No sweets or juice on an empty stomach: Sugars, including fructose, harm the good bacteria in your gut in the absence of food

It looks like it’s better to wait until after you’ve eaten breakfast before you drink some orange juice. According to researchers, drinking fruit juice on an empty stomach “overwhelms the digestive system.” The results from a U.S. study implies that this can upset the “good bacteria” in your gut.

The scientists have determined that fruit juice contains plenty of fructose, and this sugar quickly reaches the small intestine once consumed. In the mornings, the small intestine can’t process large amounts of fructose after periods of “fasting,” which means the sugar in drinks like orange juice will go to the large intestine.

Once this happens, fructose will come into contact with “good bacteria,” which are unable to process sugar. While the results of the study couldn’t confirm if this is linked to “a negative health impact,” the researchers are under the impression that this is highly possible.

How the study was carried out

For the study, which was published in the journal Cell Metabolism, the researchers fed mice a 1:1 mixture of fructose:glucose. They then traced how the sugars were processed in the animals’ digestive tracts.

While earlier research indicates that the liver processes sugar, the findings from this recent study suggests that over 90 percent of fructose is digested in the small intestine. The results also show that the small intestine can process fructose, but only when it is consumed after a meal.

Professor Joshua Rabinowitz, a study author from Princeton University, said, “We saw that feeding mice prior to sugar exposure enhanced the small intestine’s ability to process fructose and that protected the microbiome from sugar exposure.”

The researchers concluded that the findings of the study are in line with “the most old-fashioned advice in the world,” which is to “limit sweets to moderate quantities after meals.”

The researchers then cautioned people to refrain from consuming too many sweets after meals. (Related: Drink water, eat fruit: Fruit drinks marketed to children found to have shockingly high amounts of sugar.)

Foods that can boost good bacteria in your gut

To boost the good bacteria in your gut, consume more of the foods listed below:

  • Dark chocolate – Dark chocolate contains both prebiotics and probiotics. Prebiotics provide food for the microbes in your gut. Microbes then convert the chocolate into anti-inflammatory compounds. Meanwhile, probiotic bugs colonize the stomach to help with digestion and strengthen gut bacteria that can aid digestion. Chocolate is a fermented food but to enjoy these benefits, eat dark chocolate with a cacao content of 70 percent or higher. Consume at least two tablespoons of cocoa powder or three-quarters of an ounce (or a square) of a bar.
  • Greek yogurt – Always check if the product label contains the phrase “live active cultures,” and avoid yogurt that has added sugars.
  • Green peas – Fresh green peas contain Leuconostoc mesenteroides, a powerful probiotic usually linked with fermentation under low-temperature conditions. The bacteria will stimulate the immune system, and this can help protect the mucosal barrier (the body’s “second skin”), which runs through the digestive tract and helps defend you against bad bugs and toxins.
  • Kimchi – Kimchi is a Korean fermented vegetable side dish made with cabbage, radishes, and scallions. It has a distinctive red color, which comes from a “seasoned paste of red pepper, salted shrimp, or kelp powder.” The unique strains found in kimchi can help heal the gut.
  • Sourdough bread – Sourdough refers to “the fermentation process where wild yeast and friendly bacteria break down the gluten and sugar in the wheat flour,” which turns it into proteins, vitamins, and minerals. The “sour” aspect refers to the taste from the wild yeast that comes from the air around you, but this may change based on location. Since the starches from the grains are predigested by the bacteria, sourdough is easier to digest than other types of “over-processed” white breads.

You can read more stories about fresh fruit juice and tips on how to eat healthy at

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