For Sport and Exercise Nutrition practitioners the latest scientific evidence on the effects of dietary protein on muscle protein synthesis and muscle recovery highlights the importance of considering the timing and distribution of protein intake over the day. A recent study of typical meal patterns in elite athletes found they may not always be optimising the ‘eating opportunities’ for protein at breakfast and before sleep.
The “Sports Nutrition Pyramid” designed by the Dutch Dairy Organisation and Dutch Sport Dietetics Association was developed as a guide for athletes on choosing foods to ensure a good dietary intake of all the necessary nutrients. The base of the Sports Nutrition Pyramid is the starting point for each athlete, regardless of their level. The bottom layer promotes a varied diet based on fruit, vegetables, pulses, whole grains, fish, meat, eggs and dairy. Foods from each of the basic food groups provide significant amounts of essential nutrients within their natural food matrix and improve overall diet quality. For example, milk and dairy foods are a natural source of protein and calcium. Timing the intake of specific nutrients such as carbohydrate and protein, and optimising fluid and electrolyte intakes around training and competition schedules is also important.
The second layer of the pyramid represents sport-specific nutritional products such as sports drinks, bars, gels and protein shakes which may be more convenient for athletes to use. The top of the pyramid contains supplements, for example vitamin D, and ergogenic aids with a proven efficacy such as creatine, beta-alanine and nitrates.
For athletes undergoing intensive training to improve sports performance, it is important to pay special attention to the overall protein intake and distribution over the day. Current recommendations advise protein intakes of 1.2–2.0 grams of protein per Kg body weight per day depending on training goals. Consuming a snack or drink providing ~20–25 grams of rapidly digested, leucine-rich proteins within 30 minutes to 2 hours post- exercise has been shown to support recovery in terms of skeletal muscle protein remodeling and gains in muscle mass over time. (1-3)
Timing of protein intake
The metabolic basis for changes in muscle mass is net muscle protein balance (NPB), i.e. the balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). Changes in MPS are responsible for a much greater proportion of the change in muscle NPB than are changes in MPB. Latest scientific evidence highlights the importance of timing and the distribution of protein consumed over the day. An even distribution of protein intake over the three main meals has been shown to be more effective at stimulating 24 hour MPS rates than when the majority of the total daily protein intake is consumed at the evening meal (4,5). A more optimal distribution is 20 grams of protein per meal, with a 4 to 5 hour gap between meals. Athletes engaged in strength and power sports can achieve daily protein requirements by consuming ~30 g of protein per meal which is equivalent to 0.24–0.30 grams per Kg body weight per meal (6).
Use the ‘protein opportunity’ before sleep
Recent research has highlighted the role of consuming protein prior to sleep for maintaining MPS throughout the night (7-9). Pre-sleep protein in addition to 20 grams of protein immediately after an evening exercise training session was effective in offsetting the negative NPB, i.e. a higher MPB than MPS, associated with overnight fasting. Researchers found that MPS rates were approximately 22% higher during overnight recovery when 40 grams of a casein protein was ingested immediately prior to sleep. (10-12) A recent study of Dutch elite athletes found overall protein intakes to be 1.5 grams of protein per Kg body weight per day. However the protein was mainly consumed during the 3 main meals, with 38% (38 ± 15 g) of the total protein intake consumed at the evening meal and 19% (19 ± 8 g) and 24% (25 ± 13 g) at breakfast and lunch, respectively. Interestingly the protein intake was below the recommended 20 grams for 58% of athletes at breakfast, 36% at lunch and 8% at dinner. Only a small amount of protein was eaten as an evening snack (13). Therefore it is important for athletes to make the most of the protein ‘eating opportunities’ at breakfast and before sleep. For athletes aiming to increase MPS overnight, 30–40 grams of (casein) protein before sleeping is beneficial.
Aside from timing and amount, the protein source is also an important consideration for athletes. In general, protein from animal sources, for example dairy, beef, egg, fish, provide more of all the essential amino acids for optimal MPS and are considered to be of a high quality. The milk-based proteins casein and whey protein provide a higher concentration of the essential amino acids particularly leucine, and have consistently been shown to promote MPS to a greater extent than the same quantity of plant based proteins such as soy when consumed after resistance exercise. (14-15)
Key practice points
In order to maximise the benefits of resistance training in athletes and recreationally active people with respect to MPS; timing, amount, protein source and distribution over the day are all important considerations 16.
- Advise 20 grams of protein per meal and ~30 grams for athletes with a larger muscle mass.
- Distribute protein based meals evenly throughout the day with a 4-5 hour gap between meals.
- Breakfast and pre-sleep are missed ‘protein opportunities’. Advise 30-40 grams of (casein) protein before sleep to support overnight recovery.
This article has also been published in the magazine of the British Dietetic Association (May 2018).
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