Hey everyone and welcome back to another mini episode of Ask Dr Hazel. I'm your host and I'll be answering all your bringing questions.

Okay, let's hear from this week's listener.

Hi Hazel, I'm running my first marathon this year London 2022 and I've never really done any runs for longer than an hour.

And I also suffer from IBS so I was just wondering if you had any tips for what to eat, pre-run, what to have during a run to fuel because that's not something I've ever really done before.

Thank you.

First of all, big congrats on signing up to the marathon and I'm sure you'll do amazing.

So I guess there's two questions in this.

What to eat for a marathon and how to avoid triggering IBS symptoms or causing gut issues during the race.

So let's tackle the common gut issues that runners often experience first and why this happens.

So symptoms like feeling nauseous, bloated, diarrhea and cramping are some of the common symptoms that people report during exercise particularly during endurance sports such as running, cycling, triathlon, etc.

Now we don't know for certain why this happens but there's a couple of factors that come into play.

So during a high-intensity exercise, blood flow is redirected away from the gut to the working muscles, the heart and the lungs.

And this can cause your gut to be slightly low in oxygen which impairs absorption of nutrients and fluid from the gut as well.

And mechanically speaking, the repetitive movements so the up and down movement of running can also trigger symptoms.

Nutrition also plays a role so what you eat and how much you eat also contribute.

Fiber, fat, protein and fructose have all been associated with a greater risk of developing gut issues.

And pre-workout supplements are another thing to consider because they often contain caffeine and other stimulants which can trigger nausea and irritate the gut.

So don't try anything new on race day.

Also it's a pretty stressful experience so your hormones such as adrenaline and cortisol are also high and they can contribute.

And unfortunately those with a history of gut issues such as IBS are also more likely to suffer from GI symptoms during exercise.

So that's the why but what can you do about it?

Well, my top tips would be reduce your intake of high fiber and gas producing foods on the day of as well as the day before your race.

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