To many of us, a morning cup of coffee is as necessary as a shower and shave, and as sacred as our first-born child. (Disclaimer: This may be an exaggeration.) We’ve learned coffee can be great not just for its notorious jolt, but also for a long list of science-backed health benefits. It has been connected to improved mood, increased calorie burn, and the ability to help ward off certain cancers, amongst other perks Effects of breakfast and caffeine on performance and mood in the late morning and after lunch. Smith, A.P., Kendrick, A.M., Maben, A.L. Health Pyschology Research Unit, School of Psychology, University of Wales College of Cardiff, UK. Neuropsychobiology, 1993; 26(4):198-204. Effect of coffee ingestion on physiological responses and ratings of perceived exertion during submaximal endurance exercise. Demura, S., Yamada, T., Terasawa, N. Graduate School of Natural Science and Technology, Kanazawa University. Journal of Perceptual and Motor Skills, 2007 Dec; 105 (3 Pt 2):1109-16. Coffee consumption and prostate cancer risk: further evidence for inverse relationship. Shaflque, K., McLoone, P., Qureshi, K., et al. Nutrition Journal, 2012 Jun 13; 11(1):42. . But despite all the good news about our favorite caffeine source, new research suggests high doses of the brew could actually contribute to obesity and chronic disease—in mice. We break down the science and find out if it’s time to start cutting back on morning Joe.

What’s the Deal?

Conducted by researchers from the Western Australian Institute for Medical Research and the University of Western Australia’s School of Medicine and Pharmacology, the study looks at a compound in coffee called Chlorogenic Acid (also called as CGA, the stuff green coffee is well-known for). The researchers started by reading dozens of studies linking coffee consumption to a lowered risk of type 2 diabetes, among other health benefits. CGA has been studied many times before, but usually in small doses and combined with other polyphenols found in the beloved brew Chlorogenic acid exhibits anti-obesity property and improves lipid metabolism in high-fat diet-induced-obese mice. Cho, A.S., Jeon, S.M., Kim, M.J., et al. Department of Nutrition Education, Graduate School of Education, Sunchon National University, Suncheon, Republic of Korea. Food Chemistry and Toxicology, 2010 Mar;48(3):937-43. .

To find out about CGA’s solo effects, the researchers grouped male mice into three separate categories: those fed a normal diet, those fed a high-fat diet, and those fed a high-fat diet supplemented with a big dose of CGA. (The researchers calculated the dose of CGA and figured the human equivalent—five cups of coffee a day.) For twelve weeks the researchers measured metrics including body weight, adiposity (the accumulation of fat), and insulin resistance of the mice. On the final day of the experiment, they also removed liver, fat, and muscle tissue from the mice for further study.

Both the high-fat diet and the high-fat plus CGA groups showed an increase in body weight compared to mice fed a normal diet. But the researchers found the livers of mice fed CGA accumulated more fat than the other groups. The obese mice who received a cocktail of CGA also had a tendency toward increased insulin resistance (often a contributor to cardiovascular disease and diabetes). The conclusion: Too much of the coffee compound may not ward off diabetes and obesity after all, at least in rodents.

Is it Legit?

Way too early to tell, at least for humans. This small study (only 30 mice, which aren’t always the best proxies for humans when it comes to health research) shows CGA supplementation along with high-fat feeding increased body weight and the risk of other serious conditions. But what does all this mean for humans? Guzzle down a Starbucks “venti” and two “talls” in one day—the equivalent of five regular cups—and you’ve already surpassed the CGA levels examined in this study. Thankfully, the researchers also suggest up to three or four cups of coffee a day may still decrease the risk of developing cardiovascular disease and type 2 diabetes. It’s unclear how or if that fifth cup can make such a significant difference in humans.

In their conclusion, the researchers state further work is necessary using human subjects before determining the full health effects of coffee polyphenols (like CGA). Moral of the story? Don’t fret quite yet, coffee aficionados. This study was very limited in scope, and it’s far too soon to apply the findings to humans.

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