Eggs 101

The incredible edible egg, as the American Egg Board refers to them, seems to be a never ending source of controversy.  From the cholesterol bashing of the 1970s and 1980s to the practices of chicken raising and conventional vs. cage-free vs. organic, the egg never seems to get a break.  And although studies (1) have shown that there is no direct link between the amount of cholesterol in a particular food and the level of cholesterol in the blood, the egg still gets a bad rap among the old school cholesterol watchers.

For those of us who eat eggs, there are questions about how to store them, where to buy them, which eggs – conventional store-bought, organic, or farmers market – are best, how to tell if an egg is fresh and safe to eat, and whether or not eggs are healthy.  Here’s a short primer.


The Egg

An egg contains about six grams of protein and is considered a low-calorie (74 calories per egg), nutrient dense food.  Yolks are an excellent source of choline which is needed for brain development and function, the phytochemicals lutein and zeaxanthin which help prevent eye diseases, and vitamin D which aids calcium absorption and is important for our heart, colon, bones, and teeth.


Dietary Link to Heart Disease Debunked

A study published by M. Kratz in the Handbook of Experimental Pharmacology found that cholesterol intake does not impact coronary heart disease but instead found that there is an association between a high intake of total fat and low intake of fiber that increases the risk of heart disease.(2)  Another study by doctoral student Ying Rong, published in the British Medical Journal, found that higher consumption of eggs is not associated with increased risk of coronary heart disease or stroke.(3)


Where to Buy Eggs

Farmers market!  Here are five reasons to buy farmers market eggs instead of store-bought: Five Reasons to Buy Farmers Market Eggs.  If you still aren’t convinced, here is a breakdown of the difference between a store-bought and farmers market egg:  Store-Bought vs. Farmers Market.


Are All Organic Eggs Created Equal?

In a nutshell, no.  If you are purchasing store-bought eggs with the USDA Organic seal, they can range from eggs from hens with no meaningful outdoor access, sold nationwide, following the minimum organic standards to eggs sold locally from hens raised on ample pasture above and beyond the organic standards.  To see if your store-bought eggs measure up check out the Organic Egg Scorecard.



Eggs vary in color depending on the type of hen that lays them.  New Hampshire, Australorp, and Plymouth Rock hens lay brown eggs.  Leghorn, Silkie, and Ancona hens lay white eggs.  Ameraucana, Araucana, and Easter Egger hens lay green eggs.  You can also find eggs that are pink, purple, gray, and blue.  Which eggs you prefer depends on taste.

Green Eggs

Green eggs from farmers market



Egg size depends on the breed of chicken and the size/maturity of the hen.  Jumbo eggs are 71 grams or larger, extra large are between 64 and 70 grams, large eggs are between 57 and 63 grams, and medium eggs are between 50 and 56 grams.


Storing Eggs

In the United States we store our eggs in the refrigerator.  There are a couple reasons for this.  First, refrigeration extends the shelf life.   Second, the USDA requires that eggs sold in supermarkets be washed following a certain procedure.  The washing removes the protective coating on the egg making it easier for bacteria to penetrate the eggshells.(4)  And “if Salmonella is present inside eggs, it can multiply more rapidly as the temperature and storage time rise.” explains John Griffin, Chair of the Biological Hazards Panel.   In countries where egg washing is not the norm, eggs are often not refrigerated.

Eggs sold at farmers market are usually gently rinsed with water before being brought to market for sale, leaving the protective membrane intact.  This is one very good reason to buy eggs at farmers market.


Are My Eggs Still Fresh?

If you are cracking the egg open for use, your eyes and nose can tell you if the egg is still good when you crack it onto a plate.  A fresh egg won’t have much of a smell.  If the egg has a smell, it’s definitely not good.  And a fresh egg will have a bright yellow/orange yolk and the white will sit close to the yolk.  The white in an older egg will be more runny and will spread out on the plate.

If you are planning to hard boil the eggs or want a more scientific method, try the float test.

Egg Float Test

Fill a bowl with cold water and place the eggs in the water.  If they sink to the bottom and lay flat on their sides, they are very fresh.  If they sink and stand on one end at the bottom, they are a few weeks old but still good to eat.  These eggs are great for hard boiling because they peel more easily than eggs that are very fresh.  If the eggs float to the surface, they are not good to eat.

How does the float test work?  Since eggshells are porous, air gradually penetrates the shells.  The fresh eggs that have been exposed to air for less time will have less air in them and will sink to the bottom when submerged in water.  Eggs that are older have more air in them and will float.


1. Kanter MM, Kris-Etherton PM, Fernandez ML, Vickers KC, Katz DL. Exploring the factors that affect blood cholesterol and heart disease risk: is dietary cholesterol as bad for you as history leads us to believe? Adv Nutr2012: 3:711-7.

2. Kratz M. Dietary cholesterol, atherosclerosis and coronary heart disease. Handb Exp Pharmacol. 2005:195-213.

3. Rong Y. Egg consumption and risk of coronary heart disease and stroke. BMJ. 2013: 346.

4. Gole V. Effect of Egg Washing and Correlation between Eggshell Characteristics and Egg Penetration by Various Salmonella Typhimurium Strains. PLOS One. 2014: 10.1371.

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