Fasting reduces bodily inflammation

It works, counterintuitively, by pushing up levels of a lipid associated with an inflammatory state...
02 February 2024

Interview with 

Clare Bryant, University of Cambridge




We learned this week that the Prime Minister, Rishi Sunak, undertakes a fast at the start of every week, consuming only water, tea or black coffee from 5pm on a Sunday to 5am on Tuesday. But could this enforced 36 hours of what most of us would regard as hell, have health benefits? Cambridge University Immunologist Claire Bryant has published a paper this week that suggests Rishi Sunak might be on to something. Fasting, she's found, drives down levels of inflammation in the body, by pushing up the concentration of a chemical called arachidonic acid. This, she's found, blocks an inflammatory pathway that can be linked to a host of diseases and accelerated ageing. Aspirin also targets it, which might be one of the ways that the painkiller exerts its therapeutic effects...

Claire - We were really interested in the beneficial effects of fasting. People that overeat or have the western diet, the high fat diet, that led to an increase in the activity of an inflammatory complex called the inflammasome. We were interested because fasting people seem to have the reverse

Chris - Indeed because people who calorie restrict are said to live longer, aren't they?

Claire - Yeah, they are. They seem to have all sorts of other health benefits as well and it's completely reversed for people who are on a high fat western diet. So, why? That was the question. What does it mean and how does it work?

Chris - How did you pursue it?

Claire - Two things. There was a happy coincidence, actually. We had started to do some work in the lab and we were looking at, in our models, what sorts of lipids were being produced. And there was a particular profile of lipids which was totally unexpected. One of them, a lipid called arachidonic acid, which normally I would associate with an inflammatory state, was actually elevated.

Chris - That is weird because that's the starting material for making a whole load of inflammatory chemicals in the body. So it seems paradoxical that, in people with low levels of inflammation, they should have high levels of the starting material? Is that just because they're not using it to make the inflammatory materials?

Claire - That was what we thought, and that was certainly what the data we were seeing in our in vitro models were suggesting.

Chris - Putting this together then, we calorie restrict by some mechanism, this puts up the level of arachidonic acid, which turns down this inflammasome, the inflammatory complex that we know maps onto being less healthy. How does the calorie restriction push up the arachidonic acid so that you end up with less inflammation? What's going on?

Claire - Well, that's the million dollar question. In fact, what's also interesting, I've been thinking about this a lot, is how long do you need to fast? What fasting regime do you need to undertake? How many days a week, one day a week? Rishi Sunak's 36 hours? Is that the ideal way or is it short, long? There's a whole bunch of questions here that we now need to further investigate, and because we can find the arachidonic acid, obviously we can track this over time, we can map this against the inflammatory markers and see exactly what happens. But the honest answer is, this is one of the first steps in the puzzle to understand this direct switch between arachidonic acid and inflammasome activity.

Chris - The other thing that's interesting with this is, if people take aspirin for things like heart disease, they also get benefits in other things like cancers, Alzheimer's disease, other degenerative states. People have said this is because it stops the inflammation. What does aspirin do to arachidonic acid?

Claire - So aspirin inhibits the breakdown of arachidonic acid. So, one of the things we think as well, that this work has shown, is that there's yet another way in which drugs like aspirin are anti-inflammatory because the arachidonic acid is not broken down, this can then feed back to inhibit the inflammasome activity, and that will then decrease your inflammation. Aspirin is a many functional drug and the longer we do the research, the more effects and mechanisms we find in these drugs.


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