It seems that every few weeks there’s an article in the health sections of the papers about coffee or caffeine. Some of them seem to hail coffee as some kind of 'superfood', while others warn us of the dangers of drinking too much of the stuff. As with many nutritional messages reported by the media, the hype around coffee is pretty confusing and conflicting. But while we're drinking around 70 million cups of coffee every day in the UK, it’s worth knowing if we should be drinking it at all. Well, here’s a breakdown of the best scientific evidence behind that aromatic beverage so many of us love:
The Health Benefits of Drinking Coffee
As well as caffeine, coffee is loaded with potent compounds such as chlorogenic acid and polyphenols, which have antioxidant properties and contribute significantly towards antioxidant intake in Western diets (1). The combination of these compounds could delay the absorption of blood sugar, increase metabolic rate, and help blood vessels contract and relax. These actions may account for why coffee drinking is associated with lower risk of:
Developing type 2 diabetes (4)
Neurological diseases such as Alzheimer’s (5) and Parkinson’s disease (6)
Coffee has also been shown in meta-analyses (large reviews combining the results of numerous trials) to be significantly protective against several cancers, including colorectal (7), liver (8), oral (9), and pancreatic (10).
From a fitness perspective, the caffeine in coffee acts as a stimulant by blocking the inhibitory neurotransmitter adenosine (11) which can reduce fatigue, making you: Firstly, less likely to skip training sessions because you're feeling tired / sluggish; and secondly, improve alertness and concentration during training, meaning once you're at the gym, you're more likely to push yourself harder and make bigger improvements (12).
The Risks of Drinking Coffee
In some people, too much caffeine can lead to insomnia, nervousness, heart palpitations, and 'the jitters'. Caffeine taken in after lunchtime is particularly likely to interfere with sleep, and getting less sleep puts you at risk for other chronic conditions in the long term.
As mentioned, coffee reduces risk of several cancers. For most other cancers, it has no significant effect, with the exception of lung cancer, where risk is increased, but only amongst smokers (13). There is also some evidence that coffee could increase risk of non-fatal myocardial infarction (heart attack) amongst those with the gene that means caffeine is metabolised slowly (about half of us) (14, 15).
The polyphenols in coffee can inhibit absorption of non-heme iron (the kind found in plants) in a meal by between 50 and 90% (16). So vegetarians and vegans need to be particularly careful about holding back on the coffee for at least 30 minutes before or after eating to ensure iron absorption is maximised.
It’s also worth noting that all of the benefits mentioned above are referring to black coffee. The biggest risk of all comes from what you may add to it – creams, sugar, or sugary syrups add saturated fat and empty calories to your brew, raising blood sugar and promoting weight gain. It’s also important to brew coffee with filter paper, as unfiltered coffee (such as Turkish brew or French press) contains cafestol, a substance that can increase LDL (bad) cholesterol levels (17).
From an environmental perspective, it must be said that coffee isn’t great for the planet. Deforestation to make way for sun-cultivated coffee has seen off 2.5 million acres of natural ecosystems in Central America alone so far. There are also issues with water contamination, chemical use, waste, and soil quality / erosion. And take away coffees have the added impact of the used cups (7 million a day in the UK alone) that go to landfill, as most paper coffee cups are fused with polyethylene to make them waterproof and can’t be recycled. Coffee pods have also come under fire recently, with the vast majority of the 500 million pods sold just in the UK in 2015 ending up in landfill, where they will take 500+ years to break down. If this is an important issue to you, check out my five easy steps to reduce the amount of plastic you use.
The protective effects of drinking coffee against many diseases may explain why there is good evidence that overall, drinking coffee could help you live longer (18). However, some people should limit coffee consumption, especially pregnant women, smokers, those with anxiety issues, high blood pressure, or insomnia.
If you already drink coffee, try following these guidelines to maximise the benefits:
Stick to no more than five cups a day to keep your caffeine intake at a safe level
Try to drink coffee in the mornings only, to avoid disrupting your sleep
Limit the amount of unfiltered coffee you drink
Leave 30 minutes either side of eating to reduce the inhibition of iron absorption
Stick to black coffee without sugar, or use low fat nut / soy milk if you prefer
Reduce your coffee intake if you would like to lower your environmental impact, or at least stick to making your own coffee instead of using takeaway cups or coffee pods
Lastly - if coffee isn’t already part of your daily rituals, don’t worry about starting a love affair with the stuff; it's not for everyone and there are plenty of other ways to stay healthy without forcing yourself to drink it.
