The demand for high-protein supplements and prepared foods has grown in recent years as high-protein diets have become the rage in the weight-loss arena. Current research suggests that different types of protein have varying effects on exercise outcome and physique. Richard B. Kreider, Ph.D., assesses which protein source is best.

Several types of native protein sources, as well as designer blends, are found in dietary products for performance and body composition benefits. Protein sources most commonly used in dietary supplements and functional foods include egg, milk, casein, whey, soy, colostrum and gelatin, with whey being the most prevalent today. Many factors influence the availability of the various amino acids, peptides and fractions within the proteins that have been reported to possess biological activity. These variables include processing methods—for example, hydrolysed, concentrate, isolate, ion-exchange, cross-flow microfiltration; the amino acid profile of the protein; and the mode of delivery, such as foods, bars, powders or ready-to-drink supplements. Although a particular processing method may provide a marketing advantage, the central question remains whether there is really any difference in the protein sources used in products.

Researchers generally determine protein quality by using the protein efficiency ratio (PER) or the protein digestibility corrected amino acid score (PDCAAS). They determine the PER by evaluating the weight gain in growing rats fed a particular protein compared with a standard protein, egg whites being the gold standard. The higher the PER value, the greater the protein quality. The PDCAAS was introduced as a more accurate way to evaluate protein quality for humans, because it uses human, not rat, amino acid requirements to calculate the amino acid score. It compares the amino acid profile of a protein with the essential amino acid requirements for humans according to The Food and Agriculture Organization. When a protein meets this requirement, it gets a score of 1.0. PDCAAS has now been adopted as the official method by the World Health Organisation, the US Food and Drug Administration and the US Department of Agriculture.

Although the PDCAAS method is the internationally recognised standard for comparing proteins for human consumption, it does not allow for differentiation among proteins with a PDCAAS of 1.0, so proteins can have different PERs while still having a PDCAAS of 1.0. This is significant, because researchers are now exploring how variances in specific essential and/or conditionally essential amino acids, as well as the availability of various peptides and micronutrients, affect human physiology. Claims of consumer-relevant superiority or inferiority, when performance of physique modificaitons are concerned, have yet to be supported by population-specific evidence in humans.

(left) lists the PER and/or PDCAAS for the major types of protein used in nutritional supplements. The following discusses the relative strengths and weaknesses of these basic types of proteins that are often used as starting materials for nutritional supplements. Of course, adding deficient amino acids and other nutrients to these proteins may increase the PDCAAS, nutrient value and/or functionality of the protein.

Egg Proteins
Egg protein is typically obtained from chicken egg whites (ovalbumin) or whole eggs through various extraction and drying techniques. Ovalbumin is recognized as the reference for protein quality comparisons. The PER and PDCAAS of egg protein is similar to milk proteins and only slightly lower than casein, whey and bovine colostrum.

Egg protein has historically been one of the most common protein sources used in nutritional supplements, because consumers perceive it to be a high-quality protein. However, manufacturers are beginning to use other protein sources because egg protein is a relatively expensive form of protein.1

Because egg protein is viewed as the reference protein, researchers have evaluated the effects of egg protein on nitrogen retention and physiological adaptations compared with other proteins. Study results generally indicate that egg protein is as effective as milk protein, casein and whey in promoting nitrogen retention, which is a measure of the adequacy of a dietary protein.2,3,4

Milk Proteins And "Magic Blends"
Milk protein has been one of the most widely used sources of protein for use in nutritional supplements. Milk protein is comprised of about 80 per cent casein and 20 per cent whey protein. Milk protein contains several subtypes of casein (a, b, g, k) and whey protein (a-lactalbumin, b-lactoglobulin, bovine serum albumin, immunoglobulins, lactoferrin, lactoperoxidase) that are each believed to possess unique physiological properties.1

Most researchers have used milk protein to determine the effect of increased dietary protein intake on protein balance, and the results of their research have generally revealed that milk protein is a high-quality protein source. More recently, there has been interest in determining the effects of ingesting casein and whey protein on nitrogen retention, hormonal profiles, protein synthesis and sports training adaptations.

