William Ashworth

I knew from the moment I took the first bite that I shouldn't eat that sandwich.

We were out with friends in a brewpub in a nearby town. The beer was good and the conversation was better. Because I have a food sensitivity, I looked the menu over carefully. Good - they had a BLT. BLTs are always safe. This one listed a couple of extra ingredients, but not the one that I have a problem with, so I ordered it. It came, scrumptiously prepared. I bit into it.

Onions?! Who puts onions in a BLT?

Maybe it's just a tiny amount in the sauce? I took another bite. Maybe it's some combination of ingredients mimicing onion flavor? Another bite. Maybe there's not enough to trigger the reaction? I finished the sandwich.

I definitely shouldn't have. Two days later, I was just beginning to get over the effects. Bloated abdomen. Foul taste in my mouth, foul odor in my nose. It felt as though foulness was seeping from all of my pores. And, of course, there was the gas. Copious, foul-smelling gas. Stools...I don't want to talk about the stools. The bottom line (and notice that word, "bottom") is that my digestive system, from my mouth all the way through to the other end, was feeling deeply abused and was telling me so. In no uncertain terms. Pepto-bismol was my friend. Without it, I wouldn't have been able to sleep for at least two nights.

And now it's probably your turn to ask: Onions?! I've heard of peanut allergies, and gluten sensitivity, and dairy intolerance, but onions? Who is allergic to onions?

A lot of people, it turns out - including a lot of people who probably think they're having problems with something else. But "allergy" isn't the right word, although many people use it that way. True allergies - the life-threatening kind - are usually triggered by proteins, and they cause rashes and swollen tissues. Food sensitivities are usually triggered by sugars, and all they do is upset your digestion. Which is not life-threatening, but is otherwise quite bad enough, thank you very much.

With onions, the culprit is a group of sugars known as fructans: so, technically, what I am troubled with is not onion sensitivity, but fructan intolerance. And this is where things begin to get confusing - because not all fructans, and not all fructan-intolerant people, are built the same way.

Fructans - also known as fructo-oligosaccharides, or FOS - are complex sugars, built from two kinds of simple sugars, fructose and sucrose. The fructose molecules form chains which grow until they are capped off at their growing ends by sucrose molecules. These chains may be either long or short, and either straight or branched; the length and branching characteristics of the fructose chains are one factor contributing to the different effects of fructan-containing foods on different people. There are two other factors: differences in the amounts and types of other chemicals carried by a food, and differences in human metabolisms.

We'll take the human factor first. Humans have problems with complex sugars in general - we lack the enzymes necessary to break them down. Nearly all of the complex sugars that we ingest go straight through the stomach and small intestine and end up in the large intestine, which is the home of most of our intestinal fauna - the bacteria and other microorganisms we count on to do the final stages of digestion for us. A normal human digestive tract has a well-balanced community of intestinal fauna. People with food sensitivities do not. Something present in the body - some byproduct of metabolism, some secretion from an overactive gland - tilts the mix, either by selectively killing certain species of bacteria or by making it difficult for them to reproduce. Either way, some necessary components of the intestinal fauna disappear. And the rest proceed to go haywire.

The problem is not, actually, that the fructans don't get eaten by bacteria. The problem is that they get gorged on. By bacteria that produce huge amounts of gas. They also produce solid waste products that are hygroscopic - that means "water-absorbing" - which draw water from the body into the lower intestine, accounting for both the bloated abdomen and for the diarrhea which follows.

So that's the second factor: the tiny differences in cell metabolism that are part of the normal variation across any species, humans included. It's the third factor where things start getting really screwy, however. It turns out that if fructans are accompanied by certain other chemicals, balance returns. The trouble is that it is difficult to identify those chemicals, because they also vary according to invidual human metabolisms. Sucrose appears to be pretty universal - the more sucrose a food contains, the less likely its fructans are to cause problems. Other things? Your guess is as good as mine - or as the guesses of the scientists who study them.

And now we have three variables - fructan content, human metabolic differences, and other food chemicals - interacting more or less randomly with each other - only one of which, the fructan content, is quantifiable to any significant extent. As a consequence, fructan intolerance is wildly unpredictable. The effects are always roughly the same, but what triggers them varies enormously. Tiny amounts of onions cause me serious problems, but I can eat moderate amounts of garlic - which contains up to 17 times as many fructans per unit volume as onions do. Other fructan-intolerants can eat onions, but not garlic. Wheat is moderately high in fructans, but causes me little difficulty; others react strongly to it, often mistaking their reactions for gluten intolerance. I have to avoid the cabbage family (cabbage, broccoli, brussels sprouts, cauliflower, etc.); others can eat them without harm. Sometimes what causes the symptoms to appear is a mystery, in which case it is usually put down as "irritable bowel syndrome" - a condition which is probably largely, if not completely, a form of fructan intolerance rather than a separate syndrome.

And as you age, all of this grows worse. At my current age - rapidly approaching 76 - it has become bad enough that I no longer try new foods unless I know all of the ingredients, and know that all of them are safe. This means I have to pick restaurants carefully, and must check the menu thoroughly before I order. I have to avoid almost all ethnic restaurants, especially Asian, African, and Middle Eastern (including Greek, which I love) - they use too many ingredients that I have no experience with and, as a result, nothing on their menus is predictably safe. Vegan cuisine is now also out, as a result of a recent incident. Clam chowder - a longtime favorite - has recently become suspect (I have had to drop from bowl-sized servings to cup-sized servings at my favorite seafood place). I still eat Mexican food, but I always order the same thing, cheese enchiladas without salsa - usually safe, though I have been fooled a time or two by cooks who included onions in them. Onions in unexpected places, like enchiladas - or BLTs - are my constant fear. Macaroni and cheese? Who puts onions in that? But some people do - and I can no longer order it without checking.

And, of course, this affects my social life. Other people's cooking is dangerous, unless they cook with the same foods I do. I stopped attending potlucks years ago; as of this month, I have also decided to stop accepting dinner invitations unless I can control the recipes used (because I dislike being a control freak, this will probably actually mean I decline all invitations, period). I love sharing conversation over food, but from now on, I will have to do it only in restaurants - and then, only in those restaurants I have reason to believe will be safe.

So this is a long, long explanation of the plea I am about to make to all my friends: please do not be offended when I turn down your invitation to dinner, or to lunch, or to your favorite restaurant (unless it is one I already know and trust). I am not being unfriendly, or eccentric, or even picky; I am just trying to keep from getting sick.