8 biggest caffeine myths

Nutritional OutlookNutritional Outlook Vol. 22 No. 4
Volume 22
Issue 4

How and where caffeine helps, whom it might hurt-and what we just don’t know yet.

Photo © Justin-Stock.adobe.com

In the annals of “now-it’s-good-for-you/now-it’s-not” nutrition, few substances claim more hallowed ground than caffeine: demonized as a dangerous stimulant by some; prized as an indispensable performance enhancer by others. So which side is right?

The answer, perhaps, is neither. Or maybe both? It’s hard to say, because the ubiquitous bitter alkaloid has well-established benefits, and equally recognized risks, depending on who’s using it, at what levels, and in combination with what other substances.

Notes Michael A. Grandner, PhD, MTR, CBSM, assistant professor of psychiatry, psychology, and medicine, and director, sleep & health research program, University of Arizona College of Medicine (Tucson, AZ), “Caffeine has been used by humans for thousands of years.” And despite the ongoing debate over its merits-versus-drawbacks, “It’s probably becoming somewhat more ubiquitous.”

Which is all the more reason for our industry better to understand how and where caffeine helps, whom it might hurt-and what we just don’t know yet.

Drug of Choice

Leah M. Panek-Shirley, PhD, assistant professor, department of health, nutrition, and dietetics, SUNY Buffalo State (Buffalo, NY), is well aware of caffeine’s prominent role in contemporary life. In fact, she notes, “It’s one of the most widely used psychoactive drugs in the world.”

To hear such a common compound described as a “psychoactive drug” might, of course, sound dramatic. But a psychoactive drug is precisely what caffeine is-and so much more.

Notes Christine Fields, vice president, scientific affairs, Applied Food Sciences Inc. (Coralville, IA), “Caffeine is a stimulant. And no matter how you look at it, it has the ability to increase heart rate and blood flow, and to affect sleep.”

On the Plus Side

To some extent, such qualities help explain caffeine’s appeal. Who hasn’t turned to it-or the foods and beverages that are its source-for stimulation first thing in the morning or late at night?

And as far as many athletes are concerned, caffeine is the linchpin to their effective training. Fields notes that caffeine is the number-one ingredient in both pre-workout and endurance sports nutrition formulations, with many of the former delivering as much as 200 to 300 mg of caffeine per serving. “According to researchers1,” she says, “approximately three out of four elite athletes consume caffeine before or during sports competition.”

For its part, the United States Olympic Committee-which permits caffeine’s use-has concluded that by activating receptors in the brain and body that counteract many of fatigue’s inhibitory effects on performance, caffeine enhances endurance; improves reaction time, concentration, and self-perceived energy levels; increases energy expenditure and oxygen uptake at low doses without changing perceived effort, exercising heart rate, or fuel use; delays feelings of fatigue; lessens sensations of exertion and pain; and reduces time to completion for a set of work. What’s not to love?

Protecting the Vulnerable

If you’re especially sensitive to caffeine or susceptible to small changes in blood pressure, blood flow, and heart arrhythmias, quite possibly a lot.

“Caffeine is still considered a controversial substance,” says Panek-Shirley, “with the protection of vulnerable populations at the center of most controversy.” Who are those vulnerable populations? “There’s concern about the safety of fetal caffeine exposure from a pregnant woman’s intake,” Panek-Shirley continues, “the possibility of adverse cardiovascular effects among children, and the risk associated with adolescents as well as young adults combining caffeine with alcohol.”

Indeed, when caffeine lands in the hot seat, it’s often because of harm it’s meted out on the young. Citing the findings of a 2017 study2 on the safety of ingested caffeine, Panek-Shirley says, “As caffeine has become more widely available and combined with other products to mask its bitterness, the risks of caffeine consumption have increased in populations-like children-who previously wouldn’t have consumed it.”