Caseinates are produced from skim milk through a processing technique that separates the casein from the whey, then resolubilising and drying.1 Caseinates used in commercial supplements are available as sodium caseinates, potassium caseinates, calcium caseinates and casein hydrolysates. The processing method affects the amino acid profile slightly, as well as the availability of a, b, g and/or k casein subtypes. There is a lack of research on various caseinate blends as it relates to performance.

The advantage of casein is that it is relatively inexpensive and is available in a range of grades that vary in quality, taste and mixing characteristics.1

The major disadvantage of casein for manufacturers and consumers is that it is not readily soluble in liquid and tends to clump, particularly in an acidic fluid. However, research indicates that several factors influence protein synthesis, including the amount of calories consumed, the quantity and quality of protein ingested, the insulin response to the meal, and the digestibility of the food.5

The digestion rate of a particular food influences the time release of amino acid in the blood. Foods containing proteins that are digested quickly, such as whey, often expedite the amino acid release in the blood. Conversely, foods containing proteins that are digested slowly, such as casein, often result in a reduced but more prolonged increase in amino acids.6

Research from Boirie and colleagues and Dangin and associates suggests that casein may be superior to whey because of the prolonged amino acid release and influence on anticatabolic hormone profiles.7,8 Some supplements manufacturers now market casein as a superior form of protein.

A study by Demling and co-workers is often cited to support contentions that casein supplementation during athletic training is more effective than whey protein. However, this study actually compared ingesting a vitamin/mineral-fortified carbohydrate/protein meal replacement powder containing a "unique blend of milk protein isolates (caseinate, glutamine, whey protein concentrate, egg white)" with a whey protein supplement.9 Consequently, the greater gains in muscle mass and strength observed in the study could not be attributed to ingesting casein alone.

Although casein is a quality protein source, there is little evidence that it is more effective than soy, egg, whey or bovine colostrum. In fact, it has often been used as the control protein in supplements studies.

The slow and fast concept of protein digestion is certainly interesting. However, more research is needed to explore the role of ingesting various mixtures of slow and fast proteins with and without other macro- and micronutrients.

Is Whey The Way?
Whey protein is currently the most popular source of protein used in nutritional supplements, particularly in the sports nutrition market. Whey proteins are available as whey protein concentrates, isolates and hydrolysates. Whey protein concentrates (about 80 per cent protein) are produced from liquid whey by clarification, ultrafiltration, diafiltration and drying techniques.1 Whey protein isolates (about 90 per cent protein) are typically produced through ion-exchange (as with Davisco Ingredients' BiPro) or cross-flow microfiltration (as with Glanbia Ingredients' CFM/Provon) techniques. Whey protein hydrolysates (about 90 per cent protein) are typically produced by heating with acid, or preferably treatment with proteolytic enzymes, followed by purification and filtration.

Different processing methods affect amino acid availability as well as concentration of whey protein subtypes, peptides and amino acids (i.e., a-lactalbumin, b-lactoglobulin, bovine serum albumin, immunoglobulins, lactoferrin, lactoperoxidase). Theoretically, differences in protein subtypes and/or peptides may influence the physiological function of a protein.

In recent years, marketing experts have focused on distinguishing differences in the quality of whey proteins based on how they were processed. Some contend that ion-exchange (IE) whey protein is superior to other forms. However, cross-flow microfiltration (CFM) and proteolytic enzyme-treated whey hydrolysates may be the best choice because they better preserve the availability of whey protein subtypes and peptides.

