Dairy and Sports Nutrition: A Research Roundup on Athletic Performance & Recovery

Among the many foods studied in relation to athletic performance and post-exercise recovery, dairy is often recognized for having favourable effects, due to its unique nutritional profile and high nutrient bioavailability.¹ In fact, in the latest joint position statement from the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine, dairy proteins were acknowledged as being ‘superior to other tested proteins’, notably due to their leucine content and efficient digestion and absorption of branched-chain amino acids.²

This series of brief study summaries will highlight new and interesting findings related to dairy in sports nutrition, addressing how it can contribute to recovery, muscle-protein synthesis, hydration, and overall metabolic health.

Emerging perspective on post-exercise recovery nutrition

Effective post-exercise recovery is critical for enhancing athletic performance, minimizing injury risk, and maintaining overall health. During intense physical exertion, the body undergoes high levels of physical stress in the forms of muscle damage, depleted energy stores, and dehydration, all of which must be addressed to ensure readiness for future efforts. Proper nutrition is a key supporting factor in this process, supplying the necessary nutrients for the body to repair, replenish, and recover.

A 2024 review synthesized current knowledge on several dietary supplements and functional foods in the context of post-exercise recovery.³ This included supplements like protein supplements, branched-chain amino acids, and creatine, as well as functional foods such as dairy products, anti-inflammatory foods like turmeric, and omega-3 fatty acids. Dairy, in particular, emerged as a key food for supporting different facets of sports recovery, including protein and hydration. The study addressed both dairy as a supplement and as a functional food.

Supplements

Food supplements, such as protein powders or electrolyte tablets, aim to provide concentrated nutrients to address specific recovery needs when diet alone may not be sufficient. When used appropriately, supplements can complement a balanced diet by providing isolated nutrients that offer targeted support for optimal recovery.

Protein supplements are commonly used to aid muscle repair and growth after exercise, partly due to their convenience. Casein and whey protein, the two main proteins in milk, are among the most popular types of protein supplements.

Whey protein is rapidly digesting and fast absorbing, making it optimal for promoting recovery after a bout of training, according to the authors. It is also rich in essential amino acids, notably leucine, which is crucial for stimulating muscle protein synthesis (MPS). On the other hand, casein is a slow-digesting protein and provides a sustained release of amino acids in the bloodstream. Its gradual digestion supports prolonged muscle repair and growth, which the authors note make it particularly beneficial for overnight recovery.

Functional Foods

Functional food refers to a food that yields additional health benefits beyond its essential nutrients, often due to the presence of bioactive compounds that can also aid in recovery.

The authors highlight dairy products as effective functional foods, emphasizing their unique and complex composition and their ability to support various facets of recovery. For example, milk provides important nutrients for supporting bone health, such as calcium and vitamin D, which are particularly important for athletes partaking in strenuous activity. In addition, milk’s electrolyte content, namely potassium and sodium, can promote rehydration and support fluid balance regulation after training. Studies have also revealed that milk consumption post-exercise may also aid in modulating inflammation, therefore supporting recovery. The authors also recognize yogurt as an effective functional food, as its probiotic content can support gut health by helping to promote healthy intestinal flora, improve nutrient absorption, and decrease inflammation, all of which support effective recovery. They conclude with the recommendation of approximately 250-500ml of dairy products post-exercise to provide recovery benefits as a functional food, notably to support muscle and bone health.

Growing evidence on pre-sleep protein for muscle-related outcomes

The timing of protein intake has long been a topic of interest in sports nutrition, as MPS is influenced by both nutrition and exercise. While the effects of protein quantity and quality on MPS are generally well understood, the optimal timing of protein consumption remains an area of ongoing research. Recent interest has focused on the distribution of protein intake throughout the day, with some evidence suggesting that evenly distributed intake may lead to a more favourable net protein balance. Additionally, it is hypothesized that limited nutrient availability during the overnight period may result in a negative net muscle protein balance. Thus, pre-sleep protein intake has emerged as a potential strategy to enhance skeletal muscle adaptation to exercise, optimize protein balance, and promote muscle mass accretion.

In a 2023 randomized controlled trial, 36 healthy young men (18-35y) consumed either 45 grams of casein, 45 grams of whey, or a placebo approximately 30 minutes before sleep, after completing a one-hour endurance exercise session 3 hours earlier.⁴ The results revealed that protein intake before sleep was linked to higher levels of both mitochondrial and myofibrillar MPS in both the whey and casein groups, compared to the placebo, during the overnight recovery period. Interestingly, both casein and whey produced comparable results. No difference in ad libitum energy intake was observed between the groups at the subsequent breakfast meal.

These findings are supported by a previous systematic review of 9 trials, which indicated that consuming 20-40 grams of casein about 30 minutes before sleep stimulates whole-body protein synthesis in both younger and older men, regardless of any preceding resistance training.⁵ The study also found that chronic pre-sleep protein intake improved muscle adaptive responses in young men following a 12-week resistance exercise program, but no effects were observed in older men.

While these results are promising, it is important to note that this research remains preliminary. Moreover, many studies share the limitation that protein intake differs between groups, making it challenging to differentiate the effects of protein timing vs overall protein quantity. Lastly, MPS is not synonymous with muscle mass accretion and thus, more robust studies will be needed to elucidate the advantages of pre-sleep protein and its potential benefits. Overall, pre-sleep protein may present another opportunity for athletes to increase their total daily protein intake.

Nutritional strategies and the potential role of dairy for female athletes and physically active women

Female athletes and physically active women have unique nutrition needs to support their energy, performance, and recovery. Understanding inherent differences among women, including considerations related to reproductive health such as menstrual cycles and menopause, is essential for developing personalized fueling strategies. Factors like hormone fluctuations, iron levels, and dietary intake can impact all facets of exercise training, from strength to endurance. However, much of the research in sports nutrition has been based on men, meaning women's specific needs are often overlooked.

A 2024 systematic review of 71 studies including 1,654 women investigated different nutritional strategies, including dietary and supplement approaches, to improve either performance or health status of women with varying levels of physical activity, from competitive athletes to recreationally active women.⁶

Among the main findings on diet, the authors highlight the benefits of dairy, especially in recognition of its high calcium content and the crucial role this nutrient plays in several aspects of female athlete health and performance. They emphasize that calcium supports bone health and plays a key role in blood clotting, muscle contractions, protein utilization, cellular communications, and nerve signalling. Moreover, consuming a source of calcium before exercise may also help counteract calcium losses through sweat during a bout of physical activity. The authors underscore the following findings from female-participant studies on dairy foods.

• A study on trained female cyclists investigating the effects of a dairy-based breakfast (1,350 mg of calcium) 90 minutes before a prolonged, high-intensity stationary cycling session found a positive impact on iodized calcium and a decrease in parathyroid hormone (a hormone responsible for calcium regulation), thereby possibly decreasing bone resorption.⁷
• A study on well-trained female cyclists revealed that consuming a calcium-rich, dairy-based breakfast 3 hours before exercise did not cause gut discomfort or affect physical performance, suggesting that dairy may be a suitable option for meeting calcium recommendations in female athletes.⁸
• A study on competitive female runners and triathletes investigating the effects of consuming chocolate milk before sleep found enhanced carbohydrate oxidation at rest and during morning exercise compared to a nonnutritive placebo, though no improvements in 10-km running time trial performance were observed.⁹