Dietary protein, red meat and colorectal cancer risk Gerald Lobley, Alex Johnstone •Colleagues from Flinders Medical Centre, Adelaide SA: • Graham Young, Richard LeLeu, Jean Winter

London, 21st November 2017 Food Matters Live - Functional ingredients for enhanced digestive health

Dietary protein, red meat and

colorectal cancer risk

Dr Silvia Gratz

Research Fellow Gut Health - Microbiology

The Rowett Institute

University of Aberdeen

Processed meat is classified as human carcinogen

London, 21st November 2017

Lyon, France, 26 October 2015 – The International Agency for Research on Cancer (IARC), the cancer agency of the WHO, has evaluated the carcinogenicity of the consumption of red meat and processed meat. Red meat After thoroughly reviewing the accumulated scientific literature, a Working Group of 22 experts from 10 countries convened by the IARC Monographs Programme classified the consumption of red meat as probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect. This association was observed mainly for colorectal cancer, but associations were also seen for pancreatic cancer and prostate cancer. Processed meat Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer. Carcinogens in meat: nitrosamines, heterocyclic amines

WCRF colorectal cancer and diet

Food Matters Live - Functional ingredients for enhanced digestive health London, 21st November 2017

Overview – intestinal digestion and fermentation

Food Matters Live - Functional ingredients for enhanced digestive health London, 21st November 2017

Scott KP, Gratz SW, Sheridan P, Flint HJ & Duncan SH (2013): The influence of diet on gut microbiota. Pharmacol Res 69(1):52-60.

Food

Small intestine Large intestine

Non-digestible CHO (RS, NSP, FOS) Residual protein

Faeces

Absorption

Excretion of undigested CHO,

Lignin, unabsorbed nutrients

Proximal Distal

Digestion of CHO, protein, fat by

host enzymes

Absorption

SCFA Gases

other metabolites SCFA gradient

pH gradient

Bacterial fermentation products

Carbohydrate Protein

SCFA (acetate, propionate, butyrate) SCFA (acetate, propionate, butyrate) BCFA (iso-butyrate, iso-valerate)

Gases (CO2, CH4, H2) Gases (CO2, CH4, H2)

Bacterial biomass Bacterial biomass

Ammonia, Phenols, Indoles, Amines, Sulfides


Focus of the work

• Identify foods/ingredients that drive colonic fermentation and shift faecal metabolome towards health-promoting profiles

• Specifically focus on the balance between dietary carbohydrate/fibre and dietary protein/meat

Faecal SCFA profiles

Endogenously formed NOC


Effect of carbohydrates, fibre, meat on intestinal fermentation products

Le Leu RK, et al. B J Nutr (2015) 114(2):220-30.

Variable HRM HRM+HAMSB

Faecal output (g/d) 241 ± 30 309± 30

Faecal pH 7.2 ± 0.1 7.0 ± 0.1

Acetate (µmol/g) 51.0 ± 4.1 57 ± 4.6

Propionate (µmol/g) 15 ± 1.5a 20 ± 1.5b

Butyrate (µmol/g) 14 ± 1.9a 21 ± 2.7b

Total SCFA (µmol/g) 88 ± 7.5a 106 ± 8.3b

BCFA 4.5 ± 0.4a 3.7 ± 0.3b

Phenol (µg/g) 2.0 ± 1.2 1.3 ± 0.6

p-Cresol (µg/g) 67 ± 5a 50 ± 6b

Ammonia (µmol/g) 15 ± 1.0 16 ± 1.0

Randomised cross-over clinical trial 23 healthy volunteers 300 g cooked lean red meat 40g HAMSB 4 week intervention periods


Study design

MTD Body weight maintenance diet NSP Non-starch polysaccharide MTD

NPWL Normal protein weight loss diet HPMC High protein moderate carbohydrate weight loss diet HPLC High protein low carbohydrate weight loss diet


Diet composition

0

100

200

300

400

500

600

700

800

Ave

rage

inta

ke (

g/d

)

Fat

CHO

Protein

Protein intakes 80 - 153 g/d

CHO intake 22 - 448 g/d

Fat intake 63 - 142 g/d

Energy 8 - 13.5 MJ/d

MTD Body weight maintenance diet NSP Non-starch polysaccharide MTD

NPWL Normal protein weight loss diet HPMC High protein moderate carbohydrate weight loss diet HPLC High protein low carbohydrate weight loss diet


