Ironman nutrition update: I might have got it right at last

A huge part of ironman racing – or any ultra endurance event – is nutrition.  If you can’t fuel yourself properly during the race either you won’t complete it or you’ll be in a bad way once you do finish.  Unfortunately, despite doing all the ‘right’ things during training for all three of the iron distance events I’ve done,  I’ve had problems.  But for Outlaw, I think I made a breakthrough because I completed the whole event without feeling sick, ill or dizzy. And even though I didn’t feel great afterwards, it was a whole lot better than in the past.

So what made the difference?  I think – think – what made the difference was increasing the amount of electrolytes I took in during the day, but I made other changes, too.  I’m sharing this in case there’s anyone out there who’s struggling with the same issues.

Why is nutrition so critical for iron distance events?

When you’re doing a marathon, nutrition before, during and after the race is key and getting it wrong can spell disaster.  But at least you can fuel up in the days before the race, get some good sleep and the chances are you’ll get through it, even if the last few miles are unpleasant.  With ironman effectively you have to fuel up for your marathon while you’re on the bike, and by the time you’ve got on the bike, you’ve already done a biggish swim when you can’t eat at all. So on the bike you’re eating to recover from the swim, fuel the bike and pre-load for the run. It’s tricky to get right for all sorts of reasons:

  • when you exercise  it’s harder for your gastro-intestinal (GI) system to process food because blood is diverted from the gut to the working muscles.  The more intense your exercise, the harder it is to digest food.  To help digestion you have to slow down – not what you want to be doing during  a race.  You have to train your body to cope, but it doesn’t always work.
  • after a certain number of hours of exercise the GI system can stop working almost completely
  • dehydration can affect stomach emptying rates – so even if you’re getting the carbs in, they’re not getting into your gut and into your blood and…
  • … food staying in your stomach for too long can irritate the stomach which means if you put anything else in it you feel sick
  • if you eat solid food on the bike you might feel fine until you get onto the run and it starts sloshing around… and you feel sick
  • if you eat just gels on the bike all the concentrated glucose – even if you dilute them with the right amount of water – can irritate your stomach and affect kidney function, too
  • everyone seems to respond differently so what works for one person spells catastrophe for another
  • and so on. There is so much to learn and understand about nutrition!

What went wrong in past ironman races?

Finishing Roth. You can see my hand spasms.

In my first ironman (Challenge Roth 2010)  I did what I’d practiced in training ie bike fuelling was part gels and part solid food – namely malt loaf, the odd half banana and a bit of marmite sandwich.  I also took a salt tablet (Salt Stick electrolyte tablets) every hour on the bike.  I’d learned from a half ironman that stopping solid food an hour before the end of the bike still led to uncomfortable stomach bloating on the run, so I stopped solid food two hours before the end of the bike. Unfortunately I instantly felt bloated and uncomfortable on the run and discomfort turned to nausea over the first 10k and I was unable to take on anything – even water.

To cut a long story short I finished the marathon strongly and on good form having only taken in a few sips of water and a few chunks of water melon in the second half. (It was probably a good thing I’d eaten so much during the bike – it carried me through the marathon, even if it did make me feel awful).  My hands locked into a wierd spasm for the last few k. I felt brilliant for about 20 mins after the end, but failed to eat or drink anything – even though I tried. Then nausea and feeling truely awful took over and I ended up in the medical tent on a salt drip, feeling appalling for a couple of hours. Unsurprisingly my blood pressure was very low (90/60). I ate or drank nothing that evening but was absolutely fine the next day.

