Caffeine – scientific name 1,3,7-trimethylxanthine – is a central nervous stimulant and the most frequently consumed psychoactive drug in the world. It is an alkaloid found in more than 60 plants, including coffee and cacao beans, tea (Camellia sinensis) leaves and buds, yerba maté, kola nut, guarana berries, and guayusa (leaf of a holly tree, Ilex guayusa).

It’s an integral part of most of our daily lives. Whether it’s that morning cup of coffee or latte, a caffeinated soft drink, energy drink, cup of tea, or chocolate fix – caffeine is clearly here to stay. 

Caffeine by the numbers

Here are some statistics on caffeine consumption, according to the International Food Information Council:1

  • 93 percent of U.S. adults report consuming caffeine.
  • 75 percent of caffeine consumers have it at least once a day, while 25 percent consume it three or more times daily.
  • Regarding sources of caffeine, according to one survey its consumption is: soft drinks (54%), coffee (52%), tea (42%), energy drinks (25%), chocolate candies/desserts (23%), coffee-containing desserts (18%), and caffeine pills (6%).

Obviously, when weighing the health risks and benefits of caffeine consumption, it depends on the source. Much has been written about the health benefits of coffee, tea, and even chocolate – primarily because of their polyphenol content. On the other hand, it might be more difficult to identify health benefits of soft drinks. Thus, when trying to determine risks and benefits, it’s not easy to tease out the caffeine component. Is it the caffeine that is contributing to the health benefits of coffee – or is it the antioxidant polyphenols – or is it both? Is it the caffeine that is contributing to health risks of soft drink consumption – or the high fructose corn syrup? Most likely primarily the latter.

Caffeine safety

According to various governmental agencies around the world – U.S. Food and Drug Administration, U.S. Department of Agriculture, Health Canada, and European Food Safety Authority – caffeine consumption at levels of 400 mg/day or less does not appear to have any long-lasting negative consequences. For reference, there are 95 mg of caffeine in the average 8-ounce cup of coffee and 45 mg in a cup of black tea.

There appears to be a difference between the effects of caffeine on regular (habitual) consumers and those who don’t regularly consume it. Consumption of caffeine can temporarily increase heart rate, blood pressure, and jitteriness in newbies, but does not appear to have that same effect in regular coffee drinkers – or consumers of other caffeinated beverages.

What does the science say?

A comprehensive 2017 evaluation of the cardiovascular effects of caffeine published in Regulatory Toxicology and Pharmacology came to some interesting conclusions.2 The review included 270 studies of caffeinated beverages (mostly coffee or tea) – all of which specifically reported caffeine amounts. Most studies compared higher intakes with either low or no caffeine consumption. Most were between 100-400 mg caffeine daily – a few up to 600 mg daily. Below is a summary of the results.

Total cardiovascular disease (CVD) risk. CVD encompasses a range of adverse heart and blood vessel conditions, and 19 studies ranging in length from 3-28 years were included – mostly looking at coffee or tea consumption in relation to overall heart disease risk. Half the studies found a significant decreased risk for CVD (mostly at caffeine amounts of 100-400 mg daily), while the remainder found no effect one way or the other.2

Atherosclerosis/heart attack. Fifty studies included risk for coronary heart disease (CHD; atherosclerosis or plaque buildup in blood vessels of the heart) and/or acute myocardial infarction (AMI; heart attack). Of the 50 studies, 13 found significant increase in CHD or AMI (all involving coffee consumption), while 26 found no effect and 11 studies showed significant decreased risk. Nine of the studies reported on tea drinking (up to 225 mg caffeine daily) and found it either decreased or had no effect on AMI or CHD risk.2

Arrhythmia. Any change from normal heart rate and rhythm – too slow, too fast, irregular – is considered an arrhythmia, with some being potentially more dangerous than others. Thirteen studies evaluated the effect of caffeine on arrhythmia incidence and found, even at 600 mg of caffeine daily, there was no increased risk. One large study even found six or more cups of coffee per day had a protective effect. This is somewhat surprising considering one of the transitory effects of caffeine consumption (particularly in non-habitual coffee consumers) is increased heart rate. 