Alas, children are consuming more, with National Institutes of Health data3 showing that 75% of children over age five-and 50% of those under-taking in caffeine, often via energy drinks. Notes Robin Dando, PhD, associate professor, director, Cornell Sensory Evaluation Facility, department of food science, Cornell University (Ithaca, NY), “That’s one of the most interesting facts on caffeine I’ve read in the literature.”

Knowns and Unknowns

The caffeine literature is rife, and growing, as health professionals, exercise scientists, the military, the general public-oh, and the dietary supplement industry, too-all endeavor to learn more about caffeine and our relationship to it.

Fields notes a “deep dive” that the United States Department of Defense is taking into the mechanics of caffeine intake and its impact on sleep, including two recent studies4,5 outlining modelling tools developed to help predict typical metabolism and associated caffeine use on adenosine receptor activity.

Panek-Shirley hails the aforementioned 2017 safety study2 and a contemporaneous review6 exploring caffeine and coffee’s roles in appetite regulation as “invaluable reference resources, as they examine research from various databases and summarize meta-analysis results,” she says.

Another study7 from earlier this year attracted the attention of Carol DeNysschen, PhD, RD, MPH, assistant professor, department of health, nutrition, and dietetics, SUNY Buffalo State, and president, New York State Academy of Nutrition and Dietetics (NYSAND), for finding that accidental deaths from over-the-counter or dietary caffeine products represent the most common cause of caffeine-related death-a statistic that should concern our industry. “The high frequency of use, uncontrolled sale of caffeine-containing products, and potentially triggering action of caffeine on the cardiovascular system pose serious risks to the health and safety of consumers,” she cautions.

That being the case, work8 at Northwestern University School of Medicine might someday suggest a means of mitigating that risk, for, as Fields points out, the research is shedding new light on how different genomics can, and do, influence individuals’ caffeine uptake, excretion, and use. “This is a start to understanding many of the metabolic pathways into CYP1A2-mediated metabolism and the associated inter-individual variants,” she says.

Sounds impressive. But for now, caffeine users can stay safe by practicing moderation and paying attention to the evidence they observe in their own bodies. As Fields says, “Consumers are now more fully aware of how caffeine affects them individually and are responding to their personalized needs with regulated intake based on lifestyle demands.”

Click through the following pages to learn more of the truths about caffeine, the myths, and the head-scratchers we’re still muddling through.

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Myth 1: Caffeine Jumpstarts Your Day

Convinced you can’t get going without that first shot of caffeine-whether courtesy of an espresso, Americano, or plain-old cuppa Joe? Prepare to have your mind-and morning ritual-blown.

“The truth is, caffeine won’t have much of an effect first thing in the morning due to how it works in the brain,” Grandner says. Any effect, he maintains, is likely either 1) a placebo, 2) the result of removing the caffeine withdrawal you’d been experiencing since your last infusion, and/or 3) “the natural reduction in sleep inertia that would have happened in the first hour after waking anyway.”

Caffeine’s effectiveness depends a lot on timing, and it takes about 20 minutes to produce those perceived increases in alertness and performance, Grandner says. “So if you start getting your first burst of energy with that immediate first sip,” he says, “that’s a placebo response.”

Photo © iStockphoto.com/alvarez

Myth 2: Caffeine Has a Neutral Influence on Sleep Quality

The notion that caffeine keeps us awake all night is empirically false-as anyone who drifts off despite that after-dinner cappuccino can attest. But even if you do slip to dreamland post-shot, your dreams might not be as deep, nor as sweet, as you’d hope.

That’s because, as Grandner points out, “While caffeine in the afternoon or evening can make it harder for some people to wind down while others fall asleep just fine, often their sleep is shallower, especially in the beginning of the night.”

