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Four Big IssuesDung Hoang

Four Big Issues

Why are there so many food allergies now?

Robert A. Wood, MD, is chief of Allergy and Immunology, Johns Hopkins Children's Center; and professor of International Health.

It's likely that many things have changed in the environment, in our diets and in child-rearing practices that have led to an increase in food allergies in the past 20 years.

One of the most popular theories is the hygiene hypothesis. If the developing immune system is not exposed to enough levels and types of germs and bacteria, its focus may shift, leading to allergies or autoimmune diseases. Worldwide, there's a lot of evidence to support this, as food allergies are much more common in developed countries. But the hygiene theory does not seem to be the most important factor in developed countries. Higher rates of food allergies in inner-city populations contradict the hypothesis.

In terms of nutrient-related allergy causes, two theories have some evidence to support them: vitamin D deficiency and excess folate. Compared to two decades ago, there's a much higher rate of vitamin D deficiency-especially in northern climates. This may be diet-related, but it's also because most of us spend more time indoors.

And about 20 years ago, women who were pregnant began taking supplements with high levels of folic acid to prevent birth defects. So there's been a major change in developing infants' exposure to folic acid.

I think we're going to learn that there are quite a few more contributors to food allergies. Some are under investigation; some we haven't thought of yet.


  • Parag Mahale

    Houston 02/25/2014 02:57:04 PM

    Preservatives used in food, in my opinion, are the major cause of food allergies. Many of them, like sodium benzoate, can be carcinogenic after metabolism. GMOs provide foreign proteins that the body is never exposed to and cause GI related allergic issues. The food production is the main reason for increasing incidence of food allergies and it is going to get worse.

  • Livingstone

    Uganda 05/16/2014 10:27:23 AM

    first foods are responsible for most non communicable diseases since majority of people do not have choice of want to eat.

  • Livingstone

    Uganda 05/16/2014 10:31:35 AM

    GMO foods may lead to extinction of original foods since their genetic make would have changed which may lead to hung shortage of food in the world (global concern)

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