Diet and breast cancer risk: fibre and meat

Transcription

1 Diet and breast cancer risk: fibre and meat UK Women s Cohort Study Janet Cade General diet and cancer issues: Alcohol consumption increases cancer risk, particularly among smokers In England 47% of men and 30% of women exceed government recommendations for alcohol consumption. A high fibre, low fat diet with plenty of fruits and vegetables reduces cancer risk On average British people are eating only 2.5 portions of fruit and vegetables per day The consumption of salt in the UK has fallen by 2% over the last 20 years Only 28% of British men and 13% of British women are meeting the recommended daily average intake of fibre On average people in Britain get 35% of their daily energy intake from fat

2 Meat and fibre in the British diet National average intake fibre: 12g/day Recommended intake: 18g/day Average intake meat: 124g/day Recommended eat moderate amounts, choose lower fat Percentage contribution of food types to average daily total energy intake, British adults, 2003 Sugar Vegetables, preserves & Other fruits and confectionary 5% nuts 6% (excluding potatoes) 6% White meats and fish 6% Potatoes and savoury snacks 9% Breads and cereals 31% Drinks 10% Red and processed meats 11% Milk, eggs and fat spreads 16% The Complex Nature of Diet assessing relationships between diet and disease - challenging results inconsistent due to a variety of potential biases: - Measurement error - Different assessment methods - Homogeneity of diet within individual population groups

3 Key question: Do nutrients or foods influence risk of breast cancer? dietary fibre meat Established diet related risk factors: alcohol Obesity and weight gainpostmenopausally

4 Fibre: cellulose Insoluble fibre Total fibre (Southgate) Non-starch polysaccharides (Englyst) soluble fibre Insoluble noncellulose polys. soluble noncellulose polys. Lignin & resistant starch lignin Overview of previous fibre and breast cancer risk - cohort study results (from Hanf and Gonder, 2005, Eur J OBs Gynae; 123:139) Author Year Study RR (95% CI) Graham et al New York State Cohort 1.07 (0.76, 1.51) Kushi et al Iowa Women's Health Study 0.99 (0.69, 1.41) Willett et al Nurses' Health Study 1.02 (0.85, 1.23) Rohan et al Canadian National Breast Screening Study 0.68 (0.46, 1.00) Kushi et al. 1995a Iowa Women's Health Study 0.92 (0.70, 1.20) Kushi et al. 1995b Iowa Women's Health Study 1.04 (0.77, 1.42)

5 Mechanisms: Fibre may - inhibit oestrogen reabsorption inhibit oestrogen synthetase lower oestrogen synthesis reduction of androgens (affect oestrogen levels & proliferation of breast tissue) act via insulin/igfs (high IGF1 br cancer) also high fibre foods rich sources of other dietary constituents (eg. Indoles, isoflavones) oestrogen Meat case-control studies: Previous findings on meat (Boyd et al, 2003)

6 Meat cohort studies: Influence of hormone receptor status: (Cho et al,. Arch Intern Med 2006;166:2253-9) Nurses Health Study: >90,000 premenopausal women "Pre-menopausal women who ate more than 1.5 serves of red meat per day experience almost double the risk of hormone receptor positive breast cancer, compared to those who ate less than three servings of red meat per week,"

7 Mechanisms: saturated fat content of meat Saturated fat affects cholesterol production, precursor of oestrogen heterocyclic amines formed during cooking of meat nitroso-compounds found in processed meat UK Women s Cohort Study: Aim to study nutrition and cancer incidence and mortality in middle-aged UK women

8 Study outline: UK Women s Cohort: baseline data - FFQ n=35, Phase 2: q.re & food diary Quality checklist data captured n=13,406 Ongoing diary coding 1,400+ deaths 700+ incident breast 160+ incident colorectal Expected case nos will double over next 6 y The women: mean age 52 years white (99%) middle class (63% NS-SEC class 1 - professional & managerial) married (75%), with children (86%) degree + (27%) live in all areas of UK (33% in S and E) Body Mass Index 24.5kg/m 2 11% current smokers

9 Dietary patterns: 28% self-defined vegetarian (9593 subjects) 16 years 1% vegans (433 subjects) 11 years 58% take dietary supplements, vitamins or minerals 27% said changed diet in last 12 months Analysis: Survival times: Time between FFQ and event or census date (Jan 31st 2004 fibre; Oct 31st meat) incident breast cancer 257 (fibre) 283 (meat) pre-menopausal 350 (fibre) 395 (meat) post-menopausal 240,959 (fibre) person years follow up basic models adjusted: age, energy intake complex model adjusted: age, BMI, physical activity, smoking, oral contraceptive use, HRT use, number of children and total energy

