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Risks of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study

BMJ 2019; 366 doi: https://doi.org/10.1136/bmj.l4897 (Published 04 September 2019) Cite this as: BMJ 2019;366:l4897

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Vegetarian diets and health

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EPIC-Oxford study authors' reply to Mark Craig, Peter Loveridge, Shyan Goh and Mikolaj Pawlak

We thank the readers for their comments. We hope that the following clarifications will be helpful for understanding our findings.

1) Fibre intake in the EPIC-Oxford cohort, similar to many other UK cohorts, was estimated as non-starch polysaccharides (NSP) using the Englyst method, which gives lower estimates than the alternative method of estimating AOAC fibre. The dietary reference value applicable for the time of data collection was 18 g/day of NSP fibre, which equated to 23-24 g/day of dietary fibre if estimated using the AOAC method (see SACN report: https://www.gov.uk/government/publications/sacn-carbohydrates-and-health...). Therefore, all diet groups had an average intake that was above the recommendation at the time, though the current dietary reference value in the UK is 30 g/day of AOAC fibre.

2) Mortality by diet groups was examined in detail in a previous publication (https://www.ncbi.nlm.nih.gov/pubmed/26657045).

3) Although the primary aim of the EPIC study (including EPIC-Oxford) was to examine cancer outcomes, from the beginning the secondary aims included examining other health outcomes, including cardiovascular diseases. The EPIC-Oxford study specifically was funded by the British Heart Foundation at the recruitment stage (as well as by other funders), as shown on the last page of the recruitment questionnaire (http://www.epic-oxford.org/files/epic-baseline-PQ.pdf).

4) The database size of the current study is slightly smaller than reported in some previous publications because some participants have withdrawn since publication of the previous studies, and therefore their data have been deleted.

5) As stated in the methods section, data from both the baseline and follow-up questionnaires were used for the analyses, and therefore any recorded changes of diet group has been accounted for. The analyses included age as the underlying time variable; were stratified by sex, method of recruitment, and region; and were adjusted for various confounders which were shown to vary by diet groups including but not limited to education, level of deprivation, smoking, alcohol consumption (details can be found in the manuscript). Additional subgroup analyses by age, sex, BMI, smoking status, presence of risk factors, and whether they were receiving any treatment were also included in the supplementary materials (https://www.bmj.com/content/bmj/suppl/2019/09/04/bmj.l4897.DC1/tont04648...).

6) The results for ischaemic and haemorrhagic stroke can be found in Figure 1, and the results for vegetarians and vegans separately can be found in the supplementary materials (link above). While the assessment of known stroke risk factors is important, the aim of this study was to assess the association of vegetarian diets with risk of IHD and stroke, as outlined in our UK Medical Research Council grant MR/M012190/1 titled ‘Health of vegetarians’ (https://mrc.ukri.org/research/funded-research/)

Best wishes,
Tammy YN Tong, Timothy J Key
On behalf of all co-authors

Competing interests: No competing interests

12 September 2019
Tammy YN Tong
Nutritional Epidemiologist
Cancer Epidemiology Unit, University of Oxford
Oxford, United Kingdom