Walnuts: a natural prebiotic with many beneficial properties
Walnuts have a high content of omega-3 fatty acids, fibers and vitamins, and they could reduce the risk of obesity, cardiovascular diseases and colon cancer. This protection is partly afforded by intestinal bacteria.
Walnuts, hazelnuts or almonds have many beneficial properties. Daily consumption of a handful of oleaginous fruits could reduce the risk of developing cardiovascular diseases or cancer, in particular colorectal and liver cancer. These are serious disorders whose link to the billions of bacteria making up our intestinal microbiota is slowly being discovered.
42 grams of walnuts per day
Researchers from the University of Illinois (United States) assessed for the first time the impact of walnut consumption on the human intestinal flora. To his end, the scientists enrolled 18 healthy men and women with an average age of 53. During the first week of the study, the subjects did not eat any dried fruit and did not change their diet so that the researchers could study their microbiota at baseline. The following two weeks, half the subjects ate 42 grams of walnuts per day while the other half followed their original diet. The analysis of stool and blood samples showed that the composition of the intestinal flora was changed by the consumption of walnuts. The researchers also observed a larger number of bacteria that are beneficial to health. Their also detected a rejuvenation of the microbiota of nut-eating subjects compared to the control group: bacteria communities which are supposed to become a minority over time were always abundantly present in the intestine of consumers of dried fruits.
Reduced cholesterol levels
The team also observed a decrease of cholesterol levels, especially “bad cholesterol”. This finding could explain the protective effects of walnuts against cardiovascular diseases. According to the authors, these effects could also be related to the bacterial production of anti-inflammatory substances, using the polyphenol contained in the walnuts.
The key role of the microbiota has been confirmed
Finally, this study revealed a decrease in the levels of bile acids which result from the biotransformation of cholesterol. Studies have shown that excess amounts of these molecules can promote the onset of intestinal disorders and colon cancer. The authors concluded that “these results provide additional proof that there is a link between diet, microbiota and colonic health”.
Holscher HD, Guetterman HM, Swanson KS, An R, Matthan NR, Lichtenstein AH, Novotny JA, Baer DJ. Walnut Consumption Alters the Gastrointestinal Microbiota, Microbially Derived Secondary Bile Acids, and Health Markers in Healthy Adults: A Randomized Controlled Trial. J Nutr. 2018 May 3. doi: 10.1093/jn/nxy004. [Epub ahead of print] PubMed PMID: 29726951