Wednesday, June 28, 2017

Wisdom Wednesday: Corn

Very little research into corn allergy has been published. Some allergists have questioned whether corn allergy exists at all. However, a 2012 study conducted in Italy suggests that some corn proteins, specifically the prolamins (zeins) in corn, contain amino acid sequences that resemble the gluten proteins in wheat so closely that eating corn could have a similarly damaging effect on some people with celiac disease as eating wheat. Some individuals with celiac disease may have to reevaluate the use of gluten-free foods that use corn in the formulation and preparation.

During the past 15 years some investigators have found that corn allergy, especially in children, may be more prevalent than previously thought. Most reactions tend to be mild, and not all people who have been sensitized to corn will develop obvious symptoms when they eat it. In one reported study, only 6 out of 16 children who were skin-test positive to corn and who had corn-specific IgE antibodies in their blood actually developed symptoms when they ate corn.

I believe that much like soy, it is the processed corn that creates symptoms for so many people. I often counsel patients to eat corn on the cob, but avoid corn in processed foods. Additionally, it is the repeated exposure in processed foods, sometimes multiple times per day, that sensitizes the gut to mount an immune response to corn.

Symptoms associated with corn allergy or sensitivity include erythema (reddening or flushing of the skin), pruritus (itching), urticarial (hives), itching and blistering of the oral cavity, throat tightening, eczema, abdominal pain, asthma, angioedema and hay fever-like symptoms.

Delayed reactions to corn are much like wheat. People with these “cell-mediated” sensitivities will test negative to corn-specific IgE tests in skin and blood and will fail to react to challenge tests designed to reveal immediate-onset symptoms. However, they show a positive response to oral challenge on muscle testing. Most of the time strengthening a weak muscle but on occasion creating global weakness.

The symptoms associated with this delayed response are diverse but include headaches, migraine, fatigue, mood disturbances, joint and muscle pain, and upper respiratory symptoms.

It is not uncommon for a person who is allergic to wheat and other cereal grains to also be allergic to corn. As I noted in each of these blogs, you can react to any of the proteins or carbohydrates that are not fully digested.

Ten years ago a research report identified the first of the allergenic proteins in corn. These lipid transfer proteins (LTP) are found in many foods that are often responsible for the most significant allergies. They are generally heat-resistant, and their allergenicity is unaffected by cooking. They can also survive stomach acid and digestive enzymes.

The same researchers found that the corn LTP cross-reacts completely with LTPs in rice and peach, but not with those in wheat or barley. This is further evidence that foods in the same botanic family rarely cross-react, but proteins that are structurally identical in unrelated plants may trigger allergy in a person who is sensitized to only one of them.

The Bottom Line:
Corn allergies/sensitivities do exist and are much more prevalent than previously thought. However, most people with a corn allergy do not suffer severe reactions and can often eat the whole food without issue. This is because the cellulose cell wall of corn can only be broken down by chewing, not digestion. If you don’t believe me just check your stool for intact kernels of corn after eating an ear.

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