The pros + cons of coffee

This article was written by our regular contributor; dietitian – Maeve Hanan.

Coffee is one of the most popular drinks in the world, so it’s unsurprising that the health impact of this drink gains a lot of attention. This article will explain the benefits and drawbacks related to drinking coffee. 

The Caffeine Content of Coffee

A big factor when it comes to the impact of coffee is it’s caffeine content. An average 200ml cup of coffee contains ~90mg of caffeine, although this can vary depending on how it has been made and the type of coffee bean used (1). In fact, a study comparing the caffeine content of a variety of coffee drinks from 6 different shops found that the caffeine content ranged from 58-259mg per drink, and interestingly this varied widely from 259–564mg for the same type of coffee from the same shop when this was checked for six days in a row (2). 

The European Food Safety Authority (EFSA) recommend that consuming upto 400mg of coffee per day and upto 200mg in one serving is safe for most healthy adults, with the exception of pregnant and breastfeeding women who are advised to consume no more than 200mg of caffeine per day (2, 3). 

However, there is a lot of variation in the way that different people metabolise and react to caffeine, related to genetics, body size, liver health, age etc. (4). For example, it seems that older adults may be more sensitive to caffeine than younger adults overall. 

It’s important to remember that caffeine is also found in tea (including green tea), cola, energy drinks, chocolate, as well as certain medication and sports supplements.

What About Decaf Coffee?

Decaffeinated (decaf) coffee can be produced by a variety of methods such as soaking coffee beans in solvents or water, using CO2 or oils prior to roasting the beans. In Europe decaf coffee must contain less than 0.3 % caffeine (dry weight), and in the US the regulation is less than 0.1% caffeine (dry weight) (5, 6). However, studies have found that this can range from 0-18mg depending on the brand or coffee shop (2, 7). 

Although further research is needed, decaf coffee appears to provide similar health protective benefits as caffeinated coffee due the antioxidants it provides (9, 9). 

As decaf coffee contains little to no caffeine, both the benefits and drawbacks related to caffeine (as discussed below) don’t apply. So decaf coffee is a good option for those who are sensitive to caffeine or who need to limit their intake – but enjoy the taste! 

The Benefits of Drinking Coffee

Source of antioxidants

Both caffeinated and decaf coffee are a good source of antioxidants and polyphenols (beneficial plant compounds) such as hydroxycinnamic acids and flavonoids (10). Many of coffee’s health benefits are thought to be related to these compounds.Coffee also contains small amounts of certain B-vitamins and minerals like potassium and manganese (11). 

Counts towards your fluid intake

Although the caffeine in coffee can increase urine production, consuming upto 400mg of caffeine per day has not been found to have a dehydrating effect (12). Therefore, drinking coffee counts towards our daily fluid intake, and consuming enough fluid is vital for a number of body functions including concentration, temperature regulation, heart, gut and kidney health (13).  

Improves alertness and mental performance

There is strong evidence that improvements in alertness, attention and mental performance occur when at least 75mg of caffeine (roughly one small cup of coffee) is consumed (14). 

Improves endurance performance 

Consuming at least 3mg of caffeine per kg body weight one hour before exercise improves endurance performance and capacity (16). Similarly, at least 4mg of caffeine per kg body weight one hour before exercise reduces perceived effort during exercise (15).  

Helps with constipation

Coffee is also known to stimulate bowel movements, which may be helpful for those who experience constipation. The evidence related to this is sparse overall and recent studies have also started to investigate the impact of coffee on the gut-brain axis (16). 

Lower risk of certain diseases and death 

A regular moderate consumption of coffee (often defined as 3-5 cups per day) is also associated with a lower risk of a number of diseases, such as (17, 18, 19, 20, 21, 22): 

• Heart disease
• Type 2 diabetes
• Liver cancer (and potentially some other types of cancer too) 
• Non-alcoholic liver disease

There is also a possible protective link between drinking coffee and the risk of Dementia and Alzhemiers, but more research is needed (23).  

Coffee lovers will also be glad to hear that 3 to 4 cups  per day has been linked with a lower risk of overall death (22, 24).   

