Health and Coffee Pt. 4: Coffee Fads

By Julianne Bierwirth, RD


Coffee has a chemical complexity that, through the roasting process, creates a broad range of vibrant flavor characteristics. This same molecular diversity is also responsible for a variety of health effects in humans. Caffeine is certainly the most well-studied, but it is far from the only pharmacologically active molecule extracted during a brew. Some of these chemicals are elusive, and their effects poorly understood. Others, after decades of research, have concrete benefits and detriments firmly borne out by data.

In this 8-part blog series, we delve into the myriad truths, half-truths, and indeed, fallacies, related to the impact that coffee has on your health. Is it good for you? Is it bad for you? Is it going to make your teeth brown? Does coffee make you smarter? Read on to find out.


How Trends Start

The trouble begins when, on a slow news day, media outlet writers scour recent scientific papers. The resulting headline reads something like, “new study finds surprising health benefits of your morning banana”. This may seem like no big deal, but scientists inadvertently screw up studies all the time, in all kinds of ways. Even perfect studies are rarely funded well enough to fully explore a scientific theory. This means that a single study can be a jumping-off point for future research, but most scientists will not even consider forming a “scientific consensus” until hundreds or thousands of well-designed studies confirm a similar finding. The public doesn’t know this. Once it's in the news it sounds an awful lot like a fact.

Writers from other sources pick up the banana story to meet their publication quotas. In response to the acclaim, businesses in the weight loss industry (an industry worth about $20 billion)  jump to make a banana supplement or proprietary product. If its a supplement, customers can have it in hand before it has even been deemed safe, nevermind effective. Scientists said it was healthy and it was on the news. How would the average person know better than to buy it?

Post-digital consumers have a tough task parsing fact from fiction. There is too much contradictory information out there and, as a result, many consumers chose to buy-in on claims that are convenient to them (e.g. chocolate consumption leads to weight loss) and reject claims that are not (e.g. preserved meat consumption is associated with many long term health issues).

Below you will find the scientific consensus on three coffee-related health fads that have been prematurely adopted as fact. In each case there was a failure to critically validate study methodology, to frame scientific discoveries in logical grounding, or to wait for a larger body of evidence before making conclusion. The public was so excited to accept the findings that they bucked the reactionary skepticism they’ve often displayed towards other areas of science. We’ve done the hard work for you and vetted the research to determine its validity.


Green coffee extract: Insufficient Evidence

Unroasted coffee beans, called green beans, contain an antioxidant called chlorogenic acid (more on antioxidants later in this blog series). Roasted coffee also contains chlorogenic acid, although in lower quantities. This is the molecule thought to be responsible for the product’s weight loss claims. While there have been several studies that show an effect of green coffee extract on weight loss, each study has methodological issues that make its findings less credible. Additionally, these studies combined do not make for a great enough body of evidence to ensure that the product is safe to consume in high doses over a long period of time. And if that weren’t enough, regular coffee is also associated with weight loss.

In response to these preliminary studies green coffee extract was featured on the Dr. Oz show in 2012. Mehmet Oz, the host, introduced the segment saying, “You may think magic is make believe, but this little bean has scientists saying they found the magic weight loss cure for every body type”. Instead of the whole country getting skinnier, the company making claims on that supplement was charged with deception by the Federal Trade Commission and settled for $9 million in customer redress. Oz was warned to step back his ‘magical’ language and claims about weight loss supplements in a senate subcommittee meeting in 2014.


Bulletproof coffee: Mixed evidence

The most popular coffee fad in the last five years actually has nothing to do with the coffee itself. Bulletproof coffee emerged on the scene around 2013, though the recipe was available from the company’s founder as early as 2009. Bulletproof coffee, in context of the Bulletproof diet, means replacing one's entire breakfast with a cup of mycotoxin-free coffee (see the next section) topped with high-quality butter and MCT oil.

Butter and MCT oil (usually derived from coconut oil) both contain medium-chain triglycerides (MCTs). MCTs are fats that are smaller in size, molecularly, than much of the fat we regularly consume. They are transported directly into the liver and broken down for energy faster than long-chain triglycerides, which instead travel very slowly through the lymphatic system. Consuming MCTs may result in increased energy similar to the effect of increased blood sugar.

Bulletproof Nutrition asserts that these MCTs in coffee can be used in lieu of carbohydrates for energy, however the evidence actually suggests that the greatest energy benefit comes from consuming MCTs alongside carbs. Sugar is the only substance the brain uses for energy, so starting your day without any source of carbohydrates is starting at a detriment. While the MCTs may exert a genuine benefit, there’s no reason real reason for them to be paired with coffee except maybe for shock value.


Low mycotoxin coffee: Unnecessary

Low mycotoxin coffee is the second part of the bulletproof coffee recipe. Mycotoxins are poisonous chemicals produced by mold that can be found naturally on grains, beans, fruit and just about everything else we consume. Bulletproof nutrition claims that regular coffee contains these toxins (that is true) and therefore consuming that coffee slows physical and mental performance (that is likely false). A relatively large body of research on mycotoxins in the food supply shows that the levels we consume are far from causing adverse effects.

