The longer eggs are boiled, the more nutrients are lost; experts suggest the more natural the taste, the better

The Consumer Protection Committee of the Executive Yuan recently conducted spot checks on eggs sold at breakfast shops and found residues of veterinary drugs, but the Council of Agriculture pointed out that all the drugs detected were approved for use, and that the cause may have been poultry farmers failing to observe the withdrawal period; monitoring and guidance will continue. Eggs are an important source of daily protein for most people, and there are many ways to cook them. The public need not panic excessively and can eat eggs with peace of mind.

The longer eggs are braised or the more complicated the processing, the fewer nutrients they retain

There are all kinds of ways to cook eggs: fried eggs, steamed eggs, scrambled eggs, salted eggs, tea eggs, braised eggs, iron eggs, and so on. Given the same egg, which way of eating it is most nutritious? "Eggs cooked in different ways actually do not differ much in nutrient content," said Chin Hui-min, director of the Nutrition Department at Taipei City Hospital. However, Chen Chun-cheng, a lecturer at the Food Selection Lecture Hall of the Extension Education Division of Chinese Culture University, cautioned that "the harder the egg and the darker its color, the lower its nutritional value," citing braised eggs and iron eggs as examples.

Chen Chun-cheng explained that eggs contain many essential amino acids that the human body cannot synthesize on its own and must obtain from food. The richer the essential amino acids, the higher the nutritional value. The most nutritious essential amino acid in eggs is lysine. In making braised eggs or iron eggs, soy sauce and sugar are added, and the lysine in the egg undergoes the "Maillard reaction" with the sugar. The longer the braising, and the blacker, harder and sweeter the egg, the more the nutritional value is lost.

If a normal braised egg is not braised too long and only takes on the flavor of the braising liquid, its nutritional value will not decrease too much, Chin Hui-min said. But iron eggs are different, because iron eggs are repeatedly heated and braised until they are old and hard, and the structure of the protein tissue is denatured. Besides the loss of nutrients, they are also not good for human digestion and absorption.

Eating iron eggs not only provides no nutrition; the metabolites of the Maillard reaction between lysine and sugar are also harmful to the human body. Chen Chun-cheng said the Maillard reaction produces "advanced glycation end products (AGEs or AGE)," which are the culprit behind the aging of human organs and tissues. "If you eat too much AGE, it will bind with human collagen, causing the skin to age rapidly. If you want to stay young and beautiful, with delicate and smooth skin, you should eat less of this kind of thing."

As for tea eggs, Chen Chun-cheng believes that tea eggs are not braised too long; although the outer shell is somewhat dark, the egg white inside has not turned black, so they are somewhat better than iron eggs. "What is more worrisome is boiling them with caramel color added, which burns very quickly."

One egg a day is just right

Chen Chun-cheng believes that one should eat food in its original natural color. "Do not deepen the color through cooking; once it deepens, the Maillard reaction may occur, and protein denaturation is also high." Hsu Hui-yu, director of the Nutrition Department of the John Tung Foundation, also said that eggs that are cooked at high temperatures, repeatedly cooked, burned, or cooked until black are not suitable for consumption.

Besides eating fewer over-cooked eggs, Hsu Hui-yu also does not recommend frequently eating century eggs, because the processing of century eggs is complicated, and there are concerns that chemicals may be added or that heavy metal lead may be used to denature them. On this point, Su He-ping, a retired professor from the Department of Animal Science and Technology at National Taiwan University who studies egg processing, said that in the early days, operators worried that they could not achieve the desired yield of century eggs, so they did use lead to denature them, but because lead is harmful to the human body, copper is mostly used instead today. Century eggs on the market now more or less contain copper, but the state has set residue limit standards, and local health bureaus also conduct regular spot checks.

Some people love eggs but worry that the cholesterol in the yolk is too high, so they eat only the white and do not dare to eat the yolk. However, one egg contains about 250 mg of cholesterol. Dietitian Chao Han-ying said that although this looks higher compared with other foods, it is good cholesterol (high-density lipoprotein, HDL) and can protect the cardiovascular system. Hsu Hui-yu also said that the lecithin in the yolk can help metabolize cholesterol, and healthy people who eat one egg a day without going overboard actually need not worry too much.

Moreover, nutrition science emphasizes getting protein in a balanced way from all kinds of foods. "In principle, one egg a day is just right," Chin Hui-min said. One egg contains about 7 grams of protein, and a person weighing 60 kg can take in 60 to 70 grams of protein a day. Eggs are only one of the sources; other sources include meat, fish, milk, and so on, and the nutrients in different foods have different functions.

(This article was funded by the Jian Zhen Environmental Education Foundation for personnel expenses as a special project, but it does not interfere at all with news topic selection or interview writing, ensuring journalistic independence.)