Juices have also been associated with the idea that they can help you lose weight and "detoxify" the body.
All of this made juice an extremely lucrative business. In fact, the world market for fruit and vegetable juices was valued at US $ 154 billion in 2016 and is expected to grow.
But are juices really as healthy as we think?
The importance of fiber
"Almost all fiber is eliminated in fruit juices," says Emma Elvin, chief clinical consultant at Diabetes UK charity.
That's why fructose (a natural sugar found in all fruits) in juices counts as "free sugars," a group that includes honey and sugars added to foods.
The problem is that, once the fiber is eliminated, the fructose of the juice is absorbed more quickly.
Sudden increases in blood sugar cause the pancreas to release insulin to return it to a stable level. Over time, this mechanism can be reduced, increasing the risk of developing type two diabetes.
In 2013, a group of researchers analyzed information on the health of 100,000 people collected between 1986 and 2009.
What they saw is that as liquids pass from the stomach to the gut faster than solids, even when the nutritional content is similar to that of the whole fruit, the juices generate more striking and faster changes in glucose and insulin levels
Another study found a relationship between fruit juice and type 2 diabetes, following the diets and diabetes status of more than 70,000 nurses over a period of 18 years. Once again fiber was a possible explanation.
Vegetable juices, although they can provide more nutrients and less sugar, do not yet have fibers.
Diets high in fiber are associated with a lower risk of developing coronary heart disease, stroke, high blood pressure and diabetes. It is recommended that adults consume 30gr of fiber per day.
In turn, the World Health Organization recommends that adults avoid consuming more than 30g of sugars added per day, which is equivalent to 150ml of fruit juice.
Analyzing 155 studies, John Sievenpiper, an associate professor in the Department of Nutrition Sciences at the University of Toronto, sought to clarify whether the relationship between sugary drinks and health – including the risk of diabetes and cardiovascular disease – also applies to foods and beverages that we normally consume as part of a healthy diet.
As a result, he found negative effects on blood sugar and fasting insulin levels when foods contained excess calories from sugars, including fruit juice.
However, when there were generally no excess calories, there were some advantages in consuming fruit and even juice.
Sievenpiper concluded that the recommendation of 150ml of juice per day, which is the average measure, is reasonable.
Although we know that fruit juice can cause diabetes, if you eat a high-calorie diet, it is less clear how juices affect the long-term health of those who are not overweight.
"There's still a lot we do not know about how the risk changes with increasing dietary sugar without gaining weight," says Heather Ferris, an assistant professor of medicine at Virgina University.
"For how long and how well the pancreas can keep up with sugar depends in part on genetics," he adds.
But we have a greater risk of consuming more than the recommended daily amount of calories (between 2,000 for women and 2,500 for men) on the days we drink juice, according to the survey.
Numerous studies have shown that taking fruit juice does not mean that we eat less during the day.
With a twist
A study published last year may have found a way to make juices healthier.
The researchers used a blender & # 39; nutrient extractor & # 39; which, unlike the traditional juicers, extracts juice from all fruits, including seeds and bark.
They measured the effects of a blend of peeled fruit and mango while passing through a & quot; nutrient extractor & quot; compared to another group that consumed the whole fruit.
Those who took the nutrient extract showed a smaller increase in blood sugar compared to those who only ate mixed fruits. There were no differences between those who took the mango juice or those who ate the whole mango.
But this was a small study and the researchers did not compare their findings with juices made by some other method, such as squeezing the juice and leaving the peel and seeds.
Gail Rees, a professor of human nutrition at the University of Plymouth and a researcher on the study, says the results were probably the result of including the seeds in the juices. But it is difficult to offer specific advice based on the study.
"I would definitely follow the current advice of 150ml of fruit juice a day, but if you use a nutrient extractor at home, this can keep blood sugar levels relatively stable," he says.
The point is, while letting the seeds in the juice help digestion, Ferris adds that this does not necessarily affect how much it fills you up.
"(Leave the seeds or fibers) is better than a traditional juice," says Ferris.
Another way to improve the health effects of fruit juice is to look for ripe fruit to conserve as much of its properties as possible, according to Roger Clemens, a professor of pharmaceutical sciences at the University of Southern California.
It is also important to note that there are extraction methods that work best with certain fruits, Clemens found.
Grapes, for example, have most of their phytonutrients in the seed and very little in the pulp. And most of the phenolic compounds and beneficial flavonoids of orange are found in the bark, which is lost in traditional extractions.
One common argument in favor of fruit juices is that they can help to detoxify the body.
However, the only medically recognized use of the word "detoxification" refers to the elimination of harmful substances such as drugs, alcohol and poison.
In addition, juices are not a panacea for nutrients, nor the ideal way to meet the recommendation of 5 fruits daily.
"People try to eat five fruits a day and they do not realize it's not just about getting the vitamins," says Ferris.
"It's also important to reduce the carbohydrates of grains, proteins and fats in the diet and increase fiber."
Therefore, although fruit juice is better than the total absence of fruit, there are limits. The risk is when we consume more than 150ml of sugar per day or when we pass the recommended calories.
Yes, they do have vitamins, but fruit juices are not a quick fix.