Human Researchze: 18pt;">Caffeine boosts both physical & mental energy and related cognitive aspects such as mood and focus.
Caffeine is the most popular psychoactive compound known to man, taken by an estimated 80% of the world’s population. Caffeine helps with energy through:
- Blocking adenosine. This biological mechanism results in increased energy levels and improved mood, attention, and overall cognition.
Caffeine (1,3,7-trimethylxanthine) is the most widely-consumed psychoactive substance in the world, taken by billions of people in the form of coffee, tea, and soft drinks. Known primarily as a central nervous system stimulant, caffeine increases energy, focus, wakefulness, improves mood, and decreases the perception of fatigue.
In addition, caffeine is frequently added to medical preparations and supplements, and has been shown to provide beneficial effects for a wide range of health conditions including Alzheimer’s, depression, diabetes, obesity, asthma, and liver conditions.
The use of caffeine for boosting energy – as measured by improvements in alertness, concentration, mood, creativity, self-confidence, exercise performance, and reductions of sleepiness and fatigue – is backed by decades of successful research and thousands of years’ worth of use.
How Caffeine Might Help With Energy
Caffeine is absorbed into the bloodstream within 45 minutes of being taken, and easily crosses the blood-brain barrier.<
Blocking adenosine receptors
Although caffeine is believed to function via multiple mechanisms, the main one is undoubtedly its effect on adenosine – a neurotransmitter that makes you feel tired and sleepy. Caffeine blocks adenosine from binding to its receptors, which not only prevents its effects, but also results in important secondary effects:2
- Increasing the levels or signaling of several neurotransmitters that promote well-being, alertness, and feelings of increased energy, including dopamine, serotonin, acetylcholine, norepinephrine and glutamate
- Promoting epinephrine (adrenaline) release, causing further stimulating effects such as increased heartbeat, blood pressure, sugar release for energy
Caffeine Uses & Benefits for Energy
Caffeine is highly popular for increasing physical and mental energy. Although there is no standardized, scientific way for defining and measuring changes in energy, caffeine has been consistently demonstrated to result in effects associated with improved energy, namely:
- Decreased sleepiness/improved wakefulness
- Improved alertness, focus, attention, and other cognitive parameters
- Enhanced well-being and mood
- Decreased perception of fatigue
And far from only affecting improving mental performance, caffeine has also been demonstrated to boost physical energy, resulting in benefits such as increased time until exhaustion and better time trial performance during endurance activity, and improved high-intensity sports (soccer, field hockey, rowing, and others) performance. 3
Decades of clinical studies provide plenty of evidence for the stimulating effects of caffeine that aid both cognitive and physical energy.
This double-blind, placebo controlled, crossover study examined whether the effects of caffeine were age or gender-specific. Twelve participants aged 18-30 and 12 others over 60 years old were given placebo or 64/128/256 mg doses of caffeine on separate occasions. Caffeine resulted in improved measures of vigor, fatigue, and performance in the Wilkinson Auditory Vigilance (attention/alertness) Test.
- The researchers concluded that “performance and mood enhancing effects of caffeine are neither age nor gender specific.”4
In this frequently-cited meta-analysis paper, researchers reviewed 21 studies that examined the effect of caffeine on rating of perceived exertion (RPE)—a way of measuring how much an individual feels their body is working during physical activity. They found on average, caffeine reduced RPE by 5.6% and improved exercise performance by 11.2% compared.
- The authors concluded that “The results have quantified the suggestions in the literature that caffeine reduces RPE obtained during exercise. Moreover, there is evidence that the reduction in RPE may partly explain the ergogenic effects of caffeine.”5
In this randomized, double-blind, placebo-controlled study, the effects of 40 mg caffeine (in coffee, water, tea, or cola) on mood and cognitive function were tested in 144 participants. Compared to placebo, all caffeine groups reported improved alertness and performance on attention and memory tests, regardless of the drink used.
- The researchers concluded that “a dose of caffeine typical of the level found in commercial products can improve alertness and performance efficiency.“6
This double-blind, placebo-controlled trial examined the effects of caffeine in sleep-deprived individuals. A total of 50 men didn’t sleep for 49 hours and were then given placebo or 150/300/600 mg doses of caffeine. Caffeine reversed the sleep deprivation-caused changes in ratings of vigor, fatigue, and confusion, and promoted wakefulness.
- The researchers concluded that “caffeine was able to produce significant alerting and long-lasting beneficial mood effects in individuals deprived of sleep for 48 h.“7
This double-blind, placebo-controlled crossover study tested the effects of caffeine and theophylline (a compound similar to caffeine) in older adults. The participants tried both compounds and placebo on three separate occasions, and rated feeling much more alert and energetic only on caffeine.
- The researchers concluded that “caffeine is a more potent CNS stimulant than theophylline.“8
This double-blind, placebo-controlled study examined the effects of caffeine on alertness. A total of 24 young men were given placebo or caffeine (250 mg) 2 times daily for 2 days. Caffeine was demonstrated to improve alertness and auditory concentration.
- The researchers concluded that “caffeine clearly improves both alertness and vigilance performance as objectively measured.”9
This double-blind, placebo-controlled trial tested the cognitive effects of caffeine. Seven participants abstained from caffeine, and were then given two capsules in a sequence, one containing caffeine (10 – 178 mg) and the other placebo. They then attempted to guess which capsules contained the caffeine. All seven participants correctly identified the 100 and 178 mg doses of caffeine, and consumption of 100 mg of caffeine increased ratings of alertness, well-being, motivation, concentration, energy, confidence, and decreased sleepiness.
- The researchers concluded that “The present study documents biological activity of caffeine at lower doses than heretofore recognized.“10
Dosage for EnergyMost successful research studies of caffeine’s effects on energy and related benefits use 100 – 250 mg doses
Caffeine 100-200 mg for energy.
Supplements in Review Says
Caffeine is the most popular choice for boosting energy. The combination of safety and efficacy makes caffeine far and away the best supplement for improving energy levels.
200 mg is the standard dose. Although the most used and arguably most effective dose of caffeine is 200 mg, it’s always better to start out with a lower dose (100 mg) to see how you respond and assess possible side effects, especially if you don’t regularly consume caffeine-containing beverages.
- Heckman MA et al. Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. J Food Sci. 2010 Apr;75(3):R77-87. ↩
- Fredholm BB et al. Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacol Rev. 1999 Mar;51(1):83-133. ↩
- Goldstein ER et al. International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition 2010 7:5. ↩
- Amendola CA et al. Caffeine’s Effects on Performance and Mood are Independent of Age and Gender. Nutr Neurosci. 1998;1(4):269-80. ↩
- Doherty M and Smith PM. Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scand J Med Sci Sports. 2005 Apr;15(2):69-78. ↩
- Smith A et al. Effects of a low dose of caffeine given in different drinks on mood and performance. Hum Psychopharm. 14(7);October 1999: 473–482. ↩
- Penetar D et al. Caffeine reversal of sleep deprivation effects on alertness and mood. Psychopharmacology (Berl). 1993;112(2-3):359-65. ↩
- Yu G et al. A comparison of the central nervous system effects of caffeine and theophylline in elderly subjects. Br J Clin Pharmacol. 1991 Sep;32(3):341-5. ↩
- Zwyghuizen-Doorenbos A et al. Effects of caffeine on alertness. Psychopharmacology (Berl). 1990;100(1):36-9. ↩
- Griffiths RR et al. Low-dose caffeine discrimination in humans. J Pharmacol Exp Ther. 1990 Mar;252(3):970-8. ↩