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.

The coughing and sneezing you hear at home, in the office and at the gym means one thing: It’s cold and flu season. Although it’s impossible to guarantee you won’t get sick, adopting a few healthy habits can go a long way toward avoiding the sniffles and sneezes.

Start by talking with your health care provider about any concerns you may have then follow these lifestyle recommendations for natural immune system support.

Wash Your Hands: While it’s probably the first rule you learn about getting sick as a child, washing your hands remains a critical first line of defense. Use warm, soapy water and rub your hands together for at least 20 seconds. Don’t forget the backs of your hands, wrists and under your fingernails. Rinse off the soap then dry with a clean towel.

Commit to Healthier Eating: Foods like fruits, vegetables, nuts, seeds, legumes and whole grains are recommended by experts as essential foods for optimizing your immune system. Consider fresh grapes, a prime example of food that contains beneficial plant compounds linked to health benefits in humans.

Healthy cells are the foundation of good health, and the antioxidants and other polyphenols naturally found in grapes help protect the health and function of cells. The good news is that improving your diet doesn’t require a complete overhaul – small steps such as swapping in fresh California grapes for processed snacks or simply adding a handful of fresh grapes to your day will add these beneficial compounds to your daily routine.

Or, you can add grapes to recipes like this Lemony California Grape and Beet Salad, a vibrant and fresh melody of color and flavor. Roasted red and yellow beets meet sweet and juicy grapes, peppery arugula and pumpkin seeds all brought together with a zesty lemon vinaigrette.

Studies suggest some grape compounds may positively influence immune function, including resveratrol and certain flavonoids. Additional studies show adding heart-healthy grapes to your daily diet can help support brain, colon and skin health. Grapes are also a good source of vitamin K, which may help support lung health.

Avoid Others Who are Sick: Along with washing your hands frequently, steering clear of people who are ill may sound like a no-brainer, but sometimes it’s easier said than done. When loved ones, close friends or coworkers come down with a cold or flu, do your best to keep your distance and avoid touching items with which they came into contact. After bedtime routines with a sick child or afternoon meetings with an under-the-weather associate, thoroughly wash your hands and clean commonly used surfaces like doorknobs or conference room keyboards.

Prioritize Hydration: Even during cooler weather, staying hydrated remains important for immune health by keeping the body’s defenses functioning properly. Drink water throughout the day, and for an extra dose, increase hydration by eating foods with high water content like grapes, which contain about 82% water.

Find more health and nutrition information at GrapesFromCalifornia.com.

Lemony California Grape and Beet Salad
Servings: 6

1/4       cup, plus 1 tablespoon, extra-virgin olive oil, divided
3          tablespoons lemon juice
1          tablespoon honey
2          cups peeled and sliced (1/8-inch thick) raw red and yellow beets, cut into small half-moons or triangles
1/2       teaspoon sea salt
3          cups halved red Grapes from California
1/2       cup roasted salted pumpkin seeds
2          green onions, thinly sliced
4          cups (3 ounces) baby arugula
            freshly ground pepper, to taste

Heat oven to 400 F and line baking sheet with parchment paper. In large bowl, whisk 1/4 cup olive oil, lemon juice and honey; set aside.

Place sliced beets on prepared baking sheet and drizzle with remaining oil.  Add salt and toss well to coat. Spread in single layer and bake 25 minutes, or until tender; let cool. 

Add grapes and pumpkin seeds to bowl with dressing and toss well to coat.  Add cooled beets, green onions and arugula. Toss lightly; season with pepper, to taste.

Nutritional information per serving: 250 calories; 5 g protein; 25 g carbohydrates; 16 g fat (58% calories from fat); 2.5 g saturated fat (9% calories from saturated fat); 0 mg cholesterol; 320 mg sodium; 3 g fiber.

Clinical trials have shown that consumption of grapes can increase the resilience of skin to UV irradiation in about 30-50% of the subject population. 

New studies published in the current issue of the journal ACS Nutrition Science suggest the effect of consuming grapes on human skin health is much broader – most likely affecting everyone. 

The investigation was performed with human volunteers who consumed the equivalent of three servings of whole grapes each day for two weeks. Gene expression in skin was determined before and after grape consumption, with and without exposure of skin to low doses of UV irradiation. 

The results demonstrated inter- and intraindividual differences of gene expression in the skin. In other words, from the outset, gene expression in the skin of each individual was different. The expression changed when the subjects consumed grapes or when exposed to UV irradiation, but still each individual was different from one another. Further unique changes were observed when UV irradiation was combined with grape consumption. 

Consequently, while gene expression is different when comparing one person to another person, the gene expression of every person changed after consuming grapes. 

When searching for a functional commonality resulting from these changes in gene expression after consuming grapes, the investigators were able to construe the myriads of data as being indicative of enhanced skin keratinization and cornification, which are known to create a  barrier against environmental damage. This idea was reinforced by exposing skin to a low dose of UV irradiation and measuring the generation of malondialdehyde, a marker of oxidative stress, which was reduced when the subjects consumed grapes. 

 “We are now certain that grapes act as a superfood and mediate a nutrigenomic response in humans,” said John Pezzuto, Ph.D., Professor and Dean of the College of Pharmacy and Health Sciences at Western New England University. 

“We observed this with the largest organ of the body, the skin. The changes in gene expression indicated improvements in skin health. But beyond skin, it is nearly certain that grape consumption affects gene expression in other somatic tissues of the body, such as liver, muscle, kidney and even brain. This helps us to understand how consumption of a whole food, in this case grapes, affects our overall health. It’s very exciting to be working in the post-genomics era where we can finally start to employ functional genomics and actually visualize complex matrices indicative of nutrigenomic responses.”