Triathlon nutrition: the A-Z guide

The world of sports nutrition can be a veritable minefield of information. But here to separate your carbs from your fats and your l-carnitines from your omega-3s are a quintet of multisport-fuelling experts…


Meet the nutrition experts

Jo Scott-Dalgleish is a registered nutritional therapist who specialises in working with endurance athletes to improve both performance and health.


Joel Enoch is a sports scientist, nutritionist and head tri coach for the Hartree JETS, a top multisport age-group squad based in Edinburgh.

Lucy Wainwright is a two-time Olympian and lead performance nutritionist for British Triathlon working with the Olympic and Paralympic squads.

Nigel Mitchell was nutritional support for Team Sky when Wiggins and Frome took respective yellow jerseys, and for British Cycling at London 2012.

Renee McGregor is a registered sports nutritionist and author of Training Food. She works with athletes across a variety of sports.

The A-Z


Obviously there are easily accessible government guidelines on alcohol intake (see but from a purely nutritional point of view, alcohol provides little benefit. One gram of alcohol provides approximately 7kcal and very little else of nutritional value – and this is not a usable energy for exercise.

In addition, B vitamins are used to metabolise the alcohol and so excessive alcohol can also reduce recovery from hard training and injury. Alcohol acts as a diuretic, so hydration can be an issue too. It’s a personal choice and we all have real lives to live, so I advise making an informed choice. Alcohol in moderation isn’t a real problem – but be aware that if you have a binge, it’ll affect performance. NM


In general, to exercise at a certain intensity, we need a certain amount of oxygen… or so we thought. Research over the last decade has shown that drinking beetroot juice can improve the rate at which we utilise oxygen with studies showing that this can improve time to fatigue by a whopping 15-20% (in a lab)!

While real-world improvements are likely to be more like 2-5% across a triathlon, this still represents huge gains. What’s more, it’s so simple to access with around 85% of athletes responding to 2 x ‘Beet It’ shots 2-3hrs before a race. JE


Carbohydrate provides the main source of fuel for your muscles during exercise. Carbs from food are used immediately for energy or stored as glycogen in the liver and muscles until needed. Triathletes need 3-8g per kg
of their bodyweight daily, depending on the volume and intensity of training. Nutrient-dense sources include brown rice, oats, wholegrain bread, sweet potato and other root vegetables, beans, lentils, fresh and dried fruit, milk and yoghurt. JS-D

Dietary fibre

This is an important component of your diet as it promotes digestive health. There are two types of fibre. Firstly, insoluble fibre which includes whole grains, nuts, seed, fruits and vegetable. This type of fibre adds bulk to your stool. Secondly, there’s soluble fibre which includes foods such as beans, pulses, oats, root vegetables and some fruit, such as bananas and apples. This type of fibre keeps your stool soft but also has prebiotic properties, which are necessary for the effective action of probiotics. Together they encourage a healthy gut flora. RM

Energy Gels

The idea with energy gels is pretty much to give you instant energy. Plus they’re sweet, so they have an effect as soon as they enter your mouth. Gels normally provide between 20-40g of carbohydrate and may also include caffeine. Because they’re concentrated, people often experience stomach problems after consuming high volumes. I’ve found the fruit juice-based gels easiest for athletes to take, although the tolerance and use of gels tend to be very individual, so it’s worth trying a few brands until you find the one that suits you best. NM


Fats are an essential part of the diet. They aid recovery and support the immune system by helping the body cope with the stress of training. Aim to have at least two meals in the day that include some good fats, such as nuts, olive oil, avocado, olives, hummus, and oily fish (salmon, mackerel, trout). LW

Glycaemic Index

Glycaemic Index (GI) refers to the effect of carbohydrate foods on blood glucose. Carbs with a lower GI rating are absorbed more slowly into your bloodstream, which results in a steadier release of energy than from higher GI carbs. Generally choose lower GI carbs, such as oats, brown rice, wholegrain bread, legumes and vegetables. But higher GI carbs such as white bread, rice cakes and raisins can make good pre-training snacks. JS-D


There’s no strict guideline on how much water you should drink and it’ll vary person by person as smaller individuals will lose less fluid than larger. Similarly, warmer climates will mean higher fluid losses both at rest and training. With regards to how much and what to drink, aim to drink regularly throughout the day to aid hydration.