For my next race, a year later, one of my main race goals was to feel well at the end and avoid the medical tent. I’d researched it and asked advice, and the work of Asker Jeukendrup, a  professor of exercise metabolism at Birmingham University struck a chord.  He’d advised Chrissie Wellington and Haile Gabresellassie and if it was good enough for them it was good enough for me.  Key Jeukendrup teachings/suggestions:

  • the human gut is pretty much the same length whatever size or gender you are. It can absorb around 60g of glucose per hour – full stop. Therefore calculating how many grammes of carb per hour per kilo of bodyweight was pointless.    This makes sense if you think how good endurance runners are small and wiry while it’s much harder for a tall, large person to run well as easily. The smaller person is getting more fuel in per kilo of bodyweight and can therefore run better.
  • Fructose uses a different transport system to glucose across the gut wall into the blood and so if you add fructose into your carb mix, you can take in more fuel per hour – up to 90g/hr (60g glucose and 30g fructose).  Many sports nutrition products now provide a mix of glucose and fructose in that proportion so it’s not hard to do.
  • Performance is directly related to fuel intake among elite athletes.

So for ironman 2 (Ironman Regensburg 2011) I resolved to try to ingest enough gels and bars (PowerBar products were supplied on the course and that’s what I used in training – they cost a fortune!) to give me 90g an hour.  I stuck to water to make sure this was all diluted enough.  It meant I was constantly munching and towards the end of the bike you lose your appetite and eating is not really want I wanted to do. But I managed it, except for one period near the end of the bike when I suspected my stomach wasn’t happy so I stuck to water for half an hour – no eating – and I felt fine again.  I had a salt stick pill every hour on the bike again.

On the run I felt fragile, stomach-wise, but ok. I was going to play the run nutrition by ear, depending on what I felt I could stomach at the time.  At 10k I got my wierd hand spasms again and felt fuzzy and light-headed.  My whole head, lips and face were buzzing. I interpreted this as an urgent need for sugar so whopped down a gel.  Big mistake.  Actually the buzzing etc stopped but the concentrated sugar in the gel tipped my stomach over the edge and it rebelled. I felt appalling for the rest of the run. I did take on a bit of coke, isotonic energy drink, water, salt… but none of it stopped me feeling so ill.  At the end I just couldn’t wait to finish so I sprinted up the finish chute and straight into a medic who invited me to come to the medical tent – on a stretcher.  I was hyperventilating and felt sick – I was sick. This time I had two drips. But my blood pressure was ok, as was my blood sugar. I felt ill for much longer though – well into the night. But still was on top form the next day and eating like a horse again with no after effects.

In hindsight I probably should have just stuck to water after that disastrous gel. I probably needed to dilute my stomach contents (pure sugar) to promote stomach emptying. But instead I assaulted it with more stuff.  I didn’t really give it a chance to recover.

I said that night – never again, but I just wanted to know how I might do if I actually managed not to feel so bad on the run.


The strategy for ironman 3 (Outlaw 2012) didn’t come together until the last minute.   I decided to stick to PowerBar Energise Bars even though High 5 was being supplied on the course.  I’ve not been able to face High 5 since Roth. And I like Energise Bars. They’re like opal fruits and I love ’em.  But rather than spend a fortune and use them throughout six months of training, I fuelled many of my bike rides with jelly babies.  Then whenever I did a long bike without jelly babies – ie when I was practicing race day nutrition and sticking to PowerBars – I really missed them. So I decided jelly babies had to be part of the mix on the bike.

I also re-listened to various podcasts about ironman nutrition and consulted a couple of endurance-running doctor friends. As a result I made a few changes:

