By Dr Lucy Rogers, Dr Marie Korzepa and Dr Leigh Breen
School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham

An increase in the number of plant-based diets among athletes in elite sport prompts the question of how vegan diets can support athletes to build muscle mass and support sporting success.

In the Birmingham 2022 Commonwealth Games we have witnessed impressive feats of human performance. To be in the best competitive shape for the international stage, athletes need to pay special attention to their training and nutrition. As we watch on, in awe of these superhumans, it’s natural that we ask ourselves “what exactly do elite athletes eat?”

The power of protein

Be it running, cycling, or weightlifting, muscle mass and strength are important for performance success. We know that muscle is made up of proteins, and amino acids are the building blocks of this protein. Some of the amino acid building blocks of muscle protein can be made by other tissues and organs, but the most important source is in the proteins we consume in foods and supplements.

When protein is consumed around a routine of frequent and demanding exercise training, the number of amino acids deposited into muscle protein is greatly increased and this is the basis on which muscle is able to continually remodel and adapt in highly trained populations.

Elite athletes typically undertake a lot of intense exercise, multiple times each week (and sometimes each day), during training and competition, so it is unsurprising that they are advised to consume higher amounts of protein than the general population. Whilst the recommended daily protein intake is 0.8 g protein per kg body mass for the average Joe (64 g of protein for an 80 kg individual), elite athletes, or those with increased demand for muscle adaptation and recovery, should consume around 1.6 g protein per kg body mass (Morton et al., 2018). For the likes of Adam Peaty weighing in at 86 kg, this would be at least 137 g protein per day!

Importantly however, our muscles can only take on so much protein at a time. Much like a tap running and overflowing a bath with water, our muscles (the bath) can only take up a certain amount of amino acids (water) at any time. This is why athletes have multiple high-protein feedings every 3-4 hours throughout the day, with each meal or snack.

Not just quantity, but the quality of protein

Aside from the amount and pattern of intake across a typical day, protein quality is also an important consideration for muscle adaptation and recovery. The quality of a dietary protein refers to how well it is digested, as well as the amount and type of amino acids it contains. Some amino acids are ‘essential’, as we can only obtain them via the foods we eat (and not from other body tissues/organs).

Of the nine essential amino acids, leucine is particularly important for muscle adaptation following food consumption. Many foods contain protein, and the nine essential amino acids which we need to support muscle adaptation and recovery with exercise are found in different amounts in these foods.

To support muscle adaptation and recovery in high-performance athletes during training or competition, consuming higher-quality protein sources is recommended. However, for some, this is easier said than done. Typically, animal-based protein sources, such as meat, fish or dairy products are considered high quality and complete proteins, whereas many plant-based protein sources, such as soy, wheat, and maize, are lower quality or incomplete proteins. This is because plant-based proteins contain lower amounts, or are devoid, of certain essential amino acids like leucine and also are often more slowly digested. As such, to gain the essential amino acids to support optimal muscle adaptation and recovery in a single meal, a plant-based high-performance athlete would have to eat more food (which could mean more calories) than their omnivorous counterparts (i.e., 1 kg potatoes vs 70 g beef) (Gwin et al., 2020; Pinckaers, Trommelen et al., 2021).

Considerations for plant-based athletes

In recent years, more and more athletes are turning to plant-based diets, whether that be for environmental or ethical reasons, or in the hope of gaining a competitive advantage. Undoubtedly, the switch to go green should come with careful planning, to ensure training goals and athletic performance are not negatively impacted. Plant-based athletes should be aware of the potential pitfalls associated with following a vegan diet. For example, alongside lower protein, plant-based diets are typically lower in fat compared with omnivorous diets (Clarys et al., 2014). This means that more food may be needed to consume the same amount of protein and calories. This may be of particular concern when athletes are required to expend a lot of energy, during an intense training block, or when performing multiple times a day during competition. Similarly, the higher fibre content of a plant-based diet may increase satiety (Burton-Freeman, 2000), which could add to the challenge of consuming enough calories to fuel for training, recovery, and competition. In this regard, it is perhaps wise for those on plant-based diets to focus on consuming energy-dense foods more frequently, to overcome some of these issues.

Undoubtedly the major challenges faced by plant-based athletes lie in the quantity and quality of dietary protein intake. For plant-based athletes consuming lower quality proteins, there is a possibility that muscle adaptation and recovery needs may not be met and the ability to train intensely and compete to the highest standard may be hindered. However, there are strategies plant-based athletes can follow to meet their protein nutritional and total calorie requirements.

Firstly, plant-based athletes consuming a larger amount of protein from a given source may be no worse off than their omnivorous counterparts, with evidence suggesting that muscle adaptive responses are similar between high amounts (at least 30 g) of protein from animal or plant sources (Pinckaers, Kouw et al., 2021) or when the overall amount of dietary protein intake across the day is high enough (Hevia-Larraín et al., 2021).

Secondly, beyond simply eating excessive amounts of food to meet their protein and total calorie requirements, an alternative strategy for plant-based athletes is to eat a variety of foods to gain all of the essential amino acids required to support muscle remodelling and recovery (Pinckaers, Trommelen et al., 2021), which could involve the use of nutritional supplements for ease and convenience. Though undoubtedly challenging, plant-based diets are feasible in high-performance sport. Whilst diet alone cannot guarantee success, there is no reason why athletes following a carefully planned and varied plant-based diet cannot go for gold.