Most replayed moment: Can you really boost your immune system? | Professor Daniel Davis

**Jonathan Wolf** (0:01)
Hello and welcome to ZOE Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health.
Today, we're talking about the immune system. It's one of the most important systems in our body, and it's also one of the hardest to understand. You can't see it, you can't feel it working, and there's no simple way to measure whether it's strong or weak. But when it fails, we certainly notice. Everywhere we look, supplements and superfoods promise to boost our immune system.
But how many of these claims are actually supported by science? Professor Daniel Davis joins me to explain how our immune system truly works, and what the evidence says is the best way to support it.

**Daniel M. Davis** (0:46)
The immune system is very complicated. I'm sure people are very aware of the importance of your immune system in fighting off all different kinds of infections. It's also important in preventing us from succumbing to other kinds of illnesses, cancer, and all sorts of other problems that could arise in our health. It's inherently complicated because it has to fight off all different kinds of possible infections, including infections that have never before existed in the universe. A new type of virus could arise at some point, and our immune system has to be able to fight that. So the immune system is there to fight off things that are potentially dangerous, but not attack any normal part of your healthy body.
And to some extent, every single cell of you is part of your immune system, because almost all the different types of cells that make up the human body actually have some ability to know when they are infected with a virus, for example, or when they are turning cancerous.
Most cells of the body have already some inbuilt sensory mechanism to detect when they themselves have a problem, and they could signify to other bona fide immune cells that they have a problem. So all of your body is part of the immune system.

**Jonathan Wolf** (2:07)
I mean, one thing I heard really clearly was that not only does it have to be incredibly good at attacking these bad things outside, but it needs to be really smart at recognizing whether or this is actually part of my body, so it mustn't be attacked. I'm interested that you mentioned that just in the summary. Is that a very important part of what it needs to do in order to be healthy?

**Daniel M. Davis** (2:28)
Absolutely, because you will know that there are any number of products and ideas telling you how to boost your immune system. And on the face of it, that sounds quite a simple thing that we want to be doing.
But having just told you, the complexity of what the immune system has to do, a layer of depth in the idea of boosting the immune system is immediately apparent. What does that actually mean? If you just somehow boost the ability of your immune system to be very active and start fighting things, then you don't want to do that because it would inadvertently start attacking things that are part of the normal healthy body, and that would then cause you problems in itself. So it's important that we understand the complexity and the nuance in what the immune system has to be able to achieve, because already we're at the point where some of the soundbites and clickbait you might come across for, do this one thing to boost your immune system. Already now we could be questioning, what does that actually mean? I don't want to just boost my immune system in a very general way to make it more active. I need it to be restrained in some situations because I don't want the immune system to react against my own body or things that are not particularly harmful to me like would happen if your immune system starts to react against food or something and gave you an allergic reaction.

**Jonathan Wolf** (3:47)
One of the things I thought of is you were describing this like not reacting to things that are normal in the environment is seasonal allergies or hay fever. I'm probably thinking about that because I get this now regularly, which I never did as a kid. Is that an example of my immune system?

**Daniel M. Davis** (4:05)
Sometimes we belittle allergies because they're not spoken out in the same way that cancer is, because allergies are not really a top 10 cause of death. But the number of people who get allergies, you just mentioned you get allergies, I get allergies, hay fever as well. It's two billion people. So allergies are incredibly important and by and large they are the outcome of our immune system reacting against something that is not particularly harmful, like it could be pollen as an example. But there are many different types of allergies, of course. So just even that knowledge in itself, hopefully, means that thinking about the complexity of the immune system means it's all about having the immune system react to things that are truly dangerous but not overreact against things that are not really a problem for the body. There's another side to that as well, which is that when you do get a genuine infection, a virus infection, let's say, and your immune system has to deal with that, so that involves a heightened state of our immune system, the particular cells in your body that are good at fighting that virus have to multiply and number.