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.
consumption in the U.S. rose from 15 pounds per person per
year in 1975 to more than 30 pounds in 1999. And you can thank
the federal government. The USDA Report to Congress on the
Dairy Promotion Programs for the year 2000 described how the
government and industry worked with fast-food chains to make
sure that cheese was prominently displayed in menu items.
One federally sanctioned program launched Wendy's Cheddar
Lover's Bacon Cheeseburger, which single-handedly pushed 2.25
million pounds of cheese during the promotion period. Another
promoted Pizza Hut's "Ultimate Cheese Pizza"-with
an entire pound of cheese per pizza-selling five million pounds
of it during a six-week promotion in 2000. In 1996, cheese
was not a required ingredient in Subway sandwiches. So a similar
federal program helped the restaurant chain promote cheese
and include it as a required ingredient in two new sandwiches,
the Chicken Cordon Blue and Honey Pepper Melt, anticipating
the sale of an extra 70,000 pounds of cheese.
a "Cheese Forum" held December 5, 2000, Dick Cooper,
the Vice President of Cheese Marketing for Dairy Management,
Inc., showed slide after slide detailing the industry's plans
for pushing cheese in grocery chains, food services, and fast-food
restaurants. One slide asked the question, "What do we
want our marketing program to do?" and then gave the
answer: "Trigger the cheese craving." He concluded
with a cartoon of a playground slide with a large spider web
woven to trap children as they reached the bottom. The caption
had one spider saying to another, "If we pull this off,
we'll eat like kings."
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.
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.
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.
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.
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.
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.
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