雅思阅读 119: Does Fibermaxxing Work?

改编自 Scientific American 2026 年真实文章，去广告后按雅思阅读题型出题。

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Reading Passage

On social media, people are preparing "poopy" breakfasts loaded with bran and chicory root. Some use the handle "fiber daddy" while snacking on liquefied raw vegetables. This is the world of "fibermaxxing," where people try to eat as much fiber as possible. Some aim for up to 60 grams or more a day, far above the US Department of Agriculture recommendation of 25 to 38 grams. Because most Americans eat only 10 to 15 grams, experts say the trend is not entirely unwelcome, but the benefits may be limited by your gut microbiome.

Fiber plays an important role in digestion. These plant compounds cannot be digested by the human body's own enzymes; instead they pass to the colon, where bacteria break some down through fermentation. This process produces short-chain fatty acids that are essential for health. One, called propionate, is linked to lower cholesterol and feelings of fullness. Another, called butyrate, is a key energy source for colon cells.

Eating fiber also feeds the bacteria in your gut. Without fiber, gut microbes "basically start eating you," gnawing away at the colon's protective mucus lining, says Erica Sonnenburg, a microbiologist at Stanford University. Once this barrier is breached, the body launches an immune response, leading to chronic inflammation linked to diseases such as inflammatory bowel disease, obesity and type 2 diabetes.

"Everyone in the industrial world has a depleted microbiome," Sonnenburg says. But fibermaxxing alone may not fix this. In a 2021 study she co-authored, people who doubled their fiber intake for four months showed no increase in microbial diversity. Unfermented food appeared in their stool, a sign their microbiome could not break down what they were eating. None of the 19 inflammatory proteins tracked decreased either.

But people who already had the highest microbiome diversity definitely reaped the benefits, with less inflamed immune systems. Participants who ate a high-fermented-food diet saw more diverse microbes and reductions in inflammatory markers.

People's responses to fiber also depend on which bacteria dominate their guts. Two main groups are Prevotella, common in people who eat lots of plants, and Bacteroides, common in people on Western, animal-heavy diets. One study found that the Prevotella microbiome consistently produced high levels of beneficial fatty acids, while Bacteroides responded variably. A 2025 study found that a week of arabinoxylan fiber reduced hunger in people with Prevotella-dominant microbiomes but had no effect on Bacteroides-dominant individuals.

Experts caution against reading too much into this divide. The links to health are correlations, not proven cause-and-effect. What matters is getting fiber from a variety of sources. "If you're eating a complex mixture of fibers, some at least are going to match well with the community you have," Sonnenburg says.

The mistake many fibermaxxers make is relying too heavily on inulin and chicory root fibers. Because these are rapidly fermentable, they often cause gastrointestinal distress at around 20 grams a day. Experts recommend increasing fiber gradually to about 35 grams, mostly from whole foods rather than supplements, and staying consistent.

Questions 1-5

Choose the correct letter, A, B, C or D.

1. What is "fibermaxxing"?

   • A. Eating only animal-based foods.
   • B. Trying to consume as much fiber as possible.
   • C. Taking probiotic supplements.
   • D. Fasting for long periods.

2. What does propionate do?

   • A. It digests colon cells.
   • B. It is linked to lower cholesterol and satiety.
   • C. It causes inflammation.
   • D. It kills gut bacteria.

3. According to Sonnenburg, what happens when gut microbes lack fiber?

   • A. They die immediately.
   • B. They start eating the colon mucus lining.
   • C. They produce more butyrate.
   • D. They migrate to the stomach.

4. What did the 2021 study find?

   • A. Doubling fiber intake boosted microbial diversity.
   • B. Doubling fiber intake produced no increase in diversity.
   • C. Fiber supplements cured inflammation.
   • D. People lost weight rapidly.

5. Who benefits most from fiber?

   • A. People with depleted microbiomes.
   • B. People who already have high microbiome diversity.
   • C. People who eat only chicory.
   • D. People who avoid fermented foods.

Questions 6-8

Do the following statements agree with the information given in the passage? Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

6. Most Americans currently eat more than 38 grams of fiber a day.
7. Prevotella-dominant microbiomes responded more consistently to fiber than Bacteroides.
8. Experts recommend getting fiber mainly from supplements.

Questions 9-13

Complete the summary below. Choose ONE WORD ONLY from the passage for each answer.

Fibermaxxing may not work for everyone because benefits depend on gut microbiome. People with depleted microbiomes may not absorb high fiber well. Experts recommend increasing fiber gradually from whole foods rather than supplements. Too much rapidly fermentable fiber can cause gastrointestinal distress.

Answers

1. B
2. B
3. B
4. B
5. B
6. FALSE
7. TRUE
8. FALSE
9. microbiome
10. foods
11. gastrointestinal

Key Vocabulary

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