The the bulletproof diet cites how frequently these mold toxins are detected at all in regular coffee, but doesn’t mention that they are also detected in milk, breast milk, flour, peanuts, etc. These mycotoxins can be detected in just about anything, including the air we breathe. That doesn’t mean we’re all in big trouble, just that they are unavoidable and nothing new to the human experience. The legal limit in each product is set quite conservatively, yet the bulletproof literature suggests that legally compliant coffee is not good enough.

Several publications studying mycotoxins in coffee have in fact recommended discontinuing future study because of the lack of evidence at any relevant health threat. Even when green coffee beans are intentionally dosed with these toxins the resulting coffee, after roasting and brewing, showed no residual toxin.

Trying to make foods mycotoxin free is akin to avoiding all exposure to bacteria. Perfectly sterile food is not practical or sustainable. And if you’re only worrying about mycotoxins in coffee and not in peanuts, milk, and air, then getting low-mycotoxin coffee and is like a germaphobe compulsively sanitizing just one finger.

When to be suspicious of emerging food “facts”:

  1. Is the information coming from a single study?

  2. Are you hearing the claim from a source that stands to profit if you buy in?

  3. Does the endorsement include words like “miracle”, “magic”, “unbelievable”, etc?

  4. Do relevant groups like the World Health Organization, the American Heart Association, the Academy of Nutrition and Dietetics, etc. fail to endorse this product as part of a healthy lifestyle?

  5. Does it seem too good to be true?

It can be mentally draining to apply stringent logic to all of the new information we hear. If you encounter something that relates to coffee, write to us- we’ll research it and let you know what we find.


  1. Onakpoya, I., Terry, R., & Ernst, E. (2011). The use of green coffee extract as a weight loss supplement: a systematic review and meta-analysis of randomised clinical trials. Gastroenterology research and practice, 2011.

  2. Bidel, S., Hu, G., Sundvall, J., Kaprio, J., & Tuomilehto, J. (2006). Effects of coffee consumption on glucose tolerance, serum glucose and insulin levels-A cross-sectional analysis. Hormone and Metabolic Research, 38(01), 38-43.

  3. Bidel, S., Hu, G., Sundvall, J., Kaprio, J., & Tuomilehto, J. (2006). Effects of coffee consumption on glucose tolerance, serum glucose and insulin levels-A cross-sectional analysis. Hormone and Metabolic Research, 38(01), 38-43.

  4. Lopez-Garcia, E., van Dam, R. M., Rajpathak, S., Willett, W. C., Manson, J. E., & Hu, F. B. (2006). Changes in caffeine intake and long-term weight change in men and women–. The American journal of clinical nutrition, 83(3), 674-680.

  5. Henry-Vitrac, C., Ibarra, A., Roller, M., Mérillon, J. M., & Vitrac, X. (2010). Contribution of chlorogenic acids to the inhibition of human hepatic glucose-6-phosphatase activity in vitro by Svetol, a standardized decaffeinated green coffee extract. Journal of agricultural and food chemistry, 58(7), 4141-4144.

  6. St-Onge, M. P., & Bosarge, A. (2008). Weight-loss diet that includes consumption of medium-chain triacylglycerol oil leads to a greater rate of weight and fat mass loss than does olive oil–. The American journal of clinical nutrition, 87(3), 621-626.

  7. Han, J. R., Deng, B., Sun, J., Chen, C. G., Corkey, B. E., Kirkland, J. L., ... & Guo, W. (2007). Effects of dietary medium-chain triglyceride on weight loss and insulin sensitivity in a group of moderately overweight free-living type 2 diabetic Chinese subjects. Metabolism-Clinical and Experimental, 56(7), 985-991.

  8. St-Onge, M. P., Bosarge, A., Goree, L. L. T., & Darnell, B. (2008). Medium chain triglyceride oil consumption as part of a weight loss diet does not lead to an adverse metabolic profile when compared to olive oil. Journal of the American College of Nutrition, 27(5), 547-552.

  9. Papamandjaris, A. A., MacDougall, D. E., & Jones, P. J. (1998). Medium chain fatty acid metabolism and energy expenditure: obesity treatment implications. Life sciences, 62(14), 1203-1215.

  10. Mumme, K., & Stonehouse, W. (2015). Effects of medium-chain triglycerides on weight loss and body composition: a meta-analysis of randomized controlled trials. Journal of the Academy of Nutrition and Dietetics, 115(2), 249-263.

  11. Levi, C. (1980). Mycotoxins in coffee. Journal-Association of Official Analytical Chemists, 63(6), 1282-1285.

  12. Tsubouchi, H., Yamamoto, K., Hisada, K., Sakabe, Y., & Udagawa, S. I. (1987). Effect of roasting on ochratoxin A level in green coffee beans inoculated with Aspergillus ochraceus. Mycopathologia, 97(2), 111-115.

  13. Vieira, T., Cunha, S., & Casal, S. (2015). Mycotoxins in Coffee. In Coffee in Health and Disease Prevention (pp. 225-233).

  14. García-Moraleja, A., Font, G., Mañes, J., & Ferrer, E. (2015). Analysis of mycotoxins in coffee and risk assessment in Spanish adolescents and adults. Food and Chemical Toxicology, 86, 225-233.