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

You've probably heard that taking vitamin C will help prevent colds, or perhaps TikTok has inspired you to take turmeric or some other supplement to boost your immune system. The problem is that these bold statements and quick fixes are bullshit. There are a lot of myths about immunity, says Daniel Davisimmunologist at Imperial College London.

In his new book Self-defense: debunking myths about immune healthhe intends to challenge these misconceptions. Davis shows how with every technological advance, such as the use of super-resolution microscopy to demonstrate how immune cells interact with their targets, the stunning complexity of the immune system becomes increasingly clear.

But he doesn't leave us to our own devices, he says. New scientistThis complexity is empowering—helping us appreciate the importance of the immune system to mental health, informing us about lifestyle factors that can harm our immunity, and improving our ability to distinguish facts from fads.

Helen Thomson: Let's start with the phrase “immune health” and the claim that we can improve it. That's actually the wrong way to think about it, isn't it?

Daniel Davis: Yes, there are many products out there that claim to “boost” your immunity. But this is not entirely correct, because although you need your immune system To be strong against infectious agents, if you simply increase its overall power, it can attack the body's own healthy cells and cause autoimmune diseases or allergies. To be able to respond appropriately, it must act in a regulated manner.

So, is this a desire to make our immune system smarter?

Any of these trivial ways of talking about immune health are not nuanced enough. First, each person's immune system is completely unique – at the level of your genes, it is the most unique thing about you. So when we talk about immunity, we can only talk about things that have been shown to, on average, help people, but whether it will help you as an individual is extremely difficult to know.

One of the greatest discoveries is that the immune system does not work in isolation, but is influenced by diet, exercise and our microbiome. Can you 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 a lot of evidence, but proving cause and effect is still quite difficult. But when it comes to stress, we have a molecular understanding of what's actually going on.

Which?

When your body feels threatened, it initiates the fight-or-flight response—a signal sent from the hypothalamus to the pituitary gland and adrenal glands, producing the stress hormone adrenaline. [epinephrine] and cortisol, which help your body prepare for action. This condition calms the activity of your immune system. In the short term this is normal, like skydiving. When you land, there are changes in the number of immune cells in your blood within an hour. Then everything returns to normal. But if you are under chronic, long-term stress, cortisol levels remain elevated and this weakens your immune system over a long period of time, becoming a problem.

The reason we are so confident about how this will happen is that if I look at how well your immune cells kill virus-infected cells or cancer cells in a lab dish, and then add cortisol, those cells will be less effective at killing the infected or cancer cells. Adding this to the correlations we see (such as how people with long-term stress respond less well to vaccines or how they are more susceptible to infections), I can confidently say that long-term stress does affect the immune system.

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

It is still extremely difficult to prove that taking steps to reduce long-term stress is helping you. This makes sense, but it's hard to show. Hospitals measure white blood cell counts as a proxy. [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. Thus, choosing a simplified measurement is difficult.

On TikTok or podcasts, I hear experts, often famous scientists, claim that certain things will help their immunity. Should we believe them?

I use orange juice as an example. I grew up thinking that if I had a cold, I would drink orange juice. I never doubted it. But it turns out that's not true. This goes back to Linus Pauling, who received two Nobel Prizes. He was extremely famous, he was constantly played on the radio, everyone listened to him. In 1970 he wrote a book called Vitamin C and colds – it was an instant bestseller. New factories had to be built to meet the demand for vitamin C. But this was based on carefully selected data and anecdotal evidence, and then very actively promoted in the media.

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The most clearly demonstrated effect on our immune health is long-term stress.
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The truth is that high doses of vitamin C have no effect on whether you get a cold. It's true that people who take high doses of vitamin C shorten the duration of colds by about 8 percent, but even that is difficult to interpret because people who take these high doses are likely doing other things in their lives. [that might be the real reason for the shorter duration]. But this is an ingrained myth in our culture that goes back to one incredibly important scientist who had an evangelical approach to telling us something.

Which brings us to today. We need to be wary of an individual's brilliant success or understanding of anything. We need experts, but we also need to be skeptical of any voice: we need to stick to the scientific consensus.

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

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

Another line of evidence is that people with some mental disorders have higher levels of inflammatory markers in their blood. A teaching children from 9 years old whose IL-6 levels were above average [a cytokine] found that when they were 18, they were more likely to suffer from depression.

Perhaps the most compelling evidence comes from animal experiments: if you inject an animal [IL-6]then the animal will remain more in the dark part of the cage, not exploring, not interacting, simulating a state of mental health.

But we don't yet have a good way to act on this information. Taking common anti-inflammatory drugs, such as aspirin or ibuprofen, does not help depression. Several small tests have shown this. Does blocking cytokines, just as is done for patients with rheumatoid arthritis, help people with mental health problems, even if they don't?'T rheumatoid arthritis, not yet clear. Where this has been tested, the results so far have been either negative or unclear.

Future research should develop tests to detect people who might be helpful: Could it be that people with specific mental disorders and above-average blood levels of various cytokines, and perhaps some other telltale signs that have yet to be discovered, could actually be helped by anti-cytokine drugs? We don't know. But the knowledge itself can be empowering—knowing that if you suffer from a mental illness, it may be related to something like your immune system. This is a truly important milestone.

People should constantly ask you about what they can do to improve their immunity. What will you tell them?

There are some answers, but they are not black and white. Long-term stress is a problem. It is very important to get enough sleep. But I don’t know how much and when for you personally. We know the microbiome is important, but can I give you something that will definitely improve your microbiome? No, I can't. These answers may be unsatisfactory, but there is greater power in recognizing that this is all really complicated. There is always something more to history, nuances. If there's one thing you get from studying the immune system, it's the sheer wonder of how complex it is.

Self-defense: debunking myths about immune health

On New Scientist Live, world-leading immunologist Daniel Davis explores the fascinating world of our immune system, from the effects of stress and age to the impact of exercise and diet.

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