This is another one of those nutrition conundrums – “you’re damned if you do and you’re damned if you don’t”. Many of us love a cup (or 2!) of coffee and simply just enjoy the taste and the occasion. Others know that there are performance benefits to having coffee pre training and simply use it purely for functional purposes. Regardless, there are pro’s and con’s. Let’s have a look
What is it?
Before we discuss the actual workings of coffee, let’s just talk about what it actually consists of. So coffee is a plant which grows seeds, these seeds are what we call “coffee beans”, simply because they look more like a bean than a seed. Once ripe, they’re picked, processed (to remove all the fruit residue etc) dried and then roasted. They are then ground and brewed. In terms of nutrient content, there are virtually no carbs, no fats and no proteins, hence virtually zero calorie (unless you add a few spoons of sugar and a jug of milk and cream, which I obviously don’t recommend!). It does contain trace amounts of a few minerals (e.g. Magnesium and Sodium) and vitamins (Niacin, Riboflavin), but more importantly it contains 4 different types of polyphenols (flavanols and anthocyanins). It is these polyphenols which are thought to promote health benefits through their anti-oxidant and anti-inflammatory properties. And finally, coffee beans contain the organic compound – caffeine, which acts as a natural pesticide that actually paralyzes and kills certain insects that feed on the coffee plant! (Just as well we’re a bit bigger than insects then!!)
There are studies to show how coffee consumption increases blood pressure, increases adrenal fatigue, causes iron deficiencies and detrimentally affects sleep. There are also studies to show how coffee can reduced the risk of strokes (1), dementia (2), improve insulin sensitivity (3) and reduce the risk of cardiovascular disease (4). And therein lies the problem; is it good or bad for us?? Well, one of the first things to work out when assessing studies is the type of study that was actually carried out. In the case of these studies that looked at coffee consumption, many of the studies were based on “empirical” evidence. This means that the causes were “observational” only i.e. the group drinking coffee showed a lower risk of heart diseases. But they didn’t account for the fact that the same group may have exercised more, smoked less and/or had a better diet. So it’s very difficult sometimes to draw definitive conclusions from these studies.
However, thankfully, there are studies that we can rely on to make better assertions. These are studies where they actually tested the subjects to measure specific biomarkers. A recent study in the American Journal of Clinical Nutrition showed that coffee drinkers had reduced levels of inflammatory markers as well as improved LDL/HDL ratios (5). A very recent study (6) on coffee drinkers measured glucose tolerance and fasting insulin which showed that coffee consumption was positively related to insulin sensitivity.
Caffeine is one of the most researched supplements in the world of sport. There are literally hundreds of papers to show how it increases endurance capacity, improves sprinting, improves time-trialling, increases focus/concentration and enhances strength/power performance. These outcomes are all referenced in a meta-analysis journal published last year (2010) in the Journal of International Society of Sports Nutrition (7). The mechanisms by which caffeine exerts its action is through its effect on CNS, substrate utilization and neuromuscular function. So it can increase alertness and reduce the perception of pain (allowing you to sprint faster and lift more) plus it can spare glycogen and increase oxidation of fatty acids (allowing you to exercise for longer).
Rather than discussing the details of each study, I will just summarise the main points from this meta-analysis
– Endurance exercise can be improved with low – moderate doses of caffeine (2-3mg/Kg BW). For a 70Kg athlete, that would be anything between a 140-210mg of caffeine. A double espresso provides roughly 150mg of caffeine.
– Strength/Sprint/Power performance is improved at the higher doses (3-6mg/Kg BW). For a 70Kg athlete this is 200-420mg of caffeine.
– The general recommendation is to take caffeine 60mins prior to exercise. However, there is also evidence to suggest that it also works when taken 15-30mins before.
– Anhydrous caffeine has been shown to be more effective than coffee or tea.
– Caffeine does not cause dehydration during exercise.
Caffeine Content of Drinks
|Drink||Caffeine Content per Typical Serving|
Like many nutrition recommendations; no one size fits all. There are quite big variations between individuals in terms of their tolerance to caffeine. As caffeine is a psychotropic, the way in which it affects the brain and the CNS governs mood, consciousness, sleep and behaviour. In other words, it can give some people the jitters and cause insomnia. Others may be able to consume several coffee’s a day and sleep like a baby. There is research (8) that explains this which shows that some people are fast metabolisers of caffeine while others are slow and it’s due to the type of gene found in the liver (cytochrome p450). The faster you metabolise caffeine, the quicker you feel the effects and the more pronounced the effects are. Therefore, recommendations can’t really be generalised and like most things, you have to find what works best for you the individual.
There is enough evidence and arguably more convincing evidence to show that moderate amounts (3-4 cups) of coffee consumption improves health. The adverse effects are due to excessive consumption (>600mg/day) and also associated with individual tolerance. In these people, it can cause anxiety, insomnia, arrhythmia (abnormal heart rhythm) and migraines. This is most likely due to the stimulant effects of caffeine and how it is metabolized by the body. So in this case, consumption should be determined on an individual basis. If you enjoy the taste and coffee experience and do not suffer from any of the adverse effects, then a few coffees’s a day will potentially improve your health. Having said that, if you’re coffee consumption is more of a reliance and dependency to get you through the day, then this is more likely to lead to detrimental effects such as adrenal fatigue. Also, bear in mind that when I refer to the health benefits, I’m referring to coffee (and my preference would be freshly ground coffee not instant which 1. Tastes bad and has no texture and 2. contains acrylamide, a carcinogen), not other caffeinated drinks such as soft drinks (e.g. coke) or energy drinks. It’s the polyphenols in coffee that are believed to be responsible for the health properties of coffee, these are not found in commercial fizzy/energy drinks.
There are ergogenic effects of coffee which have been shown to improve performance. In this case, it is the caffeine and not the polyphenol content of the coffee that is responsible for its affects. Although anhydrous caffeine has been shown to have improved function, a couple of strong coffees 30-60mins before exercise can certainly help you along the way!
- Lopez-Garcia E, et al. Coffee Consumption and Risk of Stroke in Women. Circulation 2009:February 16, 2009.
- Eskelinen MH, et al. Midlife Coffee and Tea Drinking and the Risk of Late-Life Dementia: A Population-Based CAIDE Study. J Alzheimers Dis. 2009;16(1):85-91.
- Van Dam RM, et al. Coffee consumption and risk of type 2 diabetes: a systematic review. JAMA. 2005 Jul 6;294(1):97-104.
- J. Margot de Koning Gan, et al . Tea and Coffee Consumption and Cardiovascular Morbidity and Mortality. Arteriosclerosis, Thrombosis, and Vascular Biology. 2010;30:1665.
- Kempf K, et al. Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial. American Journal of Clinical Nutrition 2010;91:950-957.
- Loopstra-Masters RC, et al. Associations between the intake of caffeinated and decaffeinated coffee and measures of insulin sensitivity and beta cell function. DIABETOLOGIA, Volume 54, Number 2, 320-328, DOI: 10.1007/s00125-010-1957
- Goldstein et al .International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition 2010, 7:5
- Palatini et al. CYP1A2 genotype modifies the association between coffee intake and the risk of hypertension. Journal of Hypertension: August 2009 – Volume 27 – Issue 8 – p 1594-1601