"It must be something I ate," is often the explanation people give for a bout of home-grown "Montezuma's Revenge" (acute diarrhea) or some other unwelcome gastrointestinal upset.

Despite the fact that America's food supply is the safest in the world, the unappetizing truth is that what we eat can very well be the vehicle for food-borne illnesses that can cause a variety of unpleasant symptoms and may be life-threatening to the less healthy among us. Seventy-six of million cases of food-borne diarrheal disease occur in the United States every year.

The Food and Drug Administration has given high priority to combating microbial contamination of the food supply. But the agency can't do the job alone.

Consumers have a part to play, especially when it comes to following safe food handling practices in the home.

The prime causes of food-borne illness include bacteria, parasites and viruses such as: Escherichia coli O157:H7, Campylobacter jejuni, Salmonella, Staphylococcus aureus, Listeria monocytogenes, Clostridium perfringens, Vibrio parahaemolyticus, Vibrio vulnificus, Shigella, Giardia lamblia, Cyclospora cayetanensis, Cryptosporidium parvum, hepatitis A virus, and Norwalk and Norwalk-like virus.

These organisms can become unwelcome guests at the dinner table. They're in a wide range of foods, including meat, milk and other dairy products, spices, chocolate, seafood, and even water.

Unpasteurized fruit and vegetable juices and ciders; foods made with raw or undercooked eggs; chicken, tuna, potato and macaroni salads; and cream-filled pastries harboring these pathogens also have been implicated in food-borne illnesses, as has fresh produce.

Poultry is the food most often contaminated with disease-causing organisms. It's been estimated that 60 percent or more of raw poultry sold at retail probably carries some disease-causing bacteria.

Bacteria such as Listeria monocytogenes, Vibrio vulnificus, Vibrio parahaemolyticus and Salmonella have been found in raw seafood. Oysters, clams, mussels, scallops, and cockles may be contaminated with hepatitis A virus.

Careless food handling sets the stage for the growth of disease-causing "bugs." For example, hot or cold foods left standing too long at room temperature provide an ideal climate for bacteria to grow. Improper cooking also plays a role in food-borne illness.

Foods may be cross-contaminated when cutting boards and kitchen tools that have been used to prepare a contaminated food, such as raw chicken, are not cleaned before being used for another food such as vegetables.

Symptoms

Common symptoms of food-borne illness include diarrhea, abdominal cramping, fever, sometimes blood or pus in the stools, headache, vomiting, and severe exhaustion. However, symptoms will vary according to the type of bacteria and by the amount of contaminants eaten.

In rare instances, symptoms may come on as early as a half hour after eating the contaminated food but they typically do not develop for several days or weeks. Symptoms of viral or parasitic illnesses may not appear for several weeks after exposure. Symptoms usually last only a day or two, but in some cases can persist a week to 10 days. For most healthy people, food-borne illnesses are neither long-lasting nor life-threatening. However, they can be severe in the very young, the very old, and people with certain diseases and conditions.

These conditions include:

• liver disease, either from excessive alcohol use, viral hepatitis, or other causes
• hemochromatosis, an iron disorder
• diabetes
• stomach problems, including previous stomach survery and low stomach acid (for example, from antacid use)
• cancer
• immune disorder, including HIV infection
• long-term steroid use, as for asthma and arthritis.

When symptoms are severe, the victim should see a doctor or get emergency help. This is especially important for those who are most vulnerable. For mild cases of food poisoning, liquid intake should be maintained to replace fluids lost through vomiting and diarrhea.

Prevention Tips

The idea that the food on the dinner table can make someone sick may be disturbing, but there are many steps you can take to protect your families and dinner guests. It's just a matter of following basic rules of food safety.

Prevention of food poisoning starts with your trip to the supermarket. Pick up your packaged and canned foods first. Don't buy food in cans that are bulging or dented or in jars that are cracked or have loose or bulging lids. Look for any expiration dates on the labels and never buy outdated food. Likewise, check the "use by" or "sell by" date on dairy products such as cottage cheese, cream cheese, yogurt, and sour cream and pick the ones that will stay fresh longest in your refrigerator.

If you have a health problem, especially one that may have impaired your immune system, don't eat raw shellfish and use only pasteurized milk and cheese, and pasteurized or concentrated ciders and juices.

