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Nuts, Tryptophan and Heart Health

This article has been republished from Nuts for Life. Read the original article.

Snacking on a daily handful of nuts helps the body metabolise tryptophan, with potential heart-health benefits, including lowered heart rate and blood pressure, according to a new study (1).

The research involved 95 overweight people, who were tracked over six months.

Study participants were given either 42g/day of mixed tree nuts, or a pretzel control with the same kilojoule content, for 12 weeks, as part of a weight loss diet. This was then followed by a weight maintenance program for another 12 weeks.

Did you know? Tryptophan is an essential amino acid, needed to make protein. It is metabolised in the gut into bioactive metabolites, which help to regulate many processes within the body.

Key Outcomes: Nuts and Tryptophan

Daily mixed tree nut consumption led to improved tryptophan metabolism in the gut, compared with the control.

And specifically, levels of the anti-inflammatory tryptophan metabolites (or ‘by-products’), known to be heart healthy, increased with nut consumption.

The research, just published in the journal Nutrients, provides more clues into the possible mechanisms behind the well-established heart health benefits of nuts.

Did you know? A major review, of more than 145 systematic reviews and meta-analyses, found eating a handful (28g) of nuts a day, compared to eating no nuts, was linked with a 21% reduced risk for cardiovascular disease (2).

A New Finding: Nuts Linked with Serotonin

In another interesting finding, nut consumption was also linked with higher serotonin levels.

Compared to baseline measures, blood serotonin levels increased by around 61% and 82%, at weeks 12 and 24, respectively, with nut consumption.

According to the researchers, tryptophan metabolism impacts serotonin production.

And while more research is needed in this area, they say it’s an exciting finding given that serotonin (a neurotransmitter, or ‘chemical messenger’ within the body) impacts mood and overall mental health.

The study was funded in part by the International Tree Nut Council Nutrition Research & Education Foundation (INC NREF).


  1. Yang, J., et al. Mixed nuts as healthy snacks: Effect on tryptophan metabolism and cardiovascular risk factors. Nutrients, 2023. 15:569.
  2. Balakrishna, R., et al. Consumption of nuts and seeds and health outcomes including cardiovascular, diabetes and metabolic disease, cancer, and mortality: An umbrella review. Advances in Nutrition, 2022. nmac077,

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