Drawbacks of Drinking Coffee

Impacts sleep quality and quantity 

One of the biggest downsides related to coffee is the impact this can have on sleep due to its caffeine content. Consuming even 1-2 espressos 16 hours before bed has been linked with lower quality sleep for those who are more sensitive to caffeine, including older adults (25). Similarly, drinking 400mg of caffeine 6 hours before bed may delay sleep by more than an hour (26). Although we feel the effects of caffeine within 15 – 30 minutes, this can stay in the system for a long time. The average half life (i.e. the amount of time it takes for the body to get rid of 50% of the caffeine) is around 4 hours, although this can vary between 2-8 hours (1, 27). Therefore, it is usually advised to avoid caffeinated drinks like coffee for at least  6 hours before bed, although 8-12 hours is sometimes advised (28).  Mid-morning seems to be a good time to drink coffee, as this is both far away from bedtime and not too close to waking when cortisol levels are high (29, 30).  

Reduces iron absorption

Another consideration when it comes to timing is that some of the polyphenols (like tannins) found in coffee can reduce iron absorption by as much as 60 – 90% (31, 32). For this reason it is best to leave a 1-hour gap between iron-containing meals and a cup of coffee. 

May trigger anxiety

Caffeine can trigger anxiety, especially in those who are more sensitive to caffeine and also when more than 400mg per day is consumed (33). The European food safety Authority (EFSA) caution that children may experience irritability,  anxiety or nervousness if they consume 5mg or more caffeine per kg  body weight (14). 

Can be addictive 

Caffeine can also be addictive, infact caffeine withdrawal is now listed as a disorder by both the World Health Organisation and the American Psychiatric Association  (34, 35). Withdrawal symptoms from caffeine, such as headaches, mood swings and fatigue, have been seen to occur within 12-24 hours of caffeine avoidance and to last for up to 9 days (36, 37). 

Increases urine production

Although drinking coffee is unlikely to be dehydrating, caffeine can increase the production of urine. Therefore, the NHS and National Institute for Clinical Excellence (NICE) recommend that those with urinary incontinence reduce their caffeine intake (38, 39). 

Can trigger gut symptoms + reflux 

As discussed above, coffee stimulates gut movement. However, for some people this stimulation can trigger gut irritation and diarrhoea; especially for those with IBS (40, 41).  Coffee has also been seen to trigger stomach acid secretion, which may impact those who suffer with reflux or heartburn; but studies related to this are conflicted and lacking overall (42, 43). 

May increase fracture risk

Consuming a high intake of caffeine (i.e. more than 400mg per day) has been associated with an increased fracture risk (44, 45). This may be related to increased calcium losses from the body and interaction with vitamin D for those with certain genetics. But this evidence is mixed overall, and is unlikely to be an issue for those who consume a good intake of calcium and less than 400mg of caffeine per day (46).  

Can increase blood pressure and blood glucose 

Caffeine can also increase blood pressure (at least in the short-term) so excessive caffeine intake is discouraged for those with high blood pressure (47, 48). So the NHS recommends drinking no more than 4 cups of coffee per day to improve blood pressure (49). However, as discussed above, overall coffee intake is associated with improvements in heart health and a reduction in the risk of heart disease (1, 50) 

Similarly, blood glucose levels may increase in response to caffeine a few hours after drinking a cup of coffee, but glucose response is seen to improve after a few weeks of drinking caffeinated coffee (51). 

Caffeine (>200mg) not advised in pregnancy and breastfeeding 

Pregnant women are advised to limit their caffeine intake to 200mg as a high intake of caffeine can harm an unborn baby by stunting growth and increasing the risk of preterm birth and miscarriage (1, 52). Breastfeeding women are also advised to stick with the 200mg per day limit because caffeine can pass to the baby and lead to restlessness and sleep issues (53). See here for more information from the NHS about limiting caffeine intake in pregnancy.  

Summary

There are a number of pros and cons related to drinking both caffeinated and decaf coffee. For most adults, drinking 3-4 cups per day is associated with health benefits including a lower risk of certain diseases and a longer life. It is important not to drink caffeinated coffee close to bedtime and to leave roughly an hour between high-iron foods and coffee. However, our tolerance to caffeine is very individual so those who are more sensitive in terms of anxiety, gut symptoms or sleep issues may need to limit their intake further or opt for decaf. It is important to note that pregnant or breastfeeding are advised to limit their intake of caffeine to 200mg per day.

