The findings, published in Diabetes Care, appear to support claims that intake of sugary beverages should be limited in order to reduce risk of these conditions.
“Findings from our meta-analyses show a clear link between sugar-sweetened beverage consumption and risk of metabolic syndrome and type2 diabetes,” wrote the researchers, led by Vasanti Malik a research fellow in the Department of Nutrition, at the Harvard School of Public Health.
"Many previous studies have examined the relationship between sugar-sweetened beverages and risk of diabetes, and most have found positive associations but our study, which is a pooled analysis of the available studies, provides an overall picture of the magnitude of risk and the consistency of the evidence," said Malik.
High consumption
Sugar-sweetened beverages are made up of energy-containing sweeteners such as sucrose, high-fructose corn syrup, or fruit juice concentrates, all of which, the authors noted, have essentially similar metabolic effects. The consumption of such beverages, which include soft drinks, fruit drinks, iced tea, and energy and vitamin water drinks, has risen globally.
According to recent research published in the journal Physiology & Behavior, in the U.S. between the late 1970s and 2006 the per capita consumption of sugar-sweetened beverages more than doubled, from 64.4 to 141.7 kcal per day. (doi:10.1016/j.physbeh.2009.12.022)
Previous research from prospective studies has shown consistent positive associations between sugar-sweetened beverage intake and weight gain and obesity, as well as linking such beverages to other health risks high blood pressure and the risk of heart disease.
However, evidence also suggests that habitual sugar-sweetened beverages consumption is associated with increased risk of metabolic syndrome and type-2 diabetes; however the role of sugar-sweetened beverages in the development of such chronic metabolic diseases has not been quantitatively reviewed.
The researchers conducted an in depth literature search for prospective cohort studies of sugar-sweetened beverage intake and risk of metabolic syndrome and type 2 diabetes. They identified 11 studies (three for metabolic syndrome and eight for type 2 diabetes), which provided data from almost 350,000 people, for inclusion in a meta-analysis comparing sugar-sweetened beverage intake to risk of metabolic syndrome and type-2 diabetes.
Greater risks
People with high intakes of sugar-sweetened beverages (consuming between one and two servings per day) were found to have a 20 per cent greater risk of developing metabolic syndrome than those in the lowest category of intake (none, or less than one serving per month).
For type 2 diabetes, people in the intake highest category of intake had a 26 per cent greater risk of developing type-2 diabetes than the lowest intake category.
The researchers noted that, in general, larger studies with longer durations of follow-up tended to show stronger associations between sugar-sweetened beverage intake and the risk of diabetes.
Significant association
The researchers stated that the meta-analysis “has demonstrated that higher consumption of sugar-sweetened beverages is significantly associated with development of metabolic syndrome and type-2 diabetes”
“These data provide empirical evidence that intake of sugar-sweetened beverages should be limited to reduce obesity-related risk of chronic metabolic diseases,” they added.
The researchers added that although sugar-sweetened beverages increase the risk of metabolic syndrome and type-2 diabetes, in part due to their contribution towards weight gain, there may be other mechanisms involved.
Such mechanisms may include the high levels of easily absorbed added sugars in drinks contributing to a high dietary glycemic load, which is known to induce glucose intolerance and insulin resistance.
"People should limit how much sugar-sweetened beverages they drink and replace them with healthy alternatives, such as water, to reduce risk of diabetes as well as obesity, gout, tooth decay, and cardiovascular disease," said Malik.
Wrong conclusion?
Commenting on the research Richard Laming from the British Soft Drinks Association, stated that the known major risk factors for type 2 diabetes were obesity and low physical activity.
“The study does not properly take into account the role that obesity is known to play and therefore it is wrong to conclude that soft drinks, rather than obesity, are a causal factor for type 2 diabetes,” said Laming.
“Obesity itself is the result of an imbalance between calorie intake from food and drink and energy expended ... The way to tackle obesity is to bring these two into balance – Soft drinks can play a role in this,” he added.
Source: Diabetes Care
Volume 33, Number 11, Pages 2477–2483, doi: 10.2337/dc10-1079
“Sugar-Sweetened Beverages and Risk of Metabolic Syndrome and Type 2 Diabetes: A meta-analysis”
Authors: V.S. Malik, B.M. Popkin, G.A. Bray, J.P. Després, W.C. Willet, F.B. Hu