High-Protein diets that skimp on fiber may have harmful long-term effects on the colon, a small UK study suggests.
According to Reuters, a group of 17 obese men were assigned to one of three diets: One designed to maintain weight, another involving large amounts of protein with moderate amounts of carbohydrates, and another involving large amounts of protein and a small amount of carbs.
The study, which appeared in the American Journal of Clinical Nutrition, found that those placed on the high-protein diets had higher levels of N-nitroso compounds, substances often linked to cancer. Those on the high-protein, low-carb diet had lowered concentrations of fiber-derived compounds thought to help fight cancer.
According to the study, those attempting to lose weight should be sure to incorporate adequate amounts of fiber into their diets. 28 grams per day is recommended for adults, though there is doubt as to whether or not that is a sufficient amount for those on high-protein diets.
The report also notes that this study looked only at “short-term shifts in compounds that are byproducts of metabolism,” and therefore does not show conclusively whether or not high-protein diets actually raise the long-term risk of colon disease. In addition, high-protein diets have been shown to help some lose weight, while obesity itself has been linked to colon disease.
“People should not be discouraged from losing weight, as this offers important health benefits,” senior researcher Dr. Harry J. Flint told Reuters. However, “the risk of colorectal cancer might be raised by long-term adeherence to diets that are high in protein and low in carbohydrate, especially fiber.”
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