British researcher Schmidt spent five years investigating human mental flexibility before and after lunch. The surprising findings were that people who ate lunch had difficulty concentrating; those who had a substantial lunch showed significant mental distraction; while those who skipped lunch or ate only a simple, small meal experienced only a slight decrease in their responsiveness. Schmidt's research report指出 that a substantial lunch can reduce mental capacity in the afternoon by as much as 20%, equivalent to the efficiency of working late at night.
Schmidt's research report also indicates that the type of food consumed during the day has a more direct impact on mental capacity. High-protein foods, such as steak, poultry, eggs, soybeans, tofu skin, peanuts, pumpkin seeds, and shrimp, can make it difficult for people to concentrate on their work, often leading to inexplicable mental fatigue, dizziness, headaches, reduced thinking and judgment abilities, and mental distraction; the dizziness, drowsiness, and distraction caused by consuming alcohol at noon are twice as strong as those in the evening.
Therefore, to mitigate the impact of lunch on work and study, one should choose foods high in carbohydrates, such as potatoes, cakes, and sandwiches. Scientific research has also fully proven this point: eating a little sweet food in the afternoon, such as chocolate, malted milk, pastries, or sugar water, can make people more energetic when studying and working. Research on the nutrients the brain needs also shows that the brain "likes" to eat sugar, especially glucose; if the glucose concentration in the blood is too low, symptoms such as dizziness and blurred vision can occur. In summary, glucose is the primary substance that fuels brain activity and is widely found in rice, flour, and various tubers. According to an experiment conducted by American nutritionists on more than 1,000 students, among those who ate one piece of chocolate in the afternoon, only 2% dozed off during the first two classes in the afternoon, while among those who did not eat chocolate, the figure was as high as 21%. Experts have also found that eating sweets can reduce traffic accidents. They conducted an experiment on several hundred drivers. When these drivers were instructed to eat some chocolate, cake, pastries, or sweet drinks every afternoon, the number of traffic accidents in the following month was more than half that of the previous months when they did not eat sweets.