Consumption of noncaloric, artificially sweetened beverages (ASBs) is associated with an increased risk for disease variety of chronic diseases, according to an opinion article by Susan E. Swithers, PhD, a professor of behavioral neuroscience at Purdue University in West Lafayette, Indiana, published online July 10 in Trends in Endocrinology & Metabolism.
"[F]requent consumers of these sugar substitutes may...be at increased risk of excessive weight gain, metabolic syndrome, type 2 diabetes, and cardiovascular disease," Dr. Swithers writes.
"This somewhat counterintuitive result may reflect negative consequences of interfering with learned relationships between sweet tastes and typical post-ingestive outcomes, which may result in impaired ability to compensate for energy provided when caloric sweeteners are consumed," Dr. Swithers writes.
The prospective studies Dr. Swithers reviewed found an elevated risk for weight gain and obesity, metabolic syndrome, type 2 diabetes, coronary heart disease, and hypertension in those who consumed ASBs. No decreased risk for weight gain or increased body fat percentage was associated with ASB intake.
It was often difficult to compare the magnitude of increased risk with that of participants who consumed sugar-sweetened beverages (SSBs), in part because of differences in intake.
Participants who regularly consumed ASBs tended to have higher baseline body mass indexes compared with participants who did not, but some models that adjusted for that difference still found an increased risk. Studies that separately assessed risk among those who were not overweight or obese at baseline found that the risks of becoming overweight or obese, developing type 2 diabetes, and experiencing vascular events were increased even when considering baseline body mass indexes.
Hormones, Brain Response Altered
Dr. Swithers reviewed 2 interventional studies. The first found that children of normal weight who consume ASBs may have decreased weight gain compared with those who consume SSBs. The study did not compare children who consume ASBs with those who consume unsweetened beverages. In the second study, overweight and obese adults who substituted water or ASBs for SSBs had no greater weight loss at 6 months than an attentional control group. ASB intake was not associated with improved fasting glucose, but water intake was.
Brain responses are altered in those who consume artificial sweeteners compared with those who consume caloric sweeteners. In imaging studies of the human brain, sucrose activates dopaminergic midbrain areas involved with reward, but sucralose does not. Sucralose also reduces activation in other pathways related to taste when compared with sucrose.
In addition, studies in humans have found that the release of hormones and markers of postprandial glucose homeostasis typically seen does not occur after ingestion of artificial sweeteners.
Studies that combined artificial sweeteners in various ways with nutrients found that "artificial sweeteners may not augment nutrient-dependent release of insulin or the incretins in the same way that caloric sugars do," Dr. Swithers writes.
"[C]urrent findings suggest that caution about the overall sweetening of the diet is warranted, regardless of whether the sweetener provides energy directly or not," Dr. Swithers concludes.
Frank Hu, MD, PhD, a professor of nutrition and epidemiology and codirector of the program in obesity epidemiology and prevention at Harvard School of Public Health in Boston, Massachusetts, commented on the article in an email interview with Medscape Medical News.
"Overall, I think the jury is still out regarding whether drinking diet sodas instead of SSBs is truly related to obesity and [cardiovascular disease] outcomes, in part because of the complex methodological problems in studying the effects of diet sodas in epidemiological studies. Small, short-term, [randomized controlled trials] do show that drinking diet sodas instead of SSBs reduces weight gain or induces more weight loss in controlled settings," Dr. Hu said.
"Because [the] intense sweetness of ASBs may condition people towards greater preference for sweets and may enhance appetite, and because of the possibility that some consumers of diet soda may use this as a rationale for consuming other higher-calorie foods, caution is needed for recommending regular consumption of ASBs," Dr. Hu explained.
"In [the] short-term, ASBs is preferable to the use of SSBs. For those who want to kick the habit of drinking sugary soda, diet soda may be the beverage equivalent of a nicotine patch: it can be used in small amounts, for a short time. For most people, plain water and unsweetened coffee or tea are more healthy alternatives to either SSBs or ASBs," Dr. Hu concluded.
Walter Willett, MD, DrPH, Fredrick John Stare professor of epidemiology and nutrition and chair of the Department of Nutrition at Harvard School of Public Health in Boston, Massachusetts, commented on the article in an email interview with Medscape Medical News. He said that although he agrees with the author "that regular consumption of artificial sweeteners is not optimal, as these leave us conditioned to a high level of sweetness, which can distort our food choices," he considers a substantially better option than regular sugar-based choices.
He notes, however, that the review by Dr. Swithers excludes a large analysis of beverages and weight gain, and some studies are misrepresented. "The risk of obesity, diabetes, and cardiovascular disease associated with artificial sweeteners is less than the risk associated with consumption of sugar," he emphasizes.
This research was supported by the National Institutes of Health. Dr. Hu and Dr. Willett have disclosed no relevant financial relationships.
Trends Endocrinol Metabol. Published online July 10, 2013. Full text