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  • Tree nuts comprise plenty of heart-friendly vitamins, minerals, and antioxidants.
  • New research reveals that tree nut consumption can aid in tryptophan metabolization in the gut.
  • Tryptophan metabolites are known to have cardioprotective benefits.
  • After eating tree nuts, participants experienced lower heart rate and blood pressure.
  • More research is required to understand how tryptophan interacts with the body.

In a new study researchers studied how consuming tree nuts can positively affect your health.

Sudies on consuming other whole foods from berries and avocado to leafy greens and whole grains have found they are packed with an array of antioxidants, vitamins, and minerals that can positively influence blood pressure, inflammation, and cholesterol.

And in a 2021 study, a team of scientists at the University of California, Los Angeles (UCLA) revealed that eating just 1.5 oz (about 42 g) of tree nuts each day can also support heart health.

Now, through a new study published January in the journal Nutrients, the same researchers have learned more about how the nuts have an effect — and it all starts in the gut.

During the 2021 study, 95 overweight individuals were given either a portion of mixed tree nuts or pretzels each day as part of a 24-week weight loss and maintenance diet.

It was found that, in addition to weight loss, those who consumed tree nuts had decreased heart rate and diastolic blood pressure (aka the pressure in your arteries).

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

While the scientists believed that tryptophan — an amino acid found in tree nuts — played a key role in these outcomes, they weren’t sure how.

So, in the recent research (which followed the same methodology as the 2021 study), the team analyzed participants’ plasma and stool samples.

They found that eating tree nuts allowed for better metabolization of tryptophan in the gut.

This is important, noted Geeta Sikand, Associate Clinical Professor of Medicine: Cardiology at the University of California, Irvine School of Medicine, as “tryptophan metabolism is altered in persons with obesity.”

Sikand was not involved in the study.

Through the metabolization process, tryptophan metabolites are created — and these molecules are known to be ‘cardioprotective’.

After being produced, “tryptophan metabolites [are] absorbed into the blood to have an effect on the heart and blood vessels,” said Dr. Zhaoping Li, Professor of Medicine and Chief of the Division of Clinical Nutrition at UCLA and co-author of the study.

So what does this effect entail? It may impact inflammation.

“Specific indole metabolites of tryptophan have been associated with anti-inflammatory properties,” shared Dr. Rigved Tadwalkar, a Board-Certified Cardiologist at Providence Saint John’s Health Center in Santa Monica, CA.

Inflammation is a critical contributor to the development of heart disease.

The notable effect of tree nuts on tryptophan metabolization was surprising to the researchers, stated Li — but that wasn’t the only unexpected outcome.

Interestingly, Li and her colleagues also saw that tree nut consumption led to increased levels of the neurotransmitter serotonin. It’s understood that tryptophan metabolism leads to serotonin production.

“About 90% of serotonin in the body is formed in gut cells and released into the bloodstream,” Sikand told Healthline.

“Studies have revealed that serotonin modulates platelet activation and thrombus formation,” Tadwalkar explained to Healthline.

As such, the chemical “may be implicated in atherosclerosis, myocardial infarction, valve disease, hypertension, and heart failure,” he continued.

“However, the data thus far are not quite conclusive in terms of clinical effects, and this is an active area of research.”

Previous research has shown that having obesity is a risk factor for developing heart disease.

“The primary reason why being obese negatively affects the heart is that it can lead to medical issues that are risk factors for cardiovascular disease,” Tadwalkar stated. Such concerns include hypertension, sleep apnea, and diabetes.

One scientific report also noted that “obesity leads to structural and functional changes of the heart.”

Tadwalkar revealed that cardiovascular diseases most commonly associated with obesity include:

“Tryptophan is one of the 20 amino acids that make up the proteins found in the human body,” Maddie Pasquariello, MS, a Registered Dietitian and Founder of Nutrition With Maddie, told Healthline.

Nine of these amino acids — including tryptophan — are considered ‘essential’, while the remaining 13 are ‘non-essential’.

“The body cannot produce tryptophan on its own, and thus must be obtained from food,” noted Beata Rydyger, BSc, RHN, a Registered Nutritionist and Clinical Nutritional Advisor to Zen Nutrients.

“In the intestine, tryptophan is metabolized by the gut bacteria into indole and indole derivatives,” said Sikand.

“The majority of tryptophan is metabolized through the kynurenine pathway, which generates many bioactive metabolites that are important for immune regulation,” she continued.

The remaining tryptophan, Sikand added, “is metabolized into neuroactive metabolites, such as serotonin, and indole derivatives.”

It’s thought that tryptophan is an “important component” of various health aspects, Pasquariello revealed, including:

  • Cognitive and social functioning
  • Immunity
  • Psychological health
  • Gastrointestinal health
  • Kidney health
  • Sleep
  • Preventing cardiovascular disease

Participants were given a 1.5 oz portion daily, which “is considered a moderate serving size,” revealed Rydyger.

“This serving size can provide a good source of nutrients while still being mindful of overall calorie intake,” she added. “It is a good idea to choose different types of nuts to ensure a diverse nutrient profile.”

It’s also important to be mindful of added extras that could lower the nuts’ nutrient profile. “Keep an eye out for added sugar and oil, which can tack on additional calories, as well as added sodium,” recommended Pasquariello.

“Simple dry-roasted nuts containing predominantly unsaturated fat are best,” she continued. “Then, if you want to add a bit of salt before eating, you can moderate exactly how much you’re adding to avoid excess sodium.”

During the trial, the nuts consumed were cashews, walnuts, pine nuts, almonds, pecans, hazelnuts, Brazil nuts, pistachios, and macadamia.

However, other foods can also be excellent sources of this amino acid.

According to Pasquariello, ingredients of note are:

  • Lean chicken and turkey
  • Beef
  • Pork
  • Salmon
  • Eggs
  • Seeds (such as sesame, pumpkin, and sunflower)
  • Soybeans and tofu
  • Dairy products
  • Corn
  • Rice
  • Wheat

The impressive tryptophan content of nuts can aid in keeping our ticker nice and healthy.

However, Rydyger explained, this food contains plenty of other nutrients that are also beneficial for cardiovascular health.

  • Dietary fiber: “This helps to lower cholesterol levels and improve blood sugar control.”
  • Unsaturated fatty acids: Including monounsaturated and polyunsaturated, “which have been shown to lower ‘bad’ LDL cholesterol levels.”
  • Plant sterols: A natural compound that’s “been shown to reduce cholesterol and lower heart disease risk.”
  • Antioxidants: Nuts contain antioxidants such as selenium, vitamin E, and polyphenols, Rydyger noted. “These help protect the heart and blood vessels from oxidative damage.”
  • Magnesium: “An important mineral that helps to regulate blood pressure and prevent heart disease.”

Furthermore, Sikand added, “due to their fiber and polyphenol content, tree nuts have been suggested to have prebiotic activity.”

Prebiotics are natural compounds that act as ‘food’ for the good bacteria that keep our gut microbiome functioning well — supporting actions such as tryptophan metabolism.

Li explained these other nutrients might also play a role in tryptophan metabolism, and further exploration is needed.

Previous studies have explored the effects of certain foods on heart health — and the new research from UCLA scientists affirms that eating tree nuts can benefit cardiovascular function.

Li stated the findings are particularly significant as they “provide possible mechanisms responsible for the cardiovascular benefits of consuming nuts.”

Another crucial outcome, Li noted, was learning “that nut intake can increase serotonin levels, which can impact mood.”

Li stated the perceived benefits may help people with obesity but also people who do not have obesity.