Research suggests that the availability of whey protein subtypes and peptides may be more health-promoting constituents than whole whey.10,11 For this reason, most researchers who have evaluated the health and/or performance benefits of whey protein have used whey protein produced using CFM or proteolytic enzyme hydrolysis.1

Compared to casein, whey protein is digested more quickly, with better mixing characteristics and a general reputation for higher quality. Research has indicated that the rapid increase in blood amino acid levels following whey protein ingestion stimulates protein synthesis to a greater degree than casein.7,12 However, the researchers found that a single dose of whey protein had less impact over time on protein catabolism in comparison to casein. Theoretically, individuals who consume whey protein frequently throughout the day may optimize protein synthesis.

In support of this contention, Dangin and associates concluded that frequent ingestion of a small amount of whey protein increased protein synthesis to a greater degree than less-frequent ingestion of various proteins.8 Whey protein may also offer a number of health benefits compared with casein, including greater immunoenhancing and anticarcinogenic properties.10,11,13,14,15 For example, Lands and colleagues reported that 20 healthy young adults who took 20g/day whey protein during 12 weeks of athletic training experienced enhanced immune function, performance and body composition alterations over casein.16 These findings and others have helped position whey protein as a superior protein source for nutritional supplements.

Soy Protein
Soy protein is obtained from soybeans through a process of water extraction, precipitation, washing and drying that yields soy protein concentrate (about 70 per cent protein) or soy protein isolates (about 90 per cent protein).1 Although soy is lower in the essential amino acid methionine, it has a relatively high concentration of the remaining essential amino acids—particularly arginine and glutamine—and is therefore considered a complete protein. The PER and PDCAAS of soy protein is similar to dietary meat or fish and slightly lower than egg, milk, casein, whey and bovine colostrum.

Studies have shown that soy protein helps build and maintain muscle mass and lean body tissue. Dragan and colleagues conducted trials with the Romanian Olympic rowing team and found that 1.5g/kg body weight Supro soy protein, from Dupont Protein Technologies, in addition to regular intake of 2.0g/kg protein in the diet may be responsible for reduced post-exercise fatigue.17

Other studies provide evidence that soy can exert antioxidant effects in people, particularly for exercise-induced oxidant stress. Robert DiSilvestro, PhD, and co-workers at Ohio State University fed 10 young adult males a soy beverage containing 40g/day protein and 44mg genistein/day. Compared to a group of 10 males who consumed a whey beverage containing 40g protein/day, the Supro soy group experienced superior plasma total antioxidant status and a lower rise in plasma creatine kinase activity (an indicator of muscle tissue breakdown).18

Some researchers also have expressed concern over the long-term health impact of diets high in phytoestrogens. There has also been some concern that male consumption of phytoestrogens may decrease testosterone levels and/or increase the infertility rate.19,20 Finally, there is some indication that soy-enhanced diets may interfere with thyroid function and absorption of the thyroid medication levothyroxine in infants who have hypothyroidism.21,22 Although long-term studies evaluating soy protein consumption generally indicate no significant adverse effects on health, extremely high consumption of soy has not been adequately evaluated.

Bovine Colostrum
A fairly new entry into the sports nutrition market has been bovine colostrum (BC), the milk produced by cows during the first few days after calving.23,24 It has greater nutrient density and higher protein quality than ordinary dairy milk. Additionally, it has a PER comparable to egg, casein and whey protein (See Table 1). Consequently, BC is an excellent source of quality protein. In addition, BC also contains fairly high concentrations of growth factors (IGF-I, IGF-II, TGF b), immunoglobulins (IgG, IgA, IgM) and antibacterials (lactoperoxidase, lysozyme, lactoferrin) in comparison to other forms of proteins like milk and whey.24,25,26,27,28,29

Although adult digestive enzymes are believed to degrade the majority of these compounds, several studies suggest that milk30 and BC supplementation24,31 may slightly elevate levels of growth factors and immunoglobulins in the blood. Theoretically, BC supplementation during athletic training may therefore increase the availability of essential amino acids, growth factors, and/or immunoglobulins, leading to greater gains in strength and/or muscle mass during intense training.

