Monday, February 14, 2011

Food Allergies and the Risks Inherent in Medical Science

A perfect example of Medical Science and the Vanishing Truth has been provided by Jerome Groopman in a New Yorker article: The Peanut Puzzle. The phenomena of “vanishing truth” in medical science was described by Jonah Lehrer as a positive scientific finding with a veracity that seems to decay over time. Lehrer ascribes this decay to three factors: publication bias in favor of positive results, selective reporting in which researchers enhance, inadvertently or not, positive results over negative results, and to the hazards of deriving conclusions based on statistically small samples which may have uncontrolled variables. Lehrer focuses on the efficacy of certain drugs that were initially deemed to have significant effectiveness, but with subsequent studies, were found to be much less useful.

In the arena of food allergies there was an alarming trend identified. The incidence was rising dramatically in the western countries, but remained rare in Asia and Africa. The medical researchers looked for an explanation. They wanted to find some positive act that could explain and counter this trend. One study indicated that the incidence of food allergies could be reduced by eliminating cow’s milk, eggs and peanuts from the mother’s diet during the last trimester and while breastfeeding, and eliminating all foods that might cause an allergic response from the child’s diet for up to two years. The conclusion reached was:
“Reduced exposure of infants to allergenic foods appeared to reduce food sensitization and allergy primarily during the first year of life.”
These results seemed reasonable. The logic was that the human immunity system matures in a child similar to other body functions. By allowing the immune system to mature before introduction of a potentially allergenic product, it would be better able to deal with it. The medical community was satisfied with this conclusion: it suited them intellectually, and it allowed them to make a positive recommendation to their patients. In 1998 the UK formally adopted the study results as a set of guidelines for doctors and patients. In 2000 the American academy of Pediatrics did the same.

The conclusions may have been intellectually satisfying, but that did not make them correct. Less-well-funded thinking might have led them to ask “how is this predisposition to food allergies consistent with evolution?” Nuts had to be a major component of the diet of hunter gatherers, which is what mankind was for essentially all of its existence. How could such a deadly susceptibility be propagated genetically? And what was it about the manmade environment that was causing the increase in incidence of allergies?

In undeveloped countries it is still common for mothers to introduce solid food to their infants by first chewing the food and expelling the mushy product, saliva and all, into the baby’s mouth. This is presumably how infants were fed for thousands of generations. This introduced infants to a variety of food products, but in a controlled environment. Perhaps the mother’s saliva was beneficial in damping any sensitivity to the foods, allowing the infant to gradually develop a tolerance.

Further studies gradually began to undermine the formal recommendations. The evidence that suggested that the mother’s diet could be important in triggering an allergic response in her infant “vanished.” Medical researchers began to test the theory that introducing controlled mounts of a sensitive substance could allow a child to gradually develop a tolerance. This is exactly the opposite approach to that which produced the official guidelines.

In 2008
“....the American Academy of Pediatrics released a report by Mount Sinai’s Dr. Sicherer and other researchers that overturned the expert advice of the past decade: ‘Current evidence does not support a major role for maternal dietary restrictions during pregnancy or lactation....There is also little evidence that delaying the timing of the introduction of complementary foods beyond four to six months of age prevent the occurrence of [allergies].”
The author builds his narrative around the story of a mother who, under her physician’s guidance, followed the earlier recommendations to the letter. At nine months her daughter had a severe reaction to dairy products. She was also allergic to eggs, peanuts, tree nuts and sesame seeds. Her physician began trying to introduce to the child (at age seven) small doses of these allergenic foods in controlled environments in hopes of allowing her body to develop a tolerance. This approach seems to be having some success. Perhaps one day the child will be able to lead a normal life with close to a normal diet. It is possible that the medical advice the mother was given worsened the child’s experience rather than improving it. There is no way to be sure.

To say that the medical community has corrected an error and is now on the right path would be to make the same mistake that was made originally. There is probably much left to learn. Performing medical studies is extremely difficult. There are those who believe that many are so deficient as to be worthless. But that will not prevent them from being displayed prominently on the front page of your newspaper. It may take decades for the falsity or inappropriateness of a study to be recognized.

Is there a lesson to be learned here? Perhaps there are several.
Don’t assume what you read in the newspaper is true.

Don’t assume what a doctor tells you is necessarily true.

Don’t assume your doctor knows more about a topic than you could learn in a few hours of searching the web.

Get multiple opinions, and make sure you have an informed opinion of your own.

Doing nothing should always be considered as one of the possible options.

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