Washington DC: According to a recent study, fruits and other foods containing fructose seem to have no harmful effect on blood glucose levels, while sweetened drinks and foods that add excess energy to diets can have negative effects.
The study appeared in the BMJ journal. The role of sugars in the development of diabetes and heart disease raises wide-ranging debate, and the increase in evidence suggests that fructose could be particularly harmful to health.
These findings could help guide recommendations for important food sources of fructose in preventing and managing diabetes, said the study author and Dr. John Sievenpiper.
Fructose naturally occurs in a wide range of foods including whole fruit and vegetables, natural fruit juices and honey. Foods such as soft drinks, breakfast cereals, confectionery, sweets and desserts are also added as "free sugars". Diet guidelines recommend reducing the content of free sugars, especially fructose in sweetened drinks, but it is unclear whether this applies to all food sources of these sugars.
Researchers at St. Michael and the University of Toronto in Canada analyzed the results of 155 studies that evaluated the effect of various food sources of fructose sugars on blood glucose levels in people with and without diabetes monitored for up to 12 weeks.
The results were based on four study models: replacement (comparison of sugars with other carbohydrates), addition (added sugar energy to the diet), decrease (energy from sugar removed from the diet) or adlibitum (free sugar energy).
The results were glycated hemoglobin or HbA1c (the amount of glucose attached to red blood cells), fasting glucose and resting insulin (blood glucose levels and insulin after a rest period).
The results show that most foods containing fructose sugars do not have a detrimental effect on blood glucose levels when these foods do not provide excess calories. However, a deleterious effect was observed in long-term insulin in some studies.
Analysis of certain foods suggests that fruit and fruit juices when these foods do not provide excess calories can have beneficial effects on glucose and insulin control, especially in people with diabetes, while many foods that add excess "in especially sweetened drinks and fruit juices, seem to have harmful effects.
The low glycemic index (GI) of fructose compared to other carbohydrates and the high fiber content of fruits can help explain improvements in glycemia
levels, by slowing down the release of sugars, according to researchers.