In two studies that included participants with a history of atrial fibrillation, a type of arrhythmia, coffee consumption increased the risk and decreased the chance of returning to a normal heart rhythm.2 

Congestive heart failure (CHF). CHF is characterized by a weakening of the heart muscle so it doesn’t pump as efficiently as it should. Only five studies (ranging in size from 8,000-59,000 participants and lasting from 9-25 years) looked at the relationship between caffeine intake and CHF and found no significant effect of caffeine on CHF risk. One of the largest studies found a protective effect in women who drank up to six cups of coffee daily (approximately 600 mg caffeine), but not at higher amounts up to 10 cups daily.2

Sudden cardiac death (SCD). Risk for sudden cardiac death, an electrical malfunction that causes the heart to suddenly stop beating, was met with mixed results. The largest of three studies that followed 93,676 postmenopausal women for 11-16 years found no increased risk of SCD from 378 mg of caffeine from coffee or tea daily. One smaller study found an increased risk among patients who already had heart disease and drank 10 or more cups of coffee daily (but did not factor out other associated risk factors like smoking and alcohol consumption).2

Stroke. Thirty-one studies looked at the risk of stroke and caffeine consumption – from coffee or tea. No effect on stroke risk was observed in 19 studies, there was a decreased risk in nine studies, and an increased risk in three studies.2

Acute blood pressure changes. Of the 270 studies evaluated, 130 looked at caffeine’s immediate effect on blood pressure. The majority of these used controlled doses, often via caffeine pills, to evaluate the acute effects on blood pressure shortly after caffeine dosing. Most studies found transient increases in blood pressure after caffeine consumption that then returned to normal.2 

High blood pressure. Risk of hypertension or high blood pressure was assessed in various populations. In studies that looked at individuals with normal blood pressure, regular consumption of caffeine did not increase the risk for hypertension. On the other hand, some studies involving individuals who already had high blood pressure found that those who were slow caffeine metabolizers were at risk for having continued hypertension, compared to those with hypertension who were fast metabolizers.2

Research on conditions associated with cardiovascular health

Recent Take 5 Daily research extracts looked at the effect of caffeine on health conditions associated with heart disease, including fat metabolism and type 2 diabetes.

Fat metabolism. One animal study looked at several sources of caffeine and their effects on fat metabolism. Caffeine from all sources (synthetic, coffee, isolated from maté, and maté tea (yerba maté)) had a beneficial effect on body fat accumulation in animals fed a high-fat-high-sucrose diet, while decaffeinated maté tea did not.3

Type 2 diabetes. It appears that coffee and green tea have a beneficial effect on mortality risk in type 2 diabetes – a condition also associated with an increased risk for cardiovascular disease. A Japanese study found both coffee and green tea consumption reduced the risk of mortality in 4,923 diabetic patients over a 5-year period.4 But consumption of both was even better. The researchers found:

  • A 51-percent lower mortality risk in those who drank 2-3 cups of green tea plus two or more cups of coffee daily.
  • A 58-percent lower risk in those drinking four or more cups of green tea plus one cup of coffee daily.
  • A 63-percent lower risk for those drinking a combination of four or more cups of green tea plus two or more cups of coffee daily!

Although the food questionnaire that was completed by the study subjects did not differentiate between caffeinated and decaffeinated tea or coffee, the researchers reported that decaf beverages are not common in Japan. 

The takeaway

Overall, the cardiovascular benefits of consuming caffeinated beverages appear to outweigh the risks. However, since most of the studies looked at coffee and tea consumption, it is likely that many of their health benefits are also conferred by the antioxidant and anti-inflammatory polyphenols and other plant constituents. At the very least, it can be concluded that caffeine in moderate amounts does not increase the risk for cardiovascular disease in most situations. 

Research on the effect of caffeine has not been limited to cardiovascular disease. A significant body of research is amassing regarding its potential benefits for mood, cognitive support, gut health, athletic performance, and more.

Thorne products containing caffeine include Memoractiv, which contains PurEnergy (a combination of time-released caffeine and pterostilbene, providing 50 mg of caffeine per serving) and Daily Greens Plus, containing 1 g of matcha, providing 30-40 mg of caffeine per serving. 

References

  1. International Food Information Council. Caffeine: consumer consumption habits and safety perceptions. https://foodinsight.org/caffeine-consumer-consumption-habits-and-safety-perceptions/#:~:text=Soft%20drinks%2C%20brewed%20coffee%2C%20and,sources%20of%20caffeine%20among%20Americans. [Accessed Feb. 9, 2023]
  2. Turnbull D, Rodricks JV, Mariano GF, Chowdhury F. Caffeine and cardiovascular health. Regul Toxicol Pharmacol 2017;89:165-185. doi: 10.1016/j.yrtph.2017.07.025. 
  3. Zapata F, Rebollo-Hernanz M, Novakofski J, et al. Caffeine, but not other phytochemicals, in mate tea (Ilex paraguariensis St. Hilaire) attenuates high-fat-high-sucrose-diet-driven lipogenesis and body fat accumulation. J Funct Foods 2020;64:103646. doi:10.1016/j.jff.2019.10364
  4. Komorita Y, Iwase M, Fujii H, et al. Additive effects of green tea and coffee on all-cause mortality in patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry. BMJ Open Diabetes Res Care 2020;8(1):e001252. doi:10.1136/bmjdrc-2020-001252