July 9, 2010
Author(s): Loren S. Ward, PhD (Director of Research and Development, Glanbia Nutritionals)

Knowledge on the nutritional importance of dietary protein and amino acid metabolism has progressed significantly over the past 100 years.  In the early 1900s, experiments with "incomplete proteins" (lacking one or more amino acids) helped identify essential amino acids (EAAs) needed for growth and development.  For example, lysine was identified as an essential amino acid by using a lysine-deficient protein, gliadin (from wheat), as the sole source of dietary protein in animal studies.  Lack of lysine in the diet prevented growth in animals, however adding lysine back to the diet resulted in growth and validated the essential need of lysine in the diet.  A review of the pioneering research on essential amino acids using incomplete proteins was published in 1938[1] and provided a basis for future research to confirm and identify the eleven amino acids that are either essential or conditionally essential for infants and adult nutrition[2].  Research on the essential nature of amino acids in the diet has continued.

In 1985 a joint report[3] by the World Health Organization (WHO), Food and Agriculture Organization (FAO) of the United Nations and the United Nations University (UNU) provided dietary protein and amino acid intake recommendations.  Twenty-two years later in 2007, a joint report by WHO/FAO/UNU[4] reviewed the substantial increase in knowledge and understanding in dietary protein and amino acid metabolism since the report in 1985.  Scientists now better understand the amino acid requirements in a wide variety of populations including infants, adults, elderly, malnourished and HIV populations.  The 2007 WHO/FAO/UNU recommendations suggested a significant increase in isoleucine, lysine, phenylalanine + tyrosine, threonine and valine, plus a modest increase for sulfur-containing amino acids methionine and cysteine.  For example, recommended leucine levels went from 21 mg/g of protein to 59 mg/g of protein.  Figure 1 provides a comparison of the 1985 and 2007 recommendations for nine amino acids.

Populations that have limited access to protein can compensate by increasing the quality rather than quantity of protein ingested to meet dietary recommendations for EAAs.  As a result, protein quality becomes increasingly important in food formulations for malnourished populations and products destined for developing countries. 
Whey proteins are natural and contain unusually high levels of EAAs and branch chain amino acids (BCAAs)with additional bioactive properties and high bioavailability[5]. 

Whey proteins originate from milk and are isolated from the "watery liquid" obtained from milk, usually during cheese making.  Whey contains about 12.5% protein on a dry matter basis and the protein fraction is concentrated primarily through the removal of lactose using filtration technology.  When the protein levels reach 25-80% protein it is called a whey protein concentrate (WPC).  The industry standard identifies the protein content after the name:  WPC34 has 34% protein (34 gr protein/100 gr solids), whereas WPC80 has 80% protein.  The Food and Drug Administration (FDA) has strict standards and guidelines for manufacturing whey protein concentrate (21 CFR 184.1979c).  Whey protein isolate (known as WPI) has greater than 90% protein, and is obtained by reducing fat and lactose levels to less than 1%.  Both whey protein concentrate and whey protein isolate have GRAS (Generally Recognized As Safe) designation by the FDA.  Because whey protein concentrates and whey protein isolates have high levels of EAAs per gram of protein, these ingredients are better able to deliver the recommended levels of EAAs in smaller doses.

More than 50% of the amino acids in whey proteins are essential or conditionally essential amino acids.  The blue bar in Figure 1 compares the EAA profile of a whey protein isolate, compared to the 2007 WHO/FAO/UNU recommendations.  In each case, whey proteins provide a surplus of EAAs and BCAAs.  The increased levels of BCAAs (leucine, isoleucine and valine) provide additional stimulus for muscle synthesis and growth. 

Whey proteins can be used to enhance the amino acid profile and increase protein quality in a variety of foods delivered to populations with limited access to protein.  This approach was recently recommended [6] as a way to improve the nutritional quality of fortified blended foods for  malnourished populations, such as corn-soy blend (CSB) or wheat-soy blend (WSB).  Benefits from adding whey proteins could include increasing EAA and BCAA content while reducing the total amount of protein required to meet specific nutritional requirements.  

The nutritional importance of EAAs makes whey protein a premier protein for in a variety of food formulations to meet or exceed dietary recommendations for essential amino acids.

References

1. Rose, W.C., The nutritive significance of amino acids.Physiol. Rev., 1938. 18: p. 109-136.
2. Hunt, S.M. and J.L. Groff, Proteins in Advanced Nutrition and Human Metabolism. 1990, West Publishing Company: St. Paul, MN. p. 129-168.
3. FAO/WHO/UNU. Energy and protein requirements.Report of a Joint FAO/WHO/UNU Expert Consulation. 1985 (WHO Technical Report Series No. 724).
4. FAO/WHO/UNU. Protein and amino acid requirements in human nutrition.Report of a Joint FAO/WHO/UNU Expert Consulation. 2007 (WHO Technical Report Series No. 935).
5. Archibald, A., Showcasing a nutrition superstar. Today's Dietitian, 2002. 4(7): p. 1-7.
6. Hoppe, C., et al., The Use of Whey or Skimmed Milk Powder in Fortified Blended Foods for Vulnerable Groups.J. Nutr., 2008. 138(1): p. 145S-161.