Bad diets, heart disease and deaths

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).

The rationale for the approach was explained in the abstract. "Traditionally, studies investigating diet and health associations have focused on single nutrients." This study aimed to identify dietary patterns and to examine the association of these with cardiovascular disease (CVD), CVD deaths and deaths from any cause.

The concept is sound. It never made sense to focus on one food or nutrient to examine associations, when we all eat whole diets. We have had decades of articles claiming, "red meat will kill you" and "whole grains will save you" and the food intake table has then revealed that the red meat/whole grain intake was 15g a day, or similar, and the study seems farcical before it starts. When we eat 2,000 – 2,500 calories (on average) a day, trying to claim that the 50 or so calories from one food will kill or save us has always seemed an imaginary stretch.

This study aimed to look at whole dietary patterns, rather than single foods. The method used was called Reduced Rank Regression (RRR). The paper explained, "RRR is a data-dimension reduction technique that aims to identify the combination of food groups that explain the maximum amount of variation in a set of response variables (e.g., nutrients) hypothesized to be on the causal pathway between diet and health outcomes." (We’ll come back to what this means for this paper).

In terms of novelty, the introduction reported that – to the best of the researcher's knowledge, only six other (longitudinal population) studies have reviewed CVD risk and/or all-cause mortality using this RRR technique. They were in smaller populations and none focused on the UK. This was thought to be the first large, UK, study to use this approach.

The study