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Tag: red meat

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Red meat,bacteria, and atherosclerosis.From Medical Xpress:

Why does red meat increase the risk for cardiovascular disease? Blame our gut bacteria

New research provides details on how gut bacteria turn a nutrient found in red meat into metabolites that increase the risk of developing heart disease. Publishing in the November 4th issue of the journal Cell Metabolism, the findings may lead to new strategies for safeguarding individuals' cardiovascular health.

Previous research led by Dr. Stanley Hazen, of Lerner Research Institute and the Miller Family Heart and Vascular Institute at Cleveland Clinic, revealed a pathway by which red meat can promote atherosclerosis, or hardening of the arteries. Essentially, bacteria in the gut convert L-carnitine, a nutrient abundant in red meat, into a compound called trimethylamine, which in turn changes to a metabolite named trimethylamine-N-oxide (TMAO), which promotes atherosclerosis. Now Dr. Hazen and his team extend their earlier research and identify another metabolite, called gamma-butyrobetaine, that is generated to an even greater extent by gut bacteria after L-carnitine is ingested, and it too contributes to atherosclerosis.

The discovery that metabolism of L-carnitine involves two different gut microbial pathways, as well as different types of bacteria, suggests new targets for preventing atherosclerosis—for example, by inhibiting various bacterial enzymes or shifting gut bacterial composition with probiotics and other treatments.

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Very interesting. Gives people a way to eat red meat, but not increase their colorectal cancer risk (by also eating resistant starch, e.g., potato salad or beans). From Science Daily:

Eating resistant starch may help reduce red meat-related colorectal cancer risk

Consumption of a type of starch that acts like fiber may help reduce colorectal cancer risk associated with a high red meat diet, according to a study. "Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster," said one researcher. "This finding supports consumption of resistant starch as a means of reducing the risk associated with a high red meat diet.

Unlike most starches, resistant starch escapes digestion in the stomach and small intestine, and passes through to the colon (large bowel) where it has similar properties to fiber, Humphreys explained. Resistant starch is readily fermented by gut microbes to produce beneficial molecules called short-chain fatty acids, such as butyrate, she added.

"Good examples of natural sources of resistant starch include bananas that are still slightly green, cooked and cooled potatoes [such as potato salad], whole grains, beans, chickpeas, and lentils. Scientists have also been working to modify grains such as maize so they contain higher levels of resistant starch," said Humphreys.

After eating 300 g of lean red meat per day for four weeks, study participants had a 30 percent increase in the levels of certain genetic molecules called miR-17-92 in their rectal tissue, and an associated increase in cell proliferation. Consuming 40 g of butyrated resistant starch per day along with red meat for four weeks brought miR-17-92 levels down to baseline levels.

The study involved 23 healthy volunteers, 17 male and six female, ages 50 to 75. Participants either ate the red meat diet or the red meat plus butyrated resistant starch diet for four weeks, and after a four-week washout period switched to the other diet for another four weeks.

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From Medical Xpress:

Estimated risk of breast cancer increases as red meat intake increases

Higher red meat intake in early adulthood might be associated with an increased risk of breast cancer, and women who eat more legumes—such as peas, beans and lentils—poultry, nuts and fish might be at lower risk in later life, suggests a paper published BMJ today.

So far, studies have suggested no significant association between  intake and breast cancer. However, most have been based on diet during midlife and later, and many lines of evidence suggest that some exposures, potentially including dietary factors, may have greater effects on the development of breast cancer during early adulthood.

So a team of US researchers investigated the association between dietary protein sources in early adulthood and risk of breast cancer. They analysed data from 88,803 premenopausal women (aged 26 to 45) taking part in the Nurses' Health Study II who completed a questionnaire on diet in 1991. Adolescent food intake was also measured and included foods that were commonly eaten from 1960 to 1980, when these women would have been in high school. 

Medical records identified 2,830 cases of breast cancer during 20 years of follow-up.

This translated to an estimate that higher intake of red meat was associated with a 22% increased risk of breast cancer overall. Each additional serving per day of red meat was associated with a 13% increase in risk of breast cancer (12% in premenopausal and 8% in postmenopausal women).

In contrast, estimates showed a lower risk of breast cancer in postmenopausal women with higher consumption of poultry. Substituting one serving per day of poultry for one serving per day of red meat - in the statistical model - was associated with a 17% lower risk of breast cancer overall and a 24% lower risk of postmenopausal breast cancer.

Furthermore, substituting one serving per day of combined legumes, nuts, poultry, and fish for one serving per day of red meat was associated with a 14% lower risk of breast cancer overall and premenopausal breast cancer.

The authors conclude that higher red meat intake in early adulthood "may be a risk factor for breast cancer, and replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk of breast cancer."