Don’t go overboard at once with these examples. Sudden increases can lead to gas, bloating, and general discomfort. Make sure to stay hydrated while ramping up. Psyllium in particular can cause these side effects, and there’s a risk, albeit a small one, of intestinal blockage if it’s consumed without enough water, Rosenkranz says.
When increasing fiber, be cautious about having it right before a heavy workout, Rosenkranz says, since post-fiber exercise can cause GI discomfort.
Find what works for you
Fiber, perhaps even more than other nutrients, is highly individual. One reason is that gut microbes vary widely. In Krajmalnik-Brown’s study, the amount of energy harvested from the high-fiber diet differed considerably across participants.
Having more than 60 grams per day works well for some but not others, so you’ll want to monitor your bowel movements. “I’d be really worried about diarrhea,” Krajmalnik-Brown says. If high fiber is causing diarrhea, that alters the gut microbe population too quickly. “Faster growing microbes are the only ones that will thrive, as the others are washed out,” Krajmalnik-Brown explains, potentially favoring less beneficial microbes.