In support of this theory, Mero and colleagues reported that nine male sprinters significantly increased IGF-I levels by 10 to 20 per cent in a linear manner during training upon supplementing with 67.5mL BC (providing about 20g BC) twice daily for eight days.24 The change in IGF-I was significantly correlated to changes in insulin levels and was not seen as attributable to absorption of the BC-derived IGF-1.

In a series of preliminary studies, Buckley and colleagues reported that 60g/day BC supplementation during eight to nine weeks of training improved run time-to-exhaustion, vertical jump performance and rowing performance.32,33,34

Results of these studies could not be attributed to changes in IGF levels, suggesting that other factors such as amino acid profile and/or other protein subtypes may play a role. Interestingly, BC was compared to whey protein placebo in these studies.

More recently, Antonio and associates reported that 20g/day BC supplementation for eight weeks during training promoted significantly greater gains in fat-free mass (1.5 kg) compared with subjects taking whey protein (-0.1 kg).35 However, they observed no significant differences between groups in muscle strength and/or endurance.

Researchers from my lab evaluated the effects of using BC or whey protein as the source of protein in fortified and non-fortified supplements during 12 weeks of resistance training.36,37 Results revealed BC served as an effective source of protein in comparison to whey, particularly when coingested with a vitamin/mineral-fortified supplement containing creatine. Although these preliminary findings are promising, BC is currently an expensive source of protein, which may limit marketability.

Gelatin
Gelatin (collagen) was once a mainstay in the nutrition industry. However, it is a poor-quality protein that has fallen out of favor in the eyes of consumers.1 More recently, use of gelatin supplements during training have been suggested as a means to maintain joint health in athletes.38 Interestingly, gelatin has experienced a mild re-emergence in various weight-loss products such as bars. Whether this renewed interest takes off will be judged by research and consumer experience with these products.

Which Protein Is Best?
Different types of protein may offer specific advantages over others, depending on the population targeted or degree of performance of body composition goals. For example, egg protein is generally well accepted among consumers and may be an attractive alternative for lacto-ovo vegetarians. Milk proteins are inexpensive and serve as a quality source of casein and whey protein for individuals who are not lactose intolerant. Casein may serve as a good source of protein to minimize protein catabolism during prolonged periods between eating, such as during sleep, or in people maintaining a low-calorie diet.

Frequent ingestion of whey protein may optimise protein synthesis and immune function. Soy protein may be the best choice for vegetarians and individuals interested in increasing dietary availability of isoflavones. Plus, soy is typically the least expensive protein source, and it has relatively good organoleptic (taste and texture) qualities. Bovine colostrum appears to be a high-quality, but high-priced, protein that may enhance training adaptations.

Picking the best overall protein to use in nutritional supplements is not an easy choice. One has to consider cost, quality, availability of protein subtypes and constituents, research support, production characteristics and taste. At present, it is my view that whey protein using CFM or proteolytic enzyme hydrolysis techniques is probably the best choice. However, additional research is needed to understand how subtle differences in protein sources affect health and performance before definitive conclusions could be drawn.

Richard B. Kreider, PhD, EPC, FACSM, FASEP, has published more than 150 research articles and abstracts in scientific journals. He is professor and chair of the department of health, human performance and recreation at Baylor University, Waco, Texas.

References

1. Bucci L, Unlu L. Proteins and amino acid supplements in exercise and sport. In: Driskell, J., I. Wolinsky (eds): Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition CRC Press. Boca Raton, FL, 2000, pp 191-212.

2. Gattas V, et al. Protein-energy requirements of boys 12-14 y old determined by using the nitrogen-balance response to a mixed-protein diet. Am J Clin Nutr 1992;56:499-503.

3. Gattas V, et al. Protein-energy requirements of prepubertal school-age boys determined by using the nitrogen-balance response to a mixed-protein diet. Am J Clin Nutr 1990;52:1037-42.