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References

1. EFSA (2015) “EFSA explains risk assessment: Caffeine” [accessed  July 2021 via: https://www.efsa.europa.eu/sites/default/files/corporate_publications/files/efsaexplainscaffeine150527.pdf]
2. McCusker et al. (2003) “Caffeine Content of Specialty Coffees” [accessed  July 2021 via: https://academic.oup.com/jat/article/27/7/520/784168?login]
3. EFSA (2015) “Scientific Opinion on the Safety of Caffeine” [accessed  July 2021 via: https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2015.4102]
4. Yang et al. (2010) “Genetics of caffeine consumption and responses to caffeine” [accessed  July 2021 via:  https://link.springer.com/article/10.1007/s00213-010-1900-1]
5. Eur-Lex (1999) “Directive 1999/4/EC of the European Parliament and of the Council of 22 February 1999 relating to coffee extracts and chicory extracts” [accessed  July 2021 via: https://eur-lex.europa.eu/legal-content/GA/TXT/?uri=CELEX:31999L0004] 
6. USDA Website – Coffee [accessed  July 2021 via: https://www.ams.usda.gov/sites/default/files/media/CID%20Coffee.pdf0]
7. McCusker et al, (2006) “Caffeine content of decaffeinated coffee” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/17132260
8. Colombo & Papetti (2020) “Decaffeinated coffee and its benefits on health: focus on systemic disorders” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/32551832/ and
9. Liu et al, (2019) “Caffeinated and decaffeinated coffee consumption and risk of all-cause mortality: a dose-response meta-analysis of cohort studies” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/30786114/
10. Górecki & Hallmann (2020) “The Antioxidant Content of Coffee and Its In Vitro Activity as an Effect of Its Production Method and Roasting and Brewing Time” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/32290140/]
11. NutritionData “Coffee, brewed from grounds, prepared with tap water“ [accessed  July 2021 via: https://nutritiondata.self.com/facts/beverages/3898/2]
12. Ruxton (2008) “The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks” [accessed  July 2021 via: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-3010.2007.00665.x]
13. BDA (2020) “Fluid (water and drinks): Food Fact Sheet” [accessed  July 2021 via: https://www.bda.uk.com/resource/fluid-water-drinks.html]
14. EFSA (2011) “Scientific Opinion on the substantiation of health claims related to caffeine and increased fat oxidation leading to a reduction in body fat mass (ID 735, 1484), increased energy expenditure leading to a reduction in body weight (ID 1487), increased alertness (ID 736, 1101, 1187, 1485, 1491, 2063, 2103) and increased attention (ID 736, 1485, 1491, 2375) pursuant to Article 13(1) of Regulation (EC) No 1924/2006” [accessed  July 2021 via: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2054]
15. EFSA (2011) “Scientific Opinion on the substantiation of health claims related to caffeine and increase in physical performance during short-term high-intensity exercise (ID 737, 1486, 1489), increase in endurance performance (ID 737, 1486), increase in endurance capacity (ID 1488) and reduction in the rated perceived exertion/effort during exercise (ID 1488, 1490) pursuant to Article 13(1) of Regulation (EC) No 1924/2006” [accessed  July 2021 via: https://www.efsa.europa.eu/en/efsajournal/pub/2053]
16. Iriondo-DeHond, et al. (2021) “Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain–Gut Axis” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7824117/]
17. Ding et al. (2013) “Long-Term Coffee Consumption and Risk of Cardiovascular Disease” [accessed  July 2021 via: https://www.ahajournals.org/doi/full/10.1161/CIRCULATIONAHA.113.005925] 
18. Van Dam & Hu (2005) “Coffee consumption and risk of type 2 diabetes: a systematic review” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/15998896/] 
19. Larssen & Wolk (2007) “Coffee consumption and risk of liver cancer: a meta-analysis” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/17484871/]
20. Wijarnpreecha  et al. (2017) “Coffee consumption and risk of nonalcoholic fatty liver disease: a systematic review and meta-analysis” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/27824642/]
21. Hong et al. (2020) “The Effect of Caffeine on the Risk and Progression of Parkinson’s Disease: A Meta-Analysis” [accessed  July 2021 via:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7353179/]
22. Poole et al. (2017) ‘Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5696634/]
23. Eskelinen & Kivipelto (2010) “Caffeine as a protective factor in dementia and Alzheimer’s disease: [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/20182054/]
24. Gunter et al. (2017) “Coffee Drinking and Mortality in 10 European Countries: A Multinational Cohort Study” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/28693038/]
