Pragma Synesi – interesting bits

Compendium of interesting bits I come across, with an occasional IMHO

How Anecdotal Evidence Can Undermine Scientific Results

For me, this is the key quote from the article below:
“…we have evolved brains that pay attention to anecdotes because false positives (believing there is a connection between A and B when there is not) are usually harmless, whereas false negatives (believing there is no connection between A and B when there is) may take you out of the gene pool…”
Something to watch for – both in self and in others.

Scientific American Magazine – July 25, 2008

How Anecdotal Evidence Can Undermine Scientific Results

Why subjective anecdotes often trump objective data

By Michael Shermer

The recent medical controversy over whether vaccinations cause autism reveals a habit of human cognition—thinking anecdotally comes naturally, whereas thinking scientifically does not.
On the one side are scientists who have been unable to find any causal link between the symptoms of autism and the vaccine preservative thimerosal, which in the body breaks down into ethylmercury, the culprit du jour for autism’s cause. On the other side are parents who noticed that shortly after having their children vaccinated autistic symptoms began to appear. These anecdotal associations are so powerful that they cause people to ignore contrary evidence: ethylmercury is expelled from the body quickly (unlike its chemical cousin methylmercury) and therefore cannot accumulate in the brain long enough to cause damage. And in any case, autism continues to be diagnosed in children born after thimerosal was removed from most vaccines in 1999; today trace amounts exist in only a few.

The reason for this cognitive disconnect is that we have evolved brains that pay attention to anecdotes because false positives (believing there is a connection between A and B when there is not) are usually harmless, whereas false negatives (believing there is no connection between A and B when there is) may take you out of the gene pool. Our brains are belief engines that employ association learning to seek and find patterns. Superstition and belief in magic are millions of years old, whereas science, with its methods of controlling for intervening variables to circumvent false positives, is only a few hundred years old. So it is that any medical huckster promising that A will cure B has only to advertise a handful of successful anecdotes in the form of testimonials.

Take wheatgrass juice … if you can stomach it. The claims for its curative powers are bottomless. According to the Natural Medicines Comprehensive Database (the “bible” of natural medicines:, wheatgrass is “used therapeutically for increasing hemoglobin production, improving blood sugar disorders such as diabetes, preventing tooth decay, improving wound healing, and preventing bacterial infections.” And that’s not all. “It is also used orally for common cold, cough and bronchitis, fever and colds, inflammation of mouth and pharynx, tendency to infection, gout, liver disorders, ulcerative colitis, cancer, rheumatic pain, and chronic skin problems.”

The alleged salubrious effects of wheatgrass were promoted in the 1940s by a Lithuanian immigrant to Boston named Ann Wigmore, a holistic health practitioner who was inspired by the biblical story of King Nebuchadnezzar, recounted in Daniel 4:33, in which “he was driven from men, and did eat grass as oxen, and his body was wet with the dew of heaven, till his hairs were grown like eagles’ feathers, and his nails like birds’ claws.” Wigmore also noted that dogs and cats eat grass when they are ill and feel better after regurgitation, which gave her the idea of the wheatgrass detox. Because we have fewer stomachs than cows do, she hatched the idea of blending freshly cut wheatgrass into juice form for easier digestion—through either orifice—a practice still employed today. She believed that the enzymes and chlorophyll in wheatgrass constitute its healing powers.

According to William T. Jarvis, a retired professor of public health at the Loma Linda University School of Medicine and founder of the National Council against Health Fraud (, this is all baloney: “Enzymes are complex protein molecules produced by living organisms exclusively for their own use in promoting chemical reactions. Orally ingested enzymes are digested in the stomach and have no enzymatic activity in the eater.” Jarvis adds, “The fact that grass-eating animals are not spared from cancer, despite their large intake of fresh chlorophyll, seems to have been lost on Wigmore. In fact, chlorophyll cannot ‘detoxify the body’ because it is not absorbed.”

I tried wheatgrass juice at the Oh Happy Days natural food store in Altadena, Calif., as part of an investigation for the pilot episode of Skeptologists, a series we hope to sell to a television network (where another biblical phrase is apropos: “Many are called, but few are chosen”). My co-stars—Kirsten Sanford, who has a Ph.D. in physiology and is now a science journalist, and Steven Novella, director of general neurology at the Yale School of Medicine—also imbibed. If a picture is worth a thousand words, I will double this essay’s length by sharing the above snapshot.

Note: This article was originally printed with the title, “Wheatgrass Juice and Folk Medicine”.


August 1, 2008 - Posted by | behaviour, brain, decision making, evolutionary psychology | , , ,


  1. This blog hits home to me. As a family doctor one of my most difficult jobs is to convince patients that certain “cures” they are using don’t help and may actually be harmful.

    A good example of this is children’s cold and cough medicines. This one throws a twist into the works, because these medicines were “grandfathered in” through the FDA in the early 1970’s, without undergoing the rigorous safety and effectiveness studies modern medications have to go though.

    Since that time there have only been 11 well done studies on children to see if any of these medications work on children; all of the studies showed that they did not improve cold and cough symptoms, (although a few showed they were more likely to sedate children).

    There has also been growing data that a handful of children die every year from “over dose” of ALL THE MAJOR CHILDRENS COLD AND COUGH MEDICINES even when given the correct dose (

    The FDA reviewed this last fall and its expert panel said that “right now the current cold and cough medicines should not be given to children under 6.” Here is a link to the FDA’s minutes, “”, see page 6. The FDA made a public advisory in January 2008 about never using it for children under 2, because the Drug companies are fighting them on the panels ruling to never use cold and cough medications on children 2 to 6. Since the FDA previously allowed these drugs, the FDA is forced to go though “due process” before they are willing to make an official public statement about never giving these medications to children 2 to 6.

    Interestingly, some researchers from Penn State have shown that Buckwheat honey is better then the OTC children’s cough medicines for children’s cough. There is a web site that talks about this, and gives lots of research to help parents be better informed about how to help their kids.

    But when you try to tell parents to not give their children OTC cough and cold medications, they think you are making stuff up.

    -Dr. Jeff

    Comment by Dr. Jeff | August 5, 2008 | Reply

  2. Here’s another one that parents will not be convinced of: not reducing fever (not talking about overly high seizure-producing fever, just your run-of-the-mill kind).
    Given that all mammals react with fever to infections, you’d think that people would realize there is something protective about it. I’ve read that viruses and bacteria do not reproduce well at higher than body temperatures, which would confirm that protection, but I suspect there is probably more to it that we haven’t discovered yet.
    But the first thing they do in a hospital is stuff you full of Tylenol every four hours which takes you for a roller coaster ride of body temperature going down (feeling too hot!) and in three hours going up again (feeling too cold!). But they won’t let you cover up while you’re shivering, or give you more Tylenol until the four hours are up… which just starts the cycle again.
    I bet if there was a scientific study, it would confirm that people without fever-reducing medication recover better. But with drug companies and their agenda of selling more drugs, that study isn’t likely to happen any time soon. 😦

    Comment by pragmasynesi | August 5, 2008 | Reply

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