For the most part water is a good choice, but don’t forget that your consumption of tea, herbal tea and coffee will also count towards your fluid intake. If training in warmer climates or even indoor training, you may find that introducing an electrolyte will encourage more fluid into the body and maintain hydration. When training, aim for 150-250ml of fluid every 20mins. RM

Isotonic drinks

Isotonic drinks generally contain 4-8g of sugar per 100ml and have the same concentration as body fluids, which means they help with fluid absorption. They tend to contain both carbohydrate and electrolytes and are designed to be used at a specific concentration. While you can make your own if you’re on a budget (by mixing water, fresh orange juice and a little salt), the key isn’t to make them too concentrated or too weak, which is why many athletes opt for a ready-mixed version from one of the major nutrition brands. NM

Juices and smoothies

Fruits and vegetable, the typical ingredients of a smoothie, are the most nutrient-dense and antioxidant-rich foods on the planet. What’s more, if you blend them up you break down all the cell walls of the foods, allowing you to shove the maximum amount of health into your body.

Juices tend to have less fibre and so can bring about a spike in blood sugar, more like a soft drink, which (although more nutritious) isn’t ideal. Smoothies containing the whole fruit (so more fibre), however, are the best of both. Include spinach, seeds, add whey protein to improve recovery, or pour over wholegrain cereal for a pretty much perfect breakfast. These should be part of every athlete’s daily diet. JE

Ketogenic diet

A ketogenic diet is a high-fat, low-carbohydrate diet designed to force the body to utilise fats and produce ketones that can be utilised as a fuel source to the brain in the absence of glucose (during starvation). Given that a ketogenic diet can have a negative impact on training, this diet shouldn’t be attempted without fully understanding all the principles, risks and implications to training and health. LW

L -Carnitine

L-carnitine is an amino acid which plays a role in fat oxidation, the conversion of fat into energy. It’s both synthesised in the body and found in animal foods. Studies have linked l-carnitine supplementation with increased ability to burn fat, which spares muscle glycogen stores and may enhance endurance. It may also aid recovery. But results are conflicting. Vegetarian or vegan triathletes may benefit taking 1g of supplemental l-carnitine. JS-D


When it comes to red meat, I always encourage athletes to try to consume 1-2 portions a week as this helps them to achieve their iron requirements. However, stick to lean cuts of red meat and avoid processed options such as ham, bacon or sausages, limiting these to occasional treats. Poultry such as chicken or turkey can be eaten most days and is a good source of lean protein. In all cases watch your portion size – you probably don’t need more than a pack of card-size portion at each serving. RM


Nuts are great for snacking – I’m partial to pistachios. For triathletes, I tend to recommend about 30-40g as a serving, which will provide roughly 180kcals, 8g of protein, 15g fat and 11g carbohydrate. The green and purple pigments in pistachios are packed with antioxidants that can help protect the body. People often question the fat content, but we now have a better understanding of the importance of certain fats in our diets, which are important for maintaining our hormone levels. NM


Fats are divided into three main types: saturated, monounsaturated and polyunsaturated. The last of these is sub divided into omega-3 and omega-6 lipids. O6 lipids are found in vegetable oils, which are added to most processed foods, so we eat a lot of it. O3 lipids are only really found in things like oily fish, walnuts, avocado and olive oil, so we might eat 10-20 x more O6 than O3. This imbalance increases inflammation in the body, increasing recovery time and the risk of all the diseases you don’t want to get. In short, we need to reduce our intake of processed foods, while eating more natural sources of O3. JE


Protein assists in the quick repair of muscles and is vital for maintaining lean mass during the racing season.  As a triathlete it’s important to get regular protein intake throughout the day, aiming for four or five servings a day at meal times and as part of your recovery strategies.  Good protein sources include chicken, turkey, fish, lean beef, Greek yoghurt, milk, beans and lentils. LW


There are a few ways you can look at this – the simplest is to aim for a third of a plate of whole grain carbohydrates, including root vegetables and beans and pulses; a third of a plate of protein; and a third plate of vegetables, consuming as many colours as possible throughout the day. For those who want a more visual approach as a rule of thumb, at every meal aim for a fist-sized portion of whole grain carbohydrates; a palm size portion of protein and then fill the rest of the plate with veg. When it comes to essential fats, aim for around a dice-size portion at your three meals, and keep added sugar to a minimum aiming for no more than 7tsps a day. RM


