Friday, July 1, 2011

Milk as the new sports drink...!!!

Milk is as ancient as mankind itself  but its importance still remains new as man-kinds’ technological  inventions. However, milk still exists with lots of controversy till date.
There has been growing interest in the potential use of bovine milk as an exercise beverage, especially during recovery from resistance training and endurance sports.[1]
Milk represents a more nutrient dense beverage choice for individuals who partake in strength and endurance activities, compared to traditional sports drinks. Milk consumption acutely increases muscle protein synthesis, leading to an improved net muscle protein balance. Furthermore, when post-exercise milk consumption is combined with resistance training (12 weeks minimum), greater increases in muscle hypertrophy and lean mass have been observed.

Nutritional intake is important for optimizing sport and exercise performance. Finally, the nutrient composition of post-exercise nutritional intake has also been shown to be important in the recovery from endurance exercise and adaptations/recovery from resistance exercise.
Low-fat milk has a number of characteristics that theoretically make it a potentially good recovery beverage. Firstly, it contains carbohydrates (lactose) in amounts similar to many commercially available sports drinks (glucose, maltodextrin) i.e. around 6-8g/100ml. Milk contains casein and whey proteins in a ratio of 3:1 which provides for slower digestion and absorption of these proteins resulting in sustained elevations of blood amino acid concentrations which supports recovery for a longer duration.[2]
Another advantage is that whey protein also contains a large proportion of branched chain amino acids which have an integral role in muscle metabolism and protein synthesis to fasten the recovery process and slow down the muscle breakdown[6]. Finally, milk also has naturally high concentrations of electrolytes, which are naturally lost through sweating during exercise. The high concentrations of these electrolytes should aid in fluid recovery following exercise.

Milk and resistance exercise and training
Resistance exercise and resistance sports are characterized by repeated high intensity contractions of varying muscle groups that leads to well characterized adaptations in muscles.[3] The most obvious adaptation is skeletal muscle hypertrophy. For muscle hypertrophy to occur there must be a chronic increase in muscle protein net balance and resulting in less negative balance[4]. Muscle protein balance is a function of muscle protein synthesis and muscle protein breakdown.

Elliot et al. [9]investigated the influence of consuming differing milk beverages on the protein metabolic response following an acute bout of resistance exercise, all of the different milk beverages resulted in a significant increase in net balance of the measured amino acids.

Recent work has shown that one way by which consumption of fat-free milk increase protein net balance is through an increased rate of muscle protein synthesis following resistance exercise,[2] where the fat-free milk the elevation in blood amino acids[5] was slower and remained elevated for a more prolonged period, providing a more sustained delivery of amino acids for skeletal muscle protein synthesis.

Interestingly, consumption of the fat-free milk resulted in greatest increases in muscle hypertrophy, as observed through greater increases in both type I and II muscle fiber areas.

Milk and endurance exercise and training
Endurance sports and activities are generally considered to be sub-maximal activities that can be performed for more prolonged periods of time. These activities are also characterized by continuous exercise/activity that is highly dependent on oxidative metabolism as a source of energy and usually involve large muscle groups. This dependence on oxidative metabolism and involvement of a large muscle mass leads to higher rates of total substrate turnover and under certain conditions, depletion of muscle glycogen in the active muscles.

Interestingly, when milk is consumed during prolonged exercise, following completion of the exercise a reduction in whole body protein breakdown and protein synthesis was observed with a simultaneous increase in protein oxidation.

The use of milk as a recovery beverage after endurance exercise has also been investigated to a limited extent. The main goal of any post exercise nutritional intervention is usually to promote muscle glycogen re-synthesis, and fluid recovery. In regards to glycogen re-synthesis, there is very limited direct research into the efficacy of milk consumption to replenish muscle glycogen levels.

In endurance training, there is a direct relation of calcium loss due to lot of running for prolonged time, where milk serves as a excellent source of calcium by enhancing its absorption with the presence of lactose sugar of milk after the training.

Other benefits of milk

Fat mass also declined to the greatest extent in the milk group. The authors attributed the greater increase in muscle fiber hypertrophy and lean mass to the previously observed acute influences of milk consumption on protein metabolism[7]. The greater decline in fat mass observed with the milk group was suggested to be related to the greater calcium intake associated with the milk consumption, as there is growing evidence to suggest a pivotal role for dairy products in influencing adipocyte metabolism in a manner that attenuates lipid accretion.[8] This very well controlled study clearly showed multiple benefits to using fat-free milk as a post-resistance exercise beverage.

Conclusion

Milk also has the added benefit of providing additional nutrients and vitamins that are not present in commercial sports drinks. In conclusion, fat free milk is a safe and effective post-exercise beverage that has been shown to promote recovery from exercise and should be considered as a viable alternative to commercial sports drinks by lactose tolerant individuals.
References

1.  Haug A, Hostmark AT, Harstad OM: Bovine milk in human nutrition – a review.
Lipids Health Dis 2007, 6:25.
2.   Bos C, Metges CC, Gaudichon C, Petzke KJ, Pueyo ME, Morens C, Everwand J, Benamouzig R, Tome D: Postprandial kinetics of dietary amino acids are the main determinant of their metabolism after soy or milk protein ingestion in humans.
J Nutr 2003, 133:1308-1315.
3.   Kraemer WJ, Duncan ND, Volek JS: Resistance training and elite athletes: adaptations and program considerations.
J Orthop Sports Phys Ther 1998, 28:110-119.
4.   Phillips SM, Tipton KD, Aarsland A, Wolf SE, Wolfe RR: Mixed muscle protein synthesis and breakdown after resistance exercise in humans.
Am J Physiol 1997, 273:E99-107.
5.   Tipton KD, Ferrando AA, Phillips SM, Doyle DJ, Wolfe RR: Postexercise net protein synthesis in human muscle from orally administered amino acids.
Am J Physiol 1999, 276:E628-E634.
6.   Tipton KD, Elliott TA, Cree MG, Wolf SE, Sanford AP, Wolfe RR: Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise.
Med Sci Sports Exerc 2004, 36:2073-2081.
7.   Miller SL, Gaine PC, Maresh CM, Armstrong LE, Ebbeling CB, Lamont LS, Rodriguez NR: The effects of nutritional supplementation throughout an endurance run on leucine kinetics during recovery.

8.  Zemel MB: Role of calcium and dairy products in energy partitioning and weight management.Am J Clin Nutr 2004, 79:907S-912S.
9.   Miller SL, Maresh CM, Armstrong LE, Ebbeling CB, Lennon S, Rodriguez NR: Metabolic response to provision of mixed protein-carbohydrate supplementation during endurance exercise.


Hinal Gala,
Nutritionist,
Your Fitness club

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