BBC – Future – Is juice really good for you?

Freshly squeezed fruits have become a staple in many diets – especially those of health-conscious and health-conscious consumers who can save time by preparing (and perhaps even chewing) their food without missing out. of nutrients. Fruit juice has also been linked to claims that it can help you lose weight and "detoxify" your system.

Of course, all of this made the project very lucrative. The global market for fruit and vegetable juices was valued at $ 154 billion (£ 123 billion) in 2016 and is expected to grow.

But is juice really as healthy as we think?

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Most foods containing fructose – a naturally occurring sugar found in all fruits and juices – do not seem to have any negative effects as long as they do not contribute to an excess of calories per day. Indeed, the fiber present in the whole fruit is intact and the sugar is contained in the cells of the fruit. Our digestive system takes a while to break down these cells and get fructose into the bloodstream.

But this is not the case with fruit juices.

Mechanics of fibers

"Most of the fiber is extracted from fruit juice," says Emma Elvin, a senior clinical advisor at the Diabetes UK charity. That's why, unlike whole fruits, fructose in fruit juices counts as "free sugars" – which also include honey and sugars added to foods. The World Health Organization recommends that adults do not add more than 30 g of sugar a day, or the equivalent of 150 ml of fruit juice. (Read more in our recent story to see if sugar is really bad for you).

The problem is that with the fiber removed, the fructose of the fruit juice is absorbed more quickly. Sudden peaks in blood sugar cause the pancreas to release insulin to bring it back to a stable level. Over time, this mechanism can be used and increase the risk of developing type 2 diabetes. In 2013, researchers analyzed the health data of 100,000 people collected between 1986 and 2009 and found that Fruit juice consumption was linked to an increased risk of type 2 diabetes. They concluded that since liquids pass through the stomach and intestine faster than solids, even when nutritional content is Similar to that of a whole fruit, the fruit juice causes faster and larger changes in glucose and insulin levels.

Another study found a relationship between fruit juice and type 2 diabetes after following the diets and diabetes status of more than 70,000 nurses over 18 years of age. The researchers explained that the possible cause of this situation may be partly due to the lack of other components present in whole fruits, such as fiber.

Juices containing vegetables can provide more nutrients and less sugar than fruit-only juices – but they still lack valuable fiber. Diets high in fiber have been associated with a lower risk of coronary heart disease, stroke, high blood pressure and diabetes, and it is recommended that adults consume 30 g per day.

Overall excess

In addition to the link with type 2 diabetes, many studies agree that fruit juice is harmful if it contributes to excess calories.

In an analysis of 155 studies, John Sievenpiper, an associate professor in the Department of Nutritional Sciences at the University of Toronto, sought to understand whether associations between sugary soft drinks and health, including the risk of diabetes and cardiovascular diseases, applied to foods. we usually eat as part of a healthy diet. He compared studies of the effects of fructose-containing sugars (including sucrose, high-fructose corn syrup, honey and syrups) with control diets lacking or containing less of these sugars. Its goal? Isolate the effects of excessive consumption of calories from the effects of food containing different sugars.

He found negative effects on fasting blood sugar and insulin levels when foods provided excess calories from sugars, including fruit juices. However, when the calories were not excessive overall, the consumption of whole fruit – and even fruit juice – had some advantages. Sievenpiper concludes that the recommended 150 ml of fruit juice per day, which is an average portion, is reasonable.

The paper concluded that foods containing fructose may have some benefits for long-term glucose control if they do not lead to over-consumption of calories. But when they lead to too many calories, they may increase blood sugar and insulin levels. This could be due to the fact that fructose has a relatively low GI, the paper says, while high GI diets are associated with insulin resistance.

"Getting an entire fruit is better than fruit juice, but if you use it in addition to fruits and vegetables, it's fine, but not if you use juice to hydrate and drink large quantities "said Sievenpiper. .

Thus, although we know that fruit juices can cause diabetes if they are part of a generally more calorific diet, it is less clear how their influence affects the long-term health of those who are not overweight. .

"We still do not understand why increasing the level of sugar in the diet without weight gain changes the risk," says Ferris. "The extent to which the pancreas can track sugar depends in part on genetics."

However, we have a higher risk of consuming more than the recommended daily calories (about 2,000 for women and 2,500 for men) on days when we drink juice, according to research. Many studies have shown that the consumption of fruit juice does not allow us to consume less food during the day.

"It's also easy to consume large amounts of fruit juice fast enough, which means more calories. And when calories increase, it can contribute to weight gain, "explains Elvin.

With a twist

But a study published last year may have found a way to make the juice healthier. The researchers used a "nutrient extractor" mixer that, unlike traditional centrifuges, extracts whole fruit, including seeds and skin. They measured the effects of fruit mixes and peeled mangoes – both of which rank high on the glycemic index and therefore cause a spike in blood sugar – mixed with a nutrient extractor mixer, relative to to another group having eaten the same fruit.

Those who drank mixed fruits extracted from nutrients had a lower blood sugar increase than the whole mixed fruit group, while there was no difference between those who had mango juice and mangos whole.

However, it was a small study and the researchers did not compare their results with those obtained from juice obtained by another method, such as squeezing the juice and leaving the skin and seeds.

Gail Rees, a senior lecturer in human nutrition at the University of Plymouth and a researcher in the study, says the results were likely caused by the fruit seeds contained in the juices. But she says it's hard to give clear advice from this study.

"I would certainly accept the current advice of 150 ml of fruit juice a day, but if you use a nutrient extractor at home, this could keep blood sugar levels relatively stable," she says.

But if keeping the seeds in the juice can make a difference during digestion, Ferris argues that it does not necessarily change the degree of juice filling.

"When the juice contains fiber, it slows absorption, but you keep an excessive caloric intake because it is easy to consume.However, it's an improvement over traditional fruit juice," says -she.

According to Roger Clemens, professor of pharmaceutical sciences at the University of Southern California, we can also improve the effects of fruit juice on our health: we must choose ripe fruits to preserve as much as possible.

It is also important to recognize that different extraction methods are better suited to different fruits because of their physical constitution, Clemens found. For example, most phytonutrients in grapes are found in the seed and very little in the pulp. And most of the beneficial phenolic compounds and flavonoids found in oranges are found in the skin, which is lost with traditional juice extraction.

Detoxification demystified

Another reason for the recent popularity of fruit juice is the argument that it can help detoxify the body.

However, the only medically recognized use of the word "detox" concerns the removal of harmful substances from the body, including drugs, alcohol and poison.

"The whole concept of a juice-based diet being detoxified is a mistake," says Clemens. "We consume potentially toxic compounds every day and our body does a remarkable job of detoxifying and eliminating everything we eat."

And the juice is not a panacea for getting your nutrients either.

"The fruit parts contain a lot of nutrients, such as the skin of apples, which are excluded when you consume them," says Heather Ferris, an assistant professor of medicine at the University of Virginia. "You end up with some water sugars with some vitamins."

Moreover, she adds, this is not an ideal way to reach the five recommended tips. "People try to eat five servings of fruits and vegetables a day and do not realize that it's not just vitamins," she says. "It's also about reducing the amount of carbohydrates, protein and fat in our diet, and increasing fiber. "So, if fruit juice is better than no fruit at all, there are limits: It is particularly risky to consume more than 150 ml of free sugars a day or to exceed the recommended caloric intake. but fruit juice is far from a miracle solution.

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