Fruit and fruit juices as part of a diet with a healthy amount of calories appeared to have a slightly beneficial effect on blood sugar.
Sodas sweetened with fructose may have a greater impact on risk factors for diabetes than whole fruits that are natural sources of fructose, a research review suggests.
The link between fructose and diabetes has been unclear. Some research has suggested this relationship may be explained at least in part by what people eat and drink and whether they are overweight or obese.
For the current analysis, researchers examined data from 155 studies that assessed the effect of different food sources of fructose on blood glucose levels. Combined, these studies included about 5,000 people with and without diabetes.
Fruit and fruit juices as part of a diet with a healthy amount of calories appeared to have a slightly beneficial effect on blood sugar, especially in people with diabetes, the analysis found.
But foods, sodas and juices with lots of calories and few nutrients seemed to have harmful effects on blood sugar.
Most of this evidence was low quality, however, researchers report in the BMJ.
“While this analysis did not find consistent effects of fructose per se on risk for diabetes, results appear to support the adverse effects of added sugars in the form of sugar-sweetened beverages,” said Dr. Mark Herman of Duke University in Durham, North Carolina.
“This analysis also supported potentially beneficial effects of fruit,” Herman, who wasn’t involved in the study, said by email. “It is likely beneficial to restrict consumption of sugar-sweetened beverages, and someone that is craving something sweet might consider a piece of fruit instead.”
Globally, almost one in 10 adults has diabetes, according to the World Health Organization. Most have type 2 diabetes, which is associated with obesity and aging.
Doctors generally advise patients with diabetes and people at high risk for developing the condition to limit sodas, juices and other sugary treats with fructose, sucrose or other sweeteners that add lots of empty calories to the diet. This can help reduce the risk of weight gain, and help keep blood sugar within a healthy range.
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.
It’s possible fruit and certain other foods with naturally occurring fructose might help improve blood sugar levels because they are high in fiber, which can slow down the release of sugars in the blood stream, the study authors note.
“These findings might help guide recommendations on important food sources of fructose in the prevention and management of diabetes,” senior study author Dr. John Sievenpiper of St. Michael’s Hospital in Toronto said in a statement.
Sievenpiper has received money from a variety of food and beverage companies and advocacy groups including the International Dried Fruit and Nut Council, Calorie Control Council, Dr. Pepper Snapple Group, The Coca- Cola Company, and PepsiCo.
Patients should consume sweets in moderation, limit added sugars, and beware hidden sweeteners in processed foods, said Dr. Valerio Nobili of University La Sapienza in Rome.
“For example, 1 tablespoon of ketchup contains about 4 grams (about 1 teaspoon) of sugars, while a single can of sweetened soda contains up to 40 grams (about 10 teaspoons) of sugars,” Nobili, who wasn’t involved in the study, said by email.
“Both . . . patients with type 2 diabetes and healthy individuals should avoid added sugars while increasing the natural sugars, such as those contained in whole fruit,” Nobili advised.