The human digestive tract contains more than 1,000,000,000,000 bacteria cells per gram of feces.
Another way of thinking about this is that there 150 times more bacteria genes than human genes in our bodies.
In other words as complex as the human genome is the human microbiome (i.e. bacteria) another layer of complexity that was not even imagined 20 to 30 years ago.
Depending on the type of bacteria in our digestive tract, they can be either good or bad for our digestive tract and overall health.
This is where food can be very critical in changing our microbiome and improving our overall health.
A study was published in the Journal of Nutrition that tested how eating walnuts can change the bacteria in the digestive tract and markers of health.
Here are the study details
– Study design: Controlled feeding, randomized crossover study in health men and women –
– Human subjects: 18 people, average age 53.1 years with a BMI of 28.8 were enrolled
– Walnuts: Patients consumed 42 grams of walnuts or 0 grams of walnuts for two 3-week periods. A one-week washout period occurred in between the walnut or no walnut consumption.
– Fecal and blood samples: at the end of each 3-week period blood and feces were analyzed for fecal microbiota (i.e. bacteria), bile acids, and metabolic markers of health.
Here are the results
– Walnut consumption resulted in a 49–160% higher relative abundance of Faecalibacterium, Clostridium, Dialister, and Roseburia
– 16–38% lower relative abundances of Ruminococcus, Dorea, Oscillospira, and Bifidobacterium (P < 0.05).
– Fecal secondary bile acids, deoxycholic acid and lithocholic acid, were 25% and 45% lower, respectively, after the walnut treatment compared with the control treatment (P < 0.05).
– Serum LDL cholesterol was 7%, respectively, after walnut consumption compared with after the control treatment (P < 0.01).
– The non-cholesterol sterol campesterol concentrations was 6% lower after walnut consumption compared to the control treatment
Here is what the authors had to say
To our knowledge, this is the first study to examine the impact of walnut consumption on the human fecal microbiota and bacterial metabolites and metabolic health.
In addition to providing a source of fiber and unsaturated FAs, walnuts are also high in ellagic acid. Gastrointestinal bacteria can metabolize ellagic acid to produce urolithins, which can enter the enterohepatic circulation and have anti-inflammatory and beneficial vascular effects.
In summary, walnut consumption affected the gastrointestinal microbiota and microbially derived secondary bile acids and reduced serum total and LDL cholesterol in healthy adults. These results suggest that the gastrointestinal microbiota may contribute to the underlying mechanisms of the beneficial health effects of walnut consumption, including cardiometabolic and gastrointestinal health.
Take away message
This study was able to show benefits of walnuts on the microbiome in just 3 weeks. For example, bacteria that produce pro-inflammatory bile acids were decreased. In addition, good bacteria that produce butyrate were increased.
These results suggest walnuts can change the type of bacteria in our digestive tract and possibly contribute to improved overall health. Walnut consumption is linked to ellagic acid levels being increased possibly contributing to anti-inflammatory effects and improve cardiovascular benefits.
Reference
Holscher et al. Walnut Consumption Alters the Gastrointestinal Microbiota, Microbially Derived Secondary Bile Acids, and Health Markers in Healthy Adults: A Randomized Controlled Trial. J Nutr. 2018; Volume 148 (Issue 6): pages 861-867.
His research on plant medicine has led to more than 45 publications and abstracts.This research has been presented at international meetings in the USA, France, Turkey, Peru, Israel, Austria, and Italy.
Categories: Antioxidant, Cholesterol, Clinical Trials, Digestion, Fiber, Food, Inflammation