Coffee... Yay or Nay?
Approximately 80% of the world’s population consumes a caffeinated product every day - mostly in the form of coffee.
Caffeine produces stimulating effects which makes it the most widely consumed psychoactive substance in the world.
Caffeine consumption has been classified as follows:
low caffeine users: <200 mg/day
moderate caffeine users: 200-400 mg/day
high caffeine users: >400 mg/day
Depaula, J., & Farah, A. (2019).
Caffeine content depends on the beans used. According to studies, Roasted C. arabica seeds vary in range between 0.7 and 1.6 g/100 g, while those for C. canephora contain between 1.8 and 2.6 g/100 g. In Western countries commercial ground roasted coffee generally consists of C. arabica seeds alone or of a blend with a small percentage of C. canephora seeds.
The image above indicates how forms of coffee impact the availability of caffeine. For example while soluble coffee (instant) has less caffeine because it’s diluted with water, it’s more rapidly absorbed than espresso however, espresso contains more caffeine.
What does this mean? Espresso coffee uses ground coffee which is minimally processed and takes longer for the body to break down and absorb. This is due to the added ruffage of the coffee beans. Caffeine content in ground coffee has remained mostly stable and readily available whereas instant has undergone hot water and high pressure treatment to extract the water-soluble compounds. What espresso, Turkish coffee, moka and French press have in common is the use of ground coffee and heat for extraction resulting in higher caffeine content.
What about tea?
Alcohol and Drug Foundation, 2020
What about coffee in relation to other naturally caffeinated beverages? In the table above you can see that coffee contains significantly more caffeine than tea. However, black tea is also a rich source of caffeine.
What happens when you drink it?
Caffeine acts on the central nervous system by blocking adenosine receptors (a neurotransmitter which has the effect of sleepiness). Caffeine competitively antagonizes their action and causes an increased release of dopamine, noradrenalin, and glutamate as a result of inhibiting adenosine.
So basically by inhibiting sleepiness, caffeine releases the feel good hormone dopamine and excitatory neurotransmitters noradrenalin and glutamate, resulting in wakefulness, focus and concentration.
There is a consensus that in most people, at low (~50–250 mg) to moderate doses (~250–400 mg) or 1–5 mg caffeine/body weight/day positive changes occur in mood and human behavior such as enhanced energy; well-being; sociability; willingness and motivation to work; improved self-confidence and cognitive function, including enhanced alertness and mental focus; vigilance; learning and memory.
How is it absorbed in the body?
Following ingestion, caffeine is rapidly and almost completely (up to 99%) absorbed into the bloodstream. About 20% absorption occurs in the stomach, and the remaining 80% in the small intestine. It generally reaches peak plasma concentrations within 30–120 min after administration, although some individuals may fall outside this range.
So what does this mean? Caffeine is quickly absorbed and quickly excreted. That’s why we love it … it can bring a tired head into focus, and wake a weary body for a Monday morning meeting!
Caffeine is metabolised by the liver and is excreted by kidneys via urine. It has a typical half-life of four to six hours. This means after several hours half the caffeine consumed still remains in the body, so it’s a good idea to enjoy your coffee early in the morning.
Coffee and Neurological Benefits
Because of coffee’s role in the central nervous system, there is a strong link between coffee and it’s protective effect on cognitive decline.
In epidemiological reports, a link between chronic caffeine consumption and a significantly lower risk of developing neurodegenerative diseases such as Alzheimer’s disease has been reported. Antioxidants in coffee capable of decreasing reactive oxygen species may also give rise to a reduction in the risk of Alzheimer's disease.
Because of these mechanisms, coffee has also been found to have a role in the prevention of motor symptoms and loss of dopaminergic neurons in Parkinson’s disease.
Sports Performance and Endurance
A number of recent meta-analyses have demonstrated that caffeine’s effects on exercise performance are well-established and well-replicated and consistent across a range of exercise modalities.
Exercise performance is shown to be significantly improved by caffeine consumption either by avoiding fatigue, improving substrates supply, or by enhancing oxygen uptake. It also increases motor unit recruitment and muscle contractility. As a result, one is more focused during exercise and has increased musculoskeletal efficiency.
With regard to physical activity, it should be noted that until 2004 the International Olympic Committee listed caffeine in its prohibited substances list. Professional athletes who tested positive for more than 12 μg/l of urine – which corresponds to drinking about 5-6 cups of coffee in a day – were banned from the Olympic games.
The recommended consumption is of 3–6 mg/kg of caffeine, typically 60 min before the start of exercise. However, recently it has become apparent that there is considerable inter-individual variation. So?
Antioxidant
Caffeine from coffee has been reported to be an efficient scavenger of hydroxyl radicals (or inflammation within the body). Mechanisms include:
Phosphodiesterase inhibition and/or with adenosine receptor antagonism mechanisms.
Modifications in cell signaling molecules production.
Potentiates the release of anti-inflammatory cytokines, including interleukin.
Mediates immune-suppression of pro-inflammatory cytokines release.
Cardiovascular Health
Caffeine has several effects on the cardiovascular system, however most of these effects are evident when caffeine doses are in toxic doses.
The main risk caffeine has is raised blood pressure or hypertension in coffee consumers. This is caused by a coffee‐induced increase in adrenaline concentrations. In fact, a study showed that abstinence from coffee for nine weeks was able to decrease blood pressure in normotensives.
However, the blood pressure-raising effect of caffeine is mostly seen in people prone to high blood pressure and who don’t normally drink a lot of coffee. No effect was seen in habitual drinkers, suggesting regular consumption allows one to adapt to hypertensive effects.