4. Puntis JW, et al. Egg and breast milk based nitrogen sources compared. Arch Dis Child 1989;64:1472-7.

5. Beaufrere B, et al. The 'fast' and 'slow' protein concept. In: Furst, P., V. Young (eds): Proteins, Peptides and Amino Acids in Enteral Nutrition, vol 3 Karger. Basel, Germany, 2000, pp 121-33.

6. Di Pasquale M. Proteins and amino acids in exercise and sport. In: Driskell, J., I. Wolinsky (eds): Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition CRC Press. Boca Raton, FL, 2000, pp 119-62.

7. Boirie Y, et al. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci USA 1997;94:14930-5.

8. Dangin M, et al. The digestion rate of protein is an independent regulating factor of postprandial protein retention. Am J Physiol Endocrinol Metab 2001;280:E340-8.

9. Demling RH, DeSanti L. Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat mass loss in overweight police officers. Ann Nutr Metab 2000;44:21-9.

10. Bounous G. Whey protein concentrate (WPC) and glutathione modulation in cancer treatment. Anticancer Res 2000;20:4785-92.

11. Bounous G, Batist P. Immunoenhancing property of dietary whey protein in mice: role of glutathione. Clin Invest Med 1989;12:154-61.

12. Fruhbeck G. Slow and fast dietary proteins. Nature 1998;391:534-43.

13. Hakkak R, et al. Diets containing whey proteins or soy protein isolate protect against 7,12-dimethylbenz(a)anthracene-induced mammary tumors in female rats. Cancer Epidemiol Biomarkers Prev 2000;9:113-7.

14. Kennedy RS, et al. The use of a whey protein concentrate in the treatment of patients with metastatic carcinoma: a phase I-II clinical study. Anticancer Res 1995;15:2643-9.

15. Badger TM, et al. Developmental effects and health aspects of soy protein isolate, casein, and whey in male and female rats. Int J Toxicol 2001;20:165-74.

16. Lands LC, et al. Effect of supplementation with a cysteine donor on muscular performance. J Appl Physiol 1999;87:1381-5.

17. Stroescu V, et al. Effects of Supro brand isolated soy protein supplement in male and female elite rowers. XXVth FIMS World Congress of Sports Medicine. Athens, Greece. 1994.

18. Rossi A, et al. Soy beverage consumption by young men: increased plasma total antioxidant status and decreased acute, exercise-induced muscle damage. J Nutraceuticals, Functional and Medical Foods 2000;3(1):33-44.

19. Kurzer, MS. Hormonal effects of soy in premenopausal women and men. J Nutr 2002;132:570S-3S.

20. Vincent A, Fitzpatrick LA. Soy isoflavones: are they useful in menopause? Mayo Clin Proc 2000;75:1174-84.

21. Chorazy PA, et al. Persistent hypothyroidism in an infant receiving a soy formula: case report and review of the literature. Pediatrics 1995;96:148-50.

22. Bell DS, Ovalle F. Use of soy protein supplement and resultant need for increased dose of levothyroxine. Endocr Pract 2001;7:193-4.

23. Baumrucker CR, Erondu NE. Insulin-like growth factor (IGF) system in the bovine mammary gland and milk. J Mammary Gland Biol Neoplasia 2000;5:53-64.

24. Mero A, et al. Effects of bovine colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA during training. J Appl Physiol 1997;83:1144-51.

25. Campbell PG, Baumrucker CR. Insulin-like growth factor-I and its association with binding proteins in bovine milk. J Endocrinol 1989;120:21-9.

26. Hadsell DL, et al. Effects of elevated blood insulin-like growth factor-I (IGF-I) concentration upon IGF-I in bovine mammary secretions during the colostrum phase. J Endocrinol 1993;137:223-30.

27. Skaar TC, et al. Changes in insulin-like growth factor-binding proteins in bovine mammary secretions associated with pregnancy and parturition. J Endocrinol 1991;131:127-33.

