A high fiber diet that is relatively rich in plant protein could cause excess bloating, according to a new study. Researchers at the Johns Hopkins Bloomberg School of Public Health came to this conclusion after analyzing data from a clinical trial of 164 participants who follow a high fiber diet.
The study published in the journal Clinical and Translational Gastroenterology found that when the trial participants ate versions of a heart-healthy, high-fiber diet that was also rich in plant protein, they were about 40 percent more likely to report bloating symptoms compared to eating a carbohydrate-rich version of the same high fiber diet.
This study suggests that people who eat a high-fiber diet, should experience less bloating if the diet was also relatively carb-rich versus protein-rich. Consuming a high fiber diet has been shown to boost certain populations of healthful fiber-digesting gut bacteria species, which naturally produce gas as a byproduct. Researchers use these findings to hint at a role for “macronutrients” such as carbs and proteins in modifying the gut bacteria population, also known as the microbiome.
“It’s possible that in this study, the protein-rich version of the diet caused more bloating because it caused more of a healthy shift in the composition of the microbiome,” says study co-senior author Noel Mueller, Ph.D., an assistant professor in the Department of Epidemiology at the Bloomberg School. “Notably, the protein in these diets was mostly from vegetable sources such as beans, legumes, and nuts.”
The study examined a previous clinical trial that was conducted in 2003 and 2005 at John Hopkins ProHealth Clinical Research Unit in Baltimore and at the Brigham and Women’s Hospital in Boston. It included 164 participants who had above-normal blood pressure. Each participant was assigned three different diets over consecutive six-week periods. These were separated by two-week “washout” intervals during which participants returned to regular eating habits.
All three diets were considered high-fiber, low-sodium “DASH” diets and had the same number of calories. The only difference was that they varied in macronutrient emphases. The carbohydrate-rich version was, by calories, 58 percent carbohydrate, 15 percent protein, and 27 percent fat; a plant-protein-rich version was 48 percent carbs, 25 percent protein, 27 percent fat; and a fat-rich version was 48 percent carbohydrate, 15 percent protein, and 37 percent fat.
Lower Incidence of Heart Disease
The original results of the ProHealth trial suggested that the plant protein-rich and fat-rich diets were the most effective in reducing blood pressure and improving measures of blood cholesterol which could lead to a lower incidence of heart disease.
The conclusion of the new study showed that the protein-rich diet showed a 40 percent greater chance of bloating compared to the carb-rich diet. These results suggest that by substituting high quality carb calories for protein calories, bloating could be reduced, making such diets more tolerable.
Researchers did note, however, that making high fiber diets more tolerable with more carbohydrates could also make them less healthy.
“Bloating may be just a consequence of a healthy shift in the microbiome, so that if somebody is able to put up with the bloating caused by a high-protein, high-fiber diet, they may ultimately benefit more in other health measures,” Mueller says.
Researchers are currently working on a follow-on study of the effects of similar dietary patterns on the gut health microbiome.