NEW STUDY SHOWS SNACKING ON MIXED TREE NUTS MAY IMPACT CARDIOVASCULAR RISK FACTOR TMAO
New Findings Published in Nutrients in Partnership with the International Tree Nut Council Nutrition Research & Education Foundation
DAVIS, Calif., July 1, 2025 /PRNewswire/ -- In a paper1 published online this week in the journal, Nutrients, researchers found that consuming mixed tree nuts (almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts) in a hypocaloric diet resulted in reduced body weight and plasma levels of the cardiovascular risk factor trimethylamine N-oxide (TMAO). The decrease in TMAO levels was greatest among individuals with lower-quality baseline diets.
In a previous study2, 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, and decreased blood pressure and heart rate—signs of reduced cardiovascular risk. TMAO, a gut microbiome metabolite, is a novel cardiovascular disease risk factor. It is produced by the liver from trimethylamine (TMA), which is generated by gut bacteria from dietary precursors such as choline, phosphatidylcholine and L-carnitine.
Diet can impact TMAO levels by modifying the gut microbiota, effecting the production of TMA from nutrients like choline and L-carnitine. Tree nuts, which are rich in phytochemicals such as carotenoids, phenolic acids and phytosterols, may also affect TMAO production. The current study looked at whether tree nut snacks, as part of a hypocaloric diet, could influence TMAO levels and their relationship with the gut microbiome.
Plasma samples were collected and evaluated from 95 overweight or obese participants. Nutritional data were collected at baseline and week 12 via dietary recall. Each study participant was given a Healthy Eating Index (HEI) score, which is used to assess diet quality based on the Dietary Guidelines or Americans. According to lead researcher, Zhaoping Li, MD, PhD, Professor of Medicine and Chief of the Division of Clinical Nutrition at UCLA, "While the hypocaloric diet with tree nuts and pretzels both resulted in a significant reduction in plasma TMAO levels, the reduction of TMAO was more profound in those consuming mixed tree nuts with poor dietary habits and low HEI scores."
Interestingly, the dietary intervention did not significantly alter the intake of dietary sources of TMAO, including choline and phosphatidylcholine. Therefore, the observed decrease in TMAO plasma levels is unlikely due to a reduction in TMAO precursors. "Adding mixed tree nuts to hypocaloric diets may not only help in the reduction of plasma TMAO levels, but may be an important intervention for managing cardiovascular health," stated Dr. Li.
In support of these findings, Maureen Ternus, M.S., R.D., Executive Director of the International Tree Nut Council Nutrition Research & Education Foundation (INC NREF), emphasized, "This study is yet another piece of evidence showing that people should include more nuts in their diet. Just a handful of tree nuts (1.5 ounces or 1/3 cup) every day can result in numerous health benefits."
The International Tree Nut Council Nutrition Research & Education Foundation (INC NREF) is a non-profit, non-governmental organization dedicated to supporting nutrition research and education for consumers and health professionals throughout the world. Members include those associations and organizations that represent the nine tree nuts (almonds, Brazils, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts). For more information, please visit our website at www.nuthealth.org.
1 Lei, O., J. Yang, H.H. Kang, Z. Li., 2025. Impact of a 12-week hypocaloric weight loss diet with mixed tree nuts vs. pretzels on trimethylamine-n-oxide (TMAO) levels in overweight adults. Nutrients 17(13): 2137. https://doi.org/10.3390/nu17132137
2 Wang, J., S. Wang, S.M., Henning, T. Qin, Y. Pan, J. Yang, J. Huang, C.-H. Tseng, D. Heber, Z. Li., 2021 Mixed tree nut snacks compared to refined carbohydrate snacks resulted in weight loss and increased satiety during both weight loss and weight maintenance: a 24-week randomized controlled trial.Nutrients.13(5), 1512. https://doi.org/10.3390/nu13051512
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SOURCE International Tree Nut Council Nutrition Research & Education Foundation