The reason: Everybody metabolizes caffeine differently. Perhaps even more importantly, Grandner says, “Just because you fall asleep doesn’t mean you aren’t experiencing caffeine’s effects.” Which leads to the next caffeine myth…

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Myth 3: Caffeine in the Morning Can Make Up for a Poor Night’s Sleep

“Caffeine can’t replace lost sleep,” Grandner declares. “There have been excellent studies showing that although caffeine can improve alertness and reduce fatigue, it doesn’t correct the cognitive impairments associated with sleep loss.”

In other words, while caffeine make you faster and more alert, “it doesn’t improve thinking ability or decision making,” Grandner continues. Which is why he considers it solely a short-term solution for boosting alertness and taking the edge off that drowsy or lethargic feeling that follows a restless night. In the end, he says, “There’s no replacement for sleep.”

Photo © iStockphoto.com/Akirastock

Myth 4: Caffeine Is Coffee, and Coffee Caffeine

Given that coffee remains the prototypical caffeine-containing beverage, it makes sense to associate its benefits with caffeine. What’s more, it’s tempting to disregard the latter’s risks when imbibing the former’s purported benefits.

So what’s the bottom line? “The prevailing thought seems to be that moderate coffee consumption can be beneficial to health,” Dando says, “I should specify that this is coffee-not caffeine-and that coffee contains a whole lot of other compounds in addition to caffeine.”

Panek-Shirley agrees. She points to epidemiological studies9 showing correlations between coffee consumption and decreased health risks. “But there are other constituents in coffee beyond caffeine that could contribute to this benefit,” she emphasizes.

Investigation into what those constituents might be and how they work continues, and in the interim, the latest Dietary Guidelines for Americans hold that moderate coffee consumption can be healthy. “Despite this,” Dando advises, “coffee should be avoided in pregnancy and when breastfeeding, and it may be wisely avoided by those with high blood pressure.” 

Photo © iStockphoto.com/ferrantraite

Myth 5: Caffeine Is the Ergogenic Secret to Sports Success

“Because my current caffeine projects investigate the short-term independent and combined effects of caffeine and exercise on eating behavior, as well as relationships between caffeine intake and wellbeing in a high-stress, high-turnover profession, I follow studies related to those topics,” says Panek-Shirley. “And two myths I’m most concerned about relate to caffeine’s ergogenic and appetite-suppressing effects. These myths are based on truths, but there are limitations to the expected benefits.”

Let’s explore the ergogenic story first: “Some athletes and exercisers believe caffeine as a pre-workout supplement will help them exercise longer and harder with less fatigue,” she observes. And they have a point: Caffeine does improve performance and decrease perceptions of fatigue.

But to reap its gains, athletes need to have withdrawn from their usual caffeine intake-or to have consumed larger doses.

And even then, the benefits are limited. “Unfortunately,” DeNysschen adds, “high caffeine doses induce negative side effects, like diuresis, anxiety, and increased heart rate, which would detract from the benefit of caffeine and exercise.”


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Myth 6: The Caffeine Diet Is a Silver Bullet to Weight Loss

“Regarding caffeine’s effect on weight loss,” Panek-Shirley continues, “individuals looking for quick and simple solutions may use caffeine-containing products to boost metabolism and decrease appetite. And caffeine is a sympathomimetic, so it does modestly increase metabolism. Higher doses have also been shown to reduce both appetite and energy intake.”

But the higher caffeine levels needed to maintain that boost and keep appetite and food intake at bay may be neither safe nor durable. “My own research10 has identified that at typical doses, caffeine’s effect on appetite and intake is limited and transient,” she says.

Besides, adds Dando, “The slight bump in metabolic rate you may experience is likely offset by the cream and sugar in your coffee-and definitely by the cinnamon roll you eat with it. This all points back to the same boring food-and-drink advice you’ve gotten since you were a kid: Moderation is key.”

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Myth 7: You Can Safely Mix Alcohol and Caffeine if You’re Not Sensitive to Caffeine

We know the body rapidly absorbs up to 90% of the caffeine it consumes through the stomach, with plasma concentrations peaking within 20 to 40 minutes of intake, Fields says. The upshot: “Toxic levels can be reached quickly and last for prolonged periods, given caffeine’s three- to 10-hour half-life, depending on the individual.”

