Bad diets, heart disease & deaths

Executive Summary

* A study was published on April 22nd, 2021 which reviewed the association between diet and cardiovascular disease (CVD) and deaths (from CVD or any cause).

* It was different to typical epidemiological studies as it tried to look at dietary patterns rather than single foods (e.g., meat) as usually happens.

* The study used a statistical technique that relied on assumptions about certain nutrients. The researchers assumed that energy density, saturated fat and free sugars were bad and that fiber was good. The statistical technique then identified the foods that met these assumptions.

* Two dietary patterns were identified. Dietary pattern 1 was characterised by high intakes of chocolate and confectionery, butter and low-fiber bread, and low intakes of fresh fruit, vegetables, and high-fiber breakfast cereals. Dietary pattern 2 was characterised by a higher intakes of sugar-sweetened beverages (SSBs), fruit juice, and table sugar/preserves.

* Dietary patterns 1 and 2 are both junk food diets. It was claimed that people whose diet was most like dietary pattern 1 were up to 40% more likely to have a heart incident or death during the study.

* The usual three flaws of epidemiological studies applied to this study (association not causation, relative not absolute risk, the healthy person confounder).

* There were additional flaws of this study: i) the assumptions about nutrients biased outcomes; ii) the healthy person was not fully adjusted for; and iii) the idea of a 'bread/butter & jam' diet might describe the British diet of 50 years ago, but it's not a typical diet anywhere today.

* The absolute risk differences were tiny. Surprisingly small in fact. The dietary patterns were so bad that it would have been reasonable to expect far greater association with disease. The biggest finding was how small the impact actually was.

Introduction

Just when you thought nutritional epidemiology had nowhere left to go, it's gone somewhere else. A paper was published on April 22nd, 2021, called  "Associations between dietary patterns and the incidence of total and fatal cardiovascular disease and all-cause mortality in 116,806 individuals from the UK Biobank: a prospective cohort study" (Ref 1).