Many people drink fruit juice every morning in an effort to stay healthy. Fruit is considered a quintessential health food because it contains a range of nutrients, including vitamins and dietary fiber. However, experts point out that blending or juicing fruit changes how quickly it is consumed and how its sugars are absorbed, potentially placing a greater burden on blood sugar and weight management.

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Lee Jin-bok, a family medicine specialist and director of Dr. Lee Family Medicine Clinic, recently named fruit juice, along with cereal, French fries, and ice cream, as foods he does not eat on the YouTube channel Good Life.

“I would never eat these four foods, even if they were delivered to me for free,” Lee said. “People sometimes say they drink fruit juice because it is healthier than coffee, but store-bought fruit juices contain a lot of sugar and cause blood sugar to surge.”

He added, “When you blend fruit, you destroy its fiber. With the fiber removed, blood sugar rises that much faster.” The same applies to store-bought fruit juice, as well as 100% fruit juice made at home in a blender and freshly squeezed juice. “Fruit juice is one of the foods that raises blood sugar quickly, so it is not good for weight loss or health,” Lee emphasized.

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Woo Chang-yoon, an endocrinologist at Asan Medical Center, also warned about the habit of drinking blended fruit in the morning on the YouTube channel “Jang Dong-sun’s Curious Brain” in July 2025. Woo explained that blending fruit and drinking it at a time when absorption is rapid, such as in the morning, leads to faster intake of the fructose in fruit, which can cause blood sugar to rise sharply and may also affect the risk of fatty liver.

“I often compare drinking blended fruit to drinking alcohol,” he said. “It puts particular strain on the liver, and drinking blended fruit the day after drinking alcohol is the worst thing you can do.”

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These warnings are also supported by research. A study titled “The Effects of a Fruit Juice Diet on Health,” conducted by researchers in the Department of Nutrition at the University of North Carolina and published in the Journal of Nutrition in January 2025, found that juicing or blending fruit results in the loss of about 90% of its fiber and a relatively higher proportion of fructose, which can negatively affect blood sugar and weight management. The researchers explained, “Blended fruit delivers more fructose, and does so more quickly, than whole fruit. This can lead people to exceed the recommended daily sugar intake, potentially resulting in obesity or hyperlipidemia.”

So what should a healthy breakfast include? Experts agree that meals centered on refined carbohydrates and sugar should be avoided. The commonly consumed combination of bread, jam, and fruit juice is considered one of the worst eating habits for blood sugar management. Given that Korean diets tend to be high in carbohydrates, breakfast should ideally focus on unprocessed foods rich in protein, healthy fats, and dietary fiber, such as cruciferous vegetables, to promote lasting fullness and stabilize metabolism.

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