Is Coffee Bad for You?

Is Coffee Bad for You?

Many of us enjoy a good cup of coffee in the morning, or two, or three…  For others, there’s frequent stops at Starbucks, Dunkin Donuts, or Tim Hortons throughout the day.

If you drink more than one cup of coffee per day, one question that you may be asking yourself, is drinking coffee bad for your health?

Research on the safety of coffee?

To answer that question in part, a recent study published in the Journal of Clinical Nutrition (Kerstin et al, 2010), studied the impact of drinking coffee on cholesterol levels, risk factors for type 2 diabetes, oxidative stress, and subclinical inflammation.

In this particular study, people who were classified as habitual coffee drinkers refrained from drinking coffee for one month.  For the second month, they consumed 4 cups of coffee per day and a whopping 8 cups per day for the third month.

Health effects of coffee consumption:

“Significant changes were also observed for serum concentrations of interleukin-18, 8-isoprostane, and adiponectin (medians: –8%, -16%, and 6%, respectively; consumption of 8 compared with 0 cups coffee/d).”

  • Higher concentrations of Interleukin-18 (IL-18) has been previously identified as a risk factor for type 2 diabetes.
    • Coffee consumption lowered serum concentrations of IL-18.
  • 8-isoprostane is a marker of inflammation, it decreased by 16% with consumption of 8 cups of coffee/day.
  • Low levels of adiponectin is associated with insulin resistance and type 2 diabetes.
    • Adiponectin levels increased by 6% which could theoretically reduce the risk of developing type II diabetes.

“Serum concentrations of total cholesterol, HDL cholesterol, and apolipoprotein A-I increased significantly by 12%, 7%, and 4%, respectively, whereas the ratios of LDL to HDL cholesterol and of apolipoprotein B to apolipoprotein A-I decreased significantly by 8% and 9%, respectively (8 compared with 0 cups coffee/d).”

Does coffee consumption increase your cholesterol?

Their results are more difficult to interpret in the context of previous research.  However, this particular study used filtered coffee as opposed to unfiltered coffee.  HDL or ‘good cholesterol’ levels increased with consumption of coffee in this study.  The study authors suggest that at the very least, coffee consumption did not have an adverse effect on serum cholesterol.

Does coffee consumption increase your risk of diabetes?

“No changes were seen for markers of glucose metabolism in an oral-glucose-tolerance test.”

The study authors cite a number of previous studies which suggests that coffee consumption and type II diabetes is inversely related.  In that sense, drinking coffee may have a protective effect against developing type II diabetes.  This particular study may not have been long enough to observe an effect of coffee consumption on glucose metabolism.

Bottom line:  Is coffee bad for your health?

First, the results of this study are limited in context to the effects of drinking coffee on serum cholesterol, oxidative stress, and glucose metabolism.

The results of this study suggest that even drinking 8 cups of coffee per day did not have an adverse effect on serum cholesterol levels. As well, coffee consumption did not have an adverse effect on glucose metabolism.


  1. Kerstin Kempf, Christian Herder, Iris Erlund, Hubert Kolb, Stephan Martin, Maren Carstensen, Wolfgang Koenig, Jouko Sundvall, Siamak Bidel, Suvi Kuha, and Jaakko Tuomilehto.  Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial.  Am J Clin Nutr. 2010 Apr;91(4):950-7. Epub 2010 Feb 24.
Scroll to Top