Food-borne Disease and Food Safety
Food-borne Disease and Food Safety
Food-borne Disease and Food Safety
Food is necessary for our growth and survival. The nutrients in many foods that are vital to humans, however, also provide a meal for microorganisms. The organic (carbon-containing) compounds and moisture content of many foods permit the growth of microbes. Sometimes this co-existence is beneficial. For example, bacteria in the genus Lactobacillus help produce yogurt. However, the presence of some microorganisms in foods threatens the food supply and the health of those who eat it.
Some bacteria that can form structures called spores can survive for extended periods of time in foods that are too acidic to permit growth of the bacteria. But, if the food is eaten, the spores can germinate and growth can resume in the more hospitable environment of the intestinal tract.
Bacteria, viruses, parasites, and the poisons (toxins) produced by some of the microbes cause more than 200 different food-borne diseases. This is a serious health threat worldwide. For example, in the United States, food-borne diseases occur an estimated 76 million times every year—affecting 30% of the population—and kills 7,000 to 9,000 people.
Food-borne illnesses tend to be from microorganisms that usually live in the intestinal tract. Generally, the illnesses produce intestinal upset, often with nausea and vomiting. Food-borne illnesses are commonly called “food poisoning”. However, the term food poisoning obscures the fact that there are several types of foodborne illnesses that vary in cause and severity. While mild to moderate illnesses tend to pass after a few days, more serious illnesses can cause kidney damage or failure, muscle paralysis, and death.
Death most often is due to the excessive loss of fluid that occurs in diarrhea. A person can lose fluid at a rate that is difficult to replace by drinking water. If they cannot get medical attention (such as the continual provision of fluids intravenously) they can go into shock and suffer organs failure.
In countries including the United States and Canada, Campylobacter jejuni is the leading cause of food-borne illness. The major source is poultry. The bacterium is a normal resident in the intestinal tract of poultry. When poultry such as chickens are slaughtered, the intestinal contents can be spread onto the skin. Even with washing of the carcasses, bacteria can remain stuck in crevasses and other areas on the surface. Indeed, monitoring studies have proven that 70–90% of the poultry that reaches the supermarket shelf is contaminated with C. jejuni.
Even with the hundreds of millions of poultry meals eaten in the United States each year, the number of illnesses produced by C. jejuni is relatively low. This is because the bacteria are very susceptible to heat, thorough cooking will kill the bacteria long before the meal is eaten. However, improper cooking and the re-contamination of cooked meat by, for example, laying the meat on a cutting board that has not been washed after use, sickens millions of American annually.
Another bacteria, Salmonella is the next leading cause of food-borne illness in the United States, with an estimated 1.3 million cases each year. The estimated medical cost of treating these illnesses is $260 million. There are hundreds of species of Salmonella, and dozens are capable of causing illness. For example, S. enteritidis is commonly associated with egg containing prepared salad dressing or custards that have been left for several hours at room temperature. This allows the contaminating bacteria to grow to numbers that cause disease when eaten.
The third leading cause of food-borne illness in the United States is Escherichia coli O157:H7 and related E. coli that cause severe intestinal illnesses (they are collectively known as enterohemorrhagic E. coli, or EHEC). Still other varieties of E. coli are normally found in the intestinal tract of humans and animals; these are usually harmless. However, strain O157:H7 arose in the 1970s when genetic material from another bacterium called Shigella was somehow transferred to E. coli. The genetic material coded for the production of a very potent toxin, and made the new E. coli extremely dangerous. The toxin damages intestinal cells, which causes bleeding, and can spread via the bloodstream to the kidneys, potentially causing permanent organ damage or failure.
O157:H7 can be a normally part of the bacterial community found in the intestinal tract of cattle. The illness is usually produced when cattle feces contaminate drinking water. As well, the bacterium can contaminate ground beef during slaughter and packaging. As with Campylobacter, inadequate cooking allows the bacteria to remain alive. Vegetables can also become contaminated by manure supplied as fertilizer. Raw vegetables should be thoroughly washed before consumption. In September, 2006, contamination of organically grown spinach with O157:H7 killed three people and sickened hundreds in the United States.
