Nearly one-third of adults report sleeping less than seven hours a night, below the minimum amount recommended for most adults, while nearly one in five has trouble staying asleep most days or every day. At the same time, nearly one-third of people say they are seeking improved sleep from foods, beverages or nutrients. 

Pistachios have attracted researchers’ attention because they naturally bring together several nutrients and plant compounds connected to sleep. Now, a new narrative review published in Nutrition Research Reviews identifies pistachios as a promising whole food for sleep research and explores how their nutrient profile may influence processes related to sleep quality, falling asleep, staying asleep and regulation of the sleep–wake cycle. 

Three reasons pistachios are intriguing to sleep researchers and clinicians

• Supporting the body’s production of melatonin: Pistachios provide tryptophan, vitamin B6 and magnesium, which the body uses in the production of serotonin and melatonin. Serotonin is involved in sleep regulation and is also used to make melatonin, the hormone that helps regulate the sleep–wake cycle. Pistachios also contain phytomelatonin, the form of melatonin produced by plants, although its absorption and effects from eating pistachios have not been established in people.  
• Supporting calming signals in the brain: Pistachios provide vitamin B6 and magnesium, which are involved in the production and function of gamma-aminobutyric acid (GABA), a brain chemical that helps quiet nerve activity and plays a role in regulating sleep.  
• Connecting the gut and sleep: Pistachios provide fiber and polyphenols that gut microbes can break down into compounds that may influence communication between the gut and brain, including signaling involved in sleep regulation. Researchers are exploring whether these interactions could be another way pistachios influence sleep. 

How much tryptophan do pistachios provide?  

A one-ounce serving of pistachios provides about 71 milligrams of tryptophan, roughly 20% of the daily amount recommended for a 154-pound adult. Tryptophan is an essential amino acid the body uses to make serotonin, a brain chemical involved in sleep regulation, and melatonin, the hormone that helps regulate the sleep–wake cycle. 

Pistachios also provide vitamin B6 and magnesium, which help the body convert tryptophan along the pathway to serotonin and melatonin. Together, this combination is one reason researchers are interested in studying whole pistachios and sleep. 

Why the whole pistachio matters 

Most nutrition-and-sleep research has examined individual nutrients, extracts or supplements. Pistachios bring several of these components together naturally in one food, creating an opportunity to study how they may work together rather than in isolation. This natural structure, how nutrients and plant compounds are packaged together and interact within a food, is known as the food matrix, and in this context – the pistachio food matrix.  

“Pistachios are compelling for sleep research because they bring together several nutrients and plant compounds connected to sleep physiology within one whole food,” said Marie-Pierre St-Onge, PhD, the review’s senior and corresponding author and director of the Center of Excellence for Sleep and Circadian Research at Columbia University Irving Medical Center. “Rather than focusing on a single ‘sleep nutrient,’ this review provides a rationale for studying how the complete pistachio food matrix may affect sleep-related pathways.” 

As part of the review, researchers assessed laboratory studies that simulated digestion and fermentation of pistachios to explore how the pistachio food matrix may also influence how and when pistachio components become available to the body. Findings demonstrated that gut microbes can ferment pistachio fiber, transform its polyphenols and contribute to a longer release of phytomelatonin from pistachios. 

These findings suggest that researchers should study whole pistachios rather than nutrients or supplements in isolation, because nutrients may behave differently when consumed as part of the pistachio food matrix. 

Do pistachios improve sleep? 

The authors of this review concluded that pistachios could represent a promising wholefood intervention for improving sleep due to their unique combination of nutrients and bioactives, and map a clear path to additional research needed.  

The authors call for randomized controlled trials examining whole-pistachio consumption, dose–response relationships, melatonin levels, sleep outcomes and the bioavailability of key compounds. They also recommend investigating whether pistachio variety, growing conditions and processing influence the nutrient and bioactive content of pistachios. 

 “Well-designed human trials can help us determine whether the unique combination of nutrients and bioactive compounds in the pistachio food matrix produces measurable changes in melatonin, sleep quality, sleep duration or other sleep outcomes,” explains Dr. St-Onge. 

That next phase of research is already underway. American Pistachio Growers is supporting several university-led human clinical studies examining pistachios and sleep. Results are not yet available, but the studies represent an important next step from biological rationale to direct human evidence. 

Eating four to six servings of wholegrain each day reduces several major risk factors for cardiovascular disease, according to a new study published in the European Heart Journal.

The study is a systematic review and meta-analysis, meaning it brings together the results of all existing research in this area. It includes data from 87 clinical trials that tested the effects of eating wholegrain food on risk factors for cardiovascular disease.