25. Clark & Landolt (2017) “Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/26899133/]
26. Drake et al. (2013) “Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed” [accessed  July 2021 via: https://jcsm.aasm.org/doi/10.5664/jcsm.3170]
27. AASM (2018) “Sleep and Caffeine” [accessed  July 2021 via: https://sleepeducation.org/sleep-caffeine]
28. Sleep Foundation (2021) “Caffeine and Sleep” [accessed  July 2021 via: https://www.sleepfoundation.org/nutrition/caffeine-and-sleep]
29. Lovallo et al. (2008) “Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2257922/]
30. Azmi et al. (2021) “Cortisol on Circadian Rhythm and Its Effect on Cardiovascular System” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830980/#B5-ijerph-18-00676]
31. Hurrell & Cook (1999) “Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages”. Br J Nutr. [accessed July 2021 via: https://pubmed.ncbi.nlm.nih.gov/10999016/] 
32. Morck et al. (1983) “Inhibition of food iron absorption by coffee”. Am J Clin Nutr. [accessed July 2021 via: https://pubmed.ncbi.nlm.nih.gov/6402915]
33. Wikoff et al. (2017) “Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children” [accessed  July 2021 via: https://www.sciencedirect.com/science/article/pii/S0278691517301709]
34. WHO “The ICD-10 Classification of Mental and Behavioural Disorders: Clinical descriptions and diagnostic guidelines“ [accessed  July 2021 via: https://www.who.int/substance_abuse/terminology/ICD10ClinicalDiagnosis.pdf]
35. American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed).
36. Juliano & Griffiths (2004) “A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/15448977/]
37. Sigmon et al. (2009) “Caffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG and subjective effects” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738587/]
38. NICE (2019) “Scenario: Management of a woman with predominantly urgency incontinence” [accessed  July 2021 via: https://cks.nice.org.uk/topics/incontinence-urinary-in-women/management/managing-urgency-incontinence/]
39. NHS Website (2018) “Water, drinks and your health” [accessed  July 2021 via: https://www.nhs.uk/live-well/eat-well/water-drinks-nutrition/]
40. Cozma-Petruţ et al. (2017) “Diet in irritable bowel syndrome: What to recommend, not what to forbid to patients!” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5467063/] 
41. Capili et al. (2016) “Addressing the Role of Food in Irritable Bowel Syndrome Symptom Management” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4944381]
42. Kaltenbach et al. (2016) “Are lifestyle measures effective in patients with gastroesophageal reflux disease? An evidence-based approach” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pubmed/16682569] 
43. Kim et al. (2013) “Association between coffee intake and gastroesophageal reflux disease: a meta-analysis” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/23795898/]
44. Liu et al. (2012) “Coffee consumption and risk of fractures: a meta-analysis” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3506234/]  
45. Rapuri et al. (2001) “Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes” [accessed  July 2021 via: https://academic.oup.com/ajcn/article/74/5/694/4737535]
46. Nawrot et al. (2003) “Effects of caffeine on human health” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/12519715/]
47. NICE (2019) “Hypertension in adults: diagnosis and management” [accessed  July 2021 via: https://www.nice.org.uk/guidance/ng136/chapter/recommendations]
48. Mesas et al. (2011) “The effect of coffee on blood pressure and cardiovascular disease in hypertensive individuals: a systematic review and meta-analysis” [accessed  July 2021 via: https://pubmed.ncbi.nlm.nih.gov/21880846/]
49. NHS Website (2019) “Prevention -High blood pressure (hypertension)” [accessed  July 2021 via: https://www.nhs.uk/conditions/high-blood-pressure-hypertension/prevention]
50. Ding et al. 2013 “Long-Term Coffee Consumption and Risk of Cardiovascular Disease A Systematic Review and a Dose–Response Meta-Analysis of Prospective Cohort Studies” [accessed  July 2021 via: https://www.ahajournals.org/doi/full/10.1161/CIRCULATIONAHA.113.005925] 
51. Reis et al. (2019) “Effects of coffee consumption on glucose metabolism: A systematic review of clinical trials” [accessed  July 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6544578/]
52. Kuczkowski (2009) “Caffeine in Pregnancy” [accessed  July 2021 via: https://link.springer.com/article/10.1007/s00404-009-0991-6#citeas]
53. NHS Website (2018) “Breastfeeding and diet” [accessed  July 2021 via: https://www.nhs.uk/conditions/baby/breastfeeding-and-bottle-feeding/breastfeeding-and-lifestyle/diet]