Researchers from Harvard Medical School have published a study showing that the consumption of certain whole (unprocessed) fruits decreases the risk of type 2 diabetes but, on the contrary, taking fruit juice can increase the risk.

Several other studies have already been published on the importance of fruit in the prevention of type 2 diabetes, however these studies did not always give clear results. This is why these scientists carried out a study to better identify the influence of each fruit taken separately.

Type 2 diabetes is a very common metabolic disease affecting 347 million people worldwide according to the WHO, this organization also speaks of an epidemic. It is a rapidly growing condition, mainly due to bad habits such as junk food or sedentary lifestyle. The United States is particularly affected by this form of diabetes, which generates very significant costs for its health system (20% of the American GDP is devoted to health according to The Economist). Any measure that can prevent and limit the risk of type 2 diabetes is therefore very useful.

Type 2 diabetes is characterized by hyperglycemia, which is a high level of glucose in the blood. Insulin is an essential hormone in the regulation of sugar levels, it allows among other things to “return” sugar from the bloodstream to the cells of the body. In case of type 2 diabetes there is a resistance of the cells to the action of insulin. Another cause of this diabetes is insufficient production of this hormone.

187,000 people followed for 24 years

Researchers from Harvard Medical School in the Boston area (USA) have published their work in the English journal British Medical Journal (BMJ). This study focused on the analysis of more than 187,000 men and women. In this group of people, followed for 24 years, 6% (12,000 participants) had or developed type 2 diabetes during the study.

Throughout the duration of this study, researchers asked participants about their fruit consumption.

Blueberries, grapes, apples, pears, bananas as a priority to protect against diabetes

The result showed that blueberry consumption was the fruit that reduced the risk of type 2 diabetes the most, by around 33%. Other fruits reduce the risk such as grapes by 19%, apples and pears by 14%, bananas by 13%. On the other hand, melon and fruit juices increased the risk of type 2 diabetes.

The very beneficial effect of the blueberry would be explained by a high concentration of antioxidant active ingredients (eg anthocyanosides). As diabetes causes oxidative stress with free radicals, blueberry can act against these harmful substances. Each fruit has a particular nutrient profile, hence these differences in diabetes risk.

Fiber and glycemic index

Two other explanations put forward by researchers are fiber and the glycemic index. First of all, the greater presence of dietary fibers in whole fruits than in juices would play a key role. Fiber slows the dietary absorption of sugar and therefore has a direct effect on blood sugar. In addition, each fruit has a different glycemic index, fruits with a high glycemic index generate “peaks” of insulin. You should know that juices naturally have a higher glycemic index, because absorption is faster in the intestine, the food bolus passing more easily from the stomach to the intestine during liquid food.

The study does not specify whether it was natural or industrial juice. In any case it is preferable, if possible, to consume natural juices, generally richer in fiber. Remember also that juices can be caloric and cause weight gain, they must be consumed in reasonable quantities. If you are used to drinking juice, you can add flax seeds, which are rich in fibre.

Whole fruit instead of fruit juice

If you suffer from type 2 diabetes or in prevention, it is preferable to consume whole fruits rather than juices, it is also recommended to vary the fruits consumed daily, eg. Eat several different fruits every day such as a banana, apple, pear, grape, etc.

Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. British Medical Journal (BMJ) Harvard Medical School (HMS), USA

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