Download Dietary Protein Quality: Its importance in Nutrition and Health

Alpha Summit | Idaho, USA | 4-5 August 2015
Dietary Protein Quality: Its importance in
Nutrition and Health
Paul Moughan
Riddet Institute, Massey University, Palmerston North
Dietary Protein Quality is of
fundamental importance.
2 “World-wide 842 million people are
undernourished. Protein/Energy Malnutrition
is by far the most lethal form of malnutrition –
Children are its most visible victims”
WHO (2001)
“Protein / Energy
malnutrition affects
every fourth child
world-wide”
WHO/NHD (2000) >  Protein holds a central place in body metabolism.
>  Lifestyle diseases (diabetes, hypertension, cardiovascular disease etc) are all related to disturbances in
body metabolism.
>  Amino acids are critical nutrients and dairy foods are
an important source of amino acids.
5
Dietary Amino Acids:
>  Promote Lean Body Mass (LBM) and normal body
weight.
>  Support optimal organ function (eg muscle mass and
strength).
>  Amino acids have specific metabolic roles (eg leucine
and muscle protein synthesis; glutamate and gut
energy supply; tryptophan and serotonin synthesis;
arginine and nitric oxide production).
6
So, Protein and amino acids are critical
nutritionally
But, not all proteins are of equal value
nutritionally
>  Milk
>  Meat
>  Egg
>  Soya
>  Bean
>  Cereals etc
7
In particular vegetable-based proteins
are of lower quality than dairy based
proteins
>  fibre
>  anti-nutritional factors
>  different structures
8
How then should Protein
Quality be determined?
9
>  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)
10
1. 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.
11
How should ileal amino acid/
“reactive lysine” digestibility
be determined?
12
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.
Terminal
ileum
Ref: Wrong OM, Edmonds CJ and Chadwick VS (1981) ComparaHve anatomy and physiology In: The Large IntesHne, p 5, MTP Press Ltd, England. 13
13 Growing pig (a meal-eating omnivore) is preferred model:
Need to
collect ileal
digesta
14
True N digestibility in human (%)
True ileal AA digestibility in the adult
human and growing pig
True N digestibility in pig (%)
(Moughan, unpublished)
15
Processed Foods — Conventional lysine
Digestibility Is Inaccurate:
>  Conventional determination of lysine and lysine
digestibility are inaccurate for some processed foods.
>  Damaged lysine molecules revert to lysine with
conventional procedures.
>  Need for a new approach.
>  Reaction of food and digesta with o-methylisourea
(Moughan and Rutherfurd assay1) allows accurate
determination of “available” lysine.
1Moughan
and Rutherfurd (1996) Journal of Agricultural and Food Chemistry 44:2202-2209.
16
Differences can be great
Digestible reactive1 (available) lysine versus digestible total lysine
(gKg-1)
Lysine
Digestible Total
Available
Difference %
Shredded Wheat
Dried corn
1.8
2.6
1.6
1.9
11
27
Unleavened bread2
6.5
4.9
25
Puffed Rice
1.1
0.6
45
Rolled Oats
3.7
2.8
24
Wheat Bran
1.1
0.7
36
Corn
0.4
0.2
50
Evaporated milk
23.4
20.5
12
1Based
on ο-methylisourea assay; 2P Pellett, N Scrimshaw and P Moughan (unpublished data).
17
But generally not in dairy:
Ileal digestible total and “available” lysine contents (g/kg air-dry) for
12 dairy protein sources
Lysine
Whole milk protein
Digestible
26.2
Availablea
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
Weight-gain formula
24.4
24.1
Sports formula
20.4
19.1
Elderly formula
11.7
11.8
Hydrolysed lactose milk powder
27.2
25.1
High-protein supplement
14.3
14.3
aBioavailable
lysine; minimal difference between total lysine and reactive lysine denotes minimal Maillard damage.
Adapted from Rutherfurd & Moughan (2005), with permission of the publisher.