  • I took on some fat and protein during the bike.  Gordo Byrne of Endurance Corner suggests that taking on a bit of protein and fat might help to keep the stomach happy; give it something to think about other than sugar, sugar, sugar.  (PowerBars have a bit of protein and fat in them – not much, but at least they’re not pure sugar which is what I wanted to avoid.)  In Mallorca for the 70.3 in May, I’d gone out for a course recce and got lost coming home so was out for longer than I’d expected.  The only fuel I had with me after a while was some mixed nuts and raisins – but they did the trick. So I added a few almonds and walnuts to my bento box for race day.  I took enough PowerBars with me to get in 90g an hour as usual (two bars an hour), but I knew that I hadn’t had that much in most of my training rides so was more relaxed about whether or not I actually ingested that much.  I knew I was potentially taking a risk by not being fuelled up enough for the run, but I was happy to trade feeling well for moving fast.
  • I took on more electrolytes. Anecdotal evidence from friends suggested a salt stick tablet every 30 mins instead of every hour might be better than one an hour. My own experience was that if I used a Nuun or Zero tablet in my water I felt particularly good on a ride, even if it wasn’t a boiling hot day.  One doctor friend confirmed he never takes on just water but always water with added electrolytes.  So, in addition to my normal practice of drinking only electrolyte drink the day before, I had two 750ml bottles of water with added Nuun tablets on the bike, then once those were finished, rather than interrupting the bike to add tablets to new water bottles, I opted to have a salt stick tablet every 30 mins.  I extended this practice into the run as well, but cut it down to one pill an hour.
  • Assuming I got to the run in good order – after all, I’d managed that last year – I resolved to make things as easy as possible for my beleaguered GI system by sticking to the  isotonic energy drink supplied on the course.   If I felt sick I’d have some water to help dilute stomach contents, knowing I’d taken on enough electrolytes to not be at risk of hyponutremia.  My thinking was that it would be easier to get energy into my blood system if it was transported by something isotonic.  Last time I think I tried so many things to feel better I completely threw my GI system into a panic – or at the very least irritated my already-sensitive stomach.  However, on a last minute whim, I added some jellybabies to my bag for the run. Just in case.
  • As for the wierd hand spasm, I’d been told two possible causes by my doctor friends. One said it could be caused by a lack of calcium ions (used for normal muscle contraction among other things) while the other said it was caused by hyperventilation.  Since being told that, I’d noticed that I do let my breathing get away with me a bit during parkruns.  It was easy to control – I just had to consciously calm down my breathing.

Well, all this  more or less worked. Except I didn’t eat nearly as much as 90g per hour on the bike.   I came back with at least half my bars untouched. The nuts went down really well – I chewed them until they were really liquidy and I was so relieved I had the jelly babies. They were wonderful.  On the run I tried the isotonic drink but the mixed was too concentrated at the first feedstation so that put me off.  I cautiously sucked a jelly baby instead.  After that I alternated with water and correctly-mixed up energy drink at aid stations. And I confess that I did have the odd few sips of coke, too. As the run went on I felt good – knackered, but not ill or nauseous – and I celebrated every time I went past my friends telling them I didn’t feel sick.  I got braver and braver with the jelly babies, too.

In total on the run I ate about 20 jelly babies @ 20 cals each. I even felt brave enough to tackle banana and had two very small half bananas in the last ten miles. Again, nibbled and chewed to a liquid very cautiously. Each one took about 15 mins to eat. And the hyperventilation? I caught myself hyperventilating periodically on the run and just stopped it. No funny hand spasms or fuzzy face.

I finished feeling fine – but that had happened before so I was still prepared to go down hill. So I tried to be positive and negotiated my way past a friendly medic who was tactfully suggesting I had a sit down for a while. However, I was determined I was going to be ok  so got through the food tent and continued on to collect my bags. But that’s as far as I got and  about 15 mins after finishing I went back to the medical area.  The lovely medic said, “I knew you’d be back.  You didn’t look too good.” Flattery will get you everywhere. However, I didn’t feel too sick and I wasn’t sick.  I just enjoyed a really urgent lie down until I felt well enough to get myself home, showered and into bed.  I did try twice to have some soup but as soon as I did I felt sick so gave up.  Another friend sometimes feels sick after finishing and her mother, a doctor, has told her that if she feels sick it’s her body telling her not to eat so it’s ok not to eat. Makes sense to me.

Again, the next day,  I was as right as rain and starving so no long term harm had occurred, although it’s possible that delaying taking on recovery calories might slow down my overall recovery over the next few weeks.  I’ll never know.  All I do know is that I didn’t feel as ill as before and I actually enjoyed the run itself for that reason.  It’s too long a day to feel bad for the whole thing so I was relieved things went a bit better this time.

I can’t  say which elements helped.  But when I next tackle something as long, I’ll be grateful for the three years of practice I’ve already had at getting it right.

(Thank you for sticking it out this far – it’s quite a long self-indulgent post.)



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