The Nocebo Effect – How Science Should Work

The placebo effect is something that many people, even those who do not work in a context of clinical trials, have heard of and understand. It is the principle that, if a person thinks they are receiving treatment for a specific ailment, they can feel better, even if the treatment they are getting is not doing anything to ameliorate what ails them. This is the reason why clinical trials need to be randomized, double-blind and placebo-controlled, in order to determine whether or not the treatment being tested is actually doing something to help the patients. It is also the point in which homeopathy and prayer fail the test, but I digress.

The opposite of the placebo effect, on the other hand, is one that is not as commonly know, talked about or controlled for in scientific studies. It is called the nocebo effect, and it happens quite as often and can lead to similarly false results.

Due to it’s relative lack of fame, the nocebo effect is sometimes overlooked in scientific studies, and has thus led to certain faulty conclusions being published. That does not mean that the mistake cannot be corrected. In an excellent example of how science should work, the same people who “discovered” non-celiac gluten insensitivity have now shown that it does not actually exist.

In a study published in Gastroenterology, the researchers realized that the non-celiac gluten insensitivity that they discovered in the past was actually a classic case of the nocebo effect.

Since gluten is a protein found in any normal diet, Gibson was unsatisfied with his finding. He wanted to find out why the gluten seemed to be causing this reaction and if there could be something else going on. He therefore went to a scientifically rigorous extreme for his next experiment, a level not usually expected in nutrition studies.

For a follow-up paper, 37 self-identified gluten-sensitive patients were tested. According to Real Clear Science’s Newton Blog, here’s how the experiment went:

Subjects would be provided with every single meal for the duration of the trial. Any and all potential dietary triggers for gastrointestinal symptoms would be removed, including lactose (from milk products), certain preservatives like benzoates, propionate, sulfites, and nitrites, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. And last, but not least, nine days worth of urine and faecal matter would be collected. With this new study, Gibson wasn’t messing around.

The subjects cycled through high-gluten, low-gluten, and no-gluten (placebo) diets, without knowing which diet plan they were on at any given time. In the end, all of the treatment diets – even the placebo diet – caused pain, bloating, nausea, and gas to a similar degree. It didn’t matter if the diet contained gluten.

This is a perfect example of how science should work. If we make a mistake we go back and prove ourselves wrong. Of course not everyone is capable of doing this, but it is great when you get to see proper science in action.


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