Caffeine is a stimulant for the central nervous system of the body. It enhances mood and alertness, and increases mental and physical performance, reducing your perception of effort and fatigue. Some research has shown that caffeine can help with some diseases, such as reduced risk of Type 2 Diabetes (1,2), decreased incidence of headaches (3), and reduced risk for Parkinson’s disease (4). More research is required on these diseases before any firm recommendations can be made on dosing.
Sometimes having too much caffeine can have short term detrimental effects, such as sleep deprivation, increased blood pressure and heart rate, anxiety, diarrhea, sweating and tremors, or impaired fine motor control. If you are not a habitual user of caffeine, then it’s effects could be more pronounced and longer lasting than for habitual users. Check the products you buy, and compare the different amounts of caffeine that they contain.
Firstly, caffeine is not an essential nutrient and therefore you don’t have to consume caffeine as part of a healthy balanced diet (although many people would disagree). In the latest US Dietary Guidelines, it is stated that up to 5 standard 220 mL cups of coffee daily, providing about 400 mg caffeine, can be incorporated into healthy eating styles, and this amount is not associated with increased risk of major chronic diseases like cancer, or premature death from cardiovascular disease (5). For athletes, the guidelines are to consume around 1 – 3 mg caffeine/ kilogram bodyweight, to improve athletic performance (6). For a 70 kg athlete this equates to 70 - 210 mg caffeine, usually taken 15 – 20 minutes before exercise, and often during exercise if longer than 60 minutes. However, to work out an individualized dosing strategy you should see an accredited sports dietitian who will review your usual dietary patterns and the type of activity you participate in, as for some sports the use of caffeine could be detrimental. .
On February 8th 2018, the American College of Sports Medicine (ACSM) announced new recommendations and warnings regarding the safety of energy drinks (7). Energy drinks can contain high amounts of caffeine, and usually have added vitamins, minerals, amino acids and herbal mixtures, and are often consumed by children. The ACSM’s primary recommendations focus on four key areas: 1. Protecting children at risk - due to smaller body mass and caffeine naivety they may consume too much caffeine. Energy drinks are not intended for children. 2. Stop marketing to at-risk groups, especially children. 3. Do not use energy drinks before, during or after strenuous exercise - some recent sudden cardiac death events have occurred when a person consumed energy drinks before and/or after performing strenuous activity. 4. More education and research is needed, for the potential adverse effects and safe use of energy drinks.
Some research indicates that caffeine can interfere with your sleep duration and quality (8). If you are having issues with dropping off to sleep, or with staying asleep, then perhaps using decaffeinated products or abstaining from caffeine at least 4 hours before bed is a good strategy to try. Some contrasting advice for short naps is to have a cup of coffee before a 15 minute power nap, as this will have an alertness-boosting effect when you wake up (9); this is because caffeine takes about 30 minutes to peak in the blood after consumption, a good tip to try!
1 Jiang, X., Zhang, D., & Jiang, W. (2014). Coffee and caffeine intake and incidence of type 2 diabetes mellitus: a meta-analysis of prospective studies. European journal of nutrition, 53(1), 25-38.
2 Van Dam, R. M., & Feskens, E. J. (2002). Coffee consumption and risk of type 2 diabetes mellitus. The Lancet, 360(9344), 1477-1478.
3 Shapiro, R. E. (2008). Caffeine and headaches. Current pain and headache reports, 12(4), 311.
4 Costa, J., Lunet, N., Santos, C., Santos, J., & Vaz-Carneiro, A. (2010). Caffeine exposure and the risk of Parkinson's disease: a systematic review and meta-analysis of observational studies. Journal of Alzheimer's disease, 20(s1), S221-S238.
5 US Department of Health and Human Services. (2017). Dietary Guidelines for Americans 2015-2020. Skyhorse Publishing Inc
8 Sin, C. W., Ho, J. S., & Chung, J. W. (2009). Systematic review on the effectiveness of caffeine abstinence on the quality of sleep. Journal of Clinical Nursing, 18(1), 13-21.
9 Horne, J, & Reyner, L. (1996). Counteracting driver sleepiness: effects of napping, caffeine, and placebo. Psychophysiology, 33(3), 306-309.