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How walnuts prevent heart disease, bowel cancer


Cashew nuts, hazelnuts, walnuts, almonds, and pecans are all tree nuts, and a number of studies have documented their potential health benefits.

A handful of walnuts a day may prevent heart disease and bowel cancer, new research suggests.Eating just a third of a cup of walnuts for six weeks significantly reduces the production of excess bile acids, as well as lowering ‘bad’ cholesterol levels, a study found.

Previous research has linked such bile acids to bowel cancer, while lower cholesterol levels are associated with a reduced risk of heart disease.Researchers believe walnuts’ high-fibre content encourages the growth of ‘good’ bacteria in the gut, which benefits people’s heart and colon health.

The scientists also found that despite walnuts being relatively high in calories, with around 28 per nut, only 80 percent of them are absorbed, with gut bacteria using up the remaining 20 percent.Results further suggest people who eat a handful of walnuts a day produce less secondary bile acids, which are made in the bowel rather than the liver like their primary counterparts.


The findings were published in The Journal of Nutrition. How the research was carried out. The researchers analysed 18 healthy adults who ate either no walnuts or 42g every day for two three-week periods.

Forty-two grams of walnuts is the amount recommended by the United States (US) drug-approving body Food and Drug Administration (FDA) to reduce the risk of coronary artery disease. Aside from the walnuts, the participants otherwise ate the same diet.

Blood samples were taken at the start and end of the study to measure the participants’ cholesterol, glucose and inflammation levels.Faecal samples were also collected to determine their guts’ bacteria make up.Lead author Professor Hannah Holscher, from the University of Illinois, said: “Secondary bile acids have been shown to be higher in individuals with higher rates of colorectal cancer.

“Secondary bile acids can be damaging to cells within the GI tract, and microbes make those secondary bile acids. “If we can reduce secondary bile acids in the gut, it may also help with human health.”

Findings also imply people who eat walnuts have higher levels of the bacteria Faecalibacterium, Roseburia and Clostridium in their guts.Professor Holscher said: “There is a lot of interest in Faecalibacterium because it has also been shown in animals to reduce inflammation.

“Animals with higher amounts also have better insulin sensitivity. “There is also growing interest in Faecalibacterium as a potential probiotic bacteria.”Speaking of the calorie content of walnuts, Professor Holscher added: “You’re really only absorbing around 80 percent of the energy from walnuts that labels say.

“That means that the microbes get access to that extra 20 percent of calories and the fats and fiber left in them.“Our study provides initial findings that suggest that the interactions of microbes with the undigested walnut components are producing positive outcomes.”The researchers add further studies are required to determine the specific gut bacteria that benefit people’s health.

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