14 race-day nutritional questions answered

Worrying about your nutrition on race-day and all the things that could go wrong when going long, from being sick or getting diarrhoea to the value of post-race beers? We answer 14 commonly asked questions that will hopefully put your mind at rest


1. Are post-race beers really a bad idea? I don’t want to mess up my hard work


Most alcoholic drinks have a diuretic effect, but a light beer will provide you with more fluid than the fluid expelled due to its diuretic effect. So of all the alcoholic drinks you could have, it’s probably the best choice. Plus its carbohydrate content will also help you replenish your glycogen stores. However more than one or two beers will hamper tissue repair due to beer’s lack of protein, and you must be sure to take on enough hydrating fluid to counteract the dehydrating effect of your race.

2. Can I survive an Ironman on just gels and sports drinks?

Yes, assuming you and your gut are used to working on such a limited and sugary menu for such a long time. you might better off mixing things up though, to introduce some variety so as to avoid gastric distress. Plenty of water, bananas, trail mix and even some savoury snacks can all help keep you and your gut going during a long-distance event… provided you practise with your intended choice of food in training.

3. Is it possible to drink too much water?

During long races, over-hydrating yourself by constantly drinking water may dilute your blood because your sodium levels fall, a condition known as hyponatraemia. Although it’s quite uncommon, it is potentially fatal. USA Track and Field caution against drinking huge amounts of water in events lasting longer than 4hrs; instead, they advise being guided by your thirst and drinking sports drinks with sodium. But for most triathletes, there’s a bigger risk of dehydration than over hydration.

4. Are gels, bars or drinks better suited to specific disciplines?

Whether you choose solid or liquid carbohydrates makes no difference to your performance, provided you drink enough water. Liquid carbs – sports drinks – are the easiest and most practical option. Not only do they provide vital fluid as well as carbs and quench your thirst, but they also deliver a fixed concentration of carbs so you know how much you’re getting.

But carrying a sports drink with you, say, on a long run or even enough drink on a long bike ride isn’t always easy. It’s heavy and can slow you down in a race. This is where gels and bars can help – they’re lighter, and easy to carry
and eat on the move. Which to choose is really down to personal preference – you’ll need something that delivers 30-60g carbs per hour (for example, two gels per hour or one bar per hour). The important bit is to drink enough water with them, otherwise you’ll end up with a concentrated goo in your stomach. As a guide, have half a gel pouch (13g carb) with one large cupful (175ml – that’s six or seven big gulps) of water every 15-30mins.

Alternatively, have one banana per 30mins – it also supplies around 13g carbs.

5. Ironmen can be in the saddle for up to 10hrs, and many complain of becoming sick of sweet foods. Are there any savoury foods that would be a valid replacement?

Yes. If you prefer savoury options, try rolls, bagels, sandwiches, rice cakes and crackers. Soup is also a good choice because you get vital fluid, but check the salt content doesn’t exceed 1.25g per litre, because many ready-made varieties are very salty.

6. Would you recommend making up bottles the night before and leaving them in the fridge or is it best to make them up on the morning of the race?

Yes, leave them in the fridge, or if you’ll be racing in hot weather, leave them in the freezer to partly freeze. They’ll thaw during the race and the cool fluid is absorbed even faster.

7. Will the constant change in ambient temperature – from swim to bike to run – affect your strategy?

You lose more fluid in hotter temperatures so you need to factor in extra drinking during the hottest/sweatiest parts of the race. Don’t forget to drink immediately after the swim – you can still sweat and lose fluid while in the water. However, in very cold water, or short swims (say 15mins), this problem won’t amount to much. Does your strategy change if it’s boiling hot? You definitely need to drink extra, and we suggest going for a more dilute drink. For example, 4g carb/100ml and up the volume to say 800-1,000ml/hr during the bike and run. Be guided by your thirst, too, and drink more as you feel thirstier.

How to prepare for racing in hot weather

8. What if conditions are far hotter than I expected?

In terms of surviving the heat, fluid replacement (water) takes precedence over fuel replacement. Carbohydrate or sugary drinks delay gastric emptying, leading to slower absorption of water. So focus on water rather than fuel, especially during the run phase when energy demands are greatest, which means that more blood is shifted to
the working muscles and less to the gut
for digestion.

Aim for 250ml of water every 10-15mins. Of course, you’ll still need some fuel, and the best choices during hot weather are water-rich foods, such as oranges and bananas, which are full of electrolyte minerals.

If you’re used to gels, one every 30mins with water should be sufficient. Be sure to check weather conditions in the days leading up to the race, seek advice, and adjust your fuelling and hydration accordingly. Finally, some useful cooling strategies include putting ice under your helmet, sponges under shoulder straps and sucking ice.

9. What if my energy drink falls off my bike? 

Don’t panic because an aid station is probably not far away. Make sure you have ‘emergency’ gels and water, and if necessary take a gel with sufficient water to give you the necessary rehydration until you can replace your bottle.

10. What if I feel sick or vomit during the race?

Firstly, avoid overloading the stomach and eating or drinking too much too soon after exiting T1 or T2. And never try to match energy expenditure with energy intake.

Allow yourself to settle after transitions, then consume 60g of carbs an hour, along with 800ml-1,000ml water/fluid. Eating too soon – post-swim or bike – causes gut distress and nausea, so keep to your fuelling strategy.

Stick with one or two drinks and foods that you’ve practised with in training, and resist eating anything or everything on offer. If you train using gels, water and bars, race with this. Ironmans aren’t gourmet food outings; always view your food and drink as ‘fuel’.

11. What if I have diarrhoea during the race? 

Some common causes of diarrhoea include eating too many fibre-rich foods the day before; eating too much the night before or the morning before the race; eating too much too soon after the swim phase or bike phase; drinking a carbohydrate solution that is too concentrated; and taking in too much salt. Leave 30-40mins at the end of the bike phase for your stomach to empty, ready for the run.
If you do have diarrhoea, the main issue here is one of water loss and dehydration. So take in water every 10-15mins and drink at every single aid station.

12. What if I can’t stand the energy drink or foods provided at the aid stations? 

You must find out well before the race the types of fuelling products and drinks available. All companies use different types of sugars, nutrients, caffeine and flavourings, so try what you can in advance. This will help your stomach acclimatise to taking on different foods that you might need to rely on. Take your own familiar foods if you can, along with frozen water bottles and gel flasks.

13. Is magnesium good for cramp?

There’s little evidence to support magnesium supplementation reducing the risk of exercise-associated muscle cramping. However western diets don’t tend to be rich in magnesium, and given the strong evidence that supplementation helps other forms of cramps (e.g. night cramps) it is still wise to include a supplement and the following foods in your diet; unrefined breads (not white) and cereals, whole brown rice, all nuts and seeds (especially sesame seeds), beans, peas and lentils (especially chickpeas) and all green leafy veg.

14. What’s the difference between hyponatremia and hypernatremia?


Hyponatremia occurs when sodium levels in the blood are low. In athletes it can develop when more fluid or sports drinks are consumed than their kidneys can excrete. This excess water can severely dilute the level of sodium in the blood needed for organs, especially the brain. Hypernatremia occurs when sodium levels in the blood are too high

Hyponatremia: causes and symptoms of low sodium levels