Tuesday, August 07, 2012

Low-Carb Diets Detrimental to Colon

This was a clinical intervention study, not an observational study. It was small, but telling:

High-protein, Reduced-Carbohydrate Weight-loss Diets Promote Metabolite Profiles Likely To Be Detrimental To Colonic Health, American Journal of Clinical Nutrition, May 2011

There were three diets tested. Food was dispensed and consumption measured:
  • 85g protein, 116g fat, 360g carb (Maintenance diet)
  • 139g protein, 82g fat, 181g carb (High-protein Moderate-carb)
  • 137g protein, 143g fat, 22g carb (High-protein Low-carb)
It found:
"After 4 wk, weight-loss diets that were high in protein but reduced in total carbohydrates and fiber resulted in a significant decrease in fecal cancer-protective metabolites and increased concentrations of hazardous metabolites. Long-term adherence to such diets may increase risk of colonic disease."
Both of the high-protein reduced-carb diets increased hazardous compounds in the colon in just 4 weeks, compared to the lower-protein higher-carb diet.

From their literature review:
"When dietary protein is consumed in high amounts, more dietary protein may reach the colon and result in increased fermentation to products that include harmful nitrogenous metabolites. (This occurred in this study.)"

"Nitrosamine and heterocyclic amine concentrations in fecal samples are increased by high red-meat consumption, and these concentrations have been implicated in increased colon-cancer risk."

"Overall, high intakes of protein, in particular of red meat, may increase risk of developing colorectal cancer."
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6 comments:

Bix said...

So, we're back to the benefits of resistant starch.

Bix said...

I can imagine this same mechanism applies to IBS.

philippa said...

Or higher fat intake, like the Swedes do.

Reijo Laatikainen said...

Too much processed or red meat is not good for (colon) health.

But the story is not so simple and straight forward. Take fiber and veggies/fruits. The biggest source of nitrates and vitamin C are vegetables and fruits.

A clinical study recently showed "Red meat, vitamin C, nitrates and dietary fiber (!) increase the formation of NOC (N-nitroso compounds), cancer promoting metabolites in gut http://jn.nutrition.org/content/early/2012/07/24/jn.112.158824.abstract …

RB said...

I wish we could talk about these diets in terms of food and not nutrients. I eat real food not nutrients. Meat may mean high-protein but it also means high fat (especially saturated fat). Also,
when one talks about carbohydrates no one ever seems to distinguish between low nutrient refined carbs found in soft drinks, baked goods, candy, snacks and deserts and complex carbs from nutrient rich food including vegetables, fruits, legumes, nuts and grains (real whole grains). I fine it hard to eat too much when eating from the latter form of carbs. Why does no one seem to distinguish between the two ways we get our carbs. I think it is a very important distinction. There is no perfect diet, but there are a lot of good diets. I don't happen to think a high meat (protein)- low plant(carb)diet is a good diet. This study seems to back me up but it doesn't help me figure out what food to eat.

Anonymous said...

I think that it really depends on the VLC diet and how extreme people take it, including how much exercise / calories they are burning compared to their intake.
-Jackie