Is coffee good or bad?

Coffee is one of the most popular beverages in the world. Many people have the habit of drinking coffee and developed reliance on it to keep them awake during the day. In the past, coffee did not gain much appreciation from the public because of its bad influence on health, as suggested by various health professionals. However, it has recently gained its fame in public media claiming its potential health benefits. Facing this dilemma, how do we decide if coffee is good or bad?

Coffee and heart diseases

No major research apparently investigates the direct impact of coffee on heart diseases. Some scientific evidence indicated that drinking at least 5 cups of coffee every day increased the risk of heart diseases by 40-60% compared to non-coffee drinker. In contrast, some research demonstrated that coffee consumption is not associated with heart diseases.

In fact, coffee can increase blood pressure and heart beat. Consuming 2-3 cups of coffee can raise systolic blood pressure there is still inconclusive evidence on coffee consumption and its risk of developing high blood pressure and heart diseases, it is advisable for people living with high blood pressure to drink less coffee.

Coffee and diabetes

Reports have shown that coffee can reduce the risk of developing Type 2 diabetes, is this true? A 10-year research study with 17,000 people in Holland demonstrated that the risk of Type 2 diabetes was reduced as more coffee was consumed. Similar result was also shown in a 12-year study with 14,000 people in Finland where drinking 3-4 cups of coffee per day could lower the risk of Type 2 diabetes by 30% Meanwhile, a growing body of evidence revealed that caffeine in coffee reduced body sensitivity to insulin and increases blood sugar level. A study recruited 10 diabetic subjects with regular daily consumption of about 4 cups of coffee. During the study, subjects stopped drinking coffee and were given a capsule containing a dosage of caffeine equivalent to a cup of coffee to be consumed a placebo capsule, containing no caffeine. Their blood sugar leaves after consumption of caffeine and placebo capsules were monitored. The result should that the average increases of blood sugar levels after caffeine consumption was greater than the placebo. This effect was also indicated in the healthy population. Therefore, some researchers suggested that the beneficial effect of coffee on diabetes may be due to chlorgenic acid, an antioxidant in coffee, rather than caffeine.

As current evidences is still inconclusive, more studies is needed to conclude if coffee can reduce the risk of developing Type 2 diabetes. It should be noted that milk and sugar are usually added to coffee, so people suffering from high blood sugar level or diabetes should limit coffee consumption or choose decaffeinated coffee with skim milk and artificial sweetener.

Who should limit coffee intake?

While drinking coffee is a global culture, but coffee if not suitable for everyone, females especially who is pregnant or plan to have children should reduce coffee drinking because evidence shows that 3 cups of coffee or above can reduce fertility and increase the risk of miscarriage and low birth weight. Besides pregnant women, children and elderly should also reduce caffeine consumption. A study pointed out that children consuming more than 3 mg of caffeine per kilogram of body weight can lead to sleep disturbance or anxiety. Although children rarely drink coffee, but soft drinks and chocolate are sources of caffeine, so parents should be aware of these foods.. For elderly on polypharmacy of long term medication, caffeine consumption with osteoporosis should pay attention to the amount of caffeine consumed as it may increase.

Yet, there is no convincing evidence on whether drinking 3 cups (-300 mg caffeine) of coffee is beneficial or harmful.. However, if you would like to drink coffee in a healthy way, you should choose to use low fat or skim milk and artificial sweeteners. This can effectively lower calorie intake.

**As there is still inconclusive evidence on coffee consumption and its risk of developing high blood pressure and heart diseases, it is advisable for people living with high blood pressure to drink less coffee


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  2. Nurminen, M.L., Niittynen, L., Korpela, R., and Vapaatalo, H, 1999. Coffee, caffeine and blood pressure: a critical review. Eur. J. Chin. N., 53:831-839.
  3. Tuomilehto, J., Hu, G., and Bidel, S. 2004. Coffee consumption and risk of type 2 diabetes mellitus among middle-aged Finnish men and women. JAMA., 291:1213-1219.
  4. van Darn, R.M., and Feskens, EJ. 2002. Coffee consumption and risk of type 2 diabetes mellitus. Lancet., 360:1477-1478.
  5. van Dam, R,.M., Pasman, W.J., & Verhoef, P. (2004). Effects of coffee consumption on fasting blood glucose and insulin concentrations: Randomized controlled trials in healthy volunteers. Diabetes Care, 27(12), 2990-2.

Lane, J.D., P. H, D., Feinglos, M. N., M. D., & Surwit, R. S., P. H. D., (2008). Caffeine increases ambulatory glucose and postprandial response in coffee drinkers with type 2 diabetes. Diabetes Care, 31(2), 221-2.

330 Tips provided by:  Ms Grace Lam  (Senior Dietitian - Centre for Nutritional Studies, School of Public Health and Primary Care, Faculty of Medicine, CUHK)

Date: 2013-02-01