28. Vega JR, et al. Insulin-like growth factor (IGF)-I and -II and IGF binding proteins in serum and mammary secretions during the dry period and early lactation in dairy cows. J Anim Sci 1991;69:2538-47.

29. Baumrucker CR, Blum JW. Effects of dietary recombinant human insulin-like growth factor-I on concentrations of hormones and growth factors in the blood of newborn calves. J Endocrinol 1994;140:15-21.

30. Heaney RP, et al. Dietary changes favorably affect bone remodeling in older adults. J Am Diet Assoc 1999;99:1228-33.

31. Baumrucker CR, et al. Effects of dietary rhIGF-I in neonatal calves on the appearance of glucose, insulin, D-xylose, globulins and gamma-glutamyl transferase in blood. Domest Anim Endocrinol 1994;11:393-403.

32. Buckley J, et al. Effect of an oral bovine colostrum supplement (intact ) on running performance. Australian Conf Science Med Sport Abstracts 1998;79.

33. Buckley J, et al. Oral supplementation with Bovine Colostrum intact increases vertical jump performance. 4th Annual Congress of the European College of Sports Medicine July 1999;658.

34. Buckley J, et al. Oral supplementation with bovine colostrum (intact) improves rowing performance in elite female rowers. Proceedings of the 5th IOC World Congress on Sports Sciences 1999 Nov.

35. Antonio J, et al. The effects of bovine colostrum supplementation on body composition and exercise performance in active men and women. Nutrition 2001;17:243-7.

36. Kerksick C., R. Kreider, C. Rasmussen, L. Lancaster, M. Starks, M. Greenwood, P. Milnor, A. Almada, C. Earnest. Effects of bovine colostrum supplementation on training adaptations II: performance. FASEB Journal 2001;15:LB58.

37. Kreider R, et al. Effects of bovine colostrum supplementation on training adaptations I: body composition. FASEB Journal 2001;15:LB58.

38. Pearson D. Joint health: glucosamine and gelatin. Str Cond J 22:67, 2000.

Protein Quality

Protein PDCAAS PER
Gelatin/collagen 0.08 -
Beef/poultry/fish 0.80-0.92 2.0-2.3
Soy 1.00 1.8-2.3
Ovalbumin (egg) 1.00 2.8
Milk protein 1.00 2.8
Casein 1.00 2.9
Whey 1.00 3.0-3.2
Bovine colostrum 1.00 3.0-3.2

Marketing: Is Native Quality Of Any Value?

The emergence of a protein or nitrogen focus in products has shaped key developments in protein source and formulation. One of the first concepts to emerge in the whey protein isolate market, and one that is still in existence, is the concept of 'native quality,' which has been promoted by its marker, denaturation. The marketing wars based on less-denatured protein claims have dramatically shaped the whey protein market. Why the lack of these claims from the soy camp or other camps? Perhaps the producers and marketers of those proteins realise the transparency of native quality claims (less denatured) when digestion and absorption of amino acids is the key driver or target. The fact is, most healthy individuals will digest and absorb peptides and free amino acids quite adequately.

This is what the issue is really all about: Native quality of the ingested protein is a realistic concern for consumers when the intent is to derive some benefit from gut-associated, intact proteins with biological activity or when digesta of these proteins deliver a gut benefit or are transformed and transported (or simply transported as is) to the system, thereby delivering a consumer benefit. For example, immunoglobulus, lactoferrin or lactoperoxidase may provide immunity or anti-stress benefits.

However, if simple exposure of the liver or blood to amino nitrogen is the desired outcome, in an attempt to preserve or synthesise new skeletal muscle protein, then native quality of the ingested protein is of little or no value. At that point, other concepts, such as digestibility or oral availability, come into play. It seems that intentional communication by marketers or the unintentional propagation by uninformed experts have linked the denaturation (native quality) issue with oral availability and/or bioactivity.

