Protein has long been a favourite of serious athletes due to its ability to stimulate muscle growth and recovery, which may ultimately help to enhance athletic performance. Once just a staple in the bodybuilder's tool kit, today's mainstream consumer is picking up on the power of protein, realising how this important nutrient can help build lean muscle and improve body strength.

But how does protein provide muscle benefits, and do protein sources differ in their ability to positively impact muscle? Most importantly, how can manufacturers in today's competitive functional food and beverage industry tap into the power of protein ingredients to use in products that maximise the consumer benefit?

Why the body needs protein

Athletic performance and recovery from exercise are enhanced by optimal nutrition, which includes the selection of proper food and beverage choices as well as the timing of intake, according to a Joint Position Statement published by the American College of Sports Medicine (ACSM), American Dietetic Association (ADA), and the Dietitians of Canada (DC).¹

Protein plays a crucial role in the building of lean muscle and muscle recovery. Following intense resistance exercise, many athletes make use of ingesting protein to maximise muscle hypertrophy, or an increase in muscle-fibre size (though there are some athletes, like runners or cyclists, who do not want to carry the additional weight). The amount of protein the body needs varies depending on age, weight, sex, activity level and overall health. The Institute of Medicine recommends a range from 10 per cent to 35 per cent of daily calories consumed come from protein for the average healthy adult.² For example, if a 155-pound person eats 2,000 calories every day, this would be between 50g to 175g of protein per day. Research has shown that some athletes and routinely active adults may benefit from additional dietary protein. Protein recommendations outlined in the Joint Position Statement from ACSM/ADA/DC for endurance and strength-trained athletes range from 1.2 to 1.7g/kg body weight/day, which is an aggregate total of between 84 and 119g/day.¹

While proteins are all good, the quality varies based on composition. An ideal sports protein should provide a high proportion of essential amino acids, particularly branched-chain amino acids (BCAAs), especially leucine.

Quality matters

Evidence suggests that consumption of different proteins can affect the extent and possibly the duration of muscle protein synthesis (MPS) after feeding, and this effect is potentially accentuated with resistance exercise.3 A high-quality protein source can be used for the maintenance, repair and synthesis of skeletal muscle proteins in response to training.3

The advantage of whey protein is that it contains all the essential amino acids the body needs to build and repair muscle after a tough workout. Whey protein also is one of the richest sources of BCAAs, which helps athletes get the most out of their workouts. (See accompanying chart on BCAAs.) BCAAs are unique because they can be taken up directly by skeletal muscle and used in rebuilding muscle after exercise.

"The branched chains, and particularly leucine, are the key amino acids one should look for in a performance product," said Matthew Pikosky, PhD, RD, FACN, and director of research transfer for Dairy Management Inc (DMI). "Leucine is a key nutrient signal initiating protein synthesis, and the branched chains are collectively unique compared with the other amino acids in that they are preferentially taken up and utilised by skeletal muscle."

Weighing the differences

High-quality proteins such as whey, casein and soy can support MPS, but differences in the rate of digestion of these proteins may modulate MPS response after an acute bout of resistance exercise and following long-term training. Another important component in determining the effect on MPS may be the leucine content of the protein. According to research conducted by the Exercise Metabolism Research Group at the Department of Kinesiology, McMaster University, Hamilton, Ontario, when seeking to maximise MPS, milk proteins and their isolated forms, such as whey and casein, may offer an anabolic advantage over soy proteins in promoting muscle hypertrophy.3

Research also has shown that whey protein works well for workout recovery products. If combined with a high-glycaemic carbohydrate, it provides quick muscle-recovery effects compared to ingesting only carbohydrates post-exercise, according to additional research conducted by the Exercise Metabolism Research Group at McMaster University in Hamilton, Ontario.⁴ In a study using eight resistance-trained athletes, the researchers found that participants who ingested a carbohydrate drink (21g of fructose) containing 10g of whey protein following resistance exercise saw a greater increase in MPS compared to a carbohydrate-only beverage. However, this may be in part due to the poor absorption associated with fructose.5

Studies are now beginning to examine how protein hydrolysates consumed before, during or after workouts impact muscle recovery.6 Protein hydrolysates are produced from purified/intact protein sources by heating with acid or, preferably, an addition of proteolytic enzymes, followed by purification procedures. Because these proteins are partially broken down or digested, the amino acids are able to reach the blood and skeletal muscles more quickly.