10 Results Fibre - premenopausal Quintile of intake 1 (<20g) Total fibre HR % CI - (0.72, 1.81) Cereal fibre Fruit fibre Veg fibre HR 95% CI HR 95% CI HR 95% CI (0.72,1.58) 1.36 (0.89,2.06) 1.45 (0.93, 2.26) (0.64, 1.72) 0.73 (0.46,1.15) 0.81 (0.50,1.32) 1.15 (0.73,1.82) (0.34, 1.17) 0.68 (0.42,1.09) 0.61 (0.36,1.04) 1.62 (0.99,2.65) 5 >30g 0.48 (0.24, 0.96) 0.59 (0.32,1.10) 0.81 (0.44,1.49) 1.26 (0.73,2.18) P (trend) Cade et al., Int J Epid 2007, doi: /ije/dyl295 Results Fibre - postmenopausal Quintile Total fibre of intake HR 95% CI 1 (ref) (0.96, 2.03) Cereal fibre Fruit fibre Veg fibre HR 95% CI HR 95% CI HR 95% CI (1.05,2.16) 1.17 (0.79,1.72) 0.86 (0.57, 1.29) (1.00,2.24) 1.53 (1.03,2.29) 1.47 (1.00,2.16) 1.32 (0.87,2.01) (0.87, 2.07) 1.25 (0.81,1.93) 1.22 (0.80,1.86) 1.27 (0.85,1.92) (0.70, 1.99) 1.15 (0.68,1.94) 1.10 (0.66,1.84) 1.20 (0.74,1.94) P (trend)

11 Example diet: highest fibre category 30g or more per day: Breakfast bowl of bran flakes 5g 2 slices wholemeal bread 4g Snack medium apple 3g Lunch half-can baked beans 8g on 2 slices wholemeal toast 4g Dinner one medium jacket potato 4g 2 tbsp broccoli 2g Meat and breast cancer To assess meat consumption from the UK Women s Cohort Study on breast cancer To explore different types of meat in relation to risk of breast cancer

12 Results total Meat Consumption Taylor et al., Br J Ca. 2007, 96, Pre-menopausal HR 95% CI Post-menopausal HR 95% CI None (ref) Low 0.68 (0.47, 0.99) 1.52 (1.06, 2.18) Medium 1.08 (0.76, 1.53) 1.58 (1.09, 2.27) High (>103g) 1.20 (0.86, 1.68) 1.63 (1.13, 2.35) Continuous risk per 50g/day 1.12 (1.02,1.23) 1.10 (1.01, 1.20) P (trend) * adjusting for age, energy intake, BMI, physical activity, smoking status, HRT use, OCP use, parity, total fruit and vegetable intake Survival curves for total meat consumption Hazard Ratio Total Meat Consumption (grams/day) post-menopausal (predicted) post-menopausal 95% CI pre-menopausal (predicted) pre-menopausal 95% CI

13 Results Processed Meat Consumption Pre-menopausal HR 95% CI Post-menopausal HR 95% CI None (ref) Low 0.94 (0.65, 1.36) 1.48 (1.04, 2.12) Medium 1.04 (0.72, 1.51) 1.60 (1.12, 2.29) High 1.20 (0.85, 1.70) 1.64 (1.14, 2.37) Continuous risk per 50g/day 1.45 (0.95, 2.23) 1.64 (1.19, 2.27) P (trend) * adjusting for age, energy intake, BMI, physical activity, smoking status, HRT use, OCP use, parity, total fruit and vegetable intake Other results: significant positive trends: premenopausally non-processed meat p=0.003 (HR 1.13 for hi v. none) postmenopausally red meat p=0.04 (HR 1.56 for hi v. none) Poultry intake no significant associations

14 Overall conclusions Meat intake associated with increased risk of both pre- and post-menopausal breast cancer Fibre intake protective only pre-menopausally (cereal/fruit) Acknowledgements The team: Coordinator: Janet Cade Research staff: Victoria Burley (Alyson Greenhalgh, Claire Calvert) Statistician: Darren Greenwood Database: James Thomas Clerical staff: data entry team plus nutrition students Steering group: Rhys Williams, David Forman, Jenny Barrett, Barrie Margetts, Margaret Thorogood Original funder: World Cancer Research Fund Thanks to all the women who completed questionnaires.