Effect of dietary protein and carbohydrate on faecal fermentation products

0

100

200

300

400

500

600

700

800

900

1000

Fae

cal N

OC

(n

g/g)

MTD

NPWL

HPWL

b a c 50

55

60

65

70

75

80

85

90

95

100

MTD NPWL HPWL

% o

f to

tal S

CFA

Diet

Isobutyrate

Isovalerate

Butyrate

Proprionate

Acetate

*

* * • High protein weight loss diets change the faecal short chain fatty acid profile (butyrate,

isobutyrate & isovalerate) compared to normal protein weight loss diet or a balanced body weight maintenance diet

• Both normal protein and high protein weight loss diets increase faecal NOC


Effect of dietary protein and carbohydrate on faecal fermentation products

•Dietary CHO main driver of colonic CHO and protein fermentation •Dietary protein has secondary effect

05

10152025303540

0 200 400 600

Fae

cal b

uty

rate

(%

)

Dietary CHO (g/d)

MTD

NPWL

HPWL0

1

2

3

4

5

6

0 200 400 600

Fae

cal I

so-b

uty

rate

(%

)

Dietary CHO (g/d)

MTD

NPWL

HPWL

0

1

2

3

4

5

6

0 50 100 150 200Fae

cal I

so-b

uty

rate

(%

)

Dietary protein (g/d)

MTD

NPWL

HPWL0

200

400

600

800

1000

1200

0 200 400 600

Fae

cal N

OC

(n

g/g)

Dietary CHO (g/d)

MTD

NPWL

HPWL


Correlation of dietary components and NOC

Holtrop G, et al (2012): J Nutr 142(9): 1652-58.

Ac

Pro

p

Bu

TSC

FA

Ac%

Pro

p%

Bu%

IsoB

u

IsoV

al

TB

CFA

IsoB

u%

IsoV

al%

TB

CFA

%

PA

A

IAA

4O

HPL

A

NO

C

CHO

Strach

Sugars

DF

NSP

Total protein

Non-meat protein

Red meat

White meat

Total meat

CHO/protein


Random effects linear regression

AIC Akaike’s Information Criterion, used to assess model fit (lower AIC means improved fit)

NOC N-nitroso compounds NO3 Nitrate

NSP Non-starch polysaccharide

VitC Vitamin C


NOC change Log NOC %

Observed 0.31

Predicted 0.29 94%


Improved prediction of endogenous formation of NOC

Jakszyn P., et al. Carcinogenesis (2006) 27, 7, 1497-1501.

- More complex models predict higher proportion of ENOC than simple models - Our dataset better reflects complex interaction between nutrients & food groups

NOC change LogNOC %

Observed 0.464

Predicted 0.255 54%

Terms in model

ENOC ug/d = 40.5 + 18.8*MeatFe

http://carcin.oxfordjournals.org/content/vol27/issue7/images/large/bgl019f1.jpeg


Summary & Conclusions

• Diet strongly influences faecal fermentation products • CHO increase faecal SCFA

• CHO decrease faecal protein breakdown products

• Dietary protein has little effect on BCFA

• Diet drives endogenous NOC formation • Red meat strongest contributor

• Nitrate/Vitamin C ratio also increases formation

• Dietary fibre might protect against endogenous formation

• More complex statistical models allow us to assess the effect of multiple dietary components intestinal fermentation

• Dietary carbohydrate/fibre rather than protein intake drives colonic microbial fermentation


Acknowledgements

• Rowett Gut Health - Microbiology: • Tony Richardson, Sylvia Duncan, Harry Flint, Wendy Russell, Lorraine Scobbie

• Rowett Obesity & Metabolic Health: • Gerald Lobley, Alex Johnstone

• Colleagues from Flinders Medical Centre, Adelaide SA: • Graham Young, Richard LeLeu, Jean Winter

• BioSS: • Grietje Holtrop

• Funders • RESAS (Scottish Government), RSE, WCRF

Documents

Dietary protein, red meat and colorectal cancer risk Gerald Lobley, Alex Johnstone •Colleagues from Flinders Medical Centre, Adelaide SA: • Graham Young, Richard LeLeu, Jean Winter