And because the liver metabolizes caffeine via N-demethylation, acetylation, and oxidation-the same pathways used to remove alcohol and other medications from the system-the dual ingestion of both caffeine and alcohol can prolong the former’s half-life by as much as 70%, she continues, “creating an acute or prolonged toxic effect after ingestion.” Just say no?

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Myth 8: We Don’t Know What Constitutes a Safe Level

The International Life Sciences Institute (ILSI), a global nonprofit commissioned to provide science on caffeine’s health and safety, commissioned a 2016-2017 caffeine safety assessment11 whose results confirmed that previously determined caffeine doses of 400 mg/day for healthy adults, 300 mg/day for pregnant women, 2.5 mg/kg body weight/day for adolescents and children, and 10 g/day for acute effects-as also determined by Health Canada and the EU-“remain appropriate not to be associated with adverse effects,” says Fields, herself an ILSI member.

The assessment comprised “a robust and extensive review” for five outcome areas in healthy adults, pregnant women, adolescents, and children with historic negative caffeine associations-namely, acute toxicity, cardiovascular toxicity, bone and calcium effects, behavior effects, and development and reproduction effects.

ILSI used a weight-of evidence approach to draw conclusions for each of the five outcomes and to generate more specific endpoints within those outcomes, Fields adds, giving the study a “tremendous impact” and producing “a shift for caffeine research from healthy to sensitive populations.”

Nevertheless, says DeNysschen, “Because caffeine content isn’t required on any food or supplement labels and its benefits come with risks, we should be wary of using supplemented products. We should be increasingly cautious of the marketing of ‘energy’ products to adults and youth.”


  1. Del Coso J et al. “Prevalence of caffeine use in elite athletes following its removal from the World Anti-Doping Agency list of banned substances.” Applied Physiology, Nutrition, and Metabolism, vol. 36, no. 4 (August 2011): 555-561
  2. Temple JL et al. “The safety of ingested caffeine: a comprehensive review.” Frontiers in Psychiatry. Published online May 26, 2017.
  3. Ahluwalia N et al. “Caffeine intake from food and beverage sources and trends among children and adolescents in the United States: review of national quantitative studies from 1999 to 2011.” Advances in Nutrition, vol. 6, no. 1 (January 2015): 102–111
  4. Ramakrishnan S et al. “A unified model of performance for predicting the effects of sleep and caffeine.” Sleep, vol. 39, no. 10 (October 1, 2016): 1827-1841
  5. Vital-Lopez FG et al. “Caffeine dosing strategies to optimize alertness during sleep loss.” Journal of Sleep Research. Published online May 28, 2018.
  6. Schubert MM et al. “Caffeine, coffee, and appetite control: a review.” International Journal of Food Sciences and Nutrition, vol. 68, no. 8 (December 2017): 901-912
  7. Cappelletti S et al. “Caffeine-related deaths: manner of deaths and categories at risk.” Nutrients, vol. 10, no. 5 (May 14, 2018): 611
  8. Cornelis MC et al. “Genome-wide association of caffeine metabolites provides new insights to caffeine metabolism and dietary caffeine-consumption behavior,” Human Molecular Genetics, vol. 25, no. 24 (December 15, 2016): 5472-5482
  9. Zulli A et al. “Caffeine and cardiovascular diseases: critical review of current research.” European Journal of Nutrition, vol. 55, no. 4 (June 2016): 1331-1343
  10. Panek-Shirley LM et al. “Caffeine transiently affects food intake at breakfast.” Journal of the Academy of Nutrition and Dietetics, vol. 118, no. 10 (October 2018): 1832-1843
  11. Wikoff D et al. “Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children.” Food and Chemical Toxicology. Published online April 21, 2017.
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