Food Intolerance vs. Food Allergy

One link in particular from the Great Page of Food Allergy Informational Links that I posted yesterday stood out for me. Of all the thousands of questions I've received over a quarter century of talking about lactose intolerance, probably the most frequent and most confusing is the difference between a food intolerance and a food allergy. Let's start with this short article on the Palo Alto Medical Foundation site, Food Allergy vs. Food Intolerance.

A food allergy is actually an immune-system response. When someone eats certain foods (such as those listed above), the body mistakenly treats an ingredient in the food (usually a protein) as if it were a harmful pathogen. The body responds by creating a defense system (antibodies) to fight it. The allergic symptoms occur as a byproduct of the action of the antibodies that battle the invading food. Food intolerance is a broad term that describes any adverse reaction to food. ... Non-allergic food intolerance is often limited to an uncomfortable digestive-system response. The most common example of food intolerance is lactose intolerance, in which one's body is unable to break down the sugar (lactose) in dairy products. Other food intolerances can be caused by irritation to the digestive system by an ingredient in the food consumed.

That's the basics. Allergies and intolerances are different conditions, produced by the body reacting in different ways, often to a different set of triggers, with different symptoms and different severity. You wouldn't think that anybody would mix them up. And yet, life is never that simple and clearcut. The big issue for most of you reading this is dairy. Dairy is the trigger - the sole trigger - for lactose intolerance. Only the milk of mammals contains lactose: it's not found anywhere else in nature. Digestion breaks down milk into its smallest and simplest components and one of these is the compound sugar known as lactose. No digestive system of any mammal can digest lactose. It must be broken down into its own components, the simple sugars glucose and galactose, before it can be absorbed by the intestines. That's pretty weird if you think about. Why would a nursing mother go through the long series of extremely complex chemical reactions necessary to produce a unique compound sugar that can't be used in that form by the offspring? Nobody really knows. It's a scientific mystery. And a useful argument against the notion that humans or mammals or any living thing was "designed." Who would design a boondoggle like this? To break down, digest, a compound chemical the body manufactures enzymes, proteins that act as catalysts to speed up the process. The enzyme that digests lactose is called lactase. (Sugars end in "ose"; enzymes end in "ase". Remember that for your next crossword puzzle.) If the small intestine doesn't manufacture lactase, or creates too little of it, then some lactose will continue through the gut and wind up in the colon. Two things can happen during that journey, both bad. One is that lactose reverses what is called the molality of the system. Normally water enters the body from the intestines, nourishing you and leaving the end product, the stool, moist but intact. Lactose creates an environment in which water is pulled from the body into the intestines, setting up conditions that usually manifest as diarrhea. In addition, many of the dozens or hundreds of species of bacteria that live in your colon will jump on the lactose as a source of food, ferment it, and produce gas as part of the fermenting process. Heavy, smelly, long-lasting, awful gas - by itself or in addition to the diarrhea - is the consequence. Put together, those are the symptoms of lactose intolerance. Any other symptoms in an adult are extremely rare. Allergic reactions make more basic, underlying sense than lactose intolerance. You obviously want your body to fight off foreign invaders in your environment or in your food. But - here's where we question the whole "designer" thing again - the body often gets it totally wrong. Sometimes perfectly good, even healthy and helpful chemicals trigger reactions. In food, these reactions are always triggered by proteins, and never by sugar of any sort. You cannot be allergic to lactose. Only the proteins in milk, which are mostly in two families, the caseins and the wheys, can set off an allergic reaction. In theory that sounds like a great dividing point. In the laboratory it is. In life, there are few times when you have a dairy product that contains only proteins or only lactose. They almost always come mixed. How do you tell which is causing the problem? The best way is by the symptoms. Lactose intolerance always and only causes intestinal distress. A dairy allergy seldom does. Another link on that great links page lead to an informational page from the Journal of the American Medical Association.

SYMPTOMS Allergic reactions to food can be mild to severe. They usually occur within a few minutes of eating a food, though they rarely appear a few hours after ingestion. Symptoms can include runny nose, itchy skin, rash or hives, tingling in tongue or lips, tightness in throat, hoarse voice, wheezing, cough, nausea, vomiting, stomach pain, or diarrhea.

Those symptoms are in rough order of how common they are. Notice that stomach pain or diarrhea are last on the list. They do occur in certain people. Even so, the fact that the symptoms overlap coming from food in which the triggers overlap is a recipe for confusion. Doctors can usually sort this out just from listening to you describe your symptoms. And there are tests both for lactose intolerance and for food allergies that will definitely separate them. If you don't want to wait, the easiest first step is try lactase pills, available in any supermarket or pharmacy. Those work well on most people with lactose intolerance. If they don't, then the next step really is to see a doctor. A great many gastrointestinal illnesses produce the same symptoms and some, notably irritable bowel syndrome, can also be triggered by dairy. The cures for those are seldom as easy a box of inexpensive pills. Make sure you get the treatment you need.