Sometimes I dream about apples. Big red sweet apples, small green tart ones…forget visions of sugar plums, a gleaming apple is all it takes to make my mouth water! Yet it has been years since I have had a single juicy slice. In the past, I frequently munched on apples with blissful abandon, but when I hit my twenties, something changed. Apples started giving me stomachaches; a cup of apple juice would have me doubled over with gut pain. This delicious, healthy food suddenly seemed to be attacking me from the inside out!
At first I thought maybe I had developed an allergy to this beloved fruit, but the symptoms didn’t seem quite right. Then I recognized that other fruits caused similar unpleasantness, though less severe. As I crossed watermelon, pears and grapes off my “eat anytime” list, I finally determined that my problem was not an allergy, but rather something called a food intolerance or sensitivity. Similar to the more common lactose intolerance or gluten sensitivity, I am sensitive to a specific type of sugar called fructose.
So what is the difference between a food allergy and a food intolerance anyway? For one thing, a food allergy is downright dangerous, while a food intolerance is mostly just unpleasant. A food allergy, like other allergies, is an immune response. As food is broken down in the gut, a certain protein or molecular fragment might be mistakenly identified as a threat to the body. The next time the food is consumed the immune system will launch a full-out attack, creating an inflammatory response. Usually inflammation helps fight against a virus or bacteria, but in food allergies it can cause swollen tongue or lips, trouble breathing, or stomach cramps. In severe cases, the allergic response can lead to death if untreated.
On the other hand, a food intolerance is a purely digestive response. Proper food digestion includes two key steps: food must be broken down, usually with the help of many molecule-specific enzymes; then, food molecules are absorbed into the bloodstream, often pumped via transporter proteins in the small intestine. A food intolerance happens when one of these key steps is hindered. Lactose intolerance stems from insufficient lactase enzymes, while fructose malabsorption occurs because of problems with the fructose transporter proteins. In either case, the undigested sugar (lactose or fructose) winds up in the colon, where gut bacteria metabolize it via fermentation. As any home-brewers out there know, fermentation can produce copious amounts of gas, which isn’t so fun to have filling up your large intestine. While this can be extremely unpleasant, it is not life-threatening, and symptoms can often be avoided by consuming only small amounts of offending foods.
It seems that food allergies, sensitivities and intolerances are on the rise lately. Certainly, public awareness of them has increased, and “gluten-free” or “lactose-free” labels now seem to merit their own sections of the supermarket. Some of this is increased commercial hype for specialty foods, as well as a wave of health-conscious eaters who try “free-from” diets in pursuit of different health benefits. However, childhood allergies are also more widespread, with old lunch-box standbys like the PBJ sandwich banned from schools for safety.
There are a few main theories about why digestive issues are becoming more common, and the true reason probably involves a complex interplay of these factors.
One proposed culprit is the modern Western diet, with processed foods that contain higher amounts of problem ingredients. Food engineering may also lead to problems, changing the nutritional makeup of food faster than our digestive systems can evolve. There is also the ”hygiene hypothesis”: we may be simply too clean. Without early exposure to germs and allergens, the immune system develops poorly and is unable to properly distinguish between them. Frequent antibiotic use also weakens the natural immune system, and can disrupt the balance of helpful bacteria that live in the gut.
Regardless of why they occur, food issues have led to a better understanding of how important it is to have a healthy gut. Digestive woes may be intimately linked to immune and even mental disorders. And whether you have a food intolerance or not, we can all benefit from paying closer attention to what we eat and how it affects our digestion, energy and mood. Hop over to Daniel Fisher’s great article on the “gut-brain axis” if you want to understand the many ways your gut bacteria can affect you. And then… eat an apple for me!