One study at Victoria University in Victoria, Australia, examined the effects of supplementation with hydrolysed whey isolate and casein on strength, body composition and plasma glutamine levels during a 10-week, supervised resistance training programme in a group of male recreational bodybuilders.7 The study found that whey-protein hydrosolate was more effective than casein at helping these athletes achieve significant gains in muscle strength and lean body mass. Additional research is still needed in this area to compare intact proteins to partially hydrolysed proteins to determine if these differences in speed of digestion and absorption result in a practical benefit (ie greater MPS, muscle strength, etc.).

Pick your protein

In addition to differences in their amino acid composition, dairy proteins like casein and whey vary in their digestion/absorption and delivery of amino acids to the skeletal muscles. Casein is described as a 'slow' protein because of its slower rate of digestion, resulting in a prolonged delivery of amino acids to systemic circulation. Casein's primary benefit is suppressing whole body protein breakdown.8 In contrast, whey protein is known as a 'fast' protein because it is digested rapidly, leads to a large but transient increase in blood levels of amino acids and stimulates protein synthesis and oxidation.9 There is emerging evidence now on new protein forms such as whey growth-factor extracts, which could possess biological properties including tissue repair and anti-inflammatory activity.10

Research continues on discovering new ways and opportunities for performance food and beverage manufacturers to use protein ingredients to boost protein content in their products and help today's performance athletes reach new goals.

Kara McDonald is director of ingredient marketing and communications for Dairy Management Inc. and has worked in the dairy industry for 12 years in various marketing and communications roles.

Who is using whey in performance products?

Frequently used in performancebeverage product formulations, whey proteins maintain solubility across a wide range of pH levels. "The beauty of formulating with dairy protein ingredients is that one can choose which to use based on the pH conditions and the beverage's heat stability requirements," said Kimberlee Burrington, dairy ingredient applications coordinator, Wisconsin Center for Dairy Research at the University of Wisconsin-Madison. In addition, whey proteins have superior gelling and water-binding capabilities.

Specialty whey-protein concentrates and isolates can be the performance product formulator's protein of choice to develop a clear beverage or pack 20g of protein into the performance athlete's nutrition bar. These concentrates and isolates can be found in heat-stable, high-gelling, partially hydrolysed or other speciality forms to meet the ingredient challenge.

"If clarity is the goal for the beverage product, the ingredient of choice is whey-protein isolate, which has more than 90 per cent protein and very low levels of fat," Burrington said. "For hot-fill products, clear beverages can be formulated in the pH range of 2.8 to 3.4 and cloudy beverages in the pH range of 3.5 to 4.5."

Whey proteins are least stable near their isoelectric point, but are quite soluble above or below this pH. Solubility can decrease with severe heat treatments that denature whey proteins, which makes them less soluble. Performance food and beverage products on the market today use whey protein at varying levels depending on the market:

— KM

The branched-chain gang

Whey protein offers several benefits for the physically active. Easily digestible, the dairy protein is a high-quality protein with a relatively high proportion of branched-chain amino acids (BCAA) such as leucine, which plays a significant role in the rebuilding of muscle. The abundance of leucine in whey plays a significant role in the synthesis of muscle protein. See chart below for comparison of BCAA content of different protein sources.

Select suppliers: Protein powers athletes

CP Kelco
Simplesse microparticulated whey protein concentrate undergoes a unique microparticulation process that makes it a natural, multi-functional dairy ingredient.
www.cpkelco.com

Croda
Nutritional proteins and peptides are suitable for convenient health-food products, such as protein bars and sports drinks. They provide a rich source of natural amino acids, including glutamine, glycine, arginine, proline and two unique to collagen.
www.croda.com

Davisco Foods International
Produces a full line of whey protein products, including customized varieties that are customised.
www.daviscofoods.com

DSM
PeptoPro is a pre-digested milk protein, derived from casein, which is neutral in taste. A patent-protected enzyme reduces the typical bitter taste while generating tiny protein peptides that are rapidly absorbed into the bloodstream, fuelling the muscles. It can be provided in a variety of pleasant-tasting powders, drinks, gels or energy bars.
www.dsm-functionalfoodsmarketing.com

