It is healthy to drink several cups of coffee a day.

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A cup of coffee may not seem like much, but the amount of caffeine in it may exceed the amount recommended in dietary guidelines.

"X-cup coffee can increase or reduce the risk of y-disease." the headline of the health page often describes coffee as a caffeine curse or a cure for all diseases. A recent study of caffeine and caffeoylquinic acid (CQA) levels in European coffee showed that the chemical composition of "one cup" of coffee varied greatly, while the caffeine intake of coffee consumed by pregnant women could easily exceed the recommended level of 200mg per day.

Alan Crozier of the University of Glasgow (the University of Glasgow) is the director of the unfunded project. He said the study was entirely driven by curiosity. As an extension of the previous study of Sugara Coffee, the study measured the caffeine-CQA ratio of more than 100 espresso.

The results showed that the caffeine-CQA ratio of each sample varied from 0. 7 to 11 under different brewing conditions. The measured sample capacity also ranges from 13 to 104 milliliters. So it's easy to understand why Crozier says "a cup of coffee" is a hugely changing measure. Therefore, it is difficult for us to say how many cups of coffee are good for our health. The same is true for epidemiological studies.

So, what exactly is CQA? Coffee beans contain a variety of phenolic substances, such as 3-caffeoylquinic acid, 4-caffeoylquinic acid, and 5-caffeoylquinic acid, among which 5-caffeoylquinic acid is the main phenolic compound in coffee. Epidemiological studies have shown that coffee drinkers have a lower incidence of type 2 diabetes, cardiovascular disease, and endometrial cancer and liver cancer, which may be related to CQA. In this way, CQA seems to be a panacea, but the exact effect remains to be further studied.

Although the biological effects of CQA have not been thoroughly studied, we already know that these substances are more sensitive to baking than caffeine. At the same time, the type and blending of coffee beans can also affect the caffeine-CQA ratio. In common coffee beans, Robusta contains twice as much caffeine as Arabica.

Tim Bond of the British Tea Consulting Association (UK TeaAdvisory Panel) suggests that since the way coffee is brewed affects the content of caffeine and CQA, such information should be provided on the coffee package to help consumers make informed decisions.

Future research will measure people's coffee intake more accurately, said Kevin Croft, a nutrition and metabolism expert at the University of Western Australia. At the same time, using biomarkers, we will get a more precise link between coffee intake and disease risk.