Guest blog by Vicky Ware
So Many Drink it but is Coffee Good for You?
Lots of people are trying to cut back on the number of cups of coffee they have a day, but when I delved into the scientific research on whether coffee is good or bad for health there weren’t any clear cut reasons to stop drinking your favourite brew.
The research that’s been done on whether coffee is good for health has come up with conflicting results. This is thought to be due to a lack of accuracy in many studies. Asking people how many ‘cups of coffee’ they drink a day, and have drunk for the last ten years, isn’t very specific. People tend to exaggerate behaviours they believe to be good for health and downplay the behaviour they think is bad 1.
There is also a big difference between different cups of coffee. The size is an obvious one, but also how much caffeine the cup contains. One study found that the same type of coffee bought from the same shop six days in a row contained anywhere from 130 to 282 mg of caffeine per 230 ml serving 2. In addition, drinking a litre of ‘coffee’ which is mainly milk with added syrup and cream is certainly going to have different health effects than drinking an espresso.
Let’s take a detailed look at what coffee contains and why it might be good or bad for health.
Coffee is made of over one thousand different chemicals, the most well known of which is caffeine. Caffeine increases metabolic rate, energy expenditure and fat burning meaning it can help with weight loss, and reduce your chance of developing metabolic syndrome 3.
Don’t get too excited though, 300 mg of caffeine per day (approximately 3 cups of coffee) only increases energy expenditure by 79 kcal – so you can eat 1.5 more apples, not a big mac 15.
Caffeine also has downsides. It increases blood pressure and heart rate, and in excess can result in anxiety, tachycardia, palpitations, insomnia and restlessness 4. The dose needed to cause these symptoms seems to be dependent on genetic differences – some people are more sensitive to caffeine than others 5.
Coffee contains carbohydrates, fats, vitamins and minerals along with many other compounds. A 240 ml cup of brewed coffee contains the following percentage of the nutrients an adult male needs each day:
- 1-5% of magnesium;
- 1-2% of potassium;
- 6-18% of vitamin B3; and
- 0.1% of vitamin E 6
Coffee also contains a phenol known as chlorogenic acid, which is an energy source for the bacteria that live in your gut*. These bacteria break chlorogenic acid down into molecules that end up in your blood stream 6. It’s not known exactly what effect coffee has on the bacteria living in your intestine, but it is thought to increase the number of Bifidobacterium which seem to be good for health 7.
But coffee also prevents uptake of nutrients…
While coffee contains nutrients, it also prevents uptake of iron and zinc. Polyphenols in coffee can bind to non-heme iron, meaning it can’t be absorbed into your body 6. In one study, drinking 150-250 ml of coffee with a meal inhibited the absorption of iron in the meal by 24-73% 8.
Chemicals in coffee can also bind to zinc, preventing its absorption 9.
Drinking coffee outside of meal times will ensure you absorb the iron and zinc in any foods you eat 10.
Coffee drinking has been associated with less likelihood of …
One study looked at the association between drinking coffee and dying of any cause and found people who drank coffee were less likely to die. This doesn’t necessarily mean that coffee is great for health, as it could be that people who drink coffee also happen to eat more healthily in general, or exercise more or practice other healthy behaviours, but it does suggest that drinking coffee can’t be really bad for health 11.
Coffee drinking is associated with a lower risk of developing certain types of cancer, particularly endometrial and hepatocellular cancer 10.
Type II Diabetes
Regular coffee drinking is associated with a reduced risk of developing type II diabetes, by up to 50% for people who drink 7 cups of coffee a day compared to those who drink 2 cups or less 12.
People who drink coffee are less likely to develop neurodegenerative diseases such as Parkinson’s disease. In one review coffee drinkers had a 31% lower risk of Parkinsons’s disease than non-coffee drinkers 13. This protection was not seen in women who had used postmenopausal hormones 10. It’s thought that this benefit of coffee is due to caffeine.
But also associated with cardiovascular disease…
Coffee consumption has been associated with increased blood cholesterol, which can lead to heart disease, although the increase in cholesterol wasn’t massive 6;16. I explained how cholesterol is related to development of inflammatory diseases in a previous blog**.
Interestingly, another study found that boiled coffee increases serum cholesterol but filter coffee doesn’t 14. This is thought to be because filtering the coffee removes cholesterol raising chemicals in the coffee 14.
Although some research in the past showed that coffee drinking was linked to heart disease this was probably due to studies not taking into account other behaviours which people who drink lots of coffee may be more likely to partake in, such as smoking 6.
Whether or not coffee is good for you depends on what else you’re doing. If it’s your only source of magnesium then it would definitely be good for you. In Western countries, coffee is often people’s greatest course of antioxidants 15, which means if two people who had identical diets other than their coffee drinking were compared, the person who drank coffee would be healthier because they’d be getting at least some antioxidants. Ultimately, this just shows that whether an individual food or drink is good for you is often related to what else you eat, drink and do in your life.
Coffee has some health benefits which are balanced out by negative impacts on health. Overall the benefits, and negative effects, are not major and will only come into play if you consume coffee regularly for a long time. It doesn’t seem that the health benefits are great enough to make it worth drinking coffee if you don’t like it, or the negative impact on health large enough to mean you should cut back if you like drinking it. If it makes you feel good, keep at it.
Vicky has a degree in Biological Sciences with a focus on biochemistry and immunology and is currently studying for a MSc in Drug Discovery and Protein Biotechnology. She is also an endurance athlete.
For information on a study in Denmark see this article here.
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- Science Daily, 2013. People lie about their health related behaviours: truth in barcodes.
- McCusker, 2003. Caffeine content of speciality coffees.
- Heckman, 2010. Caffeine (1,3,7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters.
- Riksen, 2011. The cardiovascular effects of methylxanthines.
- Rogers, 2010. Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption.
- Higdon, 2006. Coffee and Health: A Review of Recent Human Research.
- Jacquet, 2009. Impact of coffee consumption on the gut microbiota: a human volunteer study.
- Hallberg, 1982. Effect of different drinks on the absorption of non-heme iron from composite meals.
- Wen, 2005. Effect of roasting on properties of the zinc-chelating substance in coffee brews.
- Ludwig, 2014. Coffee: biochemistry and potential impact on health.
- Freedman, 2012. Association of coffee drinking with total and cause-specific mortality.
- Van Dam, 2002. Coffee consumption and risk of type 2 diabetes mellitus.
- Hernan, 2002. A meta-analysis of coffee drinking, cigarette smoking, and the risk of Parkinson’s disease.
- Svilaas, 2004. Intakes of antioxidants in coffee, wine, and vegetables are correlated with plasma carotenoids in humans.
- Rudelle, 2007. Effect of a thermogenic berverage on 24-hour energy metabolism in humans.
- Jee, 2001. Coffee consumption and serum lipids: A meta-analysis of randomised controlled clinical trials.