Train and get fitter right? Wrong! It’s in the recovery phase between sessions, not during the exercise itself, where the magic happens. So it’s absolutely key to maximise this adaptation. Recovery nutrition and hydration should be consumed as soon as possible after exercise. In whatever form it takes (solid or liquid), athletes should look to consume 10-15g of protein, with up to 1g of carbohydrate per kg of body weight depending on how aerobically tough the session was (i.e. gym session = less carbs; race = more carbs). Supplements make this easy, and whey or soy protein isolate powders enhance recovery the most. JE


Reducing processed and refined sugar from the diet has numerous health benefits and can improve the nutritional quality of a triathlete’s diet. Avoid adding refined sugars to drinks; switch to natural whole grain foods rather than processed ready meals; use natural or Greek yoghurt instead of flavoured yoghurts. The exceptions are times when sugar is actually required for triathletes – particularly in the form of glucose/fructose in drinks and gels during racing. LW

Tea and coffee

In many studies, caffeine has been shown to help performance by reducing the perception of fatigue. Around 3mg/kg of bodyweight is needed for an effect, although individual response to caffeine differs. A 250ml cup of filter coffee has around 100mg of caffeine. A cup of tea has about half as much. Sports drinks and energy gels sometimes contain caffeine for use during training and racing, but the amount varies, so always check the label. JS-D

Unprocessed food

When training, the intensity of the session will determine how much fuel you need. Carbohydrate will need to be replaced in high-intensity and longer endurance training sessions. You want to consume a choice that’s easily digestible, providing the body with instant fuel. Unprocessed alternatives to gels include bananas or dried fruit such as raisins or dates. Alternatively, for a more savoury option, try cooking up some sweet potato wedges and eating them cold. RM


Vitamins are essential components of a triathlete’s diet, playing an important role in energy metabolism and the immune system. Most vitamin requirements should be met from eating a varied diet including lean meat, dairy products and plenty of different fruit and vegetables. However, checking your vitamin D levels and supplementing them if required, during the winter when there’s reduced sunlight, is advisable for triathletes. LW

Whole grains

The clue is in the name! These foods are the entire grain not just the refined starches contained in the grain.  This means that they supply many more nutrients than just the carbohydrate. Additional nutritional goodies provided by whole grains include fibre (essential for normal gut function and provide food for the gut bacteria, proteins, vitamins and minerals). Having wholemeal bread isn’t the only way to ensure you’re eating your whole grains – I tend  to mix different whole grains together to get a great tasting and nutritionally balanced meal; this’ll include pearled spelt, quinoa, barley and brown rice. NM

X e(X)clusion diets

If you don’t eat meat or fish, take care not to miss out on protein, iron, calcium and vitamin B12. Vegans
need to get their protein from legumes, grains, nuts and seeds. Vegetarians can add dairy products and eggs. Choose dried apricots, cashew nuts, pulses and green leafy vegetables for iron and calcium. Vegans need fortified plant sources of vitamin B12, e.g. cereals, as it’s found naturally in animal products only. JS-D


Dairy products should be integral to all athletes’ diet and you should aim for 3-4 servings a day. They encourage optimal bone health, make an ideal recovery choice post-exercise and have a high saiety value, so keep you full. Studies have shown that individuals who consume a higher intake of dairy products combined with training have a higher percentage of lean muscle mass.

Any type of milk is suitable – skimmed, semi-skimmed or whole, as all milk provides the same amount of calcium, protein and carbohydrate (fat content differs and this will be reflective in overall energy content). When it comes to yoghurt, the best option is Greek/Greek style or Icelandic and always aim for natural versions with no added sugar. While many avoid cheese due to its high fat content, a small matchbox size portion is perfectly acceptable and provides you with both calcium and phosphorus. RM

Zinc…. And other minerals

Minerals are the building blocks of the body, so we need them to get fitter. Female athletes have a greater need for iron, while male athletes have a greater need for zinc. Zinc has many roles in the body, however its most crucial role might be its link to testosterone production. This is known to be lower in male endurance athletes training more than 8hrs per week, and lower levels can lead to feelings of lethargy, poorer response to training and a reduced ability to build strength. Seafood, beans, cashews, seeds and other grains are all good dietary sources and should be a daily part of any triathlete’s diet. This can be supported by supplementation of between 10-20mg/day. J