Long heralded as a superfood with health benefits, walnuts may get a new superlative as a food magician, helping to transform the gut microbiota to healthy. That’s the finding from a new study out of the Louisiana State University (LSU), New Orleans School of Medicine.
The team from LSU, led by Dr. Lauri Byerley, added walnuts to the diet of one group of research mice. Comparing the gut bacteria of those mice to a control group, the walnut group’s gut bacterial makeup changed for the better and was higher functioning. For example, the guts of mice with a walnut-rich diet included more lactobacillus bacteria, credited with reducing the number of bad bacteria in the gut. Notably, there was a shift in the total makeup of the gut, rather than simply the addition of new, good bacteria.
Based on the findings, researchers felt walnuts may be an effective prebiotic, a dietary substance credited with increasing the number and diversity of good bacteria in the gut.
"Gut health is an emerging research area, and researchers are finding that greater bacterial diversity may be associated with better health outcomes," said Dr. Byerley.
Findings were published in The Journal of Nutritional Biochemistry. The research was supported by the American Institute for Cancer Research and California Walnut Commission.
The Bacteria in Your Gut
Gut microbiota, also called gut flora, is a complex community living in the digestive tract. The microbiota is made up of bacteria, fungi, archaea, viruses, and protozoans. The gut is the largest zone of bacteria in your body.
Microbiota regulate the gut. Bacteria prompt the release of digestive juices and enzymes to aid in food digestion and help absorb nutrients like calcium, copper, magnesium, and iron. Acids in the microbiota help the muscles contract during digestion. Microbiota also help form a membrane around your gut to prevent toxins and viruses from entering the system.
There is even evidence gut flora plays a role in the brain’s central nervous system. According to research from Johns Hopkins University, irritated guts may send signals to the central nervous system to trigger mood changes, like anxiety and depression.
Within gut flora, there are two considerations: the number of good bacteria and the diversity of the types of good bacteria available. In both cases, higher numbers are preferable. Patients in clinical studies with less diverse bacteria were found more prone to obesity and inflammatory bowel disease (IBD). And, indeed, sufferers of inflammatory bowel disease, have markedly less diversity in the gut.
Changing Gut Flora
Developed at one to two years after birth, the makeup of the gut community changes over time with diet and health. Changes can also be spurred on by pregnancy in women or broad-spectrum antibiotic use, which reduce the number and species of bacteria in the gut.
If you suffer from colitis or other IBDs, your gut is always front and center in your mind. While diet doesn’t cause IBDs, certain foods will trigger a reaction. Additionally, there is some evidence the types of foods you eat can help relieve symptoms. A number of supplements or sources in food have been identified to help adjust the makeup of the gut flora.
Probiotics is a broad term used for “good” live bacteria that aid in digestion. Commercially, some foods are touted as high in probiotics and so good for digestive health: yogurts, cheeses, kefir, sauerkraut, and kimchi. Doctors may recommend a probiotic supplement while a patient is on antibiotics in order to replenish the gut with healthy bacteria.
Probiotics can be killed by heat or stomach acid and there is still debate about which probiotics the body needs to flourish.
Prebiotics, on the other hand are fiber compounds not digestible by the gut, which stimulates growth of diverse and plentiful beneficial bacteria. It’s like a dose of nourishment for bacteria already in the gut. As noted with the LSU study results, walnuts may be a prebiotic. Other confirmed sources are raw garlic, raw leeks, onions, dandelion greens, and artichokes.
The Nutrients in Walnuts
Walnuts contain key nutrients needed to make the body run. Some of these may explain why they are able to realign intestinal bacteria for the better.
Manganese: This mineral helps the body form connective tissue, bones, blood clotting, and sex hormones. It also plays a role in metabolism, calcium absorption, blood sugar regulation, and normal brain and nerve function.
Copper: This mineral is good for your bones. It promotes bone density, collagen, and elastine, all components needed to reduce the risk of bone fracture and aid in the recovery of damaged connective tissues.
Magnesium: This mineral helps with bone formation and absorption of calcium into the bone.
Phosphorus: This mineral builds strong bones and teeth. It also helped filter waste in the kidneys, regulate energy in the body, repair damaged tissues, ad regulate the use of other minerals in the body.
Vitamin B6 (pyridoxine): This vitamin helps convert food into fuel, as well as metabolize fats and proteins. B6 also helps create the neurotransmitters that carry signals for brain development and function and key hormones, such as serotonin.
Iron: Found in the red blood cells, iron helps carry oxygen to every cell in the body. It also produces adenosine triphosphate (ATP), the energy source for the body.
Omega-3 fatty acids: Also known as polyunsaturated fatty acids, this is one of the few acids your body can’t make. It plays a key role in brain function and normal development. Importantly, omega-3s can also reduce chronic inflammation.
Other Benefits of Walnuts
Walnuts also get credit for other health benefits, again likely because of the plethora of nutrients contained inside.
Weight loss: Although walnuts get a bad rap as a fatty food source—and it’s true; nuts can be as much as 80 percent fat—they contain unsaturated fats, thought to lower bad cholesterol levels. Nuts in moderation can elevate your resting energy expenditure and promotie weight loss. Walnuts are full of protein, making them more filling than other go-to snacks. A study from the American Journal of Clinical Nutrition found women who reported eating nuts at least twice a week gained less weight over an 8-year period than women who ate nuts rarely.
A serving of walnuts is 1 ounce, or about 14 half walnuts.
Lower risk of cardiovascular disease: The FDA has approved a claim that eating 1.5 ounces of walnuts a day along with a healthy diet can reduce the risk of heart disease. The American Heart Association recommends eating about four servings of nuts a week.
Slower tumor growth: While only currently studied in mice, a study from UC Davis showed a walnut diet slowed the growth of prostate cancer. Researchers believed it was a combination of the omega-3 fatty acids in walnuts and some component that counteracts with the mechanism the promotes growth.
Improved brain health: With a deluge of omega-3 fatty acids, walnuts get credit for helping the brain to function normal and continue to develop.
While walnuts may help you re-engineer your gut bacteria and build healthy bones, it’s important to remember that good health comes from a total diet and overall eating pattern that is balanced and full of variety. Eat all foods in moderation, including walnuts. Healthy eating is a marathon, not a sprint.