18
Dairy proteins such as whey and
alpha-lactalbumin have high amino
acid digestibilities and lysine
availability/digestible reactive lysine
19
True ileal digestibility, Whey Protein
Whey Protein
Concentrate (n = 4)
Whey Protein
Isolate (n = 1)
Whey Protein
Hydrolysate (n = 1)
Lysine1
98
100
94
Methionine
99
100
80
Cysteine
100
100
94
Leucine
99
100
96
Isoleucine
99
100
96
Valine
98
100
96
Tryptophan
100
100
-
Histidine
93
100
90
Threonine
94
100
93
1Available
lysine
20
True ileal digestibility, Alpha Lactalbumin
α Lactalbumin 1
n=6
α Lactalbumin 2
n=6
α Lactalbumin 3
n=6
Lysine1
95
100
100
Methionine
99
96
97
Cysteine
96
98
97
Leucine
96
99
99
Isoleucine
95
98
99
Valine
96
96
99
-
100
100
Histidine
89
97
98
Threonine
95
97
98
Phenylalanine
97
97
98
Tyrosine
97
97
98
NEAA’s2
94
94
96
Tryptophan
1Available
2Dietary
lysine
non-essential amino acids. Sample 1 = laboratory rat. Samples 2&3 = growing pig.
21
The true ileal AA digestibility assay has been
applied to infant formulas and human milk
Bovine milk
formula1
Soya isolate
formula1
Human milk2
Lysine
96
96
98
Methionine +
Cysteine
94
92
100
Tryptophan
94
91
100
Isoleucine
96
94
98
Leucine
97
94
99
Threonine
89
89
86
1Moughan
2Darragh
et al., (1990) Journal of Paediatric Gastroenterology and Nutrition 10:385-394.
and Moughan (1998) British Journal of Nutrition 80:25-34..
22
The digestible pattern in human milk can be
used to assess amino acid contents of
formulas
True ileal digestible amino acids (g 100g DM)
Bovine milk formula
Human milk
Lysine
1.10
(100)
0.55
(100)
Methionine + Cysteine
0.59
(53)
0.36
(65)
Tryptophan
0.15
(14)
-
Isoleucine
0.82
(75)
0.45
(79)
Leucine
1.40
(127)
0.82
(148)
Threonine
0.69
(63)
0.43
(65)
-
Formula protein is reasonably well balanced (pattern) but supplies
more AA’s per gram than breast milk.
23
α Lactalbumin is well-balanced compared to
Human breast milk
True ileal digestible AAs (g/100g DM)
α Lactalbumin
Human milk
Lysine1
100
100
Methionine + Cysteine
60
65
Tryptophan
45
-
Isoleucine
74
79
Leucine
127
148
Threonine
58
65
1Available
lysine
24
When a single score of Protein Quality is needed DIAAS
2. 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)
25
Non truncation is significant
Milk Protein
Concentrate
Whey Protein
Isolate
Whey Protein
Concentrate
Non-truncated
1.31
1.25
1.10
1.10
Truncated
1.0
1.0
1.0
1.0
DIAAS
Red meat
26
DIAAS and PDCAAS values1 are different. PDCAAS
often overestimates particularly 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
1.00
1.00
0.89
0.65
0.67
0.53
0.51
0.42
0.60
DIAAS
1.10
0.97
0.82
0.58
0.54
0.41
0.43
0.37
0.58
1(Rutherfurd
1.18
and Moughan, unpublished data).
27
27 α Lactalbumin has a high DIAAS (>100) indicating that
the amino acid profile exceeds the amino acid scoring
pattern (requirement) for the six month – three year old
child
DIAAS
Limiting AA
α Lactalbumin 1
α Lactalbumin 2
α Lactalbumin 3
107
115
113
Histidine
Valine
Valine
28
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
1.71
1.29
2.35
1.93
1.43
0.97
2.74
2.03
α Lactalbumin
1.93
2.20
1.14
2.40
2.00
1.90
1.65
5.50
2.00
Soya
Protein
Isolate
1.30
0.90
1.11
1.59
1.29
1.85
1.37
1.67
1.16
29
29 Conclusions
1.  Protein (and especially dairy protein) is central to
maintaining a healthy body weight, body composition and
metabolism.
2.  The new score DIAAS is better able to promote dairy’s
superior ability.
3.  DIAA ratios can emphasise high delivery of key amino acids
(eg isoleucine, branched chain group, arginine, glutamine)
4.  Dairy proteins have a major advantage around lysine
‘bioavailability’.
5.  True ileal digestibility and DIAAS remove ability to mask
dairy/vegetable protein quality differences
30
Thank you