IS THE OBESITY EPIDEMIC BEHIND THE
“MYSTERIOUS” INCREASE IN ALLERGIES?
Rene Menguy, M.D., Ph.D.
Recently, the media reported a rise in the incidence of various types of allergic reactions in all developed countries. Apparently, Americans are sneezing and wheezing more. .Studies conducted by the National Institutes of Health between 1988 and 1994 showed that 54% of Americans are sensitive to at least one allergen, a rate two to five times higher than the one existing between 1976 and 1980. . Insurance filings for allergy care have increased and the numbers of children with food allergies have increased by 18%.
Several explanations have been offfered.
Not surprisingly, some have implicated global warming, which by increasing the length of the flowering season would raise pollen production. Plausible, but seasonal climactic variations have long been around whereas population sensitivity to pollen has increased steadily.
Others have suggested a relationship between allergies and air pollution. However, the latter began long ago and the problem under discussion is recent.
Finally, some suggest that we’re simply diagnosing these conditions better, an explanation often suggested for diseases appearing to be on the rise. However, the consensus of workers in the field is that we can’t explain this phenomenon.
Some years ago, I came across another explanation. Between 1983 and 1987 I operated on 941 patients with morbid obesity. To my surprise, I found that 9% suffered from bronchial asthma. At the time the overall incidence of asthma in the general population was around 3 to 5 percent. Later, other studies corroborated this observation.
Harvard Medical School investigators found that obese individuals are three times more likely to have asthma than lean people in the general population and that obesity comes first. British investigators studying 15,000 children between the ages of 4 and 11 discovered that 17% of the study group had asthma and that there was a positive relationship between a child’s degree of overweight and the risk of being asthmatic. Moreover, they noticed that the incidence of obesity in this population had doubled.
The long and short of all this is that the prevalence of obesity and of asthma has increased during the past 20 years. The young people at highest risk of developing obesity-linked asthma are women and adolescent girls.
It should be made clear that although obesity appears to be a risk factor for asthma, not all asthmatics are overweight; quite to the contrary.
So, is there anything to this apparent relationship between overweight and asthma? Is obesity a risk factor for asthma? Once, it was thought that asthma preceded the development of obesity and that asthmatics gained weight because they were less active. However, the Harvard studies concluded that obesity comes first, which suggests that something about obesity causes asthma, the old “Post hoc, ergo propter hoc” trap.
However, with respect to the problem under discussion, there is reason to suspect that obesity does indeed increase the risk of developing asthma and other allergic manifestations.
Our bodies’ immune system is a marvel. Without it, we could not live. Too much of it can cause a host of illnesses some, severe and some lethal.
Noxious agents called ALLERGENS have a specific chemical composition different from all other compounds. Those causing an allergic attack such as asthma are called ANTIGENS. When an antigen first enters the body, lymphocytes located in lymph nodes and in lymphoid tissue situated elsewhere, detect it as a "foreign invader". Some form antibodies that are specific for that particular antigen. Each lymphocyte, of which there are millions, can form only one type of antibody. However, each one can "clone" itself and replicate identical lymphocytes capable of producing the same antibodies for years thereafter. Each "clone" responds only to the original antigen or to another antigen with the same molecular configuration on its surface. For example Jenner discovered that vaccination with the COWPOX virus antigen conferred immunity to SMALLPOX. Those lymphocytes that react with antigens mainly by producing antibodies (GAMMA GLOBULINS), are called B-lymphocytes. In the aggregate, they constitute 20% of plasma proteins.
Other types of lymphocytes, T-cells, are processed in the THYMUS. There, they are exposed to the body’s own antigens. . To prevent T-cells from attacking the body's own tissues, any one reacting with a body antigen is destroyed. The only ones released are those reacting to a foreign antigen, bacterial or cellular. Some T-cells, known as “killer T-cells” destroy their target, a bacterium or a foreign tissue cell, by attaching themselves to it and punching into it holes through which they inject a cytotoxic substance, thus destroying it. This is how organ transplants are rejected, unless the immune system is suppressed.
These antibodies have the other vital function of ACTIVATING THE “COMPLEMENT SYSTEM”. The latter comprises about 20 different protein molecules, normally present in plasma, but inactive until an antibody reacts with an antigen. This reaction so alters the antibody that it bonds to one of the complement proteins. This bonding activates that protein, and initiates a chain reaction that, in turn, activates all of the other components of the complement system, which can then accomplish the following actions:
●Enable certain white blood cells to swallow bacteria. ●Destroy bacterial cell membranes ●Promote the release of HISTAMINE from certain cells located throughout the body.
So, how does all this relate to the association between obesity and allergic conditions? Recent research on ADIPOCYTES, the fat laden cells forming fatty tissue, shows that these not only fulfill a storage capacity, but also function like the endocrine cells that secrete hormones. Adipose tissue produces several important inflammatory markers such as TNF-α, C- reactive protein and Interleukin-6 in addition to components of the complement system. The latter originate mainly in the intra abdominal fat stores.
In short, obesity causes the development, in several body areas, of an environment favoring inflammation and anaphylaxis; and Asthma is an inflammatory process par excellence. In other words there appears to be a cause to effect relationship between obesity and allergies
To be continued