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The idea of personal nutrition continues to evolve. A new human trial study published in Gastroenterology looked at fecal microbiota transplantation as a novel approach to understand the potential impact on lessening weight regain after being on a weight-loss diet – a common issue most dieters face after coming off a weight-loss diet.

What Did the Study Find?

There are many elements of this research, but here are some of the findings: 

  • In the trial, 90 Israeli individuals (91% men) who had abdominal obesity (elevated waist circumference) or dyslipidemia (elevated triglycerides or abnormal HDL) were part of a 6 month-weight loss program in which they were randomly assigned to one of 3 diets (standard healthy diet guidelines; a Mediterranean diet; a green-Mediterranean diet) along with an exercise program. The Mediterranean diets were isocaloric and included 1 ounce of walnuts per day (containing 440mg polyphenols), provided by the California Walnut Commission1. The green-Mediterranean diet included an additional 800mg per day of polyphenols from the other plant foods included in the diet.2

  • Fecal microbiota samples were collected after 6 months of being on the weight-loss diet and processed into frozen, opaque, and odorless capsules.

  • The subjects were then removed from the weight loss program and randomly divided into two groups – one group that took their own capsulated fecal microbiome and one group that took placebo capsules. All subjects took these capsules for 8 months.

  • The researchers found that those who followed the green-Mediterranean diet had significant changes in their microbiome during the weight loss phase. Those who followed the green-Mediterranean diet and consumed the fecal transplant capsules had significantly limited weight regain compared to the group who followed the same green-Mediterranean diet but consumed the placebo capsules. Overall, regardless of the diet followed, participants who consumed the fecal transplant capsules had less weight regain compared to those who consumed the placebo capsules.

Important to note, for ethical and technical reasons, the gut microbiome was assessed in fecal matter, and not in bioactive sites along the gastrointestinal tract. Larger and longer-term studies are needed to further understand population-wide effects as well as specific dietary components that could modify the host microbiome.

What Does This Mean?

This novel approach is an emerging area in nutrition research to watch. There is still much to learn and certainly a lot to think about in terms of talking about this with those outside of a research or medical field. While the body of research builds, the California Walnut Commission is taking note about walnuts’ role. This particular study adds to existing findings suggesting walnuts may be a good choice because of their prebiotic properties which support gut health and enhance the growth of beneficial bacteria. It also underscores the role of walnuts as a key dietary component in the traditional, and green1, Mediterranean Diet.

For more research on walnuts and gut health, check out these California Walnuts resources on walnuts.org

Follow @CAWalnuts to stay up to date on the latest research, recipes and tips.

1While the California Walnut Commission (CWC) provides funds and/or walnuts to various research projects, the actual studies are conducted independently by researchers who design the experiments, interpret the results and write the manuscripts.

2The green-Mediterranean diet included 4 cups per day of green tea and 100g frozen cubes of Wolfia-globose duckweed (Mankai cultivated strain) aquatic plant consumed as a 500ml green shake.

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