Drinking a glass or more of 100% fruit juice every day is associated with a risk of weight gain in children and adults, according to a new analysis of previous studies.
"One of the main problems with juices is the quantity - consuming fruit in this way, it's very easy to overdose," says co-author and lead nutrition researcher Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard T. Kennedy School of Public Health. Х. Chan" and professor of medicine at Harvard Medical School in Boston.
"For example, how often do we eat three oranges? Yet one glass of orange juice is about three oranges that can be consumed in a minute or two, and we can go back and drink another one, which will add a lot of calories and cause a spike in blood glucose," Willett says.
Over time, too much sugar in the blood can lead to insulin resistance, metabolic syndrome, diabetes, heart disease, obesity and other chronic conditions, experts say.
While the study's findings don't show a direct cause-and-effect relationship, only an assumption, the findings are "quite reasonable and consistent with what we see in the clinic," says pediatric endocrinologist Dr. Tamara Hannon, a member of the American Academy of Pediatrics/AAP committee on nutrition.
Because of concerns about the rising rates of childhood obesity and tooth decay, the AAP advises parents and caregivers to avoid juices altogether for infants under 1 year of age, to limit their intake to 4 ounces daily for children ages 1 to 3 years, and to only 6 ounces daily for children ages 4 to 6 years.
"There's really no healthy reason to consume juice instead of whole fruits and vegetables unless your child can't consume them in their raw and natural form," Hannon says.
According to the National Dietary Guidelines, teens and adults should drink no more than 8 ounces of 100 percent juice per day, and juice should not be considered a healthy way to quench thirst.
"The general guidelines are against 'routine' intake - in other words, relying on juice rather than water to quench thirst, or consuming juice specifically for health benefits," says Dr. David Katz, a preventive medicine and lifestyle medicine specialist who founded the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.
For some, the worry of 100% fruit juice may be puzzling - fruit is healthy, right? So what's the difference between a fruit and its juice?
"Whole fruits and vegetables contain nutrient packets - carbohydrates, protein, fat, minerals and vitamins and fiber. That's the way our bodies need to eat," says Hannon. "When we take away the package, we take away the fiber and the structural parts of the food, and our bodies digest and metabolize it differently than they evolved to."
Eating a whole apple, for example, does not raise blood sugar levels because fructose, the sugar found naturally in fruits and some vegetables, is released slowly into the bloodstream. Drinking apple juice, however, floods the blood with fructose.
"Blood cannot be 'sweet'. It's dangerous for the organs, so the body has many mechanisms to quickly get rid of the sugar and keep our blood sugar in the normal range," Hannon explains. "So the liver, which metabolizes sugars, turns a lot of those calories into fat, which can be stored easily and not get into the bloodstream."
"When you consume calories in solid form, your brain better registers those calories and regulates your food intake accordingly," says Malik. "But if you drink those calories, you may not feel full and start eating again."/BGNES
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