The fiber myth: How much is too much?

High-fiber foods might as well come with a sticker saying, "Need to poop? Eat this." After all, that's pretty much what cereal commercials, doctors, and everyone else are saying. But, it turns out that fiber might actually be what's backing you up.

Research published in the American Journal of Gastroenterology found that although in some people a high-fiber diet may speed things along, in others with more severe cases of constipation, increasing fiber can have the opposite effect.

And in one study published in the World Journal of Gastroenterology, it was reducing or stopping fiber intake, not ramping it up, that finally scored constipation sufferers relief. "This study has confirmed that the previous strongly-held belief that the application of dietary fiber to help constipation is but a myth," write the study authors.

"Fiber absorbs water. Look at a bowl of high-fiber cereal that has been sitting in your sink unwashed for a few hours. Without continuing to pour water into it, it can become thick and heavy and get stuck in your bowels," says Elana Maser, M.D., assistant professor of gastroenterology at the Icahn School of Medicine at Mount Sinai. It's like trying to clear up a traffic jam by adding more cars.

That can also mean a lot more gas. The longer fecal matter sits in your system, the longer gas-spewing bacteria have a chance to do their thing. Plus, some forms of soluble fiber (meaning it dissolves in water to form a paste in your digestive tract) can ferment in your gut to cause even more gas, says Gerard E. Mullin, M.D., associate professor of medicine at the Johns Hopkins Hospital and author of The Gut Balance Revolution. However, research on 275 patients with irritable bowel syndrome (which hits about 10 to 15 percent of guys) published in the British Medical Journal showed that having soluble fiber, like psyllium, instead of insoluble fiber, like bran, reduced IBS symptoms including bloating, diarrhea, and constipation.

Confusing enough for you? That's why, before upping your fiber intake in order to clear things out, it's important to determine how much fiber you're currently consuming.

While experts disagree on how much fiber you actually need—figures range from 20 to 38 grams per day—most agree that any more than 40 grams per day is just overkill. Hitting those levels, constipation or no constipation, will help keep your blood sugar levels in check, help you feel full longer, prevent weight gain, and keep your ticker ticking away, Mullin says. The best sources include whole grains, fruits, vegetables, and legumes.

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