It shows that eating a diet rich in wholegrain food is likely to prevent heart disease by reducing body weight, blood pressure and the levels of cholesterol and glucose in the blood.

The research was led by Dr Helda Tutunchi from Tabriz University of Medical Sciences, Iran.

She said: “Although higher wholegrain intake has long been linked to better heart health in population studies, clinical trials have produced mixed findings. This left an important practical question unanswered: how much whole grain should people eat to meaningfully improve cardiovascular health? To address this, we systematically combined and analysed all available randomised controlled trials to identify the amount of whole grain associated with the greatest benefits.”

The analysis included more than 6,500 people from trials conducted across Asia, Europe, the United States, Canada, Australia, and Brazil It showed that eating more wholegrain reduced people’s body weight, waist circumference and blood pressure, as well as reducing the levels of total cholesterol and low-density lipoprotein cholesterol (LDL or ‘bad’ cholesterol), triglycerides, glucose and interleukin-6 (a sign of inflammation) in people’s blood.

These benefits could be seen in people eating 30 to 40 grams of wholegrain per day (dry weight), but the greatest benefits were found in people eating 60 to 100 grams per day. This corresponds to four to six servings of wholegrain daily, for example, a bowl of oatmeal, a sandwich made with wholegrain bread, and a serving of brown rice.

Dr Tutunchi said: “This is the largest and most comprehensive meta-analysis of randomised controlled trials on wholegrain intake and cardiovascular risk factors. Unlike previous reviews, we looked specifically at how much wholegrain people need to eat to get the greatest benefits. We also evaluated the certainty of the evidence and found high-certainty evidence for improvements in several outcomes, including body weight, waist circumference and total cholesterol.

“However, most of the trials we included were relatively short, with an average duration of about eight weeks. As a result, we cannot determine whether these benefits are maintained over the long term. In addition, relatively few studies evaluated very high wholegrain intakes, above 140 grams per day, so the effects at those intake levels remain uncertain.

“Our findings provide a practical indication of the amount of wholegrain that may be needed to achieve meaningful improvements in cardiovascular risk factors. Increasing wholegrain intake is a relatively simple, accessible and affordable dietary strategy that can complement other lifestyle and medical interventions.

“We found that most benefits occur at intakes of approximately 60 to 100 grams per day, toward the upper end of current dietary recommendations. These findings do not necessarily call for major changes to existing guidelines, but they support public health strategies that help people increase their whole-grain intake and move toward the higher end of current targets.

“One important finding is that whole grains may benefit cardiovascular health through several modest improvements acting together, rather than through one large effect on a single risk factor. We observed improvements across multiple pathways, including blood lipids, blood pressure, glucose regulation, body fat and some markers of inflammation. Although the change in each individual risk factor was generally modest, improving several risk factors simultaneously could contribute to a greater reduction in long-term cardiovascular risk. However, the included trials did not assess cardiovascular events directly, so longer-term studies are needed to confirm this.”

In an accompanying editorial [2] Dr Cecilie Kyrø from the Danish Cancer Institute, Copenhagen, and colleagues said: “More than half a century ago, Sir Denis Burkitt and colleagues proposed that the refining of staple carbohydrates, with the accompanying removal of cereal fibre (i.e. from whole to refined grains), underpinned a broad spectrum of ‘Western’ diseases via effects on stool bulk, transit time, and the colonic milieu. Whole grains refer to cereal grains where the three main parts— bran, germ, and endosperm—are all retained in the same proportions as in the intact kernel, whether consumed as whole kernels, flakes, or milled into flour and used in bread and other foods.

“A meta-analysis of trials investigating the effect of whole grains on cardiometabolic risk markers by Naghshi et al. is published in this issue of the European Heart Journal and includes 87 trials of 6529 study participants in total. The meta-analysis shows high-certainty evidence for reductions in body weight, waist circumference, total cholesterol. and interleukin-6 (IL-6), and moderate-certainty evidence for improvements in LDL cholesterol, triglycerides, systolic blood pressure, fasting plasma glucose, and insulin resistance (HOMA-IR).

“Importantly, the meta-analysis includes dose–response analyses, addressing differences in whole-grain intake between trials and providing quantitative evidence to inform food-based dietary guidelines. Overall, intakes of 60–100 g/day dry weight (∼4–6 servings) were found to be clearly related to relevant cardiometabolic improvements.

“For clinicians, the message from Naghshi et al. is reassuringly simple: encouraging patients to replace refined grain foods with minimally processed whole grains is likely to yield modest but meaningful improvements in body weight, waist circumference, and blood lipids, perhaps particularly in individuals with type 2 diabetes. At the population level, even small shifts in these markers can translate into substantial reductions in cardiometabolic events. Adding evidence from research into other disease endpoints indicates that the beneficial effects of whole- grains foods even go substantially beyond cardiometabolic disease.

