The incidence of influenza A is high, and you must have these 7 nutrients to prevent infection!

Winter and spring are the seasons when influenza is prevalent. Recently, the topic of influenza A has frequently been on the hot search list, and many of my friends have also contracted influenza A and are suffering from fever. After contracting influenza A, most people will have a fever all over the body, accompanied by symptoms such as muscle aches, fatigue, loss of appetite, headache, cough, runny nose, etc., which is particularly uncomfortable.

Don't underestimate influenza A, it is a type of influenza, not the same as the common cold, and has a higher mortality rate. To prevent influenza, what should we do in our daily lives?

7 nutrients you can’t lack in your diet

The key to preventing diseases is to have strong immunity. If you want your body to have the ability to resist diseases, a balanced and nutritious diet is the most important. First of all, don't go on a diet. Secondly, the most important thing in your diet is the following nutrients.

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▶ Protein: Protein is known as "the important cornerstone of human immunity" and is an important substance involved in the body's immune regulation. Many immune active substances in the human body are composed of protein. Our body, from hair to heels, cannot be separated from the participation of protein.

To supplement protein, it is best to choose foods rich in high-quality protein. Meat, eggs, milk and beans are recommended. For example, eat half a fist of meat, 1 fist of shredded tofu, 1 egg, and 300-500 ml of milk every day.

▶ Vitamin C: Vitamin C is a strong antioxidant that promotes the production of antibodies in the body and improves immune function by increasing the levels of other antioxidants in the body [1]. It improves the ability of neutrophils, monocytes, and macrophages to phagocytize pathogens [2].

The most recommended vitamin C supplement is fresh fruits and vegetables that can be eaten raw to avoid nutritional loss caused by cooking, such as bell peppers, colored peppers, cherry tomatoes, kiwis, strawberries, oranges, tangerines, papayas, etc.

Among them, bell peppers and kiwis are highly recommended: eating 100 grams of fresh bell peppers (about half a bell pepper) can meet 130% of the average adult's daily vitamin C needs, while eating 2 kiwis can almost meet an adult's daily vitamin C needs [3].

▶ Vitamin A: Vitamin A is not only good for eye and skin health, but also closely related to respiratory health. Influenza A is a type of respiratory infectious disease. Vitamin A deficiency can lead to atrophy and dryness of the respiratory mucosal epithelium, a reduction in cilia, and a weakening of disease resistance, increasing the risk of respiratory diseases and making it difficult to recover from respiratory diseases [1].

To supplement vitamin A, you can choose animal liver, eggs, and fruits and vegetables rich in beta-carotene, such as carrots, spinach, broccoli, chicory, papaya, mango, etc.

▶ Vitamin D: Vitamin D plays an important role in the body's immune regulation, and reduced serum vitamin D levels are a contributing factor to the occurrence and development of respiratory diseases [4]. Therefore, in order to prevent influenza A, vitamin D is also an important nutrient that cannot be ignored.

However, the vitamin D content in the food we eat is very low. Although 78-80% of vitamin D can be provided by sunlight exposure to the skin, the temperature is lower in winter and spring, people wear more clothes, and generally spend less time exercising outdoors, which can affect the synthesis of vitamin D[1].

Therefore, when it comes to supplementing vitamin D, it is recommended to supplement with vitamin D preparations, 10 micrograms per day. If you are over 65 years old, you need to supplement 15 micrograms per day.

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▶ Mineral zinc: Zinc is closely related to the body's immune function and can increase the number and activity of immune-related T lymphocytes. Zinc can promote antibody production, especially immunoglobulin G. Zinc deficiency can reduce the body's immunity, affect the body's ability to resist viruses, reduce immune function, and cause repeated infections [1].

The most recommended sources of zinc are shellfish, red meat, and animal offal. The most recommended of these is oysters, which contain up to 71.2 mg of zinc per 100 grams [3]. Eating 50 grams of oyster meat a day can meet 285% and 475% of the daily zinc needs of men and women, respectively. Eating oysters is really a good way to supplement zinc.

▶ Mineral selenium: Selenium has antioxidant properties and is important for maintaining cellular immunity and humoral immunity. It can reduce the ability of viruses to damage the body, promote the clearance of viruses, and reduce viral mutations [1].
To supplement selenium, you can choose foods such as yellow croaker, black chicken eggs, purslane, porcini, animal liver and kidney, among which yellow croaker is the most recommended.

▶ Flavonoids: A large number of literature studies have shown that flavonoids have significant anti-influenza A virus effects. Among them, baicalin can inhibit the synthesis and transcription of viral RNA, apigenin and luteolin can inhibit the expression of viral pro-inflammatory genes, flavonols can inhibit the activity of influenza A virus H1N1, quercetin can inhibit viral activity, catechins can have antiviral activity, and total flavonoids can significantly reduce influenza A virus-induced lung inflammation, cell apoptosis and water transport [5].

