'Not even for free': Why doctors avoid fruit juice

Fruit juice has long been a morning staple for health-conscious consumers. But medical experts draw a clear line: fruit itself may be healthy, but blending or juicing it leaves little more than sugar water.

Lee Jin-bok, a family medicine physician who has treated obese patients for 30 years, listed fruit juice among the foods he would "never eat" on the YouTube channel "Good Life." The four items he named were cereal, french fries, ice cream and fruit juice.

"I would not touch any of these four even if someone gave them to me for free," Lee said. "People drink fruit juice thinking it is healthier than coffee, but commercially sold fruit juice contains a large amount of sugar and causes blood sugar to spike." He added that blending fruit destroys its fiber, and that without fiber, blood sugar rises far more quickly. The warning applies not only to store-bought juice but also to 100 percent fruit juice and cold-pressed juice made at home with a blender.

"Fruit juice is one of the foods most notorious for spiking blood sugar rapidly, which makes it bad for both dieting and overall health," Lee said.

Pharmacist Kim A-reum echoed the concern on her YouTube channel "Areum Pharmacist," calling morning fruit juice "sticky sugar water" that is harmful to cardiovascular health.

Saurabh Sethi, a gastroenterologist based in the United States, also named fruit juice as a food he avoids for the sake of liver health. "Even 100 percent natural fruit juice is high in fructose and low in dietary fiber," Sethi said on his social media. "That combination can rapidly raise blood sugar and cause fat to accumulate in the liver."

A 2020 study published in Nature Metabolism by researchers at the University of California found that high fructose intake increases the risk of nonalcoholic fatty liver disease, a condition in which fat builds up excessively in liver cells. Fructose is a compound the body converts into fat with relative ease, making weight gain another likely consequence.

Fruit juice is also linked to a higher risk of type 2 diabetes. A 2013 study published in BMJ, in which Harvard T.H. Chan School of Public Health researchers tracked participants over 18 years, found that people who consumed fruit juice three or more times a week had a 21 percent higher risk of developing type 2 diabetes than those who did not.

The core problem, experts say, is that blending or juicing fruit eliminates the role of dietary fiber. Fiber slows the absorption of sugar in the body. Cold-pressed juice removes even the pulp that contains fiber, leaving almost none behind.

The cell walls of fruit pulp, which are made up of fiber, also trap sugar inside the cells. When fruit is blended, those cell walls break down and the sugar escapes freely. The result is that fructose is absorbed rapidly into the bloodstream, accelerating the rise in blood sugar.

The fiber in whole fruit also promotes satiety. A study published in Appetite in 2009 by researchers at Pennsylvania State University confirmed this. People who ate an apple before lunch consumed 15 percent fewer calories at that meal than when they ate no apple beforehand. By contrast, drinking apple juice of equivalent calories led them to eat 178 kilocalories more than when they had eaten the whole apple.

"When you eat the fructose in fruit together with vitamins and dietary fiber, you absorb the nutrients while also feeling full," said Kang Jae-heon, a professor of family medicine at Kangbuk Samsung Hospital.