Daniella Segura/FlickrIn a study published in the BMJ in July 2013, researchers from Harvard University found that eating whole fruits can reduce the risk of developing type-2 diabetes, but some are more effective than others at warding off the disease.
The report used data from three long-running health studies that included 151,209 women and 36,173 men, where participants sent back questionnaires about their lifestyle, diet, and health — specifically any diseases they'd developed — every few years for at least two decades.
The researchers asked about 10 fruits: grapes or raisins, peaches, plums or apricots, prunes, bananas, cantaloupe, apples or pears, oranges, grapefruit, strawberries, and blueberries.
Blueberries were most effective in preventing diabetes, followed by grapes and then apples. Bananas and grapefruit were also good. Strawberries did not have much of an effect and cantaloupe slightly increased the risk for type 2 diabetes.
See the chart below:
On the flip side, drinking all kinds of fruit juice, including apple, orange, and grapefruit, was associated with a higher risk of the disease. Replacing three servings of fruit juice each week with blueberries decreased the risk of type 2 diabetes by 33% on average, according to the study.
People with type 2 diabetes do not make enough of the hormone insulin, which pulls sugar (glucose) out of the bloodstream and into our cells to be stored and released later. Without enough insulin, bloodsugar hits spikes and troughs.
Researchers suggest that blueberries, red grapes, and apples may lower the risk of type 2 diabetes because they contain high levels of anthocyanins, which have been shown to increase glucose uptake in mice with diabetes.