Choose eggs that are refrigerated in the store. Before putting them in your cart, open the carton and make sure that the eggs are clean and none are cracked.

Select frozen foods and perishables such as meat, poultry or fish last. Always put these products in separate plastic bags so that drippings don't contaminate other foods in your shopping cart.

Don't buy frozen seafood if the packages are open, torn or crushed on the edges. Avoid packages that are above the frost line in the store's freezer. If the package cover is transparent, look for signs of frost or ice crystals. This could mean that the fish has either been stored for a long time or thawed and refrozen.

Check for cleanliness at the meat or fish counter and the salad bar. For instance, cooked shrimp lying on the same bed of ice as raw fish could become contaminated.

When shopping for shellfish, buy from markets that get their supplies from state-approved sources; stay clear of vendors who sell shellfish from roadside stands or the back of a truck. And if you're planning to harvest your own shellfish, heed posted warnings about the safety of the water.

Take an ice chest along to keep frozen and perishable foods cold if it will take more than an hour to get your groceries home.

Safe Storage

The first rule of food storage in the home is to refrigerate or freeze perishables right away. Refrigerator temperature should be 5 degrees Celsius (41 degrees Fahrenheit), and the freezer should be -18 C (0 F). Check both "fridge" and freezer periodically with a good thermometer.

Poultry and meat heading for the refrigerator may be stored as purchased in the plastic wrap for a day or two. If only part of the meat or poultry is going to be used right away, it can be wrapped loosely for refrigerator storage. Just make sure juices can't escape to contaminate other foods. Wrap tightly foods destined for the freezer. Leftovers should be stored in tight containers. Store eggs in their carton in the refrigerator itself rather than on the door, where the temperature is warmer.

Seafood should always be kept in the refrigerator or freezer until preparation time.

Don't crowd the refrigerator or freezer so tightly that air can't circulate. Check the leftovers in covered dishes and storage bags daily for spoilage. Anything that looks or smells suspicious should be thrown out.

A sure sign of spoilage is the presence of mold, which can grow even under refrigeration. While not a major health threat, mold can make food unappetizing.

Most moldy foods should be thrown out. But you might be able to save molding hard cheeses, salami, and firm fruits and vegetables if you cut out not only the mold but a large area around it. Cutting the larger area around the mold is important because the poisons that cause mold to form are found under the surface of the food.

Many items besides fresh meats, vegetables, and dairy products need to be kept cold. For instance, mayonnaise and ketchup should go in the refrigerator after opening. Always check the labels on cans or jars to determine how the contents should be stored. If you've neglected to refrigerate items, it's usually best to throw them out.

For foods that can be stored at room temperature, some precautions will help make sure they remain safe. Potatoes and onions should not be stored under the sink, because leakage from the pipes can damage the food. Potatoes don't belong in the refrigerator either. Store them in a cool, dry place. Don't store foods near household cleaning products and chemicals.

Check canned goods to see whether any are sticky on the outside. This may indicate a leak. Newly purchased cans that appear to be leaking should be returned to the store, which should notify FDA.

Keep It Clean

The first cardinal rule of safe food preparation in the home is: Keep everything clean.

The cleanliness rule applies to the areas where food is prepared and, most importantly, to the cook. Wash hands with warm water and soap for at least 20 seconds before starting to prepare a meal and after handling raw meat or poultry. Cover long hair with a net or scarf, and be sure that any open sores or cuts on the hands are completely covered. If the sore or cut is infected, stay out of the kitchen.

Keep the work area clean and uncluttered. Wash countertops with a solution of 5 milliliters (1 teaspoon) chlorine bleach to about 1 liter (1 quart) of water or with a commercial kitchen cleaning agent diluted according to product directions. They're the most effective at getting rid of bacteria.

Also, be sure to keep dishcloths and sponges clean because, when wet, these materials harbor bacteria and may promote their growth. Wash dishcloths and sponges weekly in the washing machine in hot water.

While you're at it, sanitize the kitchen sink drain periodically by pouring down the sink a solution of 5 milliliters bleach to 1 liter water or a commercial cleaning agent. Food particles get trapped in the drain and disposal and, along with moistness, create an ideal environment for bacterial growth.

