Tea and the post-hoc trap

March 27th, 2009 – A new food study brought to light by the BBC world news service has announced that drinking hot tea causes oesophageal cancer. The tube between mouth and stomach would be particularly targeted by oesophageal squamous-cell carcinoma (OSCC) or the most common form of the disease as suffered by 500,000 people worldwide. Carried out in Golestan province, Iran, the study lasted less than a year and focused on 300 Iranians diagnosed with OSCC, all of which drank an average of 1 litre of black tea per day.

Firstly, it would be a cheap shot on my part to question the scientificity of a study simply because it was conducted in a less than open theocracy like Iran, especially since there is so much more to question. Firstly, the researchers have seemingly fallen head-first in a post-hoc trap which is a statistical concept of error. It states that it is not because two events occurred one after the other that one necessarily caused the other. For example, the findings of this study could just as well stated that wearing sandals or eating bread causes OSCC because all the OSCC-affected test subjects were also exposed to those two factors. Secondly, their sample of 300 subjects was very small compared to the tens of millions inhabiting the region and the study was not conducted over the necessary time (5-10 years) that it should normally take to declare a universally consummated product as “cancerous”. Finally, knowing that tobacco and alcohol are proven to be the leading causes of OSCC and having red the study, I fail to see the chemical link between tea and cancer.

The “Hot” or the “Tea”

Indeed, browsing the detailed results of this study only seems to confirm that the temperature of the tea (70 degrees Celsius or more) has led some people to have more of a risk of developing OSCC than others. It could be as simple as the scalding tea wears down the barriers around your food pipe, leaving you more prone to infection and cancer (although this is in no way implied by the Iranian test masters). Whether through their own search for rapid fame and diffusion of results or whether by the BBC’s quest to make everything interesting at the risk of being blatantly misleading: “Steaming hot tea linked to cancer” is a very alarmist, misleading and potentially defamatory headline/baseless finding.

Pursuing this line of making sciency things sound more interesting and sciency, the BBC offers the advise of eminent British food specialists. These pearls of wisdom tell you to “wait a few minutes for your brew to cool from scalding to tolerable” or to “add milk, which cools it down”. Now, if only somebody would come along and tell me why my body gets all messed up when I drive into oncoming traffic on the highway…

Historic gullibility

To link this incredible story of a food fear (that is fabricated, will be in the miscellaneous section of your local news tonight and will soon be forgotten) with history, I invite you to research food specialists’ advice on egg consumption in the past 20 years. A hundred studies jolted the western world into mass-hysteria when they were shown to jack up cholesterol to heart attack levels. A hundred more would then indicate that it had amazing nutritional value and could possibly have magical curative properties (citation needed). Progressing past the twentieth century, I also bring you the Tomato in late XVIth century England.

Being grown in the New World for millennia, this pseudo-fruit only appeared on the European scene in the 1500s, brought back by the Spanish and Portuguese conquistadors. Slowly making its way up north, it eventually creeped onto the British Isles and was immediately faced by two opponents on the culinary battlefield: xenophobia and paranoia. The Native American cultivators of this new “apple of love” (as they called it) were obviously savage and primitive and therefore these new atrocities had to be no good. Furthermore, the British were well-off and sophisticated, it only made sense that this thing was a poisonous “wolf in sheep’s clothing” devised by their Spanish rivals.

Despite prejudice and jumping to conclusions, there was a modicum of botanic science involved. Physician John Gerard was the first to plant the odd fruit in England and had quickly analysed its genetic makeup (as much as possible for 1590), correctly assessing that the tomato was of the same family as the fatal Nightshade plant and the toxic tobacco plant. Also, he avidly remarked that the stems and leaves of the tomato plant were an irritant to human skin (or “terrible poison” as he put it). On the other hand, he concluded that the overly moist and cold fruit could not possibly be beneficial to one’s health and was definitely poisonous. He claimed this knowing full well that it was eaten in the North American colonies and in Spain; he seems to have shared the “good enough for barbarian foreigners but never for me” attitude of the time and place.

The result of British disdain for foreign foods and seemingly scholarly endorsement for the fears was a 200-year ban of the Tomato in England. Through famines and droughts, the British populace were prisoners of their own ignorance and credulity in faulty research. To be fair, they grew plenty of the “golden” or “love apples” but used almost all of them for random medical practices (over the eyes for glaucoma) or for table decorations (they are pretty and shiny).

For what is probably the hundredth time I incite the peoples of the world to beware what media pre-chews and feeds them, especially when “statistics” and “scientific studies” are implicated. The saying goes Caveat emptor or “let the buyer beware”; in this case not only of what you literally buy but also what you “buy” as proven fact.

(Pictured: The book for all your historical tomato-related queries - a cancerlicious Maroccan tea service)

End.