Researchers say that public health strategies to cut sweetened drink consumption could be useful, as they create a greater risk of type 2 diabetes than most foods
Sweetened drinks pose a greater risk of type 2 diabetes than most other foods containing fructose – a naturally-occurring sugar – according to a new report by The BMJ.
The findings suggest that fruit – and other foods containing fructose – seem to have no harmful effect on blood glucose levels, while sweetened drinks and some other foods that add excess energy to diets may have harmful effects.
“These findings might help guide recommendations on important food sources of fructose in the prevention and management of diabetes,” said Dr. John Sievenpiper, the study’s lead author and a researcher in the Clinical Nutrition and Risk Factor Modification Centre of St. Michael’s Hospital in Toronto, Canada.
“But the level of evidence is low and more high quality studies are needed.”
The role of sugars in the development of diabetes and heart disease attracts widespread debate, and increasing evidence suggests that fructose could be particularly harmful.
Fructose occurs naturally in a range of foods, including whole fruits and vegetables, natural fruit juices and honey. It is also added to foods, such as soft drinks, breakfast cereals, baked goods, sweets and desserts under the guide of ‘free sugars’.
Current dietary guidelines recommend reducing free sugars, especially fructose, from sweetened beverages. Currently, it’s unclear whether this should be the case for all food sources of these sugars.
As such, researchers based at St. Michael’s and the University of Toronto analysed the results of 155 studies, assessing the effects of different food sources of fructose on blood glucose levels in people with and without diabetes. The test subjects were monitored for up to 12 weeks.
Results were based on four study designs: substitution (comparing sugars with other carbohydrates), addition (energy from sugars added to diet), subtraction (energy from sugars removed from diet) or ad libitum (energy from sugars freely replaced).
Outcomes were glycated haemoglobin or HbA1c (amount of glucose attached to red blood cells), fasting glucose, and fasting insulin (blood glucose and insulin levels after a period of fasting).
The results show that most foods containing fructose sugars do not have a harmful effect on blood glucose levels when these foods do not provide excess calories. However, a harmful effect was seen on fasting insulin, in some studies.
Analysis of specific foods suggest that fruit and fruit juice when these foods do not provide excess calories may have beneficial effects on blood glucose and insulin control, especially in people with diabetes. However, foods that add excess ‘nutrient-poor’ energy to the diet seem to have harmful effects.
The researchers conclude: “Until more information is available, public health professionals should be aware that harmful effects of fructose sugars on blood glucose seem to be mediated by energy and food source.”