Interpretation of popular science:
Some milk advertisements claim that it contains immunoglobulin, which can improve human immunity and resist COVID-19. Is there really immunoglobulin in milk? Is it useful to boycott COVID-19?
First, milk may indeed contain immunoglobulin.
Immunoglobulin is an immune protein that can specifically bind to antigens, and most of them have antibody activity. Include immunoglobulin A(IgA), immunoglobulin D(IgD), immunoglobulin G(IgG), immunoglobulin E(IgE) and immunoglobulin M(IgM).
Bovine immunoglobulin contained in milk is mainly IgG. These substances are produced in the cow mother's body and then sent to the calf's mouth. When the calf's intestine is not fully developed and can absorb protein with larger molecules, it is incorporated into the body, forming calf's immunity.
But pay attention to these three points:
1, immunoglobulin is afraid of heat, and may be gradually inactivated when it exceeds 50 to 60 degrees Celsius.
Refrigerated pasteurized milk is usually heated at 70~90 degrees Celsius for a short time to inactivate some immunoglobulins. Those sterilized milk with a shelf life of six months to one year at room temperature, not to mention immunoglobulins, are heated at a temperature exceeding 120 degrees Celsius.
Therefore, only those milk that have been sterilized at low temperature can maintain the activity of immunoglobulin to the maximum extent.
2. Antibodies in milk only play a role in human intestines and will not enter the blood.
When drinking milk, the protease in our intestines will gradually decompose milk into small peptides and individual amino acids, and then absorb them into the blood. At this time, the immunoglobulin fragment has already lost its biological activity. Moreover, because bovine immunoglobulin is different from human immunoglobulin and belongs to "allogenic protein", if bovine protein really enters human blood, our immune system will automatically attack it and trigger an allergic reaction.
Cattle antibodies can only play a role in human intestines. Moreover, because human diseases are not completely consistent with bovine diseases, bovine antibodies passing through human intestines can not completely solve various gastrointestinal diseases, but may help. For example, by immunizing cows, antibodies against certain intestinal pathogens are produced. When human beings drink these low-temperature processed milk, immunoglobulin "passes through the intestine", which can eliminate some intestinal pathogens by the way and reduce the chance of bacterial food poisoning.
3. Antibodies cannot be mixed.
First of all, cow mothers have antibodies to any pathogenic bacteria, so it is possible to pass these antibodies to calves. To produce immunoglobulins such as antibodies, it is necessary to contact the corresponding antigens, such as some bacteria or some viruses. In order to make antibody production higher, antigen stimulation must be repeated many times. Finally, even if there are antibodies in the blood of the cow mother, only a part may enter the milk.
If the cow hadn't touched COVID-19 and defeated him, it wouldn't have produced this antibody and passed it on to the heifer through the milk. So far, no milk on the market dares to claim to contain COVID-19 antibody.
Therefore, although some dairy products contain immunoglobulins, these immunoglobulins are not equivalent to protein related to improving immunity in COVID-19, so it cannot be claimed that they are beneficial to prevent virus infection.
In addition, the mechanism of human milk and milk is the same. Breast-feeding mothers can transmit antibodies possessed by their bodies to their babies through breast milk, thus extending the protection of babies beyond the uterus. If the mother has recovered from the new coronary pneumonia and the virus test is confirmed negative, then she can breastfeed the baby. At this time, it is not excluded that the mother may pass the antibody to the baby in this way. But whether it contains COVID-19 antibody or not, and whether the antibody is strong enough, we haven't seen the research data, so we can't confirm it.
How to drink milk?
The main benefit of fresh milk is not the low immunoglobulin content of dairy cows, but more to improve the overall diet and nutritional balance. For example, for people with nutritional deficiency, high-quality protein, B vitamins and vitamin A in milk help to maintain the production of autoimmune globulin.
Therefore, if you drink milk every day, you are not afraid of higher prices. You can choose milk with better quality and more active ingredients. If you are just afraid of COVID-19 and want your body to be more resistant to diseases, it may be more important to drink some milk, eat three meals, improve the overall nutritional balance of your diet, have a good sleep, exercise moderately and keep a good mood.
Rumor experts: Director of China Nutrition Society, Fan Zhihong, Associate Professor of College of Food Science, China Agricultural University.