Some dietary fibers are better at helping with regularity

What’s the best strategy if you’re having trouble with regularity? High-fiber foods can help, but it’s not just a matter of checking the “Dietary Fiber” number on the food label. There’s more to it than that.

“Back in  1985, we studied people on their regular diets, which had 22 grams of fiber, or on a liquid diet with 30 grams of fiber,” says Joanne Slavin, professor of nutrition at the University of Minnesota. (The liquid diet was Ensure with added fiber.)

“Their stool weights were bigger on their regular diets than on the liquid diet. So we know that other things in food besides just the number of grams of fiber affect stool weight. And generally, bigger stools make you less likely to have constipation.”


Prunes—or, as the industry prefers to call them, dried plums—also have more than fiber going for them. “There’s no question that prunes work,” says Slavin. “They’re interesting because they have not only fiber, but also sugar alcohols and maybe other chemicals that matter.”

Sugar alcohols

Sugar alcohols, like sorbitol or mannitol, are poorly absorbed carbohydrates. They’re not alcohol. They’re found in sugar-free chewing gum, packaged sweeteners, and other sugar-free foods.

Sugar alcohols can keep things moving through the gut because they retain moisture, which can soften stool in small doses. “But if you eat a large dose of sugar alcohols, some will reach the large intestine and get fermented by bacteria,” explains Slavin. “And that can cause gas and potentially diarrhea.”


What about inulin, a key fiber in many Fiber One foods and some fiber “gummies”?

“If you look at stool weight, inulin’s impact is at the low end,” says Slavin. “And inulin gets fermented, so it does increase intestinal gas.” Does that mean it’s useless for regularity? The answer isn’t clear. Consuming a big 20 gram dose every day for three weeks increased fatulence, but had no effect on regularity.

“Inulin may make stool softer because the fermentation produces more bacteria,” says Slavin. But the evidence is muddy.

Kelloggs All Bran

 What’s most likely to work?

“I’ve worked on fiber for 40 years,” says Slavin. “When I started, I thought, ‘We should get this baby wrapped up in about five years.’ But we haven’t made a ton of progress on laxation. There aren’t a lot of studies, many are small, and the results are inconsistent.”

“If my goal were to increase stool weight, I’d pick wheat bran or psyllium,” says Slavin. “Wheat bran is best,” she adds. “Each gram of bran means 4 or 5 grams of stool. That’s because the bran fiber isn’t broken down in the gut, and it binds water, which adds fecal bulk.”

Psyllium is the fiber in Metamucil, and it supplies some of the fiber in Kellogg’s All-Bran Buds. “Psyllium definitely works,” says Slavin. “It’s an over-the-counter laxative.”

“Some people just want to take a laxative and be done. But they’d be better off if they eat a bowl of bran cereal with milk and throw some blueberries on it,” she suggests. Whether it’s the seeds or skins or sugar alcohols or fiber in grains, beans, vegetables, and other plant foods, something in there helps keep things moving.”

The bottom line: Don’t rely only on the “Dietary Fiber” number on Nutrition Facts labels to find foods that are good for regularity. Instead, try foods with wheat bran or psyllium…or that old standby, prunes.

Sources: J. Parenter. Enteral Nutr. 9: 317, 1985; Aliment. Pharmacol. Ther. 33: 822, 2011; Food Funct. 2: 72, 2011; Int. J. Food Sci. Nutr. 62: 164, 2011; Am. J. Clin. Nutr. 88: 1256, 2008; Food Funct. 2: 72, 2011.

This article was originally published in 2015 and is updated as needed.

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10 Replies to “Some dietary fibers are better at helping with regularity”

  1. I suffered from constipation for six and a half years due to a chemo drug I had to take. I found that Fibre One with prunes and a glass of prune juice for breakfast was the only thing that worked. I also had blueberries and grapes in my cereal bowl. Then the oncology pharmacist told me to drink two glasses of warm water before I ate any breakfast, and that really helped. Now I am off the drug, the constipation has disappeared. Thank goodness!

  2. My friend and I are both in our early eighties. We both had constipation for many years and tried many things you advise here, but the best result we get now comes from eating non-glutin carbs.
    For us, it really helps.Francien

    1. From Nutrition Action Healthletter: We are not aware of any good published studies showing flax is effective for constipation.

  3. Wheat bran itself it inexpensice and plentiful. buying it in bulk I add 3-4 T. to greek yogurt and fresh berries for breakfast severals days per week. It melts away and there is no taste or grit. You can add it to soup or sauces without anyone noticing, if you really want to go all out! With a diet of plenty of fluids and a lot of daily vegetables and fruit, I’ve been able to say goodbye to irregularity.

  4. Psyllium works well but my greatest discovery, after years of bowel movement discomfort, has been the cream of budwig by Dr Kousmine (I thought it was flaky until I tried it). I grind two tbs of flaxseeds (rich in omega 3), one tbs of sunflower seeds with four hazelnuts and combine them with the juice of half a lemon, 4 tbs of plain yogurt (goat milk one adds oomph), 2 tsp of canola oil, some apple sauce and dried or fresh fruits (blueberries are great). Voilà!

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