1. Svilaas, Arne, Sakhi, Amrit, & Svilaas, Tone. (2004). Intakes of Antioxidants in Coffee, Wine, and Vegetables Are Correlated with Plasma Carotenoids in Humans1. The Journal of Nutrition, 134(3), 562-7.
2. Nordestgaard, Ask Tybjærg, Thomsen, Mette, & Nordestgaard, Børge Grønne. (2015). Coffee intake and risk of obesity, metabolic syndrome and type 2 diabetes: A Mendelian randomization study. International Journal of Epidemiology, 44(2), 551-565.
3. Zhang, R., Wang, Y., Song, B., Jørgensen, H., & Xu, S. (2012). Coffee consumption and risk of stroke: A meta-analysis of cohort studies. Central European Journal of Medicine, 7(3), 310-316.
4. Jiang, Xiubo, Zhang, Dongfeng, & Jiang, Wenjie. (2014). Coffee and caffeine intake and incidence of type 2 diabetes mellitus: A meta-analysis of prospective studies. European Journal of Nutrition, 53(1), 25-38.
5. Liu, Qing-Ping, Wu, Yan-Feng, Cheng, Hong-Yu, Xia, Tao, Ding, Hong, Wang, Hui, . . . Xu, Yun. (2016). Habitual coffee consumption and risk of cognitive decline/dementia: A systematic review and meta-analysis of prospective cohort studies. Nutrition, 32(6), 628-636.
6. Qi, H., & Li, S. (2014). Dose–response meta‐analysis on coffee, tea and caffeine consumption with risk of Parkinson's disease. Geriatrics & Gerontology International, 14(2), 430-439.
7. Li, G., Ma, D., Zhang, Y., Zheng, W., & Wang, P. (2013). Coffee consumption and risk of colorectal cancer: A meta-analysis of observational studies. 16(2), 346-357.
8. Yu, C., Cao, Q., Chen, P., Yang, S., Deng, M., Wang, Y., & Li, L. (2016). An updated dose-response meta-analysis of coffee consumption and liver cancer risk. Scientific Reports, 6, 37488.
9. Li, Ya-Min, Peng, Juan, & Li, Le-Zhi. (2016). Coffee consumption associated with reduced risk of oral cancer: A meta-analysis. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 121(4), 381-389.e1.
10. Jie Dong, Jian Zou, Xiao-Feng Yu. (2011). Coffee drinking and pancreatic cancer risk: A meta-analysis of cohort studies. World Journal of Gastroenterology, 17(9), 1204-1210.
11. Fredholm, B. (1995). Adenosine, Adenosine Receptors and the Actions of Caffeine *. Pharmacology & Toxicology, 76(2), 93-101.
12. Doherty, M., & Smith, P. (2004). Effects of caffeine ingestion on exercise testing: A meta-analysis. International Journal of Sport Nutrition and Exercise Metabolism, 14(6), 626-46.
13. Anqiang Wang, Shanshan Wang, Chengpei Zhu, Hanchun Huang, Liangcai Wu, Xueshuai Wan, Haitao Zhao. (2016). Coffee and cancer risk: A meta-analysis of prospective observational studies. Scientific Reports, 6, Scientific Reports, 2016, Vol.6.
14. Cornelis, M., El-Sohemy, A., Kabagambe, E., & Campos, H. (2006). Coffee, CYP1A2 genotype, and risk of myocardial infarction. JAMA, 295(10), 1135-41.
15. Nawrot, Perez, Künzli, Munters, & Nemery. (2011). Public health importance of triggers of myocardial infarction: A comparative risk assessment. The Lancet, 377(9767), 732-740.
16. Hurrell, R., Reddy, M., & Cook, J. (1999). Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. British Journal of Nutrition, 81(4), 289-295.
17. Hingston, C., & Wise, M. (2015). Coffee brewing technique as a confounder in observational studies. Heart, 101(20), 1686.
18. Freedman, N., Park, Y., Abnet, C., Hollenbeck, A., & Sinha, R. (2012). Association of Coffee Drinking with Total and Cause-Specific Mortality. The New England Journal of Medicine, 366(20), 1891-1904.