Why everything you thought you knew about your immune system is wrong

You’ve probably heard that getting enough vitamin C will ward off a cold, or maybe TikTok has inspired you to take turmeric or another supplement to boost your immune system. The problem is that these bold claims and quick fixes are absurd. There are many myths about immunity, says Daniel Davis, an immunologist at Imperial College London.

In his new book Self-defense: a myth-busting guide to immune healthhe sets out to challenge these misconceptions. Davis shows how, with each technological advance, such as the use of super-resolution microscopy to demonstrate how immune cells interact with their targets, the mind-boggling complexity of the immune system becomes more apparent.

But far from leaving us adrift, he says New scientistThis complexity is empowering: it helps us understand the importance of the immune system in mental health, makes us aware of lifestyle factors that could harm our immunity, and improves our ability to separate fact from hype.

Helen Thomson: Let’s start with the phrase “immune health” and pretend we can strengthen it. That’s not really the right way to think about it, is it?

Daniel Davis: Yes, there are a number of products that suggest they can “boost” your immunity. But that doesn’t seem quite right, because even though you need your immune system To be powerful against infectious agents, if you just increase its potency generally, it could attack healthy cells in the body and cause autoimmune diseases or allergies. He must act in a regulated manner to be able to react appropriately.

So, is it a question of wanting to make our immune system “smarter”?

None of these ways of talking about immune health are nuanced enough. On the one hand, everyone’s immune system is completely unique – in terms of your genes, it’s the most unique thing about you. So when we talk about immune health, we can really only talk about those things that have been proven to, on average, help people, but it’s extremely difficult to know whether or not it will help you as an individual.

One of the biggest discoveries is that the immune system does not operate in a silo, it is influenced by diet, exercise and our microbiome. Is it possible to say which lifestyle factor has the most significant impact on immune health?

What has the most clearly proven impact on our immune health is long-term stress. For the other things you mentioned, there is plenty of evidence, but it’s still quite difficult to prove causation. But with stress, we have a molecular understanding of what’s really going on.

Which one is?

When your body senses a threat, it has this fight-or-flight response: a signal goes from your hypothalamus to your pituitary gland to your adrenal gland, producing stress hormones: adrenaline. [epinephrine] and cortisol – which help your body prepare for action. This state calms the activity of your immune system. It’s good in the short term, doing a parachute jump, for example. When you land, the number of immune cells in your blood changes for about an hour. Then it returns to normal. But if you’re in a state of long-term chronic stress, cortisol levels stay higher, weakening your immune system over a longer period of time, which becomes a problem.

The reason we have so much confidence in how this plays out is because if I look at how effective your immune cells are at killing virus-infected cells or cancer cells in a lab dish, and then add cortisol, those cells will be less effective at killing infected cells or cancer cells. Adding this to the correlations we observe – how people who experience long-term stress respond less well to vaccines, for example, or how they are more susceptible to infections – means I can confidently say that long-term stress impacts the immune system.

If I’m stressed and make lifestyle changes, is there a way to measure my immunity to see if it helps?

It’s still extremely difficult to prove that doing something to reduce your stress in the long term helps you. It makes sense that this is the case, but it is difficult to demonstrate. In hospitals they measure the white blood cell count as an indicator [for immune health]. But there are many different types of immune cells in the body, and to some extent, every cell in your body is part of your immune system. It is therefore difficult to choose a simplistic measure.

I hear experts, often renowned scientists, on TikTok or podcasts claiming that certain things will help with their immunity. Should we believe them?

The example I use is orange juice. I grew up thinking that if I had a cold, I would drink orange juice. I never questioned it. But it turns out this is not true. It goes back to Linus Pauling, who won two Nobel Prizes. He was extremely famous, always on the radio, everyone listened to him. In 1970, he wrote a book called Vitamin C and the common cold – it was an instant bestseller. New factories had to be built to meet the demand for vitamin C. But this was based on cherry-picked data and anecdotal evidence, and then was very strongly defended in the media.

The truth is that high vitamin C supplementation has no effect on whether or not you get a cold. It’s true that in people who take high vitamin C supplements, the duration of their colds is reduced by about 8 percent, but even that is difficult to interpret because people taking these high doses are likely doing other things in their lives. [that might be the real reason for the shorter duration]. But it’s a myth rooted in our culture, which comes down to an incredibly important scientist with an evangelical approach to tell us something.

Which brings us to today. We must pay attention to the brilliant success or insight of each individual in anything. We need experts, but we must also be wary of any single voice: it is the scientific consensus that we should favor.

Recently, there has been growing interest in the links between our immune system, inflammation and mental health. This all sounds fascinating.

The link between the immune system and our mental health is a truly exciting frontier. The initial trigger was that a group of people who were taking anti-inflammatory medications for rheumatoid arthritis reported feeling better mentally even before their physical symptoms improved. This is a type of medicine that blocks the action of a cytokine – cytokines are protein molecules that immune cells produce and secrete to communicate with other immune cells.

Another line of evidence is that people with certain mental health conditions have higher levels of inflammatory markers in their blood. A study on 9 year old children who had above-average IL-6 levels [a cytokine] found that by the age of 18, they were more likely to suffer from depression.

Perhaps the strongest piece of evidence comes from animal experiments – if you inject an animal [IL-6]then the animal will stay more in a dark area of ​​the cage, will not explore, will not interact, imitating mental health problems.

But we don’t yet have a good way to act on this information. Taking a common anti-inflammatory medication like aspirin or ibuprofen to treat depression doesn’t work. Several small tests have shown this. That blocking a cytokine, just as is done for rheumatoid arthritis patients, helps people with mental health problems, even when they don’t have any.‘t have rheumatoid arthritis, it’s not clear yet. Where this has been tested, the results so far have been either negative or unclear.

Future research should design tests to identify people who Might Benefit: Could it be that people with specific mental health issues and higher-than-average levels of various cytokines in their blood, and perhaps other telltale signs yet to be discovered, could possibly be helped by anti-cytokine medications? We don’t know. But the knowledge itself could be rewarding: knowing that if you have a mental health problem, it could be linked to something like your immune system. This is a really important boundary.

People must ask you all the time what thing they can do to improve their immunity. What do you tell them?

There are answers, but they are not black and white. Long-term stress is a problem. It is important to get enough sleep. But how much and when, for you individually, I don’t know. We know the microbiome is important, but can I offer you something that will definitely improve your microbiome? No, I can’t. These answers may not be satisfying, but the ultimate power is knowing that this is all really hard. There is always more to the story, nuances. If there’s anything you get from studying the immune system, it’s simply the wonder of its complexity.