Some musings on ultra nutrition and hydration

Amazingly, I was roughing this piece out last night with a view to publishing it today when John Ky posted a link to William Sichel's article on the same subject.

There are more than a few similarities, the stongest of which is his advice to "eat less!". He ran the Spartathlon on 100 kcal per hour which concurs with my view that most people are trying to get far too many calories down.

Anyway, have a look at William Sichel's article here and then laugh at mine, ;-)

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Reading other folks' blogs has reminded me how much my own practice with regard to nutrition and hydration has changed over the last few years. Given that this change has coincided with an improvement in my ultra distance running, I thought it might be worthwhile sharing my current thinking on the subject with anyone who is interested.

Firstly though, I must point out that we are all "experiments of one" and what works for me might not work for anyone else. In addition, what is working for me now, might not work in different weather conditions or race conditions so please bear these thoughts in mind when considering any changes to your own practice.

Nutrition

They say that you burn about a 100 calories per mile when running. Multiply that by the WHW and you get something in the order of 4 days worth of food burnt in one day. One could try and eat that amount but I doubt that anyone could manage that and run the WHW on the same day. Fortunately, training enables us to get away with eating less than that by tapping into our reserves. Anyone who has raced a marathon knows that 26 miles without eating anything is hard, the tendency is to "bonk" (i.e. suffer a collapse in energy reserves) after about 20 miles. According to those who know about these things, there just isn't enough glycogen (the storage from of glucose) in the body to take you past this distance so you have to supplement it with food of some sort.

Clearly what is needed for running 95 miles miles is more than nothing but less than four days worth of food, the big question is, how much do I (or you) need.

As I've worked my way through the WHW training runs this year, I've discovered that one can get away with very little indeed. In fact, I've discovered that about 285 calories per 10 miles works for me (one Mars Bar). This has huge advantages from the point of portability. If I can maintain this level of intake over the whole WHW, I can do it on a 10 pack of Mars Bars which I can carry myself.

On the face of it it seems improbable that this could possibly work given the energy expenditure but one thing that we all have is huge reserves of energy in the form of fat. Even if your BMI is in single figures it's reckoned that we all carry more than enough stored energy this way. The problem is in tapping into it. To "burn" fat, you have to have enough glucose in your system. No glucose = no fat burning = bonking. Just keep a trickle of glucose coming into your system though, and you can burn fat and tap into this resource. In the early stages of the run, this glucose comes from stored glycogen but as reserves fall, you need to supplement your glucose supply. This is where the Mars Bars come in. I really don't think there's any place for difficult to digest food (ham sandwiches etc.) containing protein or fat. Your digestive track is having to cope with a compromised blood supply because you're running and trying to absorb anything other than the simplest sugars is probably asking a bit much of it.

I can't pretend that any of the above will stand up to any sort of serious scientific study and most importantly, I can't say that it's possibly to be competitive on a diet of Mars Bars alone, but if you're having recurrent stomach problems with nausea & cramps, just bear in mind that it's possible that you're suffering from eating too much, not too little and that you may be able to get away with much less than you think.

Anyhow, this is just my current take on nutrition. I'm not a fan of liquid nutrition for reasons that I'll cover under hydration.

Hydration

If there are any ultra-runners out there who aren't scared of hyponatraemia, then they ought to be. Dehydration may make you perform sub-optimally, it may even in extreme cases lead to your collapse. What it will hardly ever do, is kill you. Hyponatraemia (low blood salt levels) will. The first you or your support crew may know about it is dizzyness and/or confusion. Once you have symptoms of altered conciousness, you're already in big trouble.

So, why does it happen? As the good Dr. Ellis has made clear, the commonest reason is over-hydration. In short drinking too much. The question is, why, despite the known dangers, do runners keep doing it?

The popular reason given is that the mantra "if you wait until you're thirsty you've left it too late" and the concept that dehydration is a "bad" thing have over played in the past. It was certainly true that the official advice for marathons used to be to drink "plenty" and regularly, irrespective of thirst. This advice has certainly been toned down but it's still quite common.

When it comes to ultra running, advice that might only lead to a mild to moderate degree of over-hydration in an event the length of a marathon, can lead to serious over-hydration in an event that can last over 24 hours.

Another reason that people inadvertently over-hydrate (and this is just my pet theory) is that we've started really confusing our body by taking calories in liquid form. This means that when your blood sugar is falling, you're feeling tired, you reach for the sports drink when what your body is really craving is just the glucose. "Ah but!..." I hear you say, "I'm taking salt in with my fluid so that should be okay." Well it might be if it contained the same amount of salt as your blood but sports drinks are a long way short of that for the simple reason that they would be horribly unpalatable if they were. So the more you drink, the more you dilute your blood sodium levels. To make matters worse, drinks containing some salt are absorbed more rapidly that those without so potentially, this "advantage" of sports drinks, could potentially be aggravating the very problem it's supposed to be alleviating.

I'm coming round to the idea that we evolved to eat calories, not drink them and that taking calories in liquid form leads to a muddying of the distinction between thirst and hunger, two separate needs that need to be dealt with separately. Treating hunger with inappropriate quantities of dilute calories leads to over-hydration.

My solution is simple and cheap. Drink water. Not necessarily exclusively, but certainly I think it should be your "first line" fluid. Additionally, whenever you find yourself reaching for your camelbak tube or other bottle, ask yourself seriously "Am I thirsty?". I find that when I ask myself this question I realise that I've been reaching for my bottle more often through reflex, not need. I know find myself completing long runs on much less fluids that I used to drink and feeling better for it. In February I ran 31 miles on one cup of coffee, something that I previously would have thought of as "impossible".

I don't expect anyone to change what they do based on my views but perhaps they might encourage people to experiment a bit more and potentially run a better race.