Merchants of Certainty—reading too much into a single study

Merchants of Certainty as well
Books that spread an unwarranted message of certainty on food, health and wellness

As we try to keep up with what is happening in the world, we are bombarded with BREAKING NEWS. It may be a major international event, a shooting within miles of our current location or the latest breakthrough in health and wellness. I always approach such stories with caution.  We live in a world that demands certainty and wants to separate life into good and bad. We particularly want to be certain about which foods are healthy and which ones are not. Nate Silver in his popular website reported on all the things his staff want to believe are good for them even though there is little convincing data to support the claims. The list includes detoxing, dosing with homeopathic medicines, downing coffee and working crossword puzzles to prevent dementia, drinking kombucha, and taking zinc tablets to ward off colds.

We are rescued from an uncertain world by food evangelists who are more than happy to declare with certainty that

  • any given food is either healthy or unhealthy,
  • we should “avoid processed foods” while keeping the term deliberately vague, and
  • the industrialized food system is at the root of everything that is wrong with the Western Diet.

Food evangelists like to use the phrase “At least one study shows that . . .” A problem with relying on single studies is that they are not presented in a context of overall knowledge in the field. American society is becoming victims of these merchants of certainty.

Reports of a scientific study in the media are generally contrary to accepted knowledge. That is why such a study is considered news. The headlines are frequently misleading. The story is not usually as dramatic as the headline, but it tends to offer over-simplified versions of the findings in the actual study stated without any qualifications of the results as stated in the journal article. Most of these news articles tend to provide a slanted view without giving us the big picture. Finally, advances in science are based in skepticism. It is through such skepticism that science moves forward. Many of these stories lack a healthy dose of skepticism. To illustrate my points, let’s look at three recent examples. In an effort to keep this post relevant to the topic of the month—diet and the microbiome—I sought out three recent media stories that were relevant to the topic.

If You Eat This Food Every Day, You Can Improve Your Gut Health.

It turns out that this gut-healthy food is broccoli, and the promise is based on a study published in the Journal of Functional Foods.1 The story is based on a news release from Penn State University to communicate the benefits of basic research being conducted at the university. The headline and the story seem to be an overinterpretation of the study’s conclusion that

  • “broccoli consumption elicited an enhanced response in ligand-sensitive Ahrb/bmice, demonstrating that in part the beneficial aspects of dietary broccoli upon intestinal health are associated with heightened AHR [aryl hydrocarbon receptor] activity.”

Dr. Gary Perdew, the head of that lab that conducted the research, was interviewed for the story and described the importance of preventing a leaky gut (colitis). The emphasis of the story was on prevention, but the study was aimed at treatment of an induced disease. Perdew indicated that a daily serving of 3 ½ cups of broccoli would be equivalent to treating the mice whose colitis had been given to them by the researchers. Now I might be willing to consume 3 ½ cups a day of broccoli if I was suffering from colitis and generous servings of the vegetable would help me avoid a serious operation. I would NOT force myself to eat that much broccoli daily to the exclusion of other foods if I was not that concerned about suffering from colitis in the first place. Colitis is not high on my personal list of health concerns at the moment!

Foods with Potential to Cause Inflammation Connected to Risk of Colorectal Cancer.

Actually, this headline is fairly mild. The story is a summary of a study from JAMA Oncology.2 We are cautioned to reduce consumption of inflammatory foods such as fish, processed meats (code word for cured meats), red meats, refined grains, and tomatoes. Both high-energy and low-energy beverages should also be avoided. On the good list are coffee, dark-yellow and green-leafy vegetables, and tea. Even pizza is listed on the good-for-you list, but I guess we need to hold the tomato sauce, pepperoni and a wheat-flour based crust. The study recommendations were based on an analysis of the data from two vast databases. By digging into the weeds of the study, we find that 2.1% of participants were confirmed cases of colorectal cancer (about half the 4.3% found in the general population). The results are interesting information, but I am not sure how useful they are in planning diets.

