The benefits of nuts on the intestinal microbiome and health

in health •  3 months ago

Diets rich in nuts have played a role in heart health and in the reduction of colorectal cancer as confirmed by several previous studies.

Epidemiological evidence suggests that diets high in walnuts have beneficial health effects, including reduced mortality, especially for certain types of cancer and heart disease.

Although there is accumulated preclinical evidence that walnuts beneficially affect the gastrointestinal microbiota and intestinal and metabolic health, these relationships have not been studied in humans.

A study from the University of Illinois (USA) published May 3, 2018 in The Journal of Nutrition, explains how nuts impact the gut microbiome - which is composed of billions of microbes or bacteria in the tract gastrointestinal tract - which may be the source of some of these health benefits.


Nuts are foods of interest to scientists for their impact on the microbiome and health.

The dietary fiber they contain acts as a food source for the gut microbiota, helping bacteria to do their job - by breaking down complex foods, providing us with nutrients, or helping us feel full.

Fruits, vegetables, whole grains, nuts and legumes are important vegetable sources of dietary fiber. Eating a variety of these foods helps promote a diverse gut microbiota, which in turn helps support health.

The results of this latest study show that walnut consumption has not only affected the gut microbiota and secondary microbial derived bile acids, but has also reduced LDL cholesterol levels ("bad cholesterol") in adults participating in the study. study, emphasizing the benefits of nuts for cardiovascular, metabolic and gastrointestinal health.


Researchers have discovered that when you consume nuts, it increases the microbes that produce butyrate, a metabolite beneficial to the health of the colon.

The interaction of nuts with the microbiome helps produce some of these health effects. The goal of the researchers is to get to the "black box," that is, all the microbes in our gastrointestinal tract, to see how they interact with the food we eat and the effects on the downstream health. Some of these health effects are thought to be related to metabolites produced by bacteria.

For this controlled feeding study, 18 healthy adult men and women consumed diets that included either 0 g of nuts or 42 g for two periods of three weeks. Fecal and blood samples were collected at the beginning and at the end of each period to evaluate the secondary outcomes of the study, including the effects of nut consumption on fecal microbiota and bile acids and metabolic markers of health.


Nut consumption resulted in a higher relative abundance of three bacteria of interest: Faecalibacterium, Roseburia and Clostridium.

The microbes that have increased in relative abundance in this walnut study come from one of the Clostridium microbe groups, and there is increased interest in these because they have the ability to make butyrate. Unfortunately, the researchers explain that in this study, they did not measure the butyrate rate, so they can not say that it is only because these microbes have increased that butyrate has increased.

There is a lot of interest for the bacterium Faecalibacterium because it has also been shown in animals to reduce inflammation. Animals with higher amounts also have better sensitivity to insulin. There is also a growing interest in Faecalibacterium as potential probiotic bacteria.

Finally, the results also show, with walnut consumption, a reduction of secondary bile acids compared to control. Secondary bile acids have been found to be higher in people with higher rates of colorectal cancer. Secondary bile acids can damage the cells of the gastrointestinal tract, and microbes are secondary bile acids.

Previous research that has led to this microbial research has shown that the amount of energy (calories) derived from nuts after we eat them is lower than previously thought.

To conclude, the researchers say that, "When you do calculations to determine the amount of energy that we had planned while eating nuts, it did not correspond to the energy absorbed. You only absorb 80% of the energy of nuts, which means that microbes have access to that extra 20% of calories, the fat and fiber they contain, and what happens then? Positive result or a negative result for health? Our study provides initial results that suggest that interactions of microbes with undigested walnut fruit components produce positive results. "

More research on the beneficial properties of nuts is currently underway, with the aim of examining other microbial metabolites and how they influence health outcomes, rather than simply characterizing changes in the microbiome.


"Walnut Consumption Alters the Gastrointestinal Microbiota, Microbially Derived Secondary Bile Acids, and Health Markers in Healthy Adults: A Randomized Controlled Trial". The Journal of Nutrition, 2018; DOI: 10.1093 / jn / nxy004

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