Caffeine

Caffeine is the most widely consumed stimulant in the world with some studies estimating that as many as 80-90% of people consume caffeine on a daily basis. It is found in the seeds, nuts, and leaves of a number of different plants and used in various products from coffee and tea to chocolate and snack bars. We get the safety questions regarding caffeine frequently, so we thought we would dive in on this episode of the podcast/newsletter.
We begin by looking at how caffeine affects various performance indicators. An umbrella review of 21 published meta-analyses demonstrated performance enhancing effects of caffeine on muscle endurance, muscle strength, anaerobic power and aerobic endurance. Caffeine-containing supplements have a good deal of studies behind them showing these types of benefits. They can boost not only endurance based exercise, but also resistance training performance. Dosage can vary quite a bit in these types of studies, anywhere from 179 mg of caffeine to 300, 400, and up to 6 mg/kg of body weight. It seems that when looking at the body of evidence, it is weighted in favor of the effectiveness of caffeine for improving performance.

Caffeine primarily blocks the adenosine receptors in your brain which prevents adenosine from binding. Normally, adenosine levels steadily climb through the day and will bind with these receptors and increase sleep pressure (making you tired). Therefore, as caffeine blocks these receptors, you feel less tired. Caffeine also boosts dopamine levels in the frontal lobe of the brain. Therefore, we also observe caffeine having mood boosting, attention/focus boosting, and overall pleasure boosting properties. Regular caffeine users tend to have less incidence of depression, Parkinson’s and Alzheimer’s. We discuss a number of studies showing caffeine seems to help selective attention, mental alertness, and sustained attention. Hence the use of caffeine when doing things such as studying, reading, or doing paperwork.

We discuss a few studies that center around possible negatives of caffeine consumption. The first is a study that concluded that caffeine disrupted insulin sensitivity (increasing acute glucose and insulin) beginning even at low doses. However, when the data was analyzed using the Insulin Sensitivity Index (which estimates insulin sensitivity at the whole body level and takes into account mean glucose and insulin levels during an oral glucose tolerance test) the results were much less concerning. Also, this study used an isolated caffeine dose as opposed to caffeine found in a food or beverage (like coffee or tea) which also could have different effects. Also, studies have consistently shown coffee consumption to decrease type 2 diabetes risk.

We then looked at a meta-analysis evaluating caffeine induced diuresis (urine volume) during rest and exercise. There are a number of concerns regarding caffeine increasing urine volume and possibly negatively affecting fluid balance. This study’s analysis showed doses of 300-500 mg failing to produce significant diuresis. Therefore the authors concluded that the concerns regarding fluid loss and adverse effects on fluid balance due to caffeine consumption to be unfounded.

Finally, we look at a few studies on blood pressure and caffeine consumption. It seems that caffeine may have a short term increase in blood pressure. However, long term consumption of caffeine does not seem to associate with increased blood pressure or an increased risk of cardiovascular disease. It seems like the data states that if you are someone with hypertension, limiting your caffeine intake is probably wise. In healthy people, regular coffee intake is associated with reduced risk of cardiovascular disease.

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Simplified Takeaways…

1. Caffeine has a number of performance enhancing benefits documented in the literature.

2. Caffeine can also enhance focus, mood, and attention.

3. Concerns about becoming dehydrated (or having poor fluid balance) from consumption of caffeine seem to not hold up in the literature.

4. Caffeine consumption is associated with decreased risk of Type 2 diabetes and cardiovascular disease.

5. If you have hypertension, monitoring your caffeine intake is wise. However, the data does not suggest long term consumption of caffeine causes high blood pressure.

Further Reading…

1. Large review of studies showing the performance enhancing effects of caffeine consumption

2.   Study looking at caffeine consumption and diuresis

3.   Study looking at caffeine and blood pressure

Disclaimer: This newsletter is for general informational purposes only and does not constitute the practice of medicine, nursing, or other professional healthcare services, including the giving of medical advise. No doctor/patient relationship is formed. The use of information on this newsletter or materials linked from this newsletter is at the user’s own risk. The content of this newsletter is not intended to be a substitute for professional medical advise, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advise for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.