Sugar additive may cause bowel issue

This article is found in a Chicago newspaper. The sugar additive is trehalose. We learn that trehalose “may stimulate a specific bowel organism Clostridium difficile to become more virulent.” This article written by William Massey, a medical doctor and PhD of alternative medicine, is more well written than most popular articles. It simplifies the conclusion of the original study3

  • “the implantation of the trehalose as a food additive into the human diet, shortly before the emergence of these two epidemic lineages, helped select for the emergence and contributed to hypervirulence.”

Both the news article and the study published in Nature indicate that even low doses of the molecule can enhance the effect and that the beginning of the C. difficile epidemic coincides with the increase of the use of trehalose as an additive in packaged foods. The story cautions that just because two events coincided does not imply cause and effect. The news article mentions that trehalose is a natural component of fungi, but the original article does not. It should have mentioned mushrooms as only food microbiologists admit to eating fungi. The evidence presented here on the ability of C. difficile to thrive in the gut with the aid of trehalose should be studied further to see if the effect can be reproduced. I am on the record opposing knee-jerk reactions condemning popular food additives, in this case polysorbate 80, based on data from a single study with no credible mechanism proposed. The study on trehalose differs from the one on polysorbate 80 as a plausible mechanism of action was proposed for the trehalose effect. Both studies involve induced diseases in mice which may or may not be directly relevant to humans.

The danger of single studies

The point here is that news stories about the latest study in the scientific literature tend to spread fear rather than useable information about our food supply in general and ingredients in processed foods specifically. The relevance of basic research on induced colitis to a decision to include large servings of broccoli to humans every day seems to be a stretch. Analysis of large datasets to answer specific questions about nutritional habits is more likely to be relevant. The idea of eating pizza and drinking coffee to ward off inflammation, however, makes little sense if processed meat, tomatoes and refined grains are problem ingredients. The mining of these datasets in this case provides too much information with too little clarity. Finally, the study about a specific additive that might be contributing to a serious disease epidemic that presents a plausible mechanism deserves more careful consideration than one not mechanistically based. No regulatory decision, however, should be made on the basis of a single study.

Science is not advanced by statements of certainty. Rather, it is advanced by skepticism and experimental inquiry. Science does not ever get us to absolute truth. Rather it helps to debunk myths and get us closer to the truth based on careful analysis and interpretation of data and not on speculation. The purpose of this blog is to provide a skeptical, alternate viewpoint to the prevailing food evangelists who have declared all processed foods to be unhealthy.

Next week: The Potlikker Papers: A Food History of the Modern South


1 Hubbard, T.D., I.A. Murray, R.G. Nichols, K. Cassel, M. Podolsky, G. Kuzu, Y. Tian, P. Smith, M.J. Kennett, A.D. Patterson and G.H. Perdew, 2017. Dietary broccoli impacts microbial community structure and attenuates chemically induced colitis in mice in an Ah receptor dependent manner, Journal of Functional Foods 37:685-698.

2 Tabung, F.K., L. Liu, W. Wang, T.T. Fung, K. Wu, S.A. Smith-Warner, Y. Cao, F.B. Hu, W. Ogino, C.S. Fuchs, and E.L. Giovannucci, 2018. Association of dietary inflammatory potential with colorectal cancer prevention, JAMA Oncology doi:10.1001/jamaoncol.2017.4844.

3 Collins, J., C. Robinson, H. Danhof, C.W. Knetsch, H.C. van Leeuwen, T.D. Lawley, J.M Auchtung and R.A. Britton, 2018. Dietary trehalose enhances virulence of epidemic Clostridium difficile. Nature doi:10.1038/nature25178.

22 thoughts on “Merchants of Certainty—reading too much into a single study

  1. “Science is not advanced by statements of certainty. Rather, it is advanced by skepticism and experimental inquiry.”

    So important to remember, especially in this day and age. Another great piece. Thank you!

    Liked by 1 person

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