Ingestion of sufficient amounts of dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. Protein recommendations for athletes is an important topic when we consider the controversy that surrounds protein intake for all active individuals.
While some researchers have focused on the total daily intake of protein in relation to either strength or endurance, others note that protein requirements should take into consideration the training load and volume, and the overall goals of the athlete such as muscle hypertrophy, strength, or a reduction in body fat.
What is Muscle Protein Synthesis?
Muscle protein synthesis is a marker of growth and repair, and often relates to the optimal refuelling of glycogen stores within the muscle via co-ingestion of carbohydrate. Considering that the processes of growth, repair and adaptation within the muscle all complement one another, it is conceivable that muscle protein synthesis is a combined measure of all of these.
Looking at the results of these ongoing processes from a long-term perspective, it is evident that they contribute to the hypertrophic response to resistance training, the maintenance of the immune function during times of intense training, and the remodelling of proteins in muscle, bones, tendons and ligaments. This remodelling process makes the tissues more resilient to the stress and strain caused by later training sessions or performances.
Due to the potential benefits of increased protein consumption for athletes, many individuals consume protein in amounts far higher than recommendations for general populations, but do they really need to? How about adventure sport athletes whose sport is somewhere along the endurance-resistance training continuum?
In this article, we are going to dive in to the protein recommendations for athletes and propose some guidelines relating to the following 3 areas;
What protein sources should we be consuming?
How much protein should we eat per meal/per day?
When is the best time to consume protein in our diet?
Let’s get started with where the majority of your protein should be coming from.
Protein-rich foods include foods such as meat, fish, eggs, dairy, legumes, nuts and seeds. While essential amino acids provide the anabolic stimulus for muscle protein synthesis, leucine is the main amino acid that triggers the processes involved in muscle protein synthesis.
So far, most of the studies that have evaluated muscle protein synthesis following a nutritional intervention have used protein powders created from whey, casein, soya, egg and rice. In a study conducted by Vliet and colleagues in 2015, it was found that most plant-based protein sources have a leucine content of 6-8%, while animal-based sources have around 8-9% and dairy proteins, 10+%. Because of this, plant-based protein sources are commonly considered inferior to animal-based proteins when it comes to effectively stimulating muscle protein synthesis. However, Vliet’s study showed this leucine deficit is cancelled out when the protein ingested exceeds 3g so all protein sources may contribute to increasing muscle protein synthesis adequately.
In a real-life setting, mixed meals that combine proteins with other important macronutrients and micronutrients provide a more complete approach to the protein requirements for adventure sport athletes. However, protein powders may provide a convenient alternative when a complete meal is not accessible.
Amount of Protein Needed Per Meal
When considering the amount of protein we need to consume per meal, we need to look at studies that have investigated the post-exercise stimulation of muscle protein synthesis in athletes.
- 20g of egg has been shown to adequately (90%) stimulate muscle protein synthesis (equated to 0.25g/kg)
- 20g of whey protein powder showed effective stimulation (90%) of muscle protein synthesis (equated to 0.25g/kg)
- A 2009 study showed that consuming 30g of protein in the form of lean beef increased muscle protein synthesis by 50%, but consuming a higher amount does not enhance the stimulation of muscle protein synthesis further
Based on the evidence presented, a practical approach to dosing protein consumption is 20-40g of protein per meal when making protein recommendations for athletes.
Protein Timing Considerations
When to consume our protein sources throughout the day is another topic that is regularly debated in the protein recommendations for athletes discussion, and is a question best answered by considering relative goals for health and performance.
Protein-timing is the consideration and subsequent manipulation of protein intake before, during and after exercise or performance to influence recovery and training adaptation brought about by nutrient-specific effects on muscle protein synthesis.
When we train our adventure sports or participate in an aerobic or resistance training session, our muscles experience an increase in both muscle protein synthesis and, to a lesser extent, muscle protein breakdown. After exercise, protein balance will remain in a negative state if we do not consume any food. Ingesting dietary protein during or immediately after exercise or performance promotes muscle protein synthesis and suppresses muscle protein breakdown.
In a 2013 study, three evenly distributed patterns of whey protein ingestion were investigated over a 12-hour period for their effects on muscle protein synthesis;
- Large (4 x 20g every 3 hours)
- Small (2 x 40g every 6 hours)
- Pulsed feeding (8 x 10 g every 1.5 hours)
Over the 12-hour period, 4 x 20g of protein every 3 hours produced the highest muscle protein synthesis response.
In an “evenly distributed vs skewed” pattern of protein consumption, even distribution has been shown to be superior in terms of maximising protein muscle synthesis. A ‘skewed’ distribution of protein intake is one which mimics the patterns of eating associated with the general population whereby moderate amounts of protein are consumed at breakfast and lunch, and larger quantities are ingested in later meals.
A 2014 study investigated the effects of two protein distribution protocols on muscle protein synthesis (even vs skewed);
- 30g of protein at breakfast, lunch and dinner.
- 10g of protein at breakfast, 15g at lunch and 65g at dinner.
In this experiment, the evenly distributed protocol of 30g of protein at breakfast, lunch and dinner stimulated muscle protein synthesis to a greater extent over a 24-hour period.
In addition to daily feeding, pre-sleep (casein) protein consumption has also been shown to increase overnight rates of muscle protein synthesis in men who performed resistance training, demonstrating that this practice improves whole-body protein balance during post-exercise overnight recovery. Researchers have also found that ingesting 28g of casein protein before sleep during a 12-week resistance training program lead to greater increases in strength and hypertrophy compared to non-caloric placebo consumption. Although the total daily protein intake for the casein group was higher than in the placebo group, consuming a pre-sleep protein supplement may be a suitable strategy to increase total daily protein intake for those adventure sport athletes who find it difficult to meet the recommendations laid out in this article.
Although the majority of studies are restricted to 12- to 24-hour periods, it demonstrates, to an extent, that protein-timing can be optimised to enhance the stimulation of muscle protein synthesis and that frequent meals providing evenly-distributed doses of 0.25–0.40 g/kg per meal may be optimal.
Protein Recommendations For Athletes – Practical Application
As adventure sport athletes, we do not always have the opportunity to consume the ‘correct’ amount of protein at the ‘correct’ time as we are normally training and performing on the move and the timing of our activities are very often dictated by the weather. While protein consumption shouldn’t be obsessed over, the following protein recommendations for athletes serve as guidelines for any type of adventure sport and can be adhered to when the situation permits.
Daily intake – 1.2–2.0 g/kg (Higher intakes indicated for short periods during intensified training or when reducing energy intake, providing 0.25–0.40 g/kg protein per meal evenly distributed across the day and following strenuous training sessions
Fat loss and calorie restriction – 1.8–2.7 g/kg (combined with a 500-kcal total daily energy expenditure deficit in addition to performing resistance training)
Post-exercise – 0.4 g/kg (Combined with 0.8 g/kg of carbohydrate with the aim of replenishing muscle glycogen stores and to maximally stimulate muscle protein synthesis)
Bedtime – 28–40 g (g/kg guidelines have not yet been established – Higher intake promotes overnight recovery; lower intake supports hypertrophy goal)
Injury – 1.6–2.5 g/kg (Energy balance should be maintained, but energy intake must reflect a reduced total daily energy expenditure)
(Adapted from Dr. Brendan Egan’s review in the Nutrition Bulletin journal)
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If you want to read more about food recommendations for adventure travellers, you can read the article ‘When should I eat carbs‘.