You Don't Need to Delay Your Morning Coffee
14 infamous caffeine myths debunked.
This study, in the International Journal of Sport Nutrition and Exercise Metabolism, systematically reviews the scientific literature to address 14 frequently asked questions about caffeine supplementation, particularly in the context of exercise, hydration, and overall health. The goal is to clarify misconceptions and provide evidence-based insights for athletes, fitness enthusiasts, and the general population.
Key Points
Aim
To evaluate the scientific literature and address 14 specific questions related to caffeine's effects on hydration, performance, health, and daily habits.
Methods
The authors conducted a thorough review of existing research, analysing studies that examined caffeine's impact on various physiological parameters in diverse populations.
Answers to the 14 Questions Posed in the Study
Does caffeine dehydrate you at rest?
No, moderate daily doses of caffeine (3 mg/kg or ~250-300 mg) in habitual drinkers do not augment urine volume. Excessive doses (6 mg/kg or ≥500 mg) may induce acute diuresis.
Does caffeine dehydrate you during exercise?
No, caffeine does not cause dehydration during exercise when proper hydration strategies are followed.
Does caffeine promote the loss of body fat?
Caffeine can increase fat oxidation during exercise but has limited direct effects on long-term fat loss unless paired with a calorie deficit.
Does caffeine affect upper vs. lower body performance/strength differently?
The study does not specify any significant difference between upper and lower body performance enhancement from caffeine. It generally improves both strength and power output.
Is there a relationship between caffeine and depression?
The relationship between caffeine and depression is highly individual; moderate caffeine may offer temporary relief for some, while excessive intake can worsen anxiety and sleep. Individuals with depression should carefully monitor their caffeine consumption and seek professional advice, considering other physical conditions.
Can too much caffeine kill you?
While extremely high doses of caffeine can be toxic or even fatal, this is rare and typically involves doses far exceeding normal consumption levels. The lethal dose is estimated to be around 150-200 mg/kg.
Are there sex differences regarding caffeine’s effects?
Current evidence suggests no significant sex-based differences in responses to caffeine for performance or metabolism.
The research on sex differences in caffeine response is inconsistent, potentially due to hormonal variations (estradiol, oral contraceptives) affecting caffeine metabolism. While caffeine is an ergogenic aid with a placebo effect, some studies suggest greater performance benefits in males, but results are mixed overall.
Does habitual caffeine consumption influence the performance response to acute caffeine supplementation?
Yes, habitual caffeine consumption can influence the performance response. Regular users may develop a tolerance and require slightly higher doses to achieve similar effects as non-habitual users.
Does caffeine work for everyone?
While caffeine is generally effective as an ergogenic aid, individual responses can vary. Factors like genetics, tolerance, and sensitivity can affect how someone responds to caffeine.
Does caffeine cause heart problems?
Moderate caffeine consumption is not typically associated with heart issues in healthy individuals. However, those with pre-existing heart conditions should consult their healthcare provider.
Does caffeine promote the loss of bone mineral?
Limited evidence suggests that consuming more than 4 cups of coffee (≤400 mg caffeine) daily might negatively affect bone mineral density, primarily in women. However, the impact of caffeine source and confounding factors remains unclear, necessitating further research, especially randomised controlled trials, to establish definitive conclusions.
Should pregnant women avoid caffeine?
The study does not make a specific recommendation, but on the strength of observational studies and meta-analyses, it is typically advised that pregnant women limit caffeine intake due to potential risks.
Is caffeine addictive?
Caffeine can lead to dependence and withdrawal symptoms upon cessation, particularly in habitual users. This is not typically considered addiction but rather a physical dependence.
Does waiting 1.5–2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?"
While delaying morning caffeine intake might slightly enhance its effects if you're well-rested, it's not due to manipulating cortisol or adenosine levels, nor does it prevent an afternoon "crash." The arguments about cortisol are flawed, and there's no strong evidence supporting other proposed mechanisms.