Fonterra
Exports dairy ingredients. The company's ingredients include milk powders, cream products, cheese and cheese ingredients, milk and whey proteins, clinical products, and organic dairy ingredients.
www.fonterra.com

Glanbia Nutritionals
Offers a wide range of speciality whey proteins, from Avonlac whey protein concentrates to Provon whey protein isolates and Salibra bioactive whey fraction. Suitable for healthy beverages, nutrition bars, processed foods, and supplements solutions that are formulated to enhance applications.
www.glanbiausa.com

Hilmar Ingredients
Produces whey proteins ranging from 80% whey protein concentrate to hydrolysates. The company also produces a range of high-purity edible, refined, and USP lactose.
www.hilmaringredients.com

Metabolic Technologies Inc
HMB is hydroxy beta-methylbutyrate, which is naturally produced during the metabolism of the essential amino acid leucine. HMB stimulates protein synthesis, thereby increasing lean mass and strength gains from weight training.
www.mtibiotech.com

Premium Ingredients Intl
Instant Whey Protein Concentrate is produced via a proprietary filtration process that concentrates native whey proteins in a highly purified form. Instantised via an in-line agglomeration procedure that creates a highly soluble nutritive ingredient.
www.premiumingredients.com

Solbar Industries
Provide solated soy proteins, including the new Bontex steam-textured soy protein that's processed from non-GMO IP soybeans in a variety of sizes and shapes. Available in natural colours and flavours. Bland flavour and quick water-absorption properties. Suitable for both savoury and sweet applications.
www.solbar.com

Stauber Performance Ingredients
Cranberry Protein Powder is produced by a patented cold extrusion and filtration process from the seeds of the American cranberry (Vaccinium macrocarpon Ait) without enzymes or extraction solvents. The powder is a concentrated source of complete protein, as well as potassium, calcium, insoluble fibre and oxygen-resistant essential fatty acids.
www.stauberusa.com

TGR Biosciences
Lactermin is derived from the whey fraction of milk and contains the proteins lactoperoxidase and lactoferrin, together with a variety of minor proteins and peptides such as the growth factors IGF-I, IGF-II, PDGF, FGF, TGF- ß and betacellulin. This bioactive component of milk is proposed to contribute to the biological properties of Lactermin such as the promotion of tissue repair and anti-inflammatory activity. A Phase I trial has demonstrated the safety of the extract as a mouth rinse in lymphoma patients undergoing high-dose chemotherapy.
www.tgr-biosciences.com.au

Triarco Industries
Aminogen accelerates fat loss and boosts the weight-loss benefits of protein while supporting lean muscle mass. MyTosterone increases testosterone levels.
www.triarco.com

UniChem
Amino acids are building blocks that give each protein a different characteristic. All amino acids contain an amino base, a carboxyl group and a side chain accompanied with an alpha-carbon atom.
www.unichemsupply.com

References
1. American Dietetic Association. Position of the American Dietetic Association, Dietitians of Canada and the American College of Sports Medicine; Nutrition and Athletic Performance. J Am Diet Assoc 2009:100:1543-1546.
2. Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington D.C.: National Academy Press, 2005.
3. Tang JE, et al. Maximizing muscle protein anabolism: The role of protein quality. Curr Opin Clin Nutr Metab Care 2009.
4. Tang J, et al. Minimal whey protein with carbohydrate simulates muscle protein synthesis following resistance exercise in trained young men. Appl Physiol Nutr Metab 2007; 32:1132-1138.
5. Beyer PL, et al. Fructose intake at current levels in the United States may cause gastrointestinal distress in normal adults. J Am Diet Assoc 2005 Oct;105(10):1559-66.
6. Manninen A, Protein hydrolysates in sports nutrition. Nutr Metab 2009;6:38.
7. Cribb PJ, et al. The effect of whey isolate and resistance training on strength, body composition and plasma glutamine. Int J Sport Nutr Exerc Metab 2006;16:494-506.
8. Boirie Y, et al. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci USA 1997;94:14930-14935.
9. Dangin M, et al.The rate of protein digestion affects protein gain differently during aging in humans. J Physiol 2003;549:635.
10. Dyer AR, et al. In vitro and in vivo safety studies of a proprietary whey extract. Food Chem Toxicol 2008 May;46(5):1659-65.