Aside from being a fascinating phenomenon, what´s the deal with eating raw eggs?
The egg is a nutritious, versatile and tasty food. Its shelf life is long and it can be used in a wide variety of ways in many different dishes or just be cooked and eaten as is, plain and simple.
Many of you have probably seen or heard people recommend eating raw eggs. Some add it to their morning shake or have them after a hard training session.
But how healthy and beneficial is it to consume raw eggs?
Protein from raw eggs
Many add raw eggs to their smoothies or similar beverages in an attempt to increase the protein intake of the meal to build or preserve muscle mass. Eggs are an excellent source of protein with a favorable amino acid (the building blocks of protein) profile with a fair amount of essential amino acids (amino acids we cant produce ourselves but have to get from the diet) (Miranda et al., 2015).
What you should know though is that what you thought would be a sufficient protein dose to maximally stimulate muscle protein synthesis (the building of muscle) after exercise, around 20-40 g protein per meal (Witard et al., 2014; Macnaughton et al., 2016; Jäger et al., 2017), might not be.
If you, for example, added 3 eggs to your smoothie (around 180 g) you think you would have added almost 22 g of protein, right? That is correct. However, the bioavailability (the ability of your body to break down and absorb any nutrient) is not 100%, especially not when it comes to raw eggs. Cooked eggs have a bioavailability of around 91% for protein, while protein from raw eggs only is 50% bioavailable (Evenepoel et al., 1998). This means that you can only absorb and utilize around 11 g of protein from your 180 g of raw eggs! This is hardly enough to reach the goal of around 20-40 g of protein.
So, why does protein in cooked eggs have higher digestibility and bioavailability? The simple answer is, heating eggs changes the protein structure (denaturing the proteins) in the eggs making them more accessible for our digestive enzymes (Evenepoel et al., 1998) and thereby more easily absorbed.
Energy and macronutrient content in hen eggs (100 g) (Miranda et al., 2015)
Energy (Kcal) 162
Protein (g) 12.1
Carbohydrates (g) 0.68
Fats (g) 12.1
Water (g) 74.5
Micronutrient deficiency and raw egg whites?
Now we have just learned that cooking eggs increase the body´s ability to utilize the protein in egg due to denaturing of proteins when heated. What’s more, eating raw eggs denatures the protein avidin found in eggs, which in larger amounts can cause a deficiency of the B vitamin biotin (Stratton et al., 2012). Biotin is for example important for several steps in metabolism (the nutrient turnover). The reason for possible biotin deficiency is due to avidin binding to biotin in the intestines and hampering the biotin uptake.
The dose of raw egg whites you have to consume before you risk a biotin deficiency (even though egg whites contain biotin) is several egg whites per day during a few months. This is, therefore, an amount that a person eating a relatively normal, varied diet would have a very difficult time reaching.
Salmonella and raw eggs
Additionally, one of the most infamous foodborne illnesses, Salmonella, can be contracted from eating raw eggs. Actually, one of the major causes of foodborne Salmonella is contamination of eggs (Whiley and Ross, 2015). Salmonella is a bacterial infection usually contracted via the diet (foodborne illness). It can cause gastrointestinal illness, fever, diarrhea, vomiting and stomach cramps. Symptoms usually begin 12 h to 3 days after consuming the contaminated food and can persist for 4 to 7 days. It can usually be managed by drinking lots of fluids (Medicine, n.d.). Diagnosis can be made by a fecal sample.
However, in Sweden for example, it is very uncommon to get infected by raw eggs.
How can you protect yourself from Salmonella?
Methods that are recommended to protect yourself against salmonella in raw eggs are pasteurization (heating food to kill bacteria). Also, control of temperature and pH could be used to minimize the risk of salmonella in foods containing raw eggs (Whiley and Ross, 2015).
The bacteria can usually be killed by cooking the egg at 70°C (160°F) for 1 min or at 60°C (140°F) for 5 min. For people wanting a runny yolk, the second alternative would be your preferred method, since the yolk hardens if you use the first option due to proteins coagulating.
With all this said, usually there´s no harm in eating raw eggs now and then if you live in a country with proper sanitation and hygiene with regards to egg and hen handling. Preferably though, you should eat raw eggs that have been pasteurized and have been kept cool by refrigeration.
In summary, consuming raw eggs regularly or in excess could possibly have adverse effects (like everything in excess). However, adding a raw egg to your occasional homemade smoothie, ice cream or eggnog usually have a low likelihood of being harmful. Just know that you probably won´t be able to utilize all the protein in the egg and therefore have a harder time reaching a protein dose that stimulates muscle protein synthesis maximally.
Post written by: Fredrik Wernstal
Evenepoel, P., Geypens, B., Luypaerts, A., Hiele, M., Ghoos, Y., Rutgeerts, P., 1998. Digestibility of cooked and raw egg protein in humans as assessed by stable isotope techniques. J. Nutr. 128, 1716–1722.
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Miranda, J.M., Anton, X., Redondo-Valbuena, C., Roca-Saavedra, P., Rodriguez, J.A., Lamas, A., Franco, C.M., Cepeda, A., 2015. Egg and Egg-Derived Foods: Effects on Human Health and Use as Functional Foods. Nutrients 7, 706–729. doi:10.3390/nu7010706
Stratton, S.L., Henrich, C.L., Matthews, N.I., Bogusiewicz, A., Dawson, A.M., Horvath, T.D., Owen, S.N., Boysen, G., Moran, J.H., Mock, D.M., 2012. Marginal biotin deficiency can be induced experimentally in humans using a cost-effective outpatient design. J. Nutr. 142, 22–26. doi:10.3945/jn.111.151621
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