Adding onions, garlic and other spices to food
does a lot more than make meals taste better. Research shows that
the spicy cuisine of some cultures developed not because of taste
alone—rather, spices hold antibiotic properties that kill bacteria
that would otherwise contaminate food.
Garlic, onion, allspice and oregano contain powerful
bacteria-fighting compounds and are the most powerful of the
antibiotic spices, according to researchers at Cornell University,
whose findings were published in the March 1998 Quarterly Review of
Biology. Those spices killed all thirty microorganisms they were
tested against, including E. coli and Salmonella, two bacteria that
cause food poisoning.
Further, the study found a direct link between a country’s
climate and the type and amount of spices used in cultural dishes.
The researchers theorized that spicy cuisine—which is usually
associated with warm-climate cultures and commonly contains high
amounts of garlic and onion—may be born of necessity: Food spoils
faster in warmer climates, and spices inhibit that.
The researchers noted that chiles and other hot peppers also are
common ingredients in dishes in warmer countries; they found that
capsicums, a name that refers to various pepper plants, kill up to
75 percent of bacteria in laboratory tests.
Spice Use North to South
Paul Sherman, an evolutionary biologist and professor of
neurobiology and behavior at Cornell, and colleague Jennifer
Billing analyzed forty-three spices used in more than 4,500
traditional meat recipes from thirty-six countries. The spices
ranged from the relatively bland parsley and sage to the more
pungent bay leaves and mustard. Spices that don’t have strong
antibiotic power—those that kill only 25 percent of bacteria in
tests—include white and black pepper, ginger, aniseed, celery seed
and the juice of lemon and lime, according to the study.
The researchers also analyzed spice use by individual countries
and found that hot spices were commonly used in the warmer climates
of Thailand and India, for example, but sparingly or not at all in
such cold-climate countries as Norway and Sweden.
In more than 80 percent of Indian recipes, onions, ginger,
capsicums and garlic were used more than 76 percent of the time,
the researchers found. By contrast, Norwegian recipes called mostly
for black and white pepper, and spices were used in only half of
the seventy-seven Norwegian recipes studied. Onions were used in a
mere 20 percent of those recipes, and peppers weren’t included at
The study showed a similar climate-spice correlation for the
United States, exemplified by the spicy Cajun food of Louisiana and
the blander meals of New England.
The researchers also compared the rate of food poisoning in
Japan and Korea, two countries with similar climates but a
surprising variation in foodborne illnesses. In Japan, nearly
thirty cases of food poisoning for every 100,000 people were
reported between 1971 and 1990, compared with only three cases per
100,000 people in Korea. The researchers speculated that the lower
number of food-poisoning cases in Korea may be because Korean food
is spicier than the more delicate flavors of Japanese cuisine.
According to Sherman, when Japanese recipes were created, fresh
fish was perhaps more readily available and fewer spices were
needed to kill bacteria. But today, he says, fish may not be as
fresh, and the original, non-spicy recipes may be insufficient to
kill bacteria, so more food poisoning occurs.
The Spicier, the Better?
Although the Cornell researchers acknowledge that spices are
used foremost as flavoring, they say that spices ultimately are
used to rid foods of pathogens, leading to the good health and
survival of the people who use them.
“There’s a correlation between what tastes good and what’s good
for you,” Sherman says.
Spice use evolved by people watching and imitating how others
prepared their food, he says. When people eating spicy foods
weren’t getting sick as often as their neighbors who ate spice-free
food, spices were incorporated into the cuisine, and the culture
developed a taste for them.
And it seems that the more spices used on food, the better. The
researchers found that combined herbs may have more powerful
antibiotic effects than herbs used alone. Such combinations include
chili powder, made up of red pepper, onion, paprika, garlic, cumin,
and oregano and five-spice powder, which contains pepper,
cinnamon, anise, fennel and cloves.
“Blends used habitually together may be especially potent
synergistic combinations,” says Sherman, adding that white and
black pepper and the juice of lemon and lime are notable synergists
and increase the effectiveness of other spices.
Take salsa, for example. Loaded with hot peppers, onions and
garlic, this spicy sauce typical of warm-climate cuisines is a
microorganism’s nightmare because of each spice’s ability to fight
bacteria. Add a squeeze of lime and you’ve got a really potent
Antibiotic compounds evolved in plants to deter threatening
invaders such as fungi, bacteria and insects. These secondary
compounds aren’t required for the plant’s basic metabolism but do
contribute to its flavor and are the result of an evolutionary
protection response by the plant, Sherman says.
“We’re using the plants’ recipes in our own recipes, and for
basically the same purpose,” he says.