Nutrition for Triathlon

Ian Craig, MSc, DipCNE, INLPTA is an exercise physiologist, nutritional therapist, NLP practitioner and an endurance coach. Previously a competitive middle-distance runner, Ian specialises in sport from an integrative health perspective. He is the editor of Functional Sports Nutrition magazine and also lectures and writes extensively in the UK and South Africa on the concept of ‘Functional Sports Nutrition’. Find Ian online at and @ian_fsn on Twitter. Read more articles like this in Totally Active Magazine.


What should you eat to fuel a swim, bike and run?

What you eat on race day can make or break you. I frequently pick up Ironman clients simply because they have attempted to go-it-alone on their first attempt at the distance, only to have their race ruined by stomach cramps or what cyclists delightfully refer to as ‘bonking’.


What is your distance?

With regards to nutrition, this is the very first question that you should be asking yourself. If you are completing a sprint tri (typically 750m swim – 20km cycle – 5km run), you won’t have much time to feed and you will potentially be going at a pretty full-on pace, which doesn’t allow your stomach much digestive capability. It has been observed that blood flow to the abdominal area can shift from around 1 1/2 litres per minute at rest to only 1/3rd of a litre during maximal exercise. So, if you’re really pushing the pace in a short race, don’t attempt solid food. The Olympic distance (1500m-40km-10km) is pretty much the same: it’s too short for most fast athletes to eat, although a gel on the bike is usually tolerated. However, if you are just trying to get round at a moderate pace, and have practiced solid food (e.g. a healthy energy bar) in training, it can work.

Long distance triathlons, including the 1/2 Ironman (1.2mile-56mile-13mile) and full Ironman distances (2.4mile-112mile-26mile), are a completely different kettle of fish. I know one elite lady who completed Kona on just sports drinks, but I truly think that she did herself a disservice, not to mention the nauseous pit in her stomach after 10 hours of drinking the same brightly coloured, sugary solution. I also know a guy who raced well on just Mule Bars and water.

The distance, combined with the pace that you compete at, with a bit of genetics and learned behaviour thrown in, dictate your feeding strategies. When you lengthen out the race, you slow your pace and allow your stomach the luxury to digest a wider range of foods and drinks.


*What do you drink and when?

Studies have shown consistently that a sugary solution will support sports performance better than water alone and have shown a 6 per cent sugar solution (60g sugar within 1 litre water) to be optimal. That concentration provides rapid absorption rates into the body, meaning good levels of hydration, plus it gets a fair amount of sugar into the blood stream, ready for the muscles to use. All of the commercial sports drinks on the market provide around this concentration of sugar (if mixed correctly). However, a lot of them also provide a lot of colours, flavours and sweeteners, which can be quite irritating to a sensitive stomach, especially after several hours of competition. So, take your time and find one that works for you in training. The better companies also have a good electrolyte profile (crucial for the longer distances) and possibly some well-chosen amino acids or protein powders, mixed in.

Take a look at this graph: it shows the sweating rate during cool and dry versus hot and humid conditions. Sweating rates are also related to exercise intensity. Since we’re not all going to keep pace with Alistair Brownlee, please don’t try to match the three litres per hour rate of fluid intake. For sprint and Olympic tris, I generally recommend one or two 750ml bottles on the bike and a top up from a drink station while running, if needed. Your body can cope with some losses in fluid over the short term.


Long-distance tris are very different though, you should try and mostly match fluid losses if you’re going to be on the road for 5+ hours. Try this: on one of your long brick sessions (bike-run), weigh yourself before and after. Convert your loss of weight in kilos to litres (1 kg is close to 1 litre) and then add on the number of litres of fluid that you consumed during the session. In order to calculate your hourly sweat rate, divide the total number of litres sweated by the number of hours that you exercised.


For long distances, I also recommend some solid foods – generally one item per hour on the bike and run. Because you will extract some sugars from the food, you don’t necessarily need as concentrated a sports drink, or you might wish to alternate sports drinks and plain water. This is very much down to personal choice and the longer the race distance, the more I encourage triathletes to practice their eating strategies during training; months ahead of their race. Solid foods that I suggest trying include: bananas, heathy energy bars (made from dried fruit, nuts and oats), flapjacks, protein bars, fruit cake, baby potatoes cooked in sea salt, dried fruit, and even nuts.

Remember you are an individual: figure out what works for you and only you. Alistair Brownlee’s drink sponsor’s product may appeal to him, but may not work for you; Chrissie Wellington’s Ironman feeding schedule is unique to her and only her.

This article was originally published 23rd September 2016 and is a feature piece from Totally Active, a completely interactive online magazine written by active people for active people. Totally Active are on a mission to push endurance to its limits, to help readers achieve their potential, whatever the sport or activity. Totally Active have brought some of the world’s foremost endurance, performance, nutrition and fitness experts together in a publication which informs and inspires readers to go to the edge, to break boundaries, and to succeed. Read more articles like this at Totally Active today.

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