Family Medicine
Question: We are planning a picnic this 4th of July, and I’m concerned about making sure that it’s safe and that we don’t end up with food poisoning. I know that mayonnaise should be avoided in picnic food. Can you give me any other picnic safety tips? Answer: You are wise to be thinking ahead; however, you repeated an old myth in your question. Mayonnaise is not a frequent culprit in picnic food poisoning cases.
This mayonnaise myth seems to get repeated from generation to generation. It probably stems from the large number of food poisoning cases over the years that was blamed on contaminated potato salad containing mayonnaise. Actually, while potato salad can be the source of several types of food poisoning, the problem in these cases was probably improper food storage or handling – not the presence of mayonnaise.
In fact, you might be surprised to learn that the mayonnaise itself may have made the situation a little better in these food poisoning cases than it would otherwise have been. This is because most brands of mayonnaise contain some vinegar, which makes it more acidic, and this inhibits the growth of the bacteria that can cause food poisoning.
The most common cause of food poisoning at picnics is actually improperly prepared or stored meats. The bacterium most often responsible is Campylobacter jejuni. It is followed by Salmonella enteritidis and Staphylococcus aureus.
C. jejuni takes two to five days to produce illness. Symptoms are often relatively mild – fever, watery diarrhea, headache and muscle aches. These bacteria can be found in raw poultry, raw milk and water contaminated by animal feces.
S. enteritidis bacteria can be present in dairy products, eggs, beef and poultry. Once the tainted food is consumed, the bacteria reproduce inside the body and causes diarrhea, vomiting and fever within eight to 48 hours.
Illness caused by S. aureus usually begins one to eight hours after eating the contaminated food, and the vomiting is more severe, but the diarrhea is less intense than in S. eneritidis poisoning. S. aureus food poisoning is the result of consuming a poison made by the bacteria, not the bacteria themselves.
The best way to prevent these types of bacteria from attacking your food and your family is to keep all foods “cooking hot” – above 140 degrees – or “refrigerator cold” – below 45 degrees – until they’re consumed. Transporting your picnic meal in separate insulated containers for hot and cold items should be satisfactory for meals that are to be consumed within four or five hours. For meals that are to be eaten later than this, it’s safest to take canned or frozen food, along with a camp stove, and then cook the hot dishes immediately before the meal.
The reason for this concern with cooked foods can be illustrated with an example.
A cooked ham can be contaminated with a small number of S. aureus bacteria when it’s put in the picnic basket. As the ham cools these bacteria can grow from an almost undetectable level to a sufficient number to produce S. aureus poisoning that will ruin your picnic.
Other bacteria as well as viruses, chemicals and parasites can also cause food-borne illnesses. To lessen your risk of these, wash your fruits and vegetables before you leave home.
Here’s wishing you a nice picnic and a happy Fourth of July.
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Editor’s note: Family Medicine(r) is a weekly column. To submit questions, write to Martha A. Simpson, D.O., M.B.A., Ohio University College of Osteopathic Medicine, P.O. Box 110, Athens, Ohio 45701, or via e-mail to readerquestions@familymedicinenews.org. Medical information in this column is provided as an educational service only.
It does not replace the judgment of your personal physician, who should be relied on to diagnose and recommend treatment for any medical conditions.
Past columns are available online at www.familymedicinenews.org.