Eggs are an excellent source of nutrients for people — and a species of bacteria called Salmonella enteritidis. Chickens frequently harbor Salmonella and pass the bacteria in their eggs. Eating raw eggs contaminated with Salmonella can lead to an infection called salmonellosis. Raw and undercooked eggs are the leading source of salmonella infections in the United States.
Hiding in Plain Sight
The Centers for Disease Control and Prevention estimates that roughly one in every 20,000 eggs produced in the United States contains Salmonella. Unfortunately, there is no way to tell whether an egg in your refrigerator contains Salmonella. A contaminated egg looks, smells and tastes just like one without bacteria. Although the rate of Salmonella egg contamination is low, the U.S. Food and Drug Administration reports that approximately 142,000 Americans get salmonellosis each year from eating raw or undercooked eggs.
The symptoms of salmonellosis typically begin 12 to 72 hours after eating Salmonella-contaminated food. Nausea and intense abdominal cramps develop first, followed by a fever, chills, watery diarrhea and possibly vomiting. Most people recover from salmonellosis within a week without treatment. However, some people end up in the hospital because of severe dehydration caused by ongoing diarrhea. Salmonella bacteria occasionally cross from the intestines into the bloodstream, causing a potentially life-threatening condition called sepsis. People with HIV or cancer, the elderly and young children are most vulnerable to Salmonella sepsis.
Heat Before You Eat
Heating eggs to an appropriate temperature kills any potentially disease-causing Salmonella that may be present. When making scrambled, fried, poached or boiled eggs, cook them until both the yolks and the whites are no longer runny. Bake quiches and egg casseroles until the eggs are firm. For added safety, check the internal temperature with a cooking thermometer to be sure it reaches at least 160 F. If you're preparing a recipe that calls for uncooked eggs, such as Caesar dressing, eggnog, mayonnaise or homemade ice cream, use pasteurized eggs. These eggs undergo heat treatment to kill bacteria and other germs. Liquid, pasteurized whole eggs and egg whites are sold in containers that resemble milk cartons. Some stores also carry pasteurized eggs still in their shells.
The Raw Egg Myth
If you're tempted to eat raw eggs because you've heard they're more nutritious than cooked eggs, put that erroneous thought out of your head. Cooked eggs provide more nutrition because heating makes the protein more digestible and absorbable. In a hallmark study published in the "American Journal of Physiology — Gastrointestinal and Liver Physiology," Dr. Pieter Evenepoel and colleagues report that more than 94 percent of the protein from cooked eggs gets digested and absorbed compared to 64 percent of the protein from raw eggs.
Don't buy or use eggs with cracked shells because the breaks may allow bacteria into the eggs. Wash your hands with soap and water after handling eggs to get rid of any bacteria from the shell that may have contaminated your hands. And no matter how tempting it may be, don't eat raw cookie dough or batter that contains uncooked eggs.
- Centers for Disease Control and Prevention: Salmonella Serotype Enteritidis
- U.S. Food and Drug Administration: Playing It Safe with Eggs
- Centers for Disease Control and Prevention: Salmonellosis
- Merck Manual for Healthcare Professionals: Nontyphoidal Salmonella Infections
- Centers for Disease Control and Prevention: Tips to Reduce Your Risk of Salmonella from Eggs
- U.S. Department of Agriculture: Shell Eggs from Farm to Table
- American Journal of Physiology — Gastrointestinal and Liver Physiology: Amount and Fate of Egg Protein Escaping Assimilation in the Small Intestine of Humans
Dr. Tina M. St. John owns and operates a health communications and consulting firm. She is also an accomplished medical writer and editor, and was formerly a senior medical officer with the U.S. Centers for Disease Control and Prevention. St. John holds an M.D. from Emory University School of Medicine.