Direct bioactivity of larger proteins either in the gut or as absorbed subcomponents are distracting mechanistic issues. Almost all whey protein products on the market have been pasteurised at some minimum temperature. Only the use of 'raw' milk-based products would avoid that, and these may be considered potentially illegal food products.

Magic Blends
Looking to the future in this regard, it should motivate marketers and product development teams to pursue 'magic blends' that use new sources of native proteins such as potato, canola, mycoprotein and the vast array of tried-and-true bovine- and soy-derived proteins or peptides. These blends—which may include specific ratios of amino acids, amino acid and nitrogen-containing novel compounds—must be tested using widely available measures of skeletal muscle-specific utilisation and accretion. It is not difficult to imagine the marketshare advantage a company might gain if they were to develop such a unique product, demonstrate and compile evidence in humans that it works, and, perhaps, even establish through research a metric or score. Can you say "SMPA"? (Skeletal Muscle Protein Accretion).

Consumers and experts alike would stand in line to buy such a product. Let's get busy.

—Tim Avila

Intellectual Property: Which Whey Is Up?

The fascination with whey as the premier protein source for the physique enthusiast manifests in numerous patent filings and awards, but lacks human substantiation on the key issue of influences on body size and/or strength.

Intriguing research, funded by Nestle, has delineated a difference between whey and casein proteins, leading to an international filing (WO 02/15720) and a US application (US 2002/ 0044988). This patent describes a superior effect of using whey protein over casein in relation to boosting muscle-mass accretion, preventing muscle wasting and accelerating muscle recovery. However, the data within the patent do not substantiate any superior gains in muscle mass.

Similarly, a suite of patents held by Immunotec in Canada claiming immune- and muscle-boosting effects using an undenatured (thermally isolated processing) whey protein (e.g. EP634934; US5451412; EP0339656) lacks rigorous head-to-head comparison studies showing superiority over other proteins. Indeed, a study last year (Eur J Clin Invest 31:171-8, 2001) showed a different whey protein to be equal in its immune-modifying effects. Interestingly, some of these patents were licensed to a US-based marketer of equine nutritional products, in the complete absence of any equine data.

For a company seeking to develop an innovative and effective product for the physique enthusiast market, it would appear prudent to focus on taste, solubility and complexity—integrating several different protein sources, both hydrolyzed and unhydrolyzed to maximize digestibility and minimize allergenicity. Moreover, the strategic investment would be to demonstrate a physique-boosting effect superior to that of the category leader by ingredient, such as whey protein isolate or by brand.

Soy Sans Estrogens
Despite the nearly universal credo that soy is an inferior protein to whey for building muscle, several comparator studies suggest that it is equal, if not superior, to milk-derived proteins in physically active individuals (however, the totality of evidence remains less than equivocal). One identifier aspect of soy protein is the presence of phytoestrogenic isoflavones. Given the pejorative treatment of anything "estrogenic" by sports nutrition marketers, coupled with the aforementioned credo, processes that can remove the isoflavones without modifying the inherent proteins may have commercial appeal.

To this end, Abbott has been awarded both a European and US patent (EP0929231 and US6020471; other international patents are pending) on a method to remove isoflavones (in addition to manganese and nucleotides) from plant proteins. Dupont Protein Technologies International has filed a European patent for compositions that are isoflavone-depleted combined with an isoflavone concentrate, indicating their capability to produce an isoflavone-depleted soy protein.

Another population that may gravitate to isoflavone-free soy protein products would be fitness-seeking postmenopausal women with a history of, or at high risk for, breast cancer, based upon several recent animal studies that suggest genistein can promote breast cancer. The creation of isoflavone-free soy thus may be one step closer to addressing group-based nutritional needs and preferences.

