Is it a misconception that getting a cold is due to a weakened immune system?

“Dr. Takao Takahashi’s Ask Anything” Is it a misconception that getting a cold is due to a weakened immune system? A story about what you need to know about “immunity” for your child.

When hearing about an unknown virus for which there is no established cure, you start to worry about how you can protect your little one. Many people have heard information about this virus such as “elderly people with weakened immune systems are more likely to become seriously ill,” and start to think about ways to boost the immunity system of their children. Thus, we asked Dr. Takao Takahashi, a pediatrician and professor at Keio University School of Medicine, about immunity and infection prevention.

Is it a misconception that getting a cold is due to a weakened immune system?

Covid-19 is an unknown virus in which no one in the world is immune to.

Edit Staff I:The spread of this new coronavirus is causing anxiety not only among the elderly people who are considered to be at high risk of serious illness, but also among those who are raising children.

Dr. Takahashi: I understand your anxiety. Covid-19 is a major threat to humans. The reason is that this virus is something that no one in the world has ever experienced before. A wide variety of viruses and bacteria exist in the world, and once the human body experiences each virus or bacteria, it remembers the information and obtains the ability to defend itself, making the body difficult to become infected, or even if infected, it can be healed with only mild symptoms.

I: I wanted to ask you about “immunity” this time. It is said that if we correct our diet and lifestyle, our immunity will improve, right? There is a conception that it is harder to catch a common cold if we have a high immunity.

Dr. Takahashi: Is that so… However, in most cases, catching a cold easily or getting sick easily have nothing to do with whether you have a strong or weak immunity, except for a few people with a disease called immunodeficiency.

I: Oh, really? There are many tv shows and programs that talk about what to eat to boost our immunity to avoid catching a cold.

Dr. Takahashi: There is nothing wrong with enjoying eating, believing that the food is good for you, but it doesn’t do much in terms of boosting your immunity. Basically, eating a particular food a lot doesn’t boost your immunity. Immunity is the ability of the human body to recognize “foreign” substances, such as pathogens, toxins, and in some cases, cancer cells, and to block or eliminate them from entering into your body. This is very important for human life, so it will not be deficient easily. The power of immunity is protected by the genes that people originally possess, and there is basically no significant difference in the power of immunity between individuals unless they have an extremely unbalanced diet or are under extreme stress.

I: But it is said that if your immunity is weakened, you are more likely to get cancer, right?

Dr. Takahashi: There is certainly scientific data but having low immunity doesn’t always lead to cancer nor does it mean that immunity of those who have cancer is necessarily low. In the first place, it is not normal for the immunity to be weakened to the point of being susceptible to cancer. Moreover, immunity against cancer cells is not something that can be detected by tests.

I: I didn’t know that…It was an eye-opening truth. There are no individual differences…

Dr. Takahashi: Simply put, immunity is supported by two types of lymphocytes, T cells and B cells, and white blood cells called neutrophils. These cells are used to make immune antibodies against viruses and bacteria and to eat (phagocytosis). I can say that there are no differences in the functions of these immune cells. If the immunity is low and is in a depressed state, it is a serious disease. In fact, there is a disease called immunodeficiency, and if a person was born with it, it will cause them to contract rare infections that they would not normally get or become seriously ill with a cold-like illness that would normally not be so severe. But these are really rare cases.

I: As long as it’s not a special disease, the immunity of most people is doing its job, right? Even so, there are some children who catch colds easily. I thought it was because of the difference in immunity.

environment is key factor

Dr. Takahashi: The biggest cause of easily getting infectious disease is the “environment.” The living environment, the season, and the prevalence of infectious diseases are the typical environmental factors. By the way, when someone says to me, “My child has been catching a cold easily these days,” the first thing I ask is, “Hasn’t he/she started going to kindergarten?” When children start going to kindergarten, they are exposed to so many children every day, so this makes them prone to catch a cold.

I: Does it mean that regardless of our individual immunity, if you go to a place where there is “close contact” as we often hear these days, you will be infected with some kind of virus?

Dr. Takahashi: That’s right. Pediatricians who are in the first year catch colds from children with infectious diseases very easily. But by experiencing this many times, we will build up immunity to various infectious diseases, and eventually become invincible (laughs).” I haven’t had a cold in over 30 years. You just “live and learn!.”

A first-year pediatrician catches a lot of colds, but eventually becomes invulnerable.

I: I learned that immunity is built through the “experience” of exposure to foreign substances such as viruses. If so, does that mean that newborn babies, who have not been exposed to anything (supposedly), have little or almost no immunity?

Dr. Takahashi: I can’t say that’s the case. Babies receive immune proteins through the umbilical cord while they are in the mother’s belly. Children are exposed to various kinds of viruses right after they are born, but mothers have given their children antibodies to prevent them from getting sick easily. Babies are less likely to get sick right after birth because they are protected by their mother’s immunity. Other than that, breast milk is also thought to play a key role in boosting a baby’s immunity.

A first-year pediatrician catches a lot of colds, but eventually becomes invincible.

I: Come to think of it, newborn babies don’t get sick that often.

Dr. Takahashi: However, about six months after birth, the immunity inherited from the mother disappear. From then on, they are able to protect themselves with their own immunity. There are times when babies catch a cold virus from a friend without realizing it and develop a fever causing their parents to worry, but through these experiences, babies acquire and develop immunity. There are a lot of immunities that you can’t acquire until you have experienced them. Foreign substances include not only viruses and bacteria, but also foods such as milk, proteins, and egg whites. It has also been found that early and gradual exposure to these foods can help the body develop a proper immune system and become less prone to allergies.

I: Vaccinations are based on this concept, aren’t they?

Dr. Takahashi: That’s right. Some infections can cause very severe symptoms or even permanent disability. The mechanism of vaccination is to build up immunity by introducing a toxin-free virus into the body beforehand to avoid contracting infectious diseases. When a real virus enters your body, your body is going to say “Oh, I know this one” and can attack it.

I: I see. I learned a lot as usual.

Dr. Takahashi: One last word. If your immunity is weakened for some reason, you are at a high risk of contracting infections, but if the immunity is too strong, you will develop allergies. A weak immunity is a problem, but an overly strong immunity is also a problem. Just like the relationship between the gas pedal and the brake in the car, balance is important. If you step on the gas pedal of your immunity too much, you may experience allergic reactions to foods, or even hay fever. But if you step on the brake too much, viruses and bacteria will invade your body easily. If you live a normal life, your immunity will naturally maintain the right balance. Balance is the key to everything.

I: Yes, it’s all about balance. Every time I hear about your stories, I am amazed at the wonders of the human body and the wonderful power we have. Thank you again for your time today!

How was the story about infectious diseases and immunity? The topic was different from usual, but it was very interesting and I was very moved.

The threat of Covid-19 seems to be continuing. No one is immune to this virus, so please wash your hands and disinfect with alcohol to avoid infection. I hope that we will be able to return to a peaceful life as soon as possible.


Dr. Takao Takahashi

Keio University School of Medicine, Head Professor of Pediatrics, Medical Doctor specializing in General Pediatrics and Pediatric Neurology

After graduating from Keio University School of Medicine in 1982, Dr. Takahashi served in the Department of Pediatric Neurology at Harvard’s Massachusetts General Hospital and as a neurology lecturer at Harvard Medical School. He returned to Japan in 1994, and has been active as both doctor and professor at Keio University Pediatrics since. His hobby is running, and his best marathon time is 3 hours 7 minutes at the 2016 Tokyo Marathon, earning the nickname of “fastest pediatric professor in Japan.”


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