New approaches to the assessment of protein quality: Whey proteins Paul Moughan Riddet Institute, Massey University, New Zealand

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“Not all proteins are created equal nutritionally” Milk Meat Egg Soya Bean

In particular vegetable-based proteins are of lower quality than dairy based proteins fibre anti-nutritional factors different structures

An accurate description of Dietary Protein Quality is of fundamental importance: Dietary Assessment Nutritional Planning Regulatory Environment Trade

How then should Protein Quality be determined?

In the past PDCAAS (protein digestibility corrected amino acid score) has been the recommended scoring method (FAO 1989) There are a number of shortcomings of PDCAAS. New Recommendations (FAO, 2013)

Emphasis on individual digestible amino acid contents rather than a single score (ie treat each amino acid as an individual unit). This maximises the information on the nutritional (protein) value of food. Amino acid digestibility is determined at the end of the small intestine (True ileal digestibility). For processed foods ‘reactive lysine’ is determined in diet and ileal digesta rather than ‘total lysine’ to give lysine availability measures. 1.

How should ileal amino acid/ “reactive lysine” digestibility be determined?

In humans: Digesta can be collected using ileostomates Ref: Wrong OM, Edmonds CJ and Chadwick VS (1981) Comparative anatomy and physiology In: The Large Intestine, p 5, MTP Press Ltd, England. Terminal ileum In humans: Digesta can be collected using ileostomates Digesta can be collected using a naso-ileal tube Both methods have drawbacks and are not routine Need for an animal model. 10

Growing pig (a meal-eating omnivore) is preferred model: Need to collect ileal digesta

True ileal AA digestibility in the adult human and growing pig True N digestibility in human (%) True N digestibility in pig (%) (Moughan, unpublished)

Conventional digestible lysine can be higher than available lysine Digestible reactive1 (available) lysine versus digestible total lysine (gKg-1 DM) Lysine Digestible Total Available Difference % Shredded Wheat 1.8 1.6 11 Dried corn 2.6 1.9 27 Unleavened bread2 6.5 4.9 25 Puffed Rice 1.1 0.6 45 Rolled Oats 3.7 2.8 24 Wheat Bran 0.7 36 Corn 0.4 0.2 50 1Based on -methylisourea assay; 2P Pellett, N Scrimshaw and P Moughan (unpublished data).

But not so in dairy: Ileal digestible total and “available” lysine contents (g/kg air-dry) for 12 dairy protein sources Lysine Digestible Availablea Whole milk protein 26.2 24.0 Infant formula A 8.3 8.6 Infant formula B 9.1 9.2 Infant formula C 11.1 11.7 Whey protein concentrate 79.9 77.5 UHT milk 31.7 31.4 Evaporated milk 23.4 20.5 Sports formula 20.4 19.1 Elderly formula 11.8 Hydrolysed lactose milk powder 27.2 25.1 aBioavailable lysine; minimal difference between total lysine and reactive lysine denotes minimal Maillard damage. Adapted from Rutherfurd & Moughan (2005), with permission of the publisher. 14

Amino acids in whey proteins are generally highly digestible Whey Protein Concentrate (n = 4) Whey Protein Isolate (n = 1) Whey Protein Hydrolysate (n = 1) Lysine 98 100 94 Methionine 99 80 Cysteine Leucine 96 Isoleucine Valine Tryptophan - Histidine 93 90 Threonine

When a single score of Protein Quality is needed DIAAS replaces PDCAAS. With DIAAS (FAO, 2013): Ileal AA digestibility replaces faecal CP digestibility Reactive lysine replaces total lysine (conventional AA analysis) Scores are not truncated (unless diet or sole-source food) AA Reference Pattern (for regulatory purposes): Infants: AA composition human milk All others: AA requirement pattern for child (6 months – 3 years) 2.

Non truncation is significant DIAAS Milk Protein Whey Protein Whey Protein Red meat Concentrate Isolate Concentrate Non-truncated 1.31 1.25 1.10 1.10 Truncated 1.0 1.0 1.0 1.0 DIAAS

DIAAS and PDCAAS values1 are different DIAAS and PDCAAS values1 are different. PDCAAS often overestimates for lower quality proteins Milk Protein Concentrate Whey Protein Isolate Soya Protein Isolate Pea Protein Cooked Beans Cooked Rolled Oats Wheat Bran Roasted Peanuts Rice Protein Cooked Peas PDCAAS 1.00 0.89 0.65 0.67 0.53 0.51 0.42 0.60 DIAAS 1.18 1.10 0.97 0.82 0.58 0.54 0.41 0.43 0.37 1(Rutherfurd and Moughan, unpublished data). 18

But single scores omit much useful information: (eg leucine supply for optimal muscle function versus body protein maintenance). Threonine Met + Cys Valine Isoleucine Leucine Tyr + Phe Histidine Tryptophan Lysine Whey Protein Isolate 1.80 2.29 1.21 2.22 2.57 1.71 1.09 3.35 2.51 Whey Protein Concentrate 2.53 1.29 2.35 1.93 1.43 0.97 2.74 2.03 Soya Protein Isolate B 1.13 0.91 1.02 1.38 1.65 1.18 1.69 0.99 Milk Protein Concentrate 1.56 1.55 1.81 1.77 2.39 1.60 1.94 Isolate A 1.30 0.90 1.11 1.59 1.85 1.37 1.67 1.16 19

Conclusions Considering amino acids as individual nutrients gives maximum information. DIAAS incorporates recent scientific advances, and is an improvement over PDCAAS. Before DIAAS can be implemented we need more data on the true ileal amino acid digestibility of foods. Establishment of such a world food data-set is greatly needed. This is an important step in the fight against malnutrition.

“Protein/Energy malnutrition affects every fourth child world-wide” WHO/NHD (2000)