Some bacteria in the genus Listeria also cause food-borne illnesses. Listeria monocytogenes, causes listerosis, a rare but serious illness. Listeria especially threatens people with compromised immune systems, the elderly, and pregnant women. In addition to the usual symptoms associated with food poisoning, listerosis can cause a severe form of meningitis. Listeria bacteria flourish in temperatures between 39°F(4°C) and 98.6°F (37°C).
Another common source of food-borne illness is a virus known as the Norwalk-like virus. The virus normally lives in the human intestinal tract, and is usually spread to food when the food is handled by people who have not washed their hands properly after a bowel movement. Over nine million infections are estimated to occur each year in the United States alone. Most of these could be eliminated by proper handwashing.
Food-borne infections can affect anyone, anywhere. The World Health Organization (WHO) estimates that over two million people around the world die each year from diarrhea caused by food-borne infections. Most deaths from food-borne illnesses occur in developing nations.
Because food-borne illnesses are mainly caused by microorganisms that are residents of the intestinal tract, most outbreaks are related to fecal contamination of food and water rather than to the time of year or particular aspect of a culture. Worldwide, poor hygiene is the culprit.
WORDS TO KNOW
FOOD PRESERVATION: The term food preservation refers to any one of a number of techniques used to prevent food from spoiling. It includes methods such as canning, pickling, drying and freeze-drying, irradiation, pasteurization, smoking, and the addition of chemical additives. Food preservation has become an increasingly important component of the food industry as fewer people eat foods produced on their own lands, and as consumers expect to be able to purchase and consume foods that are out of season.
IONIZING RADIATION: Any electromagnetic or particulate radiation capable of direct or indirect ion production in its passage through matter. In general use: Radiation that can cause tissue damage or death.
IRRADIATION: A method of preservation that treats food with low doses of radiation to deactivate enzymes and to kill microorganisms and insects.
IN CONTEXT: SCIENTIFIC, POLITICAL, AND ETHICAL ISSUES
Although food irradiation is opposed by some advocacy groups and research continues, Centers for Disease Control and Prevention (CDC) states that “food irradiation is a promising new application of an established technology. It holds great potential for preventing many important food-borne diseases that are transmitted through meat, poultry, fresh produce and other foods. An overwhelming body of scientific evidence demonstrates that irradiation does not harm the nutritional value of food, nor does it make the food unsafe to eat. Just as for the pasteurization of milk, it will be most effective when irradiation is coupled to careful sanitation programs. Consumer confidence will depend on making food clean first, and then using irradiation or pasteurization to make it safe. Food irradiation is a logical next step to reducing the burden of food-borne disease in the United States.”
Prevention of food-borne illness must consider a number of factors. The type of disease-causing organism can be important. For example, Campylobacter can be effectively treated by the proper cooking of foods, whereas Clostridium, which can form an environmental hardy structure called a spore, may still be capable of causing an infection even after heating of the food. The environment is another factor; temperature and the amount of moisture in the food can influence the type of organisms that can thrive. Environment also includes the various places that the food passes through on its way to the dinner table; a food entering a processing plant may be safe only to become contaminated during processing. These factors are inter-related. For example, protecting a food from questionable environments, but failing to decontaminate the food does little to lessen the chance of a food-borne illness.
Treatment of foods prior to eating is absolutely important in preventing illness. Some treatments, such as drying or preserving food in salt prior to a sea voyage, were done centuries ago. Canning of foods as a means of preservation and protection from spoilage began in the eighteenth century. In the nineteenth century, the association of an unhygienic environment and disease was recognized. As food began to be shipped further to market, the problem of food deterioration during transit became apparent.
Food safety owes a great deal to Louis Pasteur, who developed the process of pasteurization. Pasteurization began in the 1890s. The process heats milk for a short time at temperatures high enough to be lethal to those microbes that would be expected to be contaminants without altering the taste or appearance of the milk. Milk is now routinely pasteurized before sale. Innovations in the pasteurization technique have increased the shelf-life of refrigerated milk and developed means of transporting and storing milk without the need for refrigeration.
Another prevention strategy is the development and legal enforcement of standards of food preparation, handling and inspection. In many places, food quality must be demonstrated or else the product can be pulled from the shelf and, if necessary, those responsible for its manufacture or distribution prosecuted. In the United States, the Food and Drug Administration (FDA) regulates processing and labeling of most foods. However, the Department of Agriculture (USDA) regulates and oversees the safety of all meat, poultry, and egg products. The two agencies work together to ensure the safety of food produced within and imported into the United States. Both agencies also provide assistance to international organizations and developing nations who wish to implement or strengthen food safety programs.