—Anthony Almada

Approximate Amino Acid Profile Of Various Types Of Commercially Available Protein (mg/100g)

Ingredient

Soy
Protein
Concentrate

Soy
Protein
Isolate

Egg
Protein
(Dried)

Milk
Protein
Isolate

Calcium
Caseinate

Sodium
Caseinate

Alanine

4.60

4.30

5.77

3.50

3.00

3.00

Arginine

7.90

7.60

5.43

3.50

3.70

3.70

Aspartic Acid

11.90

11.60

10.18

8.00

6.90

6.90

Cysteine/Cystine

1.40

1.30

2.59

0.60

0.40

0.40

Glutamic Acid

19.00

19.10

13.29

20.80

20.90

20.90

Glycine

4.60

4.20

3.49

1.90

1.80

1.80

Histidine

2.80

2.60

2.26

2.70

2.90

2.90

Isoleucine

5.20

4.90

5.66

4.40

4.60

4.60

Leucine

8.50

8.20

8.41

10.30

9.10

9.10

Lysine

6.90

6.30

6.80

8.10

7.70

7.70

Methionine

1.50

1.30

3.44

3.30

2.90

2.90

Phenylalanine

5.40

5.20

5.82

5.00

5.10

5.10

Proline

5.60

5.10

3.91

9.50

10.40

10.40

Serine

5.10

5.20

6.88

6.20

5.80

5.80

Threonine

4.20

3.80

4.55

4.50

4.30

4.30

Tryptophan

1.20

1.30

1.23

1.40

1.20

1.20

Tyrosine

4.00

3.80

3.91

5.20

5.50

5.50

Valine

5.40

5.00

6.37

5.70

5.70

5.70

Aromatic Amino Acids
(phe & tyr)

9.40

9.00

9.73

10.20

10.60

10.60

Sulfur Amino Acids
(met & cys)

2.90

2.6

6.03

3.90

3.30

3.30

Branched Chain Amino Acids
(leu, iso, val)

19.10

18.10

20.45

20.40

19.40

19.40

Ingredient

Potassium
Caseinate

Casein
Hydrolysate

Ion-Whey
Protein
Concentrate
85%

Cross-
Flow
Exchanged
Whey
Protein
Isolate

Micro-
filtration
Whey
Protein
Isolate

Whey
Protein
Isolate

Alanine

3.22

3.00

4.82

5.60

5.60

5.20

Arginine

3.59

3.70

3.18

3.00

1.70

3.00

Aspartic Acid

7.18

6.90

12.26

12.30

12.70

12.30

Cysteine/Cystine

0.37

0.40

2.28

1.90

2.50

2.90

Glutamic Acid

19.80

20.90

15.41

17.70

19.70

18.30

Glycine

1.73

1.80

2.00

1.90

2.00

2.30

Histidine

3.09

2.90

2.41

2.00

1.80

1.90

Isoleucine

4.95

4.80

6.41

5.40

6.80

5.50

Leucine

8.42

9.10

11.60

13.50

10.90

14.20

Lysine

7.30

7.70

9.83

10.90

9.50

10.20

Methionine

3.22

2.90

2.35

3.50

3.10

2.40

Phenylalanine

4.95

5.10

3.56

3.40

2.50

3.80

Proline

9.65

10.40

6.28

4.80

6.30

5.10

Serine

5.82

5.80

6.24

4.50

5.30

5.00

Threonine

4.58

4.30

8.44

5.30

8.30

5.50

Tryptophan

1.24

1.20

1.80

1.50

2.00

2.30

Tyrosine

4.70

5.50

3.26

3.90

3.10

3.90

Valine

6.19

5.70

6.09

5.40

6.40

5.90

Aromatic Amino Acids
(phe & tyr)

9.65

10.60

6.82

7.30

5.60

7.70

Sulfur Amino Acids
(met & cys)

3.59

3.30

4.63

5.40

5.60

5.30

Branched Chain Amino Acids
(leu, iso, val)

19.55

19.60

24.10

24.30

24.10

25.60