same way fructose does? We can't yet be sure, but there is at least one well designed animal study that says yes.
What we can be sure of is that sugar-sweetened beverages add a lot of calories to your diet that aren't very satisfying. Drink water, tea or coffee instead. We know for sure that they're good for you.
Follow Tim Harlan, M.D. on Twitter: www.twitter.com/DrGourmet