Plant-based dietary patterns and ultra-processed food consumption: a cross-sectional analysis of the UK Biobank

Abstract

Background: Dietary shift towards more plant-based options is increasingly popular, but the quantity of ultra-processed foods (UPFs) they contain is largely unknown. This study assessed the level of UPF and minimally processed food consumption among regular and low red meat eaters, flexitarians, pescatarians, vegetarians and vegans in a large dataset of United Kingdom (UK) adults.

Methods: This is a cross-sectional analysis of the UK Biobank participants recruited between December 19, 2006, and October 1, 2010. Responses to food frequency questions were used to identify diet types for vegans (never eating any animal-based foods); vegetarians (never eating meat/fish); pescatarians (never eating meat); flexitarians (consumed fish/meat under twice a week); low red meat eaters (consumed fish/poultry more than once a week but red/processed meat under twice a week); and regular red meat eaters (consumed red/processed meat more than once a week). Consumption of all food and drinks collected in 24-h recalls between April 29, 2009, and June 28, 2012, were categorised using the Nova classification. The primary outcomes are the consumption of UPFs and minimally processed foods, expressed as a percentage of daily food intake (grams/day). Multivariable linear regression assessed the mean percentage point difference in UPF and minimally processed food consumption between diet types.

Findings: This study included 199,502 UK Biobank participants (mean age 58.2 [standard deviation 7.9] years; 55.1% women). The mean UPF consumption was 24.2%, 21.9%, 22.0%, 20.4%, 23.8%, and 22.7% among 75,091 regular red meat eaters, 70,144 low red meat eaters, 45,057 flexitarians, 4932 pescatarians, 4119 vegetarians and 159 vegans, respectively. The adjusted results suggested that compared with regular red meat eaters, UPF consumption was 1.3 percentage points higher among vegetarians (95% confidence interval [CI]: 0.9, 1.7) and lower among low red meat eaters (-1.3, 95% CI: -1.4, -1.1), flexitarians (-0.8, 95% CI: -1.0, -0.7), and pescatarians (-1.6, 95% CI: -1.9, -1.2). The UPF consumption in vegans were not significantly different from regular red meat eaters (1.2 percentage points, 95% CI: -0.7, 3.2). Minimally processed food consumption was higher in all other types of diet than regular red meat eaters, with an adjusted percentage point difference ranged from 0.4 (95% CI: 0.005, 0.9) for vegetarians to 3.2 (95% CI: 1.0, 5.5) for vegans compared with regular red meat eaters.

Interpretation: This UK-based study found higher UPF consumption in vegetarian diets and lower in diets with a modest amount of meat or fish. It is important that policies which encourage the urgently needed transition to more sustainable dietary patterns also promote rebalancing diets towards minimally processed foods.

Funding: National Institute for Health and Care Research (NIHR) School for Public Health Research, World Cancer Research Fund.

Keywords: Flexitarian; Plant-based diet; Ultra-processed foods; Vegan; Vegetarian.

Fig. 1

Flowchart for the derivation of study population from the UK Biobank.

Fig. 2

Mean proportion of the total diet from each Nova food group as measured by: a) daily food intake; and b) daily energy intake. Nova 1 includes unprocessed and minimally processed foods, Nova 2 includes processed culinary ingredients, Nova 3 represents processed foods, Nova 4 represents ultra-processed foods. ^†p < 0.05; ^‡p < 0.01 from ranksum test comparing distribution of consumption against regular red meat eaters.

Fig. 3

Mean proportion of daily food intake from subsidiary food groups of: a) Nova 1; b) Nova 2 and Nova 3; and c) Nova 4 food group. Nova 1 includes unprocessed and minimally processed foods, Nova 2 includes processed culinary ingredients, Nova 3 represents processed foods, Nova 4 represents ultra-processed foods.

Fig. 4

Mean percentage points difference between diet types for the consumption of each Nova food group as measured by daily food intake. Abbreviations: Coeff, coefficient; CI, confidence interval. Nova 1 includes unprocessed and minimally processed foods, Nova 2 includes processed culinary ingredients, Nova 3 represents processed foods, Nova 4 represents ultra-processed foods. All linear regression models were fully adjusted for age, sex, ethnicity, smoking status, physical activity, body mass index category, highest education attainment, average household income, Index of Multiple Derivation quintile, and total daily energy intake.

Fig. 5

Mean percentage points difference between diet types for the consumption of each Nova food group as measured by daily energy intake. Abbreviations: Coeff, coefficient; CI, confidence interval. Nova 1 includes unprocessed and minimally processed foods, Nova 2 includes processed culinary ingredients, Nova 3 represents processed foods, Nova 4 represents ultra-processed foods. All linear regression models were fully adjusted for age, sex, ethnicity, smoking status, physical activity, body mass index category, highest education attainment, average household income, and Index of Multiple Derivation quintile.