Is drinking coffee good or bad? Evaluate the quality of coffee in detail

Whether coffee is the next superfood or the next source of public health hazards depends on who you ask. Looking at recent news or research, you will find that coffee "protects against heart disease", reduces the incidence of breast, colon and multiple sclerosis, and reduces Alzheimer's disease. A recent survey by National Health Graduate students and researchers at Yale University found that those who drank at least four cups of coffee a day had a 20% lower incidence of melanoma than those who did not drink coffee.

But if you do more research, you will find that coffee also increases your risk of contracting various diseases. A 2010 integrated analysis of 13 surveys found that drinking two cups of coffee a day increased the risk of lung cancer by 14%. More recently, an integrated analysis in 2014 found a link between coffee drinking and throat cancer.

Why do the results contradict each other? Part of the reason may be that some ingredients in coffee are good for the body, while others are harmful. Coffee, for example, contains antioxidants that help cells resist damage caused by unstable molecules called free radicals, which are linked to cancer. At the same time, some researchers speculate that drinking hot coffee may increase people's risk of developing esophageal cancer because hot coffee can scald the esophagus.

But most of the confusion comes from so-called confounding variables, foreign factors (such as diet and genes) that can influence the results of the study. The greater the variable, the more difficult it is to infer cause and effect.

People make coffee in many ways, and the way you make coffee may change the way it behaves in your body. In the case of dripping coffee, this method flushes away some lipids in coffee beans, including caffeine alcohol and coffee white fat. These compounds increase your body's levels of low-density lipoprotein, also known as bad cholesterol. For this reason, drip coffee may be better for heart health than coffee made from French filter pots.

Lifestyle factors can also influence the results of the study. Marilyn Cornelis, an assistant professor of preventive medicine at Northwestern University, pointed out that people who drink more coffee also smoke and drink, and they are usually under a lot of stress, and these habits can affect the positive effects of coffee drinking habits on the body. Even seemingly harmless habits, such as adding milk or sugar to coffee, can confuse the results. Although most studies use statistical tools to control these variables, older studies do not control them.

Don't leave out the genes, which regulate the metabolism of caffeine and other molecules in a cup of coffee. Unfortunately, not many studies have investigated the role of DNA in the health effects of coffee, mainly because scientists have only gradually discovered genes associated with caffeine metabolism in the past decade. The combination of genes and environmental factors may reconcile the differences between the experimental results.

At the same time, if you don't know if you should keep drinking coffee, don't worry, most public health experts believe that the benefits of coffee outweigh the disadvantages. The strongest view comes from a 2014 integration analysis that integrates studies on the relationship between long-term coffee consumption and cancer, heart disease and mortality between 1996 and 2013. Overall, coffee is beneficial. Don't worry about it.