Fertilized and Unfertilized Eggs—Is There a Nutritional Difference?
What Is a Fertilized Chicken Egg?
A fertilized egg is one that has been laid by a chicken who has mated with a rooster. These eggs appear a slight bit more opague than unfertile eggs. If you are getting farm-fresh eggs, you may be getting fertilized eggs, but eggs produced commercially are rarely fertilized. Occasionally when there is an overstock of hatching eggs in chickens raised for meat, the eggs will be sold. Those eggs are nearly all fertile.
A Question of Cholesterol
I had been told that fertilized eggs had less cholesterol than non-fertilized eggs, so I decided to see if there were any studies on the matter. When searching the internet, I saw many people asking this same question.
There were a number of references from respected institutions stating that there is no difference between the two. For example, in their fact sheet PS-51, Designer and Specialty Eggs, the Florida State Cooperative Extension Services, Institute of Food and Agricultural Sciences says that there is no nutritional difference in fertilized and unfertilized eggs.
I did find one study titled "Cholesterol and phospholipids content of yolk from fertilized and unfertilized hen eggs" in which total cholesterol and total phospholipids were measured from 3 portions of fertilized and unfertilized chicken egg yolks. The eggs were all fresh being 7 days old or less. They found that there was no significant difference in either the cholesterol nor the phospholipid in yolk granules or LDL. There was a slight difference in the infranatant portion. Cholesterol was not found in the infranatant fraction of the unfertilized egg, but was found in the fertilized egg. In addition, total phospholipids were lower in the fertilized egg than in the unfertilized eggs. The authors suggested that total cholesterol was transferred from the LDL into the infranatant and that phospholipids were consumed during the fertilization process.
Does This Difference Matter?
While there may be a slight difference in the structure of the cholesterol and where it is found, it seems that this is not enough to make a difference in the total nutrition of the egg.
Eggs are a nutrititous food and are part of a healthy diet. The cholesterol in eggs, either fertilized or unfertilized, does little to contribute to heart disease. Eating up to 4 egg yolks per week has not been shown to increase your risk of heart disease and the recommendation by the American Heart Association is to limit cholesterol intake to 300 mg or less. If you already have heart disease, you should limit your cholesterol intake to 200 mg per day.
All of the 186 mg of cholesterol in an egg resides in the yolk, as are most of the vitamins, minerals and phytonutrients. That means, if you eat an egg, you may want to limit dietary cholesterol for the remainder of the day. One way of reducing your cholesterol intake while still enjoying the nutritious benefits of eggs is to use 1 whole egg and 2 egg whites for every 2 eggs you enjoy.
Another way of getting maximum nutrition from eggs is to purchase the freshest eggs you can find from organically raised chickens, since egg nutrition has a lot to do with what the hens are fed. You can also find eggs from chickens who are fed high levels of omega-3 fatty acids and other nutrients.