Consuming half a cup of walnut per day may help protect the digestive system by increasing the amount of probiotic bacteria in the gut and ward off risks of heart and brain disease as well as cancer, researchers say.
The findings, from the animal study, showed that a walnut-enriched diet reshapes the gut microbe community and causes a significant increase in beneficial bacteria including Lactobacillus, Roseburia, and Ruminococcaceae.
Walnuts act as a probiotic to help nourish and grow the bacteria that keeps the digestive system healthy, the researchers said.
"The health of the gut is related to overall health in the rest of the body. Our study is showing that walnuts change the gut, which could help explain why there are other positive health benefits to eating walnuts such as heart and brain health," said lead researcher Lauri Byerley, associate professor at the Louisiana State University in the US.
Consuming walnuts also has been associated with health benefits including a reduced risk of heart disease and cancer, Byerley added.
The bioactive components of walnuts may be contributing factors in providing these health benefits, the researchers explained in the paper appearing in the Journal of Nutritional Biochemistry.
"Greater bacterial diversity may be associated with better health outcomes, whereas low diversity has been linked to conditions such as obesity and inflammatory bowel disease," Byerley noted.
Walnuts are the only nuts that contain a significant amount of alpha-linolenic acid (ALA), the plant-based omega-3 fatty acid (2.5 grams per one ounce) and also offer protein (4 grams per one ounce) and fibre (2 grams per one ounce).
For the study, rats were randomly assigned to a diet containing ground walnuts, equivalent to about 2 ounces (1/2 cup) per day in humans, or a diet without walnuts for up to 10 weeks.