Regardless, I wouldn’t take the risk. If you have high blood pressure, you should avoid, or at least limit coffee consumption.
Fat Loss
Caffeine switches the substrate preference from glycogen to lipids, resulting in increased fatty acid oxidation. Therefore caffeine has been associated with fat loss.
Studies have shown that coffee intake (3 × 250 mL/day for 4 weeks) can also decrease energy intake, by improving satiety hormones (ghrelin and serotonin) and therefore decreasing levels of body fat. However, as a holistic nutritionists, I would discourage more than a coffee a day for the reasons previously mentioned.
Metabolic Health
The majority of evidence shows beneficial effects of coffee consumption and type 2 diabetes via a decreased insulin resistance (or improved insulin sensitivity) and/or improved glucose tolerance.
With the added benefits of fat loss mentioned above, coffee can encourage improved body composition, which in turn improves insulin sensitivity and prevents development of type 2 diabetes.
Fertility
Scientific reports show a 37% increased risk of experiencing a miscarriage when consuming 300 mg or more a day during early pregnancy. Mechanisms are unclear however, coffee or caffeine consumption may affect hormone levels through changes in ovarian function or alterations in hormone metabolism. However, contrary to some circulating thoughts, coffee consumption has no effect on natural fertility. Health organizations such as European Food Safety Authority (EFSA) and World Health Organization (WHO), advise a limit of a maximum of two to three cups of coffee/200–300 mg caffeine per day may be too high.
Osteoporosis
Caffeine can induce calcium release and inhibit the reuptake resulting in calcium loss. In a study, 112 mg of caffeine intake increased calcium loss by 10 mg/day. This may increase risk of osteoporosis.
Nevertheless, risk of osteoporosis is mostly seen in lean compared to overweight/obese individuals, and in females not males with high daily coffee consumption.
Intoxication
Common features of caffeine intoxication (4-7 cups a day), also known as “caffeinism” (i.e., a state of chronic toxicity from excessive caffeine consumption), include:
Anxiety
Agitation
Restlessness
Insomnia
Gastrointestinal disturbancesTremors, tachycardia
Psychomotor agitation
And, in some cases, death.
Despite these warnings, it is generally the case that life-threatening caffeine overdoses entail the ingestion of caffeine-containing medications rather than caffeinated foods or beverages, and also in combination with drugs and alcohol.
So is coffee good or bad?
Overall, results indicate that the health benefits of low to moderate coffee consumption for adults clearly outweigh the risks. People who should avoid coffee include pregnant women and those who suffer from insomnia or anxiety disorders.
In fact one coffee a day (preferrable in the morning) can have many health benefits! Less processed coffee’s such as espresso, moka (percolator), French press, Turkish coffee are superior as they are richer in antioxidants which have added health benefits.
5 KEY TAKEAWAYS
Aim for no more than 400mg of caffeine a day from natural sources like coffee, tea, and chocolate (not energy or soft drinks).
Ground coffee (espresso, percolator, French press) beans has more antioxidant value than soluble (instant) coffee, but more caffeine.
Caffeine is quickly absorbed and quickly excreted. However, it has a half-life of four to six hours. This means after several hours half the caffeine consumed still remains in the body, so it’s a good idea to enjoy your coffee early in the morning.
Avoid coffee or limit intake if you are pregnant, have cardiovascular disease (particularly hypertension) or suffer from anxiety disorders.
Want to optimise sports performance? A prework out snack with a shot of coffee has been shown to improve endurance during exercise.
The large array of evidence suggest coffee has more health benefits than negative effects. Like my Grandma says, everything in moderation is key and coffee is no different.
REFERENCES
Cappelletti, S., Piacentino, D., Sani, G., & Aromatario, M. (2015). Caffeine: cognitive and physical performance enhancer or psychoactive drug?. Current neuropharmacology, 13(1), 71–88. https://doi.org/10.2174/1570159X13666141210215655
Choi, M. K., & Kim, M. H. (2016). The Association between Coffee Consumption and Bone Status in Young Adult Males according to Calcium Intake Level. Clinical nutrition research, 5(3), 180–189. https://doi.org/10.7762/cnr.2016.5.3.180
Depaula, J., & Farah, A. (2019). Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks. Beverages, 5(2), 37. doi:10.3390/beverages5020037
Lyngsø, J., Ramlau-Hansen, C. H., Bay, B., Ingerslev, H. J., Hulman, A., & Kesmodel, U. S. (2017). Association between coffee or caffeine consumption and fecundity and fertility: a systematic review and dose-response meta-analysis. Clinical epidemiology, 9, 699–719. https://doi.org/10.2147/CLEP.S146496
Mullaicharam, A., El-Khider, M., & Amaresh, N. (2011). Chemistry and pharmacology of caffeine in different types of tea leaves. International Journal of Nutrition, Pharmacology, Neurological Diseases, 1(2), 110. doi:10.4103/2231-0738.84198
Pickering, C., & Grgic, J. (2019). Caffeine and Exercise: What Next?. Sports medicine (Auckland, N.Z.), 49(7), 1007–1030. https://doi.org/10.1007/s40279-019-01101-0
Pourshahidi, L. K., Navarini, L., Petracco, M., & Strain, J. (2016). A Comprehensive Overview of the Risks and Benefits of Coffee Consumption. Comprehensive Reviews in Food Science and Food Safety, 15(4), 671-684. doi:10.1111/1541-4337.12206
Willson C. (2018). The clinical toxicology of caffeine: A review and case study. Toxicology reports, 5, 1140–1152. https://doi.org/10.1016/j.toxrep.2018.11.002
