Nutrition,  Top Tips

Nutrition planning for a 5km swim

Although 10km might be the Olympic gold standard for a marathon swim, 5km is also an increasingly popular distance, and one achievable by most people who swim regularly. Nevertheless, given that a swim will typically take between 1 and 2 hours, it is a challenge that needs to be taken seriously – perhaps the swimming equivalent of a sprint triathlon or half-marathon run. 

Pre-event carb loading

Carb loading refers to a period before an event where carbohydrate intake is slightly increased, or maintained while training volume is reduced. However, for a 5km swim, increasing carbohydrate levels in the days before a race is unlikely to help performance. This is because carb loading only helps athletes competing in events that are longer than 1.5hrs and above 70% max effort. Many of the swimmers in this race will complete it faster than this time, or at a lower intensity.

Still, for those that do employ a carb loading strategy, it is important to realise that the traditional massive bowl of pasta the night before a race is NOT the best way to do this. Here’s why. Studies have shown that carbohydrate stores remain elevated for three to five days after a three-day loading phase. If the event is on a Saturday, the carb loading may take place as early as the preceding Monday-Wednesday with three normal, healthy days of eating before the race. Although you should try this in training, a strategy such as this may reduce the risk of heavy/bloated feelings before and also stomach problems during the race, while maintaining maximised energy stores. Don’t scrimp on carbs the week before, but don’t go too crazy either, for a 5K with a 2hr cut off, unless you’re swimming flat out, it’s unlikely to help you too much.

Pre-event hydration

Dehydration limits endurance performance and so making sure that you are hydrated before the event is of huge importance. Athletes should ensure that they are well hydrated in the days leading up to the race and further guarantee hydration by consuming 500mls of fluid 3-4 hours before exercise and a further 200mls 2hrs before. This will allow you time to nip to the porta-loo to get rid of unnecessary fluid. Monitor your urine colour to ensure you are adequately hydrated (it should be clear not dark yellow).

Pre-race nutrition

Three to four hours preceding race

Whatever time of morning an event starts you should aim for a good pre-race breakfast – ideally, this should be based around medium GI* carbs and 3-4 hours before you swim. Something like a bowl of muesli with honey and two slices of wholegrain toast is about right. Caution should also be taken with fruit and vegetables as these have been shown to cause stomach problems for some people.

Right before you get in

If you are one of the athletes able to swim this distance at a high intensity, it may be that you chose to take gels or sweets before the race. If you do, to maximise the benefits athletes should ingest about 30g of carbs within 5-10mins of the event start with a small amount of water (unless the gel is isotonic).

During the event

Carbohydrate and hydration 

In cool water but while wearing a wetsuit and swimming hard, you would ideally try to consume around 150-200mls (three to four gulps) of fluid every 15-20mins throughout the event as evenly spaced as possible to drip feed your body with what it needs. In reality, you won’t be able to do this, so now you know the ideal, just try to get as close as you can. On a lapped swim you may have an opportunity to sip some drink each lap so take advantage of this. You should also choose a sports drink as you will then be replacing the carbohydrate, fluid and electrolytes that your body uses and loses during exercise. Finally, make sure your drink is isotonic, and not an energy drink which contains too much carbohydrate and not enough electrolytes. The exception to this may be for extremely competitive swimmers who anticipate completing the swim in around an hour and have trained themselves to exercise for that duration and at that intensity. If stopping to drink means you lose your place in the pack or the feet you’re drafting you will want to weigh up the merits of refuelling against holding your position.



When you finish the race try to consume around 50-80g of carbohydrate as soon as possible and again every 2-3hrs for the rest of the day. Also crucial after all racing and training is protein. It is key to consume 15-20g of protein as soon as possible after the race, and then also repeat this every 2-3hrs. Commercially available recovery bars may be useful for this. Otherwise, some canned mackerel in tomato sauce over cous cous, quinoa or pasta is a healthy why to kick start recovery.


By monitoring urine colour an athlete will be able to self-regulate their own rehydration strategy. However, the consumption of drinks containing electrolytes at a rate of around 500mls per hour until urine colour is pale in colour would be advisable in this situation.

*GI is a scale that ranks foods in order of how quickly they affect blood sugar levels. Simpler carbs (like white bread or cereals that have been played about with during manufacturing) tend to be near the top of this list.

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