To supplement flavonoids, it is recommended to eat more dark-colored vegetables, such as onions, celery, purple cabbage, broccoli, kale, etc. It is also recommended to drink green tea every day.

In addition to paying attention to nutritional supplements in diet to prevent influenza, you should also pay attention to your lifestyle habits.

Maintain good living habits

▶ Sufficient sleep: Sufficient sleep and good sleep quality are conducive to the body's self-repair, reducing inflammation levels and enhancing the body's immunity. It is best to fall asleep before 23:00 every day and ensure 7-8 hours of sleep.

▶ Moderate exercise: Daily exercise is the key to improving the body's immunity. In addition to daily life activities, it is recommended to perform moderate-intensity exercise for at least 5 days a week, totaling 150 minutes, such as walking, jogging, cycling, aerobics, swimming, etc. Active physical activity needs to reach 6,000 steps per day; appropriately perform high-intensity exercise and strength training 2 to 3 days a week.

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▶ Open windows for ventilation: Develop a good habit of opening windows for ventilation every day to keep the indoor air fresh. Ventilate at least twice a day, each time for more than half an hour. When opening windows, pay attention to keeping warm and avoid catching a cold.

▶ Wear a mask when going out: Influenza is mainly spread through droplets such as sneezing and coughing. Whenever you go out, you must wear an N95 mask, keep a distance from others, and avoid crowded places. Cover your mouth and nose with a tissue when coughing or sneezing, and throw the tissue into the trash can after use.

▶ Wash your hands frequently: Whether you are returning home from outside or dining at a restaurant outside, you should wash your hands frequently with soap and water. If soap and water are not available, you can use alcohol-based hand sanitizer.

▶ Don’t touch things randomly: Don’t touch door handles, escalators and other public facilities when you are outside. Also avoid touching your eyes, nose and mouth. Bacteria and viruses can easily spread in this way.

▶ Carry disinfectant with you: If it is convenient, it is best to prepare a small spray bottle that can be put in your bag, fill it with disinfectant, and use it at any time to disinfect at all times.

▶ Separate meals: Even when eating at home, it is best to eat separately to prevent cross-infection of various diseases. No matter where you eat outside, you must use public chopsticks and spoons, especially when taking children out to eat, it is best to bring their own bowls and chopsticks.

In addition, it is important to maintain a healthy weight and keep the BMI between 18.5 and 23.9, as obesity can aggravate the symptoms of influenza A infection and increase the risk of hospitalization or death. Severely obese H1N1 patients with a BMI ≥ 40 were twice as likely to be admitted to the ICU or die as non-severely obese H1N1 patients[6].

BMI = weight (kg) ÷ height (m)²

Summary: We are currently in the influenza transmission stage, so everyone must pay attention to protection and a balanced diet. Even if you are infected, don't panic, take medication in time according to the doctor's advice, get more rest, and take isolation measures.

References:

[1] Yang Yuexin, Ge Keyou. Chinese Nutrition Science Encyclopedia 2nd Edition (Volume 1)[M]. People's Medical Publishing House, 2019

[2] Calder PC. Nutrition and immunity: lessons for COVID-19. Eur J Clin Nutr. 2021;75(9):1309-1318. doi:10.1038/s41430-021-00949-8

[3] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 1 and 2[M]. Peking University Medical Press, 2018

[4]Yao Yanyang. Study on the correlation between vitamin D level and respiratory diseases[J]. Chinese Journal of Rational Drug Use, 2018, 15(01): 12-13+23.

[5] Feng Maoxiu, Cui Qinghua, Liu Miaomiao, Hou Lin, Tian Jingzhen. Research progress on the anti-influenza A virus activity of flavonoids[J]. Chinese Journal of Traditional Chinese Medicine, 2021, 39(03): 151-155. DOI: 10.13193/j.issn.1673-7717.2021.03.037.

[6]Fezeu L, Julia C, Henegar A, Bitu J, Hu FB, Grobbee DE, Kengne AP, Hercberg S, Czernichow S. Obesity is associated with higher risk of intensive care unit admission and death in influenza A (H1N1) patients: a systematic review and meta-analysis. Obes Rev. 2011 Aug;12(8):653-9. doi: 10.1111/j.1467-789X.2011.00864.x. Epub 2011 Apr 4. PMID: 21457180.

Author: Xue Qingxin, registered nutritionist

Review｜Ding Heyuan, Deputy Chief Physician of Endocrinology, Shanghai Fifth People's Hospital

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