Use smooth cutting boards made of hard maple or plastic and free of cracks and crevices. Avoid boards made of soft, porous materials. Wash cutting boards with hot water, soap, and a scrub brush. Then, sanitize them in an automatic dishwasher or by rinsing with a solution of 5 milliliters chlorine bleach to about 1 liter of water.

Always wash and sanitize cutting boards after using them for raw foods, such as seafood or chicken, and before using them for ready-to-eat foods. Consider using one cutting board only for foods that will be cooked, such as raw fish, and another only for ready-to-eat foods, such as bread, fresh fruit, and cooked fish.

Always use clean utensils and wash them between cutting different foods.

Wash the lids of canned foods before opening to keep dirt from getting into the food. Also, clean the blade of the can opener after each use. Food processors and meat grinders should be taken apart and cleaned as soon as possible after they are used.

Do not put cooked meat on an unwashed plate or platter that has held raw meat.

Wash fresh fruits and vegetables thoroughly, rinsing in warm water. Don't use soap or other detergents. If necessary--and appropriate--use a small scrub brush to remove surface dirt.

Keep Temperature Right

The second cardinal rule of home food preparation is: Keep hot foods hot and cold foods cold.

Use a thermometer to ensure that meats are completely cooked. Use a thermometer with a small-diameter stem. Insert the thermometer 1 to 2 inches into the center of the food and wait 30 seconds to ensure an accurate measurement. For instance, beef, lamb, and pork should be cooked to at least 71 C (160 F); whole poultry and thighs to 82 C (180 F); poultry breasts to 77 C (170 F); ground chicken or turkey to 74 C (165 F). Don't eat poultry that is pink inside./P>

Eggs should be cooked until the white and the yolk are firm. Avoid foods containing raw eggs, such as homemade ice cream, mayonnaise, eggnog, cookie dough, and cake batter, mayonnaise, and eggnog, because they carry a Salmonella risk. Their commercial counterparts usually don't because they're made with pasteurized eggs. Cooking the egg-containing product to an internal temperature of at least 71 C (160 F) will kill the bacteria.

Seafood should be thoroughly cooked. FDA's 1999 Food Code recommends cooking most seafood to an internal temperature of 63 C (145 F) for 15 seconds. If you don't have a meat thermometer, look for other signs of doneness. For example:

• Fish is done when the thickest part becomes opaque and the fish flakes easily when poked with a fork.
• Shrimp can be simmered 3 to 5 minutes or until the shells turn red.
• Clams and mussels are steamed over boiling water until the shells open (5 to 10 minutes). Then boil 3 to 5 minutes longer.
• Oysters should be sautéed, baked or boiled until plump, about 5 minutes.

Protect food from cross-contamination after cooking, and eat it promptly.

Cooked foods should not be left standing on the table or kitchen counter for more than two hours. Disease-causing bacteria grow in temperatures between 4 and 60 C (40 and 140 F). Cooked foods that have been in this temperature range for more than two hours should not be eaten.

If a dish is to be served hot, get it from the stove to the table as quickly as possible. Reheated foods should be brought to a temperature of at least 74 C (165 F). Keep cold foods in the refrigerator or on a bed of ice until serving. This rule is particularly important to remember in the summer months.

After the meal, leftovers should be refrigerated as soon as possible. (Never mind that scintillating dinner table conversation!) Meats should be cut in slices of three inches or less and all foods should be stored in small, shallow containers to hasten cooling. Be sure to remove all the stuffing from roast turkey or chicken and store it separately. Giblets should also be stored separately. Leftovers should be used within three days.

And here are just a few more parting tips to keep your favorite dishes safe. Don't thaw meat and other frozen foods at room temperature. Instead, move them from the freezer to the refrigerator for a day or two; or defrost submerged in cold water flowing fast enough to break up and float off loose particles in an overflow; in the microwave oven, or during the cooking process. Never taste any food that looks or smells "off," or comes out of leaking, bulging or severely damaged cans or jars with leaky lids.

Though all these do's and don'ts may seem overwhelming, remember, if you want to stay healthy, when it comes to food safety, the old saying "rules are made to be broken" does not apply!