A new study suggests that walnuts may reduce certain risk factors for cardiovascular disease by altering the metabolism of the amino acid L-tryptophan. In a parallel controlled trial, obese or overweight people who snacked on nuts as part of a 24-week weight loss and weight maintenance program saw an increase in serotonin levels, which can improve mood. Nuts are nutrient dense and eating them instead of other snacks was not associated with weight gain.

The authors of a new study recently linked the consumption of nuts: almonds, cashews, hazelnuts, macadamia, pecans, pistachios and walnuts to a reduction in blood pressure, an important risk factor. cardiovascular disease (CVD). They have just published a new study that could explain this link.

Researchers found that tree nuts increased levels of cardio-protective L-tryptophan metabolites in plasma and stool samples taken from study participants.
The study was a randomized, controlled, parallel study involving 131 people who were obese or overweight during a 24-week weight loss and weight maintenance program.

The diet of all participants included a daily snack of 40 grams. Of the 95 people who took part in the study, 39 snacked on pretzels as a control, while another 56 people ate nut-based snacks of the same caloric value. At the end of the study period, the researchers analyzed fecal and blood plasma samples from each participant to determine the effects of their different snacks.

People who ate nuts experienced significant increases in blood serotonin levels at week 12 (60.9%) and week 24 (82.2%), compared to their baseline levels. Those who ate the pretzels experienced an increase in blood serotonin levels during the maintenance phase of the study, between weeks 12 and 24. Tryptophan is the only precursor to serotonin in the body, which is believed to support a range of bodily functions including mood, sleep and digestion. The study is published in the journal Nutrients.

Heart-healthier snacks

Snacking can lead to unwanted weight gain, and unhealthy snacks often end up replacing more nutritious foods in the daily diet.

Tree nuts and tryptophan metabolism

Tree nuts contain significant amounts of tryptophan, an essential amino acid that aids in growth and overall health. Tryptophan is metabolized by three pathways, the kynurenine and serotonin pathways in body cells, and the indole pathway in intestinal bacteria. Disruption of tryptophan metabolism has been associated with metabolic diseases, including obesity and cardiovascular disease.

Researchers found novel associations between tryptophan metabolites and blood pressure, heart rate, and satiety in overweight/obese subjects, suggesting a broader impact of tryptophan metabolism on overall health, including cardiovascular health. The gut microbiome and its metabolites can help regulate our metabolism and our mood.

There are other reasons why the study makes sense. The authors’ interpretation of the results of this study that tree nuts promote CVD-protective tryptophan metabolites and heart health makes sense because of its ability to help reduce inflammation, one of the main causes atherosclerosis and heart disease.

The benefits of more serotonin

Emotional eating is a major contributing factor to obesity. Walnuts can improve mood through an increase in serotonin which is one of the key neurotransmitters to regulate mood. The researchers were surprised to see an increase in serotonin levels in the nut group during the weight loss and weight maintenance phases of the study. Only the tree nuts group experienced an increase in stool serotonin levels. At the end of the study, both groups had higher serotonin blood levels.

The authors speculate that this final increase in blood serotonin in all participants could be evidence of the body’s response to weight loss. Indeed, an increase in serotonin levels may benefit overweight or obese people trying to lose weight due to its role in energy expenditure and appetite suppression.

What’s good in nuts

40g of walnuts or peanuts provides over 10% of the recommended nutrient intake for adult males of protein, iron, magnesium, phosphorus, zinc, copper, thiamin and vitamin E. In addition, 40g of walnuts provides over 10% of the Recommended Dietary Allowance for Adult Males of Vitamin B-6 and Selenium.

As an example, here are some important nutrients associated with some tree nuts:

Pistachios contain phytosterols, potassium, and carotenoids that support healthy blood vessels and blood lipids.

Brazil nuts contain selenium, which helps fight oxidative stress and support heart health and immune health.

Pecans are high in copper, which aids in blood sugar metabolism and can help maintain a healthy thyroid gland.

Almonds are rich in antioxidants, fiber and protein.

Just one Brazil nut provides 100% of the recommended daily intake of selenium. Although nuts are high in energy, concerns about their link to weight gain seem unwarranted. Studies have shown that a higher intake of tree nuts is associated with reduced weight and body fat, suggesting that they do not contribute to weight gain.

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