What about contaminants?

Posted by John Peterson Myers at Nov 23, 2008 07:05 AM |

Tribune reporter Sam Roe paints a devasting picture of how companies and the government manage allergens in food during an era when food allergies, especially among children, are becoming much more common and much more severe.

In theory, food labels are supposed to identify ingredients that have been identified as major allergens, mainly peanuts, milk, eggs and wheat.  Parents with kids that are allergic to these ingredients actually pay close attention:  "Millions of parents, teachers and baby-sitters scrutinize these labels to ensure that they are not giving children unsafe food."

But the Tribune's investigation found "an alarming number of products sold as allergen-free actually contain harmful amounts."

Compounding the problem, the Tribune's analysis showed that when consumers report labeling errors, only 7% of the products are recalled.  And fully 47% of products that were recalled because of hidden allergens were not announced to the public.

According to Roe: "In essence, children are used as guinea pigs, with the government and industry often taking steps to properly label a product only after a child has been harmed."

The Tribune's story establishes beyond a doubt that the system is broken and that children's health is at risk.  It is superb investigative reporting. Where it could have done a better job is in the sidebar titled "Why the allergy spike?" 

The issue addressed by the sidebar is the question: Why is the number of kids with food allergies soaring?  Pointing out that scientists disagree, it first focuses on two explanations ... 

- that awareness is growing and parents may be quicker to seek a medical diagnosis than they were in the past

- that children's environments have become too sterile and their immune system overreacts to common food proteins ... the 'hygiene hypothesis.'

And then the sidebar goes on to observe that "other theories abound." It lists two improbable ones and then comments that "few studies confirm such speculation."

Here's my reaction:  Neither of the two first explanations is supported by much evidence in the scientific literature, although mainstream media coverage of allergic diseases, including asthma, invariably gives the 'hygiene hypothesis' at least a passing mention. Despite the paucity of evidence, the theory has gained a life of its own, perhaps because it has an air of a 'man bites dog story': We are sicker because we are cleaner.  And the 'awareness' explanation doesn't seem remotely plausible.  Parents and physicians would not have missed the severe shock reactions that have become increasingly common among children. 

What is missing is a discussion of the potential role of contaminants like the phthalate DEHP and some environmental estrogens in heightening immune system sensitivity.  This explanation runs as follows:  In the womb or early in life, the immune system's 'thermostat' is set, but exposures to contaminants can increase its sensitivity.  As a result, reactions to common allergens become stronger.

There actually is a growing body of experimental literature on this, with animals, and also some supporting epidemiology.  It's far from proven, but there are more data establishing plausibility for this than any of the explanations discussed by Roe in the sidebar.

For example, work by Narita et al., published in 2007, shows that very low levels of several environmental estrogens increase the severity of a key immune system reaction in human and mouse cells. 

The maximum reaction was seen at a dose well within the range of common human exposure (graph to right). Not unusual for endocrine-disrupting compounds, the dose-response curve is the shape of an inverted-U.

 
 

Similarly, in a study testing the effect of a common plasticizer, the phthalate DEHP, on the severity of a mouse's allergic reaction to a common allergen, Takano et al. found that very low doses of DEHP made the reaction much worse.

The two flat curves at the bottom of the graph (left), along with the purple line (Dp + vehicle) are three different types of controls.  The strongest effect was produced by a dose  of 20 micrograms of DEHP, while the highest dose used, 100 micrograms, did not differ from the control.  As in the experiment above, this is an inverted-U dose-response curve.  The most effective dose is 1,000 times lower than what is currently considered toxic, based on liver experiments. And again, it's well within the range of human exposure.

Results like these actually predict that we should be experiencing an increase in the rates of strong allergic reactions.

This area of research--how contaminants may be heightening immune system sensitivity--is relatively new, and it has not received much attention in the mainstream media.  Practicing physicians, without the time to keep up with the torrential pace of new scientific discoveries appearing in the scientific literature, most likely would be unaware of this new body of research.  Hence, if they were the sources that Roe turned to for possible explanations, it's not surprising that contamination didn't make his list of potential explanations.