“The dose–response analyses by Naghshi et al. suggest that intakes of around 60–100 g/day whole grains (∼4–6 servings) are needed to achieve measurable cardiometabolic benefits. Current US dietary guidelines recommend 2–4 servings of whole grains per day within an overall pattern that emphasizes ‘real food’ and reduced intake of ultra-processed products. While this is an important step in the right direction, the trial evidence indicates that higher whole-grain intakes than presently recommended in some guidelines may be optimal for cardiometabolic health.

“From a policy perspective, the challenge is to make minimally processed whole-grain staples accessible, affordable, and culturally acceptable, while avoiding a drift towards ultra-processed products that merely add whole grains to otherwise highly processed formulations.”

Previous studies have found that caffeine is the world’s most popular stimulant and psychoactive sub­stance, and coffee is the most common way people consume caffeine. The latest research supports the conclusion that for most adults, consuming up to 400 mg of caffeine/day (or up to 5, 8-ounce cups of caffeinated coffee per day) is safe and appears to be linked to a lower risk of cardiovascular disease for some individuals.

However, higher doses of caffeine, such as levels found in energy drinks including energy shots, may cause cardiovascular harm, according to a new American Heart Association scientific statement, “Caffeine and Cardiovascular Disease,” published in the American Heart Association’s flagship peer-reviewed scientific journal Circulation.

“Caffeine consumed in coffee is a key part of daily life for millions of people, and in our review of the most recent research, for most adults, intake of up to 400 mg of caffeine/day, the equivalent of up to 5 cups of caffeinated coffee per day without added sugars or fillers, is safe and does not increase cardiovascular risk,” said Chair of the scientific statement volunteer writing group Gregory M. Marcus, M.D., M.A.S., FAHA, a professor of medicine at the University of California, San Francisco School of Medicine and the associate chief of Cardiology for Research at the University of California, San Francisco Health. “However, high doses of caffeine, such as those found in energy drinks including energy shots, may have harmful effects on the heart and should be avoided.”

The statement authors note that studying the effects of caffeine on the cardiovascular system is challenging. Coffee is the main source of caffeine in most research studies, and the observed cardiovascular effects may be due to other compounds in coffee. For example, experimental studies suggest that the bioactive compounds in coffee may have antioxidant and anti-inflammatory properties, which may help explain some health benefits. It’s also difficult to separate the effects of caffeine from other ingredients usually added to coffee, such as milk, cream, flavored syrups and/or sugar. In addition, most studies on caffeine are observational, meaning they cannot prove cause and effect. 

Although coffee is the main source of caffeine for most adults, tea, chocolate, soda and energy drinks, as well as over-the-counter and prescription medications, also contribute to overall caffeine intake. More research is needed about other products with caffeine in order to understand caffeine content and caffeine’s impact on cardiovascular health.

The new scientific statement details the most recent research primarily on caffeinated coffee and the potential impact of caffeine in coffee on high blood pressure, cholesterol, Type 2 diabetes, coronary heart disease, stroke, heart failure, atrial fibrillation, other arrhythmias and other cardiovascular conditions.

Caffeine and cardiovascular health: key things to know

• Based on the results of the latest research studies reviewed, consuming up to 400 mg of caffeine per day, or no more than 3 to 5, 8-ounce cups of regular black caffeinated coffee per day (without sugars, sweeteners, flavors or added fillers), is considered safe for most adults. A regular brewed, non-specialty, caffeinated coffee typically contains 9.4-20.6 mg of caffeine per fluid ounce.
• Consuming caffeinated coffee without added sugars, flavors or cream was linked to a lower risk of Type 2 diabetes, heart disease, stroke, heart failure and some irregular heart rhythms.
• Randomized trials, the most rigorous and reliable type of study design, have shown that caffeine consumption in coffee is associated with a lower risk of atrial fibrillation but also a higher risk of premature ventricular contractions.
• Adding sugar, flavored syrups, milk and/or cream to coffee likely reduces its potential health benefits, and more research is needed to understand the impact of these additives.
• Higher caffeine intake, such as levels found in energy drinks including energy shots, was associated with cardiovascular harm, such as increased risk of high blood pressure and irregular heart rhythm. Energy drink shots may contain 40-69 mg of caffeine per fluid ounce, 3-4 times more caffeine than regular caffeinated coffee.

How does caffeine affect the body?

