From the beginning of November, the season turns to winter, and the temperature becomes lower and lower. Winter is originally the season with high incidence of respiratory infectious diseases. This year, it gets cold later and it may be a warm winter. Respiratory infectious diseases are more likely to spread, which is a severe test for everyone.
The best way to deal with the endless emergence of pathogenic bacteria is to strengthen the body’s own resistance. Improving nutritional status is one of the important measures.
Multiple studies have found that a lack of vitamin A and vitamin D is related to poor resistance to a variety of infectious diseases. People who are deficient in these two vitamins are at greater risk of severe mycoplasma pneumonia and are at increased risk of severe COVID-19. Especially children and the elderly, whose resistance is relatively low, must be careful about insufficient intake of these nutrients.
Vitamin A is an important anti-inflammatory vitamin
Vitamin A helps improve mechanisms related to resistance to viral infections, including strengthening immune responses, inhibiting inflammatory responses, and promoting mucosal repair.
Several studies have found that in patients infected with the new coronavirus, plasma vitamin A levels will be significantly reduced (the viral infection consumes vitamin A in the body), and this lack of vitamin A will promote more pro-inflammatory factors Release, including IL-6, IL-1β and TNF-α, etc., thereby increasing inflammatory indicators such as C-reactive protein.
Some studies have found that vitamin A supplementation effectively improves the condition of COVID-19 infection. Fever, body aches, weakness and fatigue are less severe, and white blood cell counts and C-reactive protein levels are also reduced.
Some studies have also found that patients with lower vitamin A levels have more severe disease scores and a greater risk of hospitalization.
Vitamin A deficiency increases risk of severe mycoplasma pneumonia in children
In addition, existing studies have found that vitamin A malnutrition increases the risk of severe mycoplasma pneumonia in children. Children with lower serum vitamin A levels are more likely to develop severe mycoplasma pneumonia. Vitamin A supplementation can effectively reduce the risk of severe mycoplasma pneumonia. In short, vitamin A makes an important contribution to fighting infection.
The risk of pneumonia and tracheitis is also increased with vitamin D deficiency
A large number of studies have confirmed that vitamin D deficiency is associated with a higher risk of COVID-19 infection, severe disease, and death. Recent studies have suggested that serum 25-hydroxyvitamin D levels are related to the severity of the disease and the levels of inflammatory factors in patients with mycoplasma pneumonia, and are related to the risk of bronchial mucus plugs.
A variety of acute respiratory diseases are related to viruses, including coronavirus, influenza virus, respiratory syncytial virus, adenovirus, enterovirus, etc. The infection rate of these diseases will increase in children lacking vitamin D. In addition, the risk of severe pneumonia and bronchitis is increased when vitamin D is deficient. A meta-analysis of 25 studies supports an association between vitamin D insufficiency and acute respiratory tract infections.
How to self-check whether there are vitamin A and vitamin D deficiencies?
Think about it, are you and your family possibly suffering from vitamin A and vitamin D deficiency?
Check for vitamin A first.
If you and your family rarely eat:
——Orange vegetables (carrots, pumpkins, etc.)
——Orange fruits (such as papaya, mango, citrus, etc.)
——Orange potatoes (orange-yellow-fleshed sweet potatoes)
——Dark green vegetables (such as spinach, broccoli, kale, rapeseed, etc.)
– Whole milk (including full-fat yogurt, cheese) or butter
——Egg yolk (including the yolk part of eggs, duck eggs, quail eggs, goose eggs, etc.)
——Various animal livers (chicken liver, duck liver, foie gras, pig liver, sheep liver, etc.)
—— Fatty marine fish (such as saury, sardines, salmon, etc.)
Then it is easier to be deficient in vitamin A, because they are all sources of vitamin A. Even if you eat 1 egg yolk and 1 cup of whole milk every day, the vitamin A you get is still far from reaching the standard. If you have symptoms of dry skin and eyes, or difficulty seeing at night, you are more likely to have a vitamin A deficiency.
Check for vitamin D again.
