Although they have been controversial for years, today we know that eggs are an almost perfect food. They are rich in complete proteins, essential fats, vitamins and minerals. It must be taken into account that inside an egg there are all the necessary elements for a chick to hatch. For years, moderation was recommended when eating eggs because of an unjustified fear of dietary cholesterol and disease. Today we know that this has no scientific supportand you can eat several eggs a day, not only safely, but it can also reduce inflammation and improve tissue renewal.
However, the way eggs are cooked can influence the absorption of these nutrients. To understand how nutrient bioavailability varies depending on whether eggs are eaten boiled, fried, or in an omelet, it is important to explore what happens during cooking and how each method affects the key components of the egg.
Proteins and their digestibility
Eggs are a complete source of high-quality protein, with all the essential amino acids that our body cannot produce. Cooking eggs does not cause protein loss, but it does change the degree of absorption in the body. When consumed raw, the proteins in eggs are not fully absorbed. This is because the egg proteins are in a structure that makes it difficult for digestive enzymes to break them down.
A study published in the Journal of Nutrition found that the human body can only absorb 51% of the protein from a raw egg, compared to 91% from a cooked egg. This is because heat denatures the egg proteins, making them easier to digest.
Proteins are very large molecules and in them the atoms are arranged in a three-dimensional structure similar to a tangled thread. With heat, some of the bonds break, and the proteins ‘unravel’ or denature. Additionally, this process causes the egg to solidify. The bonds are exposed and cause the proteins to stick to each other, forming a rubbery substance instead of a liquid one.
When fried or made into a tortilla, proteins are also denatured. In frying, for example, high temperatures can cause greater denaturation than if the egg is cooked at lower temperatures, such as when boiling.
There is experiments that have found that maximum protein absorption occurs in poached eggs, which have a solid white and a liquid yolk. The solid yolk is more difficult to digest, so hard-boiled eggs use less protein.
Fats and fat-soluble vitamins
Eggs are a good source of healthy fats, especially the yolk, which contains monounsaturated and polyunsaturated fats. These fats are not significantly affected by cooking, although additional fats may be added when cooking fried eggs, depending on the oil used.
More relevant for the absorption of nutrients are the fat-soluble vitamins that eggs contain: vitamins A, D, E and K, present in the yolk. These vitamins depend on fats to be absorbed by the body. In this case, the absorption of vitamin A is higher in omelettes than in boiled or poached eggs. However, when the yolk solidifies, it affects the absorption of vitamin D3, which is more digestible in the liquid yolk of poached eggs.
Water-soluble vitamins and cooking
Group B vitamins, especially B12, are essential in the nutrition provided by eggs. However, water-soluble vitamins can be partially lost during cooking due to the action of heat and their dissolution in water. In poached eggs, the losses of B vitamins may be greater, since they are immersed in water, which facilitates the dissolution of these vitamins. In the case of fried or omelette eggs, the losses of group B vitamins are lower, since they are not in contact with water. Although these losses are not large, they are enough to make fried or omelette eggs preferable if seeking to maximize retention of water-soluble vitamins.
Avidin and biotin
Avidin is a protein found in raw egg whites that can interfere with the absorption of biotin (vitamin B7). However, heat inactivates avidin, which means that cooking eggs, whether boiled, fried or in an omelette, eliminates this problem. This ensures so that the body can fully absorb biotinregardless of the cooking method chosen.
Antioxidants and cooking
Eggs also contain antioxidants such as lutein and zeaxanthin, which are crucial for eye health. Cooking can reduce levels of these antioxidants, but not uniformly. A study showed that boiled eggs They reduce lutein and zeaxanthin levels by 20%, while in fried eggs the reduction can be greater, around 40%. Despite this loss, eggs remain an important source of these compounds, and their regular consumption, regardless of the cooking method, can provide health benefits.
Ultimately, cooking eggs, by any method, will make it easier to absorb their nutrients, especially proteins. However, it must also be taken into account that in very cooked hard-boiled eggs, prolonged heat and having a solid yolk can hinder the absorption of some vitamins. The most important thing is that eggs, in any of their forms, deserve to be part of our diet.
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