Caffeine consumed in coffee is metabolized by the liver and generally reaches peak concentration for most people within an hour. However, how quickly individuals process caffeine depends on their genetics, metabolism, age and past caffeine use. When more caffeinated coffee is consumed regularly, some people may develop a tolerance to higher levels of caffeine.

Other people may feel stronger effects from the same amount of caffeine. Short-term effects of caffeine may include temporary increases in blood pressure, heart rate, blood sugar and alertness. Some people may experience heart palpitations and/or sleep disruption.

Specific health impacts of caffeine

• Effects on blood pressure: Studies have found that caffeinated coffee consumption may affect blood pressure differently depending on how much is consumed. In people with optimal blood pressure, drinking 1–3 cups a day was associated with an increased risk of developing high blood pressure, while drinking more than 3 cups per day was associated with a lower risk. High doses of caffeine (such as those from energy drinks or energy shots) can significantly increase blood pressure, especially in people who already have high blood pressure.
• Effects on Type 2 diabetes: Research suggests that caffeinated coffee may reduce insulin sensitivity in the short term. In addition, drinking black, caffeinated coffee (no additives, flavors or sweeteners) regularly was linked to a lower risk of developing Type 2 diabetes. However, this benefit may be due to compounds in coffee other than caffeine. More research is needed to clarify the impact on Type 2 diabetes of caffeinated coffee vs. various compounds in coffee.
• Effects on cholesterol: Data from randomized clinical trials indicate cafestol, a component in both caffeinated and decaffeinated coffee, was associated with higher levels of low-density lipoprotein (also known as “bad” cholesterol). Cafestol is present in unfiltered coffee (such as espresso, French press, Turkish coffee or boiled coffee) but not present in coffee brewed with paper filters or instant coffee. More research is needed to understand which products have higher levels of cafestol and their mechanisms.  
• Effects on heart rhythm: The most recent analyses of health measures with self-reported information from participants have found that drinking 1-3 cups of caffeinated coffee per day was not associated with an increased risk of atrial fibrillation or abnormal heart rhythm. However, caffeinated coffee at that same level may be associated with more early beats from the lower chamber of the heart, called premature ventricular contractions (or PVCs). Very high doses of caffeine (such as those in caffeinated energy drinks or energy shots) have been linked to abnormal heart rhythm in people usually considered to have low cardiovascular disease risk, such as healthy adults younger than age 30.
• Effects on heart disease and stroke: Drinking 2-4 cups of caffeinated coffee per day was linked to a lower risk of heart disease, heart failure and stroke. However, drinking more than 4 cups of caffeinated coffee a day may increase the risk of heart failure.

Not all sources of caffeine are the same

More research is necessary to investigate the different health impacts of various types of caffeinated coffee and other products with caffeine, such as tea, soda, energy drinks and energy shots, and foods. There have been fewer studies focused on tea vs. coffee; however, tea has been associated with reduced risk of atrial fibrillation, heart failure and stroke, similar to caffeinated coffee. Energy drinks, bars, gels and caffeine-based supplements often contain other added ingredients that may increase the absorption of caffeine, may accelerate its effects on the body, may raise blood pressure and increase the risk of cardiovascular harm.

More randomized controlled trials investigating the effects of caffeine in coffee and other products that have caffeine on cardiovascular health are needed to better understand how caffeine affects different people and how different sources of caffeine impact heart health. The writing group emphasized that there is also a need for research focused on caffeinated energy drinks and other popular products containing caffeine. Due to the lack of sufficient, rigorous data to develop guidance on recommendations for caffeine intake, caffeine was not referenced in the Association’s 2026 Dietary Guidance to Improve Cardiovascular Health. 

“Although research suggests that caffeine consumption may be associated with certain cardiovascular benefits for some people, it’s important to remember that there is no ‘one-size-fits-all’ strategy for safe caffeine consumption. People can respond very differently to caffeine based on various factors, such as age, medications, underlying health conditions, genetics and how quickly their bodies metabolize it. What may be a reasonable amount for one person could cause unwanted effects, such as heart palpitations, anxiety or sleep disruption, in another. That’s why it’s important to pay attention to how your body responds to caffeine and talk with your healthcare team about what is right for you,” Marcus said.

Co-authors are Vice Chair Frank B. Hu, M.D., M.P.H., Ph.D., FAHA; Rob M. van Dam, Ph.D.; Marilyn C. Cornelis, Ph.D.; Thomas A. Dewland, M.D.; JungHee Kang, Ph.D., M.P.H., R.N.; Susanna C. Larsson, Ph.D.; Robert L. Page II, Pharm.D., M.S.P.H., FAHA; and Niyati Parekh, Ph.D., FAHA. Authors’ disclosures are listed in the manuscript.