Caffeine is well absorbed by the body, and the short-term effects are usually experienced between 5 and 30 minutes after having it. These effects can include increased breathing and heart rate, and increased mental alertness and physical energy. Depending on the individual, these effects can last up to 12 hours. Harpaz E, Tamir S, Weinstein A, Weinstein Y. The effect of caffeine on energy balance. Journal of basic and clinical physiology and pharmacology. 2017 Jan 1;28(1):1-0. These results suggest that it’s important to pay attention to both the amount and timing of caffeine to optimize your sleep. Summary Be aware that ‘legal highs’ and controlled drugs often contain caffeine. This is a problem as you do not know how much caffeine you are taking, and it could also increase the harms of some. One study of 6 ‘legal high’ products found that some contained around 90% caffeine. This means that taking one gram of the product would be like taking around 13 litres of cola, 3.75 litres of energy drink, or 12-15 cups of coffee.

In one case study, a woman who took a massive dose of caffeine powder and tablets in an attempted suicide developed a very rapid heart rate, kidney failure and other serious health issues ( 40). Giving up caffeiene may not be the most comfortable process, but if you really have been going overboard, you should see some benefits to moderating your consumption.

Scientists have measured the difference caffeine makes to mental performance by testing regular users and non-users. Here's what they discovered from their study: In addition, a study linked drinking 2–3 cups of caffeinated coffee (providing about 200–300 mg caffeine) per day to a 45% lower risk of suicide ( 7). Knowing your caffeine intake is particularly important in childhood and adolescence. There's a reason energy drinks are set to be banned for children in England: younger brains are more sensitive to caffeine. As a rule of thumb, children should consume no more than 3 mg of caffeine a day for every kilo of their body weight. (For a child weighing 40 kg, this would equate to 120 mg - about the same as one strong coffee.) People often develop a “caffeine tolerance” when taken regularly, which can reduce its stimulant effects unless a higher amount is consumed. When suddenly stopping all caffeine, withdrawal symptoms often follow such as irritability, headache, agitation, depressed mood, and fatigue. The symptoms are strongest within a few days after stopping caffeine, but tend to subside after about one week. [3] Tapering the amount gradually may help to reduce side effects. Sources of Caffeine Guest NS, VanDusseldorp TA, Nelson MT, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1. doi: 10.1186/s12970-020-00383-4

Interestingly, consuming decaffeinated coffee was also linked to a 21% lower risk of diabetes. This indicates that other beneficial compounds in coffee can also protect against type 2 diabetes ( 36). SummaryEnergy drinks contain caffeine, as well as ingredients such as taurine and guarana (a natural source of caffeine). Energy drinks do not hydrate and should not be confused with sports drinks. Spilling the beans: How much caffeine is too much. Food and Drug Administration. https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much. Accessed Sept. 20, 2019. It is unlikely that a toxic amount of caffeine can be consumed from caffeinated beverages alone. 8 However, large doses of caffeine are dangerous and there have been deaths from people consuming caffeine in tablet or powder form. 9

Regular high intake of caffeine is thought to cause behavioural changes including restlessness and anxiety/nervousness. It may increase the frequency of headaches in some. Brands B, Sproule B, & Marshman J. Drugs & Drug Abuse. 3rd ed. Ontario: Addiction Research Foundation; 1998. The average cup of coffee contains 150-200 milligrams (mg) of caffeine per cup, while a cup of tea will have about 60 mg of caffeine. Cola products have about 30-40 mg of caffeine, and most energy drinks have about 60-70 mg. Be sure to account for any dietary caffeine that is consumed. if you have anxiety, agitation or nervousness, liver or stomach (ulcer) problems, insomnia (trouble sleeping), seizures (convulsions), or heart disease, especially any abnormal heart rhythms or high blood pressure

More Caffeine resources

A study on caffeine-infused chewing gum determined that close to sixty percent of caffeine was absorbed within ten minutes and nearly 100 percent absorbed within 40 minutes. Chewing on gum — or a caffeine gummy — means caffeine absorbs through the mucosal membranes in the mouth, which is one of the fastest methods of absorption.

Semiz S, Serdarevic F. Prevention and management of type 2 diabetes and metabolic syndrome in the time of covid-19: should we add a cup of coffee? Front Nutr. 2020;0. doi: 10.3389/fnut.2020.581680Regardless of the mixed study results, if you notice any changes in your heart rate or rhythm after drinking caffeinated beverages, consider decreasing your intake. Summary