SPORTS NUTRITION
Milk is a natural source of many nutrients that are valuable to an athlete’s health and performance on the field. It provides:
- carbohydrates in the form of lactose (milk sugar) to supply energy
- calcium, protein and phosphorus for normal bone health
- protein for the growth and maintenance of muscles
- iodine, vitamin B12 and riboflavin to support energy release
- fluid with naturally present electrolytes to support hydration.
Milk is an affordable and widely accessible beverage choice, and many athletes consider it a convenient and versatile recovery drink, whether consumed just as it is or blended with fresh fruit to create a post-exercise smoothie.
Adequate recovery following intense exercise is essential in order to perform well in subsequent training sessions, a match or a competition. Milk is considered by many to be a natural, convenient, accessible and affordable post-exercise drink to address the three key aspects of recovery:
- Refuel: Milk naturally contains carbohydrates in the form of lactose (milk sugar), which assists in refuelling energy stores.
- Repair: Milk provides high-quality protein in the form of casein and whey, which contributes to muscle growth and repair.
- Rehydrate: Milk contains electrolytes (e.g. potassium) and consists of approximately 87% water, which aid rehydration.
Milk and liquid dairy foods provide the body with a great source of water and electrolytes, which help to both replace water lost through sweat and retain electrolytes, and so aids effective rehydration. The sodium concentration of milk is similar to that of other sports drinks, with several studies showing that it is equally effective (or even better) than sports drink or water for rehydration. Milk also contains additional electrolytes, e.g. potassium, which contribute in fluid absorption.
An intake of 20–25 g of high-quality protein, such as found in milk, contributes to muscle repair and adaptation as naturally occurs after intense physical activity such as resistance exercise, high-intensity interval training and endurance events. Emerging research suggests a volume of 500 mL low-fat milk post exercise is effective in aiding muscle recovery.
Milk protein provides all the essential amino acids the body needs and specifically leucine, which is recognised for its role in muscle protein synthesis. Dairy protein has also been found to be superior to other protein sources in optimising muscle protein synthesis following resistance training.
Muscle anabolism implies that protein synthesis must exceed protein breakdown. Building muscle requires sufficient stimulation (e.g. resistance exercise) as well as a healthy, balanced diet that provides adequate energy and muscle-friendly nutrients such as protein. Milk can contribute to building muscle as it is rich in high-quality protein, meaning that it provides all the essential amino acids (building blocks of protein) the body needs. Milk protein consists of 80% casein and 20% whey. Whey is particularly high in the amino acid leucine, which is recognised for its role in rebuilding muscle protein. Research has shown that the having milk after resistance exercise is an effective option for stimulating muscle growth in both men and women.
Low-fat chocolate milk has been highlighted as a popular post-exercise beverage. This is because chocolate milk provides nutrients that address the key considerations of post-exercise recovery:
- Refuel: Chocolate milk contains lactose, a carbohydrate naturally present in milk, as well as added sugars such as glucose and sucrose, which all assist in refueling energy stores.
- Repair: Chocolate milk provides high-quality protein in the form of casein and whey to stimulate muscle growth and repair.
- Rehydrate: Chocolate milk naturally contains electrolytes (e.g. potassium) and is approximately 87% water, which aids rehydration.
Chocolate milk is considered a tasty option after exercise, as well as being a convenient, accessible and relatively affordable recovery choice. Owing to its added sugar and therefore higher carbohydrate content compared with plain milk, having chocolate milk as a recovery drink is best following an intense exercise session.
Generally, all of the energy and nutrients we need can be provided by a healthy, balanced diet – with no need for supplement use unless a deficiency is identified. Athletes with a high protein need can fulfil the need with protein-rich food sources such as dairy products, meat, fish, eggs and soy. The intake of supplemental protein when the diet is already sufficient in protein will probably pose no additional benefit for the athlete. There is also little evidence to support the benefit of supplementing with individual amino acids when athletes are consuming an adequate diet. Some athletes although find it difficult to consume protein food sources at the ideal time and a protein supplement may add some convenience. Athletes should although be aware of protein supplements that contain extra ingredients and impurities.
Generally, ‘high-protein milk’ contains additional protein, which increases the protein content from approximately 3.5% (as typically in plain milk) to 5%. Unless other ingredients (such as flavourings) are added, ‘high-protein milk’ reflects a similar nutrient profile as plain milk.
In contrast, protein supplements are usually in powdered form and can vary in source. Those that provide milk protein may be either isolates of casein or whey, which provide only the specified protein constituent, or concentrates of casein or whey, which may include additional ingredients.