Researchers argue that public health strategies to reduce sweetener consumption could be helpful as they pose 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.
Findings show that fruits and other foods containing fructose do not seem to have a harmful effect on blood sugar levels, while sweetened beverages and some other foods that add excess energy to diets can have harmful effects.
"These findings can help make recommendations for important dietary sources of fructose in the prophylaxis and treatment of diabetes," said Dr. John Sievenpiper, principal investigator and researcher at the Center for Clinical Nutrition Change and Risk Factor Hospital, St. Toronto, Canada.
"But the level of evidence is low and higher quality research is needed."
The role of sugars in the development of diabetes and heart disease attracts a widespread debate and rising data suggests that fructose can be particularly harmful.
Fructose is naturally found 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, cereals, baked goods, sweets and desserts under the guidance of "free sugars".
These nutrition guidelines recommend reducing free sugars, especially fructose, from sweetened beverages. At present it is not clear whether this should be the case for all food sources of these sugars.
Researchers based in San Francisco and Toronto University are thus analyzing the results of 155 studies evaluating the effect of various dietary sources of fructose on blood sugar levels in people with and without diabetes. Test subjects were observed for up to 12 weeks.
The results are based on four projects: substitution (comparison of sugars with other carbohydrates), addition (energy from sugars added to the diet), subtraction (energy from sugars removed from the diet) or ad libitum.
The results were glycated hemoglobin or HbA1c (amount of red blood cell glucose), fasting glucose and fasting insulin (blood glucose and insulin levels after a fasting period).
The results show that most foods containing fructose sugars have no harmful effects on blood sugar levels when these foods do not provide unnecessary calories. However, some studies have seen a detrimental effect on fasting insulin.
The analysis of certain foods suggests that fruit and fruit juice, when these foods do not provide extra calories, can have a beneficial effect on blood sugar and insulin control, especially in people with diabetes. However, foods that add excess "low-nutrient" energy to food appear to have a detrimental effect.
The researchers conclude: "Until more information is available, public health professionals should be aware that the harmful effects of fructose sugars on blood sugar appear to be mediated by energy and the source of food."
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