Editor’s Note

As a science teacher, do you find yourself fielding questions about everything from steroids to skin cance to swine flu? this is where Health Wise comes in. This column in The Science Teacher provides up-to-date information on personal health topics to share with your students to help them make healthy choices every day!

What causes foodborne illness, and how can I avoid it?

First, let’s clarify some terms. Foodborne disease includes food poisoning, which is caused by eating harmful toxins and chemicals (e.g., poisonous mushrooms), and foodborne illness, which occurs when we consume food contaminated by bacteria or other infectious organisms (i.e., viruses and parasites). When it comes to nasty bugs we get from food, foodborne illness is the most recognized offender.

Mild cases of foodborne illness causing symptoms for a couple of days are common. An estimated 76 million cases occur each year in the United States. However, more serious cases—most often affecting the very old or young and people with compromised immune systems—lead to an estimated 325,000 hospitalizations and 5,000 deaths each year (CDC 2005). The chief culprits of foodborne illness are Campylobacter (which live in the intestines of healthy birds); Salmonella (prevalent in bird, reptile, and mammal intestines); Escherichia coli (often found in cow feces); and Norwalk-like virus (most likely spread via infected persons) (CDC 2005).

Although bacteria are a widespread source of food illness, not all bacteria are harmful. Thousands of good bacteria are naturally present in our environment and our bodies. The bacteria and other microbes that cause disease are called “pathogens.” And when certain pathogens enter our food supply, they can make us sick.

After pathogens are swallowed, there is an incubation period—from hours to days—before the symptoms of illness occur. During this phase, microbes pass through the stomach into the intestine and attach to cells lining the intestinal walls. There, they begin to multiply. The pathogens may stay in the intestine, produce a toxin that is absorbed into the bloodstream, or directly invade other body tissues—at which point, the dreaded symptoms emerge. These depend greatly on the type of bacteria one is infected with, but diarrhea, abdominal cramps, and nausea are common.

Some foods are more likely to be contaminated than others. Raw foods of animal origin—meat and poultry, eggs, unpasteurized milk, and shellfish—are a gamble. Bulk raw milk, pooled raw eggs, ground beef, and other foods that combine the products of many individual animals are particularly risky because the pathogens present in just one of the animals can contaminate the whole batch. Raw fruits and vegetables are also among the usual suspects. Many outbreaks have been traced back to fresh fruits and vegetables processed under unsanitary conditions (e.g., rinsed with unclean water or fertilized with fresh manure) (CDC 2005).

A few simple precautions can reduce the risk of catching foodborne diseases. Wash your hands with soap and water before preparing food. Cook meat, poultry, and eggs thoroughly. Do not cross-contaminate foods. Refrigerate leftovers without delay. Wash produce thoroughly, and remove and discard the outermost leaves of lettuce and cabbage.

Finally, we are all responsible for food safety: Consumers should demand it, industry should work hard to ensure it, researchers should devise ways to improve it, and the government should regulate it.

Note: Health-related content appearing in these pages is intended for information only and is not presented as a substitute for individual medical advice, diagnosis, or treatment by a qualified health professional.

Acknowledgment

This column was reviewed by Jonathan Links, professor and deputy chair of Environmental Health Sciences, director of the Center for Public Health Preparedness, and deputy director of the Office of Critical Event Preparedness and Response at Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.

Reference

Centers for Disease Control and Prevention (CDC). 2005. Foodborne illness: Frequently asked questions. www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm#typeschanging.