What is the real risk of consuming raw eggs? As kids we licked spoons coated with batter left over from making cookies. Some body-builders swear by protein shakes blended with uncooked eggs — as Sylvester Stallone memorably demonstrated in the 1976 movie Rocky. Yet, the fear of bacterial infection is real, though quite small, and there are ways to minimize it.
Salmonella enteritidis is a type of bacteria that is the most common culprit in food poisoning cases in the United States. The bacteria can be found on both the inside and outside of eggs. Eggs can become contaminated two ways: 1) internally from the reproductive tract of a hen infected by salmonella, or 2) externally due to contact with salmonella-infected soil, feces or unwashed hands. Egg shells are porous, and micro-organisms can cross the shell boundary.
However, the risk of an egg being contaminated with salmonella is extremely low. The Centers for Disease Control estimates that perhaps 1 in 20,000 eggs, 0.005%, may be internally contaminated — this is five one-thousands of one percent.
If eggs are eaten raw or undercooked, this bacterium can cause Salmonella poisoning , also called salmonella enteritis, or salmonellosis — which usually manifests as a fever, coupled with abdominal cramps, diarrhea and/or vomiting. Symptoms typically appear within 12 to 72 hours of consuming contaminated eggs, and may last four to seven days. Most individuals recover without treatment. In severe cases, the infection may spread to the blood, then to the rest of the body, requiring hospitalization and treatment with antibiotics.
The elderly and young are particularly susceptible to salmonella poisoning, as are pregnant women and those with suppressed immune systems. The U.S. Food and Drug Administration estimates that there are 142,000 cases of salmonella poisoning each year.
To wash or not wash? Refrigerate or not refrigerate?
Even if the egg did not originate from a hen infected with salmonella, it may have come in contact with the bacteria through manure or feces. In the United States, it is standard USDA practice to wash chicken eggs in warm water with mild detergent and then treated with a chlorine sanitizer. This sounds like a logical step, and yet, in Europe, it is actually illegal to wash and sanitize eggs. The EU maintains that washing removes the egg’s natural wxy cuticle coating, which provides a natural barrier to bacteria and pathogens. Some U.S. producers spray the washed eggs with a thin layer of colorless mineral oil.
Eggs sold in the European Union (EU) are not required to be refrigerated prior to sale, as EU regulations maintain that chilled eggs left at room temperature could be covered in condensation — and this moisture could facilitate bacterial growth. Research by the National Institute of Health showed that for eggs infected with salmonella, storage at room temperature for up to two weeks had no significant effect on the growth of bacteria; after twenty-one days, bacteria contamination of unrefrigerated eggs was pronounced.
Another difference is that British producers vaccinate their hens against salmonella; only a small percentage of American producers vaccinate.
Note that eggs purchased from grocery stores may already be one to three weeks old.
To cook or not cook?
Some fitness pros believe that there is more bioavailable protein from an uncooked egg — hence their inclusion in protein shakes. In fact, the data suggests the opposite. A 1998 study by Belgian physiologists determined that 94% of the protein is digested for cooked eggs, versus 55 to 64% of the protein for raw eggs. In fact, you’d be better off eating a hard boiled egg with your protein.
According to an article on Bodybuilding.com, “Some older athletic diets used to propose eating just raw eggs. This is a foolish attempt at taking in additional protein. Eating raw eggs (or raw egg whites) will only result in about 50% absorption of the available protein. That means that if you eat enough raw eggs to give you 40 grams of protein, your body will only absorb 20 grams. Eating just raw egg whites results in the same (or worse). Egg whites have a huge amount of a substance called ‘avidin,’ which loves biotin. As a matter of fact, once the avidin-biotin forms a bond, the body can’t break it apart. So y ou will develop a partial or full Biotin Deficiency Syndrome. Cooking your eggs (or egg whites) will quickly denature the protein avidin and will allow you to absorb 90% of the protein. In short, always cook your eggs.”
Primatologist Richard Wrangham further explores the health benefits of cooking food in his book, Catching Fire: How Cooking Made Us Human, arguing that our evolutionary success is, in part due to our shift to using fire to cook food.
To prevent the risk of salmonella infection, purchase eggs from a refrigerated case, and dispose of any cracked or dirty eggs. At home, eggs should be kept refrigerated at ≤ 40° F (≤ 4° C). Eggs should be thoroughly cooked, to a temperature of at least 160° F, until the yolk and white are firm. Note that sunny side up eggs and eggs over easy do not attain this minimum temperature. Casseroles and other egg dishes should also be cooked to a temperature of 160° F (72° C). Eat immediately, or refrigerate any leftovers. Obviously, wash hands and kitchen surfaces after contact with raw eggs or chicken.
Salmonella outbreaks often occur in restaurants, where large quantities of eggs are mixed and left at room temperatures for extended periods. One bad egg can literally spoil the whole bunch.
Dishes that call for raw eggs — such as Hollandaise sauce, Caesar salad dressing, homemade ice cream and eggnog — should be made with pasteurized eggs. Most eggs are not pasteurized, but some are labeled “Pasteurized Shell Eggs” – these eggs have been treated to a temperature sufficient to destroy Salmonella bacteria. The patented process that allows eggs to be pasteurized in their shells (without cooking the egg), involves immersing the eggs in warm water paths for set time periods. Pasteurized eggs are more expensive, but just as nutritious; they are safe to use in smoothies, or undercooked in sunny side up eggs…or if you wish to lick the spoon from your cake or brownie mix.
New safety regulations went into effect in 2010 for egg producers having 50,000 or more egg-laying hens; in 2012 these regulations expanded to medium-scale producers (3,000 to 50,000 hens). These regulations require preventative measures involving testing and monitoring of hens, rodent control, and the use of refrigeration during egg storage and transportation.
Theoretically, organically grown eggs should have a lower incidence of salmonella, since chickens are not kept in tightly packed conditions where diseases can easily spread. Statistically, this seems to be supported by data: larger commercial producers have a higher incidence of bacterial infections. Read this article for an argument for buying eggs from Farmer’s Markets.
Not just eggs: Outbreaks of salmonellosis have been attributed to consumption of chicken, pork, raw milk and cheese.The U.S. Department of Agriculture found that one in eight broiler chickens was contaminated with salmonella. Poultry should be thoroughly cooked, to an internal temperature of 165° F (74° C).
Salmonellosis can also arise from fruits and vegetables such cantaloupe, tomatoes, raw almonds, spinach, lettuce, and alfalfa sprouts – largely due to bacterial contamination from soil or groundwater contaminated with animal feces. “Once Salmonella gets on and into a tomato, the fruit acts like an incubator,” writes Ewen Callaway in New Scientist. Particularly when you’re traveling, it is be cautious of fruits and vegetables which may be unwashed or washed in contaminated water. Washing fruits and vegetable in cold water doesn’t necessarily eliminate salmonella, as the bacteria can adhere tightly to the surfaces, forming an adhesive biofilm.
In the end, take reasonable precautions.