While government agencies monitor the safety of food as it is produced and sold, monitoring food preparation and hygienic practices in the home must be done by individuals. Improper storage of foods prepared with raw or undercooked eggs, can cause growth of microorganisms in the food. Improper cleaning of cutting boards and other preparation surfaces can cross-contaminate one food by another. Many cases of food poisoning due to Clostidium botulium are related to improper home-canning of foods; the spores of the bacterium can survive the food preparation steps and remain capable of causing illness when the food is eaten, even years later.
The impact of food-borne illnesses on the individual is substantial. The 76 million food-borne illnesses that are thought to occur each year (likely an underestimate, since many people will suffer from an illness without seeking medical attention) hospitalizes 325,000 people and kills 7,000 to 9,000, according to the Centers for Disease Control and Prevention. Society suffers as well; medical costs, lost work days, travel costs to seek treatment, and the premature loss of people who would otherwise contribute wealth to the economy costs the United States almost seven billion dollars a year.
In February 2007, peanut butter was responsible for a nationwide Salmonella outbreak in the United States affecting over 300 people in approximately 40 states. The FDA warned consumers not to purchase or eat certain brands of peanut butter manufactured at a facility in Georgia. Soon afterwards, companies with brands associated with the salmonella outbreak recalled all potentially contaminated products. While Salmonella is typically associated with poultry products, the 2007 outbreak was not the first associated with peanut butter. A similar Salmonella event that occurred in Australia in the mid–1990s was traced to contaminated peanut butter.
In underdeveloped countries, where medical care is not as available or advanced, food-borne illnesses can be even more devastating. Diarrheal illnesses afflict millions of people every year, many of them are children. The illnesses are a major cause of the malnutrition that is a part of everyday life in many underdeveloped regions.
Prevention of food-borne illnesses does have some controversial aspects. Many food safety organizations advocate irradiation, or cold pasteurization, as method of preventing food-borne illnesses. Irradiation involves exposing food to extremely low levels of ionizing radiation to sterilize food. Proponents cite irradiation's ability to the causes of harmful bacteria such as E. coli, Listeria, and S. enteritidis. Irradiation can also destroy parasites and agricultural pests, as well as prolong the shelf-life of fruits and vegetables by preventing sprouting and delaying spoilage. Critics of irradiation cite the use of radioactive materials in some (mostly older) irradiation technology as a potential environmental and health threat. Others assert that irradiation forms new chemical compounds in treated foods and that the long-term effects of ingesting irradiated products have not been thoroughly studied. Furthermore, while irradiation is effective at killing the sources of many food-borne illnesses, food can still become contaminated after irradiation by improper storage or handling. Irradiation is approved to sterilize meat, egg, poultry, and other agricultural products in several countries, and most require labeling to indicate its use.
A food safety issue that has become more urgent since the 2001 terrorist attacks in the United States is the monitoring of foods to ensure their safety from deliberate tampering. The chain from the field to the supermarket leaves food vulnerable to the deliberate addition of microbiological agents that cause illness or death. While storage conditions, monitoring programs and even the design of packing that can detect contamination is useful in protecting foods from accidental contamination, it is very difficult to protect food from deliberate harm.
IN CONTEXT: EFFECTIVE RULES AND REGULATIONS
The Food and Drug Administration (FDA), one of the oldest consumer protection agencies in the United States (formed in 1927), is charged with the responsibility to ensure that foods are safe and wholesome, that medicines and medical devices are safe and effective, that cosmetics and products that emit radiation are harmless, and that products are honestly labeled and packaged. FDA is also responsible for feed and drugs for pets and farm animals.
Federal law requires that food manufacturers place labels on most foods. The food label must provide complete, useful, and accurate nutrition information. The requirement that packaged food be labeled has the effect of raising the quality of foods sold. It also gives the consumer a basis for making healthy food choices. Food labels appear in a consistent format to facilitate direct comparisons of the nutritional contents of various foods. These labels always appear on a package under the title Nutrition Facts.
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United States Food & Drug Administration. Bad Bug Book: food-borne Pathogenic Microorganisms and Natural Toxins Handbook. McLean: International Medical Publishing, 2004.