Many people have experienced food addictions. Take chocolate, for example. To some people, chocolate is an occasional treat. But for a true chocolate addict, it is a deep-seated need.

University of Michigan researchers showed that chocolate does not merely tickle your taste buds; it actually works inside your brain in much the same way opiate drugs do. The researchers gave 26 volunteers a drug called naloxone, an opiate-blocker used in emergency rooms to stop heroin, morphine, and other narcotics from affecting the brain. It turned out that naloxone blocked much of chocolate's appeal. When they offered volunteers a tray filled with Snicker's bars, M & M's, chocolate chip cookies, and Oreos, chocolate was not much more exciting than a crust of dry bread.

In other words, chocolate's attraction does not come simply from its creamy texture or deep brown color. It appears to stimulate the same part of the brain that morphine acts on. For all intents and purposes, it is a drug-not necessarily a bad one and not a terribly strong one, but strong enough nonetheless to keep us coming back for more.

As common as chocolate addiction may be, it is by no means the only potentially addictive food, nor is it the most dangerous. In PCRM's research studies, when we take people off meat, dairy products, and other unhealthy fare, we often find that the desire for cheese, in particular, lingers on much more strongly than for other foods. While they might like ice cream or yogurt, they describe their feelings for cheese as a deep-seated craving. Could cheese really be addictive?

Well, in 1981, Eli Hazum and his colleagues at Wellcome Research Laboratories in Research Triangle Park, N.C., reported a remarkable discovery. Analyzing samples of cow's milk, they found traces of a chemical that looked very much like morphine. They put it to one chemical test after another. And, finally, they arrived at the conclusion that, in fact, it is morphine. There is not a lot of it and not every sample had detectable levels. But there is indeed some morphine in both cow's milk and human milk.

Morphine, of course, is an opiate and is highly addictive. So how did it get into milk? At first, the researchers theorized that it must have come from the cows' diets. After all, morphine used in hospitals comes from poppies and is also produced naturally by a few other plants that the cows might have been eating. But it turns out that cows actually produce it within their bodies, just as poppies do. Traces of morphine, along with codeine and other opiates, are apparently produced in cows' livers and can end up in their milk.

But that was only the beginning, as other researchers soon found. Cow's milk-or the milk of any other species, for that matter-contains a protein, called casein, that breaks apart during digestion to release a whole host of opiates, called casomorphins. A cup of cow's milk contains about six grams of casein. Skim milk contains a bit more, and casein is concentrated in the production of cheese.

If you examined a casein molecule under a powerful microscope, it would look like a long chain of beads (the "beads" are amino acids-simple building blocks that combine to make up all the proteins in your body). When you drink a glass of milk or eat a slice of cheese, stomach acid and intestinal bacteria snip the casein molecular chains into casomorphins of various lengths. One of them, a short string made up of just five amino acids, has about one-tenth the pain-killing potency of morphine.

What are these opiates doing there, hidden in milk proteins? It appears that the opiates from mother's milk produce a calming effect on the infant and, in fact, may be responsible for a good measure of the mother-infant bond. No, it's not all lullabies and cooing. Psychological bonds always have a physical underpinning. Like it or not, mother's milk has a drug-like effect on the baby's brain that ensures that the baby will bond with Mom and continue to nurse and get the nutrients all babies need. Like heroin or codeine, casomorphins slow intestinal movements and have a decided antidiarrheal effect. The opiate effect may be why adults often find that cheese can be constipating, just as opiate painkillers are.

It is an open question to what extent dairy opiates enter the adult circulation. Until the 1990s, researchers thought that these protein fragments were too large to pass through the intestinal wall into the blood, except in infants, whose immature digestive tracts are not very selective about what passes through. They theorized that milk opiates mainly acted within the digestive tract and that they signaled comfort or relief to the brain indirectly, through the hormones traveling from the intestinal tract to the brain.

But French researchers fed skim milk and yogurt to volunteers and found that, sure enough, at least some casein fragments do pass into the bloodstream. They reach their peak about 40 minutes after eating.

Cheese contains far more casein than other dairy products do. As milk is turned into cheese, most of its water, whey proteins, and lactose sugar are removed, leaving behind concentrated casein and fat.

Cheese holds other drug-like compounds as well. It contains an amphetamine-like chemical called phenylethylamine, or PEA, which is also found in chocolate and sausage. And there are many hormones and other compounds in cheese and other dairy products whose functions are not yet understood. In naloxone tests, the opiate-blocking drug eliminates some of cheese's appeal, just as it does for chocolate.

Cheese Heads, Meat Heads

Meat-lovers defend their food of choice with remarkable ferocity. An April 2000 survey of 1,244 adults revealed that about one in four Americans wouldn't give up meat for a week even if they were paid $1,000 to do it. People from Asian and Hispanic backgrounds were more willing to accept the hypothetical offer (fewer than 10 percent turned it down), presumably because meatless choices are major parts of their traditional cuisines. But others were more reluctant, with 24 percent of whites and 29 percent of blacks absolutely unwilling to swap meat for cash. Cholesterol, fat, salmonella, E. coli, Mad Cow disease, and foot and mouth disease may come and go in the public's mind, yet meat-eating goes on.

The reason may be physical, just as it appears to be for chocolate or cheese. British researchers found that opiate-blocking drugs cut the appetite for ham by ten percent, knocked out the desire for salami by about twenty-five percent, and cut tuna consumption by nearly half. In other words, a person might still eat some of it to quell hunger or simply out of habit. But blocking an opiate response knocks out the added chemical appeal a food may have, reducing the tendency to choose it.

Detoxing

If you are hooked on sugar, chocolate, cheese, or meat, what do you do about it? Actually, foods can come to your rescue. If you start your day with a good breakfast, hunger is less likely to fuel cravings. And if your lunch, dinner, and snacks include foods that keep your blood sugar steady throughout the day-beans, green vegetables, unprocessed grains, and fruits, for example, instead of sugary foods or white bread-you'll be less likely to dip into unhealthy foods later on.

Be sure to eat enough food, so that your appetite-taming hormone leptin is working right. Leptin shuts down whenever you go on a starvation diet, leaving your appetite out of control. Exercise, rest, and social support all help, too.

And there's nothing like taking a three-week break from unhealthy foods. A low-fat, vegan diet skips the worst of the food seductions. And if, for even a few weeks, you set aside whatever foods are leading you astray, you'll find your resolve is much stronger than if you had had them yesterday.

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