Americans have a love-or-hate relationship with daylight saving time. Changing our clocks forward can be a time of joy and a sign that spring is near, but it also can bring feelings of irritability and annoyance in response to “losing” a precious hour of sleep. Many of us look to various ways—including consuming caffeinated foods and beverages—to cope with the time change. To be sure, caffeine can help us power through our day and make the most of all the extra outdoor activities, such as gardening, hiking, and other forms of exercise, that become easier with that extra hour of daylight.

Caffeine is an FDA (Food and Drug Administration)-approved food additive and stimulant that is popular in the U.S. Recent data from 2022 found that more than nine in ten Americans surveyed reported consuming caffeine, with about 75% of survey participants saying they had caffeine at least once a day. The survey, “Caffeine: Consumer Perception Habits and Safety Perceptions,” also revealed that among U.S. consumers, caffeine is most often consumed through soft drinks, coffee, and tea. People tended to seek out sources of caffeine for the taste, the jolt of alertness caffeine provides, and the familiarity of their caffeine-consumption routine. Interestingly, the main reasons for caffeine consumption in older adults were taste and routine, whereas people under the age of 45 were more likely to report consuming caffeine to improve mood, help with focus, and relieve stress for social events. People under age 45 also more frequently sought out high-caffeine sources, including instant coffee, energy drinks, energy shots, and caffeine pills.

There is evidence behind the feeling of productivity an afternoon cup of coffee can bring. Indeed, caffeine use can have benefits, including boosting feelings of alertness and maximizing performance on mental tasks. Having some caffeine can also improve memory and reasoning if you’re short on sleep. The source of your caffeine can also provide additional benefits. For instance, coffee is full of bioactive compounds, and research has found that coffee consumption may be linked to improved insulin sensitivity and heart health (although there are also conflicting findings in the literature). For people who are physically active, caffeine has been found to enhance athletic performance by improving endurance, delaying fatigue, and helping with achieving peak activity. Caffeine has also been linked to increased fat oxidation and aerobic capacity. This increase in fat use during exercise can help conserve glycogen stores and improve endurance. However, too much caffeine can have negative side effects, including increased anxiety, elevated heart rate and/or blood pressure, insomnia, gastrointestinal distress, irritability, and more. Sensitivity to caffeine varies from person to person, so it’s difficult to identify what level of caffeine is too much for any given individual. The current caffeine recommendation from the FDA for heathy, non-pregnant-or-lactating adults is up to 400 mg/day, an amount equivalent to four cups of coffee. However, according to a recent IFIC survey, most consumers underestimate the safe amount of caffeine, and about a third of respondents don’t know the recommendation.

The increasing availability of high-caffeine products on the market, and their potential for adverse effects, has started to gain attention in recent years. Variations in physiological exposure and response to caffeine means the effects of caffeine can last anywhere between two and 12 hours, with tolerable amounts of caffeine being vastly different. Some people are sensitive to caffeine and can feel jittery after one cup of coffee, while other people are less sensitive and can have a few cups of coffee with no adverse effects. Genetics also play a role in determining a person’s response to caffeine and influence how fast the body is able to metabolize caffeine.

How much caffeine is too much? If you’re a non-pregnant, healthy adult, it’s advised to keep your daily caffeine consumption under 400 mg. You can slowly incorporate caffeine sources into your day to identify your tolerable amount of caffeine (e.g., start with a morning cup of tea instead of an energy shot or multiple cups of coffee). By steadily increasing your caffeine consumption, you can more readily identify when potential side effects appear—such as increased heart rate, feeling dizzy or jittery, or poorer sleep quality.

There are certain populations who are advised to limit their caffeine intake. These include pregnant and lactating people, who are recommended to keep daily caffeine consumption to less than 200 mg, and young adults or those under 18, who are advised to avoid caffeine altogether or keep consumption under 100 mg per day. Coffee drinkers with high blood cholesterol may be advised to consume filtered coffee instead of boiled or unfiltered coffee, like French press or Turkish coffee. This is because the diterpenes found in unfiltered coffee can modestly raise blood cholesterol levels. Filtered coffee helps limit exposure to diterpenes because the filter helps remove these compounds.

Although caffeine has potential benefits, it’s crucial to be mindful of its potential side effects and to avoid caffeine overdose. Most Americans recognize soda, coffee, and energy drinks as sources of caffeine. However, there’s still confusion regarding caffeine quantities in certain foods and supplements. Many people may be consuming more caffeine than they think, and this ignorance can cause unhealthful side effects. Greater awareness about everyday sources of caffeine in our diet, along with practical, science-based guidelines for consumption, are needed to help consumers safely incorporate caffeine into their diets. In the meantime, being mindful about sources of caffeine in your own daily routine can help limit its negative side effects. If, after evaluating your typical caffeine consumption, you find that it’s too high, consider other energy-boosting strategies, such as taking a quick walk or striking up a conversation with a friend.

This article was written by Debbie Fetter, PhD.