Consumption of mixed tree nuts increases serotonin and has cardioprotective effect in obese

USA: The consumption of mixed tree nuts (MTNs; cashews, Brazil nuts, walnuts, pistachios, pine nuts, pecans, macadamias, and hazelnuts) has a positive impact on the metabolism of tryptophan, an essential amino acid, in overweight and obese people, says a recent study published in Nutrients. 

The researchers observed an increase in cardioprotective tryptophan metabolites and the neurotransmitter serotonin. 

In a previous study, researchers at UCLA demonstrated that consuming 1.5 ounces of tree nuts per day (versus pretzels) during 24 weeks of weight loss and weight maintenance, resulted in weight loss, increased satiety, decreased diastolic blood pressure and decreased heart rate. Tryptophan (found in tree nuts) has been indicated as an important factor in cardiovascular disease (CVD). It is metabolized in the gut, producing many bioactive metabolites that are important in immune regulation affecting chronic diseases such as diabetes and CVD. The current study examined whether tree nut snacks, as part of a hypocaloric diet, could modify the gut microbiome, resulting in increased cardio-protective tryptophan microbial metabolites.

Plasma and stool samples were collected from 95 overweight or obese participants and were evaluated in the current study for tryptophan metabolites and for gut microbiota. “We’ve known for a long time that tree nuts can help decrease CVD risk, and these findings provide some possible explanations,”

stated lead researcher, Zhaoping Li, MD, PhD, Professor of Medicine and Chief of the Division of Clinical Nutrition at UCLA. “We discovered some new associations between tryptophan metabolites and blood pressure, heart rate, and satiety in overweight/obese subjects, suggesting a broader impact of tryptophan metabolism in overall health, including cardiovascular health.”

Another interesting finding was the significant increase in blood serotonin levels (60.9% and 82.2% increase from baseline at week 12 and 24, respectively) in both the weight loss and weight maintenance phases, in the those who consumed mixed tree nuts. “This is the first time we’ve seen mixed tree nut consumption associated with an increase in serotonin levels in the body,” explained Dr. Li. “While more research is needed, this is exciting since serotonin can have an important impact on mood and overall mental health.”

Research has shown that people get about 25% of their calories each day from snacks and a large proportion come from desserts, sugar-sweetened beverages, sweets and salty snacks.“Replacing just one of those snacks with 1.5 ounces of tree nuts may help improve overall health and reduce the risk for various chronic diseases,” stated Maureen Ternus, M.S., R.D.N, Executive Director of the International Tree Nut Council Nutrition Research & Education Foundation.

Reference:

Yang, J.; Lee, R.; Schulz, Z.; Hsu, A.; Pai, J.; Yang, S.; Henning, S.M.; Huang, J.; Jacobs, J.P.; Heber, D.; Li, Z. Mixed Nuts as Healthy Snacks: Effect on Tryptophan Metabolism and Cardiovascular Risk Factors. Nutrients 2023, 15, 569. https://doi.org/10.3390/nu15030569