If you and your family:
——You cannot wear short-sleeved shirts and exercise in the sun for half an hour every day
– Wear sunscreen on all parts of your skin exposed to the sun
——Wear sun protection clothing, a hat or an umbrella whenever you see the sun
Then you can’t get vitamin D from sunlight, which is the most natural and main source of vitamin D.
If you and your family:
——Do not eat animal livers and kidneys
——Don’t eat too much egg yolks, whole milk, and cream
—— Fatty sea fish are rarely eaten
It is also difficult to obtain vitamin D from food sources because they are the main sources of vitamin D. Even if you eat 1 egg yolk and 1 cup of whole milk every day, the vitamin D you get is still far from reaching the standard.
How to eat three meals to increase the intake of these two vitamins?
How to eat enough of these two vitamins? It’s very simple, just eat the foods mentioned in the self-examination tips above.
Here is a food suggestion for three meals that can increase the supply of vitamin A and vitamin D:
Have a cup of whole milk and an egg with the yolk. It is best to add 100 grams of orange fruits such as oranges, oranges, mangoes, and papayas. If you are not obese and have normal triglyceride and cholesterol levels, you can also use 2 slices of cheese instead of whole milk.
Eat animal liver twice a week, fried, boiled, or braised in sauce. For example, salted duck liver, braised pork liver, fried chicken liver, etc. are all delicious. Add at least 100 grams of dark green vegetables, such as broccoli, bok choy, etc.
Have a piece of steamed pumpkin, or steamed sweet potatoes, or a dish containing sautéed carrots, and add at least 100 grams of dark green vegetables. Eat fatty marine fish, such as saury, springfish, sardines, etc., twice a week.
Although taking too many vitamin A supplements may cause overdose problems, it is very safe to eat more orange and green fruits and vegetables and absorb carotene on a daily basis. Even if you eat too much carrots and your skin turns a little yellow, it will slowly subside as long as you stop.
However, increasing vitamin D mainly depends on sun exposure. If you supplement it from food, you may consume too much cholesterol, which is more difficult for people with high blood lipids.
In winter, a simple way to increase vitamin D is to bask in the back: When the sun is good and there is no wind, open the window and let the sun directly shine on the exposed back skin (it will not be cold, and the whole body will start to heat up after a few minutes of sun exposure).
Since the back area is relatively large, basking on the back can effectively increase vitamin D without worrying about tanning the face or increasing wrinkles. Sunbathing will not cause vitamin D poisoning.
How to avoid overdose poisoning by supplementing vitamin A and vitamin D?
The best way is to ask a nutritionist or registered dietitian to help you confirm whether the dosage is appropriate.
However, we also need to understand the basic knowledge ourselves. Vitamin A in the human body includes three forms, retinol, retinaldehyde and retinoic acid. Retinol can be converted into retinaldehyde (to maintain normal vision in dim light) and retinoic acid (to maintain normal immunity and child growth and development), but retinoic acid cannot be converted back to retinol.
Generally, the vitamin A in supplements is retinol, or retinol ester. There are also carotene supplements, which can be turned into vitamin A in the body. However, for infants and some people with weak digestive abilities, the conversion efficiency of carotene is relatively low, and it is not as effective as directly supplementing vitamin A.
Therefore, the source of vitamin A = retinol (ester) + carotene. To unify the two sources, “retinol equivalents” are often used to express the total amount in food.
According to my country’s nutrient reference intake standards, the daily supplementation of vitamin A cannot exceed 3,000 retinol equivalents (10,000 international units), and the amount of vitamin D supplementation cannot exceed 50 micrograms (2,000 international units). Higher doses should only be used unless prescribed by a doctor. The amount in a vitamin supplement usually does not exceed the limit, but if you take more than one vitamin supplement at the same time, you need to carefully check whether the combined amount may be too much.
In short, at the end of the year when respiratory infectious diseases are at high incidence, you must take good care of yourself and your family. It is important not to stay up late, go to bed early, maintain a good mood, exercise moderately, and eat enough nutrients. In addition to vitamin C, which attracts more attention, vitamin A and vitamin D, two easily overlooked anti-infective nutrients, must also be eaten enough! Text/Fan Zhihong (Director of the Chinese Nutrition Society, chief scientific communication expert employed by the China Association for Science and Technology)