Some athletes and bodybuilders add raw egg yolks to protein drinks to boost their nutritional content. Egg yolks have valuable nutrition, whether cooked or raw. However, if you eat raw yolks, reports the Egg Safety Center, you risk becoming sick if the egg is contaminated with bacteria. Therefore, it may be healthier for you to eat cooked yolks rather than raw ones.
Eggs can become infected with bacteria as they exit the hen's body, coming in contact with feces in the dirt or surroundings. This is why eggs are washed and sanitized. However, some chickens are infected with salmonella within the oviduct and produce eggs that are contaminated with bacteria. The salmonella is in the egg even before the egg shell is formed, according to MayoClinic.com. Researchers at the Egg Safety Center note that because the yolk is rich in nutrients, that's the most likely place for bacteria to grow. This is why the FDA and the Egg Safety Center recommend against eating raw eggs. Cooking the yolks to 149 degrees Fahrenheit kills any bacteria.
Salmonella infection in humans causes diarrhea, abdominal cramps and fever within eight to 72 hours after eating contaminated food. Other symptoms may include vomiting, headache and chills. Symptoms usually subside in four to seven days.
When the egg yolk is cooked, the protein coagulates, which changes its physical nature but not its nutritional content. A study published in "The Journal of Nutrition" in 1998 found that cooked egg protein is more digestible than raw egg protein. When egg yolks are cooked, the proteins in them become denatured, meaning the bonds in the proteins are disrupted. According to the Elmhurst College Virtual ChemBook, it is easier for enzymes to digest denatured proteins in food.
As the source of food for a growing baby chicken, an egg yolk is packed with nutrients. One raw or cooked egg yolk contains 55 calories, 4.5 grams of fat, 2.7 grams of protein and 0.61 grams of carbohydrates, according to the USDA National Nutrient Database. It is also a good source of vitamin A, vitamin D, vitamin E, vitamin B-12 and folate. Yolks have minerals, too -- phosphorus, potassium, iron and calcium. An April 2012 article in the "Chicago Tribune" reported that yolks used to be considered bad because of their cholesterol content, but recent research indicates that eggs raise the level of HDL, or good, cholesterol, and only slightly raise the level of LDL, or bad, cholesterol. One of the most important benefits of the yolk is the presence of the antioxidants lutein and zeaxanthin, carotenoids that give yolks their bright-yellow color and are valuable in helping maintain good eyesight. The nutritional content remains the same when the egg is cooked, according to the USDA National Nutrient Database.
When buying eggs, always purchase them from a refrigerated case. Open the carton and make sure there are no small cracks or leaks in the shells. Check that none are broken and stuck to the carton. Also, look at the expiration date, and don't buy them if they are out of date. Once home, put the eggs in the refrigerator and store at a temperature of 45 degrees Fahrenheit or lower. Keep them in the carton and never place them in the door of the refrigerator, where temperatures may vary. After handling eggs, wash your hands and any dishes or utensils that have come in contact with raw egg. Hard-cooked eggs can be stored in the refrigerator for up to one week.
- Egg Safety Center: Egg Food Safety Frequently Asked Questions
- MayoClinic.com: Salmonella Infection
- USDA National Nutrient Database: Egg, Raw, Yolk, Fresh
- Egg Safety Center: Pathogens
- Egg Safety Center: Egg Safety
- The Journal of Nutrition: Digestibility of Cooked and Raw Egg Protein in Humans as Assessed by Stable Isotope Techniques
- Elmhurst College Virtual Chembook: Denaturation of Proteins
Deila Taylor received a bachelor's degree in biochemistry from Occidental College with graduate work towards a Ph.D. in pharmacology and nutrition at the Keck School of Medicine of the University of Southern California. Taylor has written for LoopLane, The Nutrition Counselor, Eve Out of the Garden and produces interviews for The Mormon Women Project. She is a member of the American Society for Nutrition.