Does a balanced diet play a role in preventing respiratory infectious diseases by enhancing body immunity?

There is no black-and-white answer to this question. Improving immunity is indeed one of the core ways a balanced diet can help prevent respiratory infectious diseases, but it is by no means the only role. There has been controversy in the academic community about the weight of different roles.

Over the years of doing community nutrition follow-up, I have seen too many real comparisons. When adenovirus, influenza, and COVID-19 peaked at the beginning of last year, there were two elderly people living alone in our jurisdiction who lived in the same old community. Aunt Wang, 72, was very particular about her diet. She had a cup of warm milk and an egg every day, dark green vegetables for every meal, and some fish and shrimp every other day. She didn’t even catch a cold during that epidemic.； Another Aunt Li, who is 3 years younger than her, is always afraid of waste. She often eats leftovers and is reluctant to buy meat and eggs. Her nutritional intake is not enough for a long time. Not only did she contract influenza and turn into pneumonia, she was hospitalized for almost a week. Her granddaughter, who came to take care of her, also suffered from fever for several days. Nutritionists who hold this view generally believe that sufficient nutrients such as protein, vitamin C, zinc, and iron are necessary raw materials for the synthesis of immunoglobulins and lymphocytes. Without these, the immune system is like a soldier short of ammunition and has no strength to fight against invading viruses.

However, many scholars in the field of public health have put forward different views. In their view, the preventive effect of a balanced diet on respiratory infectious diseases is to a greater extent in maintaining the first barrier of the respiratory mucosa, rather than simply improving immunity. You can think of the respiratory mucosa as the anti-theft door of your home. A diet high in oil, sugar, and over-processing will keep the body in a low-grade inflammation state for a long time. This anti-theft door will become riddled with holes. No matter how strong your immune system (that is, the security guard at home) is, it will be easier for viruses to break in, making it impossible to prevent it. This is why many young people who usually look strong and have fried chicken and milk tea are more likely to get infected during the flu season than people who eat regularly - it's not that their immunity is poor, it's that the first line of defense collapsed first.

What’s more interesting is that other studies have given more detailed conclusions. For healthy adults whose nutritional status is up to standard, adjusting their diet to pursue a more balanced diet will actually have a very low marginal effect on improving immunity. At this time, if you spend a few more dollars to buy a qualified mask and wash your hands twice more before meals, the effect of preventing respiratory infections is much higher than if you deliberately take multivitamins and calculate the nutritional ratio every time you eat. When I usually do science popularization, I always tell everyone that there is no need to deify a balanced diet, and there is no need to think that it is useless. Eating well is to prepare the body, and the rest should be protected. If you really feel uncomfortable, seek medical treatment in time, which is better than anything else.