A Look Inside the Shell

By Eirenel G. Eclevia B.S.

Image: MasAnyanka/Shutterstock

Ever since I was old enough to help my mom cook in the kitchen I was in charge of either cracking eggs in a bowl or separating the egg yolk from the egg whites. Eggs are common in our household and we always have dozens of them stocked in our refrigerator. Stigma regarding egg consumption continues to linger as medical literature has presented conflicting data related to eggs, risk of cardiovascular disease (CVD), and high cholesterol. 

A 2019 study in the Journal of the American Medical Association (JAMA), concluded that the risk of CVD and mortality was higher by 17% and 18% for every extra intake of 300 mg of dietary per day.1 They also found that for each half egg consumption per day increased risk of CVD by 6% and 8% for mortality.1 Reviewing this study, The Harvard Public Health2 commented that these associations become nonsignificant when adjusting for intake of red meat. So what is a person to do with these conflicting studies? Dr. Frank Hu, Chair of the Department of Nutrition at the Harvard Chan School of Public Health, summarizes it best with, “For those who are generally healthy, low to moderate intake of eggs can be included as part of a healthy eating pattern, but they are not essential. For example, there is a range of other foods one can choose for a variety of healthful breakfasts, such as whole grain toast with nut butter, fresh fruits, and plain yogurt.”2 If you choose to include eggs in your diet, let’s crack that oval exterior and find out the nutrients within an egg.

Eggs are composed of an eggshell (10%), egg white (60%), and yolk (30%).3 The egg white provides 3.6 grams of protein, while the yolk provides 2.4 grams of protein with a total of about 6 grams of protein per egg.3,4 The egg yolk contains choline which plays a role in infant brain and fetus development.4,5 Eggs contain lutein and zeaxanthin, antioxidants that are important for eye health and reducing risk of macular degeneration.4,5 Egg yolks also include fat soluble vitamins A, E, D, and K.4,5

An egg has 70 calories and 185 milligrams of dietary cholesterol. The Dietary Guidelines for Americans recommend no more than 300 mg of dietary cholesterol per day.5Dietary cholesterol is important in hormone function and brain cell formation.5 

Brown Colored Eggs vs White Colored Eggs

The breed of chicken determines the color of the egg shell and they all contain the same nutritional value.4

Cooking with Eggs

Eggs are simple and very versatile and adaptable in any dish you cook it in. When eggs are cooked their proteins are denatured, causing coagulation.  When whipped, egg whites have foaming and gelling properties and can be used for icing, macarons, and souffles.3 Egg yolks are used as emulsifiers and thickeners and give a beautiful color to pastries.  Eggs must be thoroughly cooked to prevent food borne illnesses. Egg contents can get contaminated with Salmonella by internal transmission or by cross contamination from the eggshell when the shell is broken.3,6 Do not be alarmed if you find your hard boiled egg with a green ring. The hard-boiled eggs that were cooked for a longer time had a green ring, caused by hydrogen sulfide in the egg white binding with iron in the egg yolk.3 Eggs should be used no longer than three to five weeks of purchase date and should be purchased before the “sell by” date.7 After purchase, eggs should be stored in the refrigerator below 40F and kept in their original container displaying the expiration date.7 At CSUN, dining areas provide egg dishes for breakfast. Try adding hard boil eggs to your salad. You can try making your own egg dish such as the California-Style Fried Egg Avocado Toast on our YouTube Channel. Or try my quick petite quiche recipe made in a mini cupcake pan.

Quick Petite Quiche

Author: Eirenel Eclevia


  • 4 large eggs (or ½ cup of egg whites) 
  • ½ cup of finely chopped spinach (or other leafy greens)
  • ¼ cup of cheese of your cheese 
  • ½ teaspoon of paprika
  • ¼ teaspoon of black ground pepper
  • 2 tbsp of parsley
  • 2 tbsp of chopped green onion


  1. Preheat oven to 325°F.
  2. Beat eggs and add all ingredients and mix together.
  3. Pour the egg mixture evenly in a 24 mini cupcake pan. 
  4. Place the pan in the oven and cook for 25 minutes or until eggs are set. Cool for 5 minutes and enjoy!
  5. Meal Prep Tip: You can store the leftover quiche in the freezer and heat them up later when you are on the go.

What to Do with the Eggshell?

Instead of disposing those eggshells, there are a few things you can do with them. In the garden, you can add them to your compost or crush them to use as a soil amendment. The eggshell itself can be used as a little pod to plant your seedlings and once they grow you can plant them into a bigger plot of soil. You can also break those eggshells and sprinkle them on the premises of soil and to deter unwanted pests in your garden. Visit our Wellness Garden to learn more about sustainable gardening practices.


  1. Zhong VW, Horn LV, Cornelis MC, et al. Associations of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. JAMA. 2019;321(11):1081. doi:10.1001/jama.2019.1572. Accessed October 23, 2019
  2.  Harvard T.H. Chan School of Public Health. Eggs and cholesterol back in the spotlight in new JAMA study. The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/2019/03/18/eggs-and-cholesterol-back-in-the-spotlight-in-new-jama-study/. Published March 18, 2019. Accessed October 23, 2019.
  3. Jeantet R, Trystram G, Legrand J. From eggs to egg products. In: Handbook of Food Science and Technology 3: Food Biochemistry and Technology. 1st ed. London, UK: John Wiley and sons; 2016:115-143.
  4. American Egg Board. Incredibly Nutritious. Nutrition – American Egg Board. https://www.aeb.org/foodservice/egg-production/nutrition. Accessed April 10, 2019.
  5. Levinson JF. The Truth about Eggs. Food & Nutrition Magazine. https://foodandnutrition.org/blogs/stone-soup/the-truth-about-eggs/. Published August 20, 2019. Accessed October 23, 2019.
  6. Lasagabaster A, Arboleya JC, Marañón IMD. Pulsed light technology for surface decontamination of eggs: Impact on Salmonella inactivation and egg quality. Innovative Food Science & Emerging Technologies. 2011;12(2):124-128. doi:10.1016/j.ifset.2011.01.007.
  7. Wolfram T. Egg Essentials. Eat Right. https://www.eatright.org/health/lifestyle/holidays/egg-essentials. Published April 14, 2017. Accessed October 23, 2019.

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