Why fruit juice is a bit of a blood sugar bomb

Of course, fruits and vegetables are good for your health. Since fruit juices are often considered healthy products, companions are also welcome to respect the sacred rule of 5 fruits and vegetables per day. But are they really that flawless? It is not at all clear. Fruit juices can actually promote weight gain in children and adults. Why ? How often is it safe to drink? What is the difference between homemade juice and industrial juice? Le Figaro takes stock.

As much sugar as soda

Each fruit provides essential nutrients for the proper functioning of the body. Sugar obviously, in the form of fructose, glucose or sucrose, but also vitamins (vitamin C, pro-vitamin A carotenoids), minerals and especially fiber, are essential for good digestion. However, most industrial fruit juices come without pulp and contain very little fiber (0.3g compared to 2g for whole fruit). Likewise, after opening, they are subject to rapid depletion of vitamins and minerals as these elements oxidize within a few hours of exposure to air.

Minus: In an already opened glass of fruit juice, water-soaked nutrients and large amounts of sugar remain. Not to mention that when we drink a glass of juice we actually swallow more than the whole fruit. “ A glass of juice, about 150 ml, contains 2 to 3 fruits if it is homemade but up to 5 for some industrial juices.

», explains Marie Behar, dietitian nutritionist and doctor of public health at the Bichat-Claude Bernard Hospital in Paris. In addition, the nutritional composition of the juice varies depending on the fruit, underlines Professor Marie-Joseph Amiot-Carlin, Research Director of the INRAE ​​in Nutrition and Public Health. “ Grape or apple juice is usually higher in sugar and lower in vitamins than some citrus or multifruit juices. ” After all, a glass of juice contains an average of 20 grams (2 quarts of sugar), about the same as soda.

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Effects on blood sugar

By combining all these elements, the risk of weight gain becomes clear. First of all because juice is high in sugar and low in fiber. “ Fiber traps nutrients and thus slows down the process of digestion and absorption of carbohydrates, which contributes to a slower release of glucose into the bloodstream, Dr. Behr says. Because juice is low in fiber, the carbohydrates in it are absorbed more quickly. Specifically, when the body receives more sugar than it needs, this overstimulates the secretion of insulin, a hormone from the pancreas, which allows the excess sugar to be stored in fat, lipids. This promotes weight gain », adds the nutritionist.

Another problem is that fruit juices can confuse satiety signals, which contributes to their addictive potential. Normally, chewing stimulates the release of hormones such as ghrelin or leptin, which send satiety messages to the brain. Chewing for a long time gives the brain time to understand that you have eaten enough. When you drink fruit juice, this mechanism is suppressed. The result: the brain absorbs food less quickly and when you are not hungry, the body has already accumulated a lot of sugar. For this reason, drinking fruit juice is not the same as consuming whole fruit, which has the opposite, regulatory effect. “ We can see this clearly: the child has a lot of trouble chewing the fruit and small children often cannot eat it whole.

», underlines Dr Behar.

Thus in France, recommendations from the National Nutrition and Health Program (PNNS) suggest that children should drink no more than half to one glass of fruit juice per day (i.e. 125 ml) compared to one glass for adults. “ Fruit juice is not recommended before the age of two », adds Professor Amiott-Carlin. According to a study published in 2024, which took stock of 42 scientific studies, each additional portion (240 ml) (or 100%) of pure industrial fruit juice was associated with an increase in a child’s body mass index (BMI). As a reminder, BMI is a reference index for assessing body size based on height and weight. A child is overweight when their BMI is equal to or greater than 97^E Percentage (this means that at least 97% of children are underweight).

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Which industrial interest to favor?

Fruit juices should be consumed in moderation and never on an empty stomach to reap the benefits of fiber provided by other foods. Categories of Interest “ Pure juice (or 100%) “, the” concentrates ” and “ Amrit » Because manufacturers are likely to add sugar to the recipe in addition to the sugar naturally present in the fruit. “ This only worries Amrit Which are the sweetest, especially since their composition may include sweeteners “, Dr. Behar says. interest” concentrates » It contains only pressed fruit but the juice is heated to high temperatures before being diluted when placed on the shelves and then frozen, to facilitate transport. Such processes can lead to significant loss of minerals and vitamins.

Even if it means choosing, “pure juice » Get the closest to homemade juice. They are obtained by pressing the fruit without added sugars. But here again, you need to be careful. Before bottling, the refrigerated pure juice undergoes a process Pasteurization This involves heating the juice at high temperatures and thereby denatures the vitamins and minerals. To be stored in the refrigerated section, the Pure “fresh” juice were subjected to “flash pasteurization”: the temperature of the juice is raised for a few minutes before bottling. “ The advantage of flash is that the heating time is so fast that it prevents discoloration of the juice in vitamins and minerals. », underlines the professor. It is best to favor fresh juices that have not undergone these temperature raising processes but have been cold frozen. Then they fully retain their minerals and vitamins.