OPTIMEAT

Dietary shifts toward more plant-based eating patterns are increasingly promoted to improve public health and reduce the environmental impact of food systems. However, animal-source foods remain important contributors of several essential nutrients, and concerns have been raised regarding nutrient adequacy and bioavailability in diets with little or no animal products.

A change from an animal-protein–based diet to a plant-protein–based diet has been suspected to compromise the intake and/or bioavailability of a number of micronutrients. Some nutrients are present in insufficient amounts in plant-based diets (e.g. calcium, vitamin B12 and vitamin D), while others are available in lower amounts (e.g. iron, zinc, copper, vitamin B2) or are negatively affected by dietary compounds mainly present in plant foods, such as phytates, or not present in plant-based diets alone (meat factor affecting iron).

There is also very limited knowledge about the risk of micronutrient deficiencies in a Danish food context when shifting from diets with a high proportion of animal-source foods to diets with a larger proportion of plant-source foods. In addition, little is known about the feasibility of such dietary changes and the willingness of consumers to adopt and maintain them within Danish food culture. What we do know is that adherence to dietary guidelines has historically been virtually nonexistent.

Controlled human intervention studies are therefore needed to understand how diets with different proportions of animal- and plant-source foods influence micronutrient status and health outcomes under real-life conditions. At the same time, evidence from existing research and insights into consumer behavior are essential to assess the feasibility and acceptability of dietary changes within a specific cultural context.

Randomized controlled dietary intervention

This is a 3-month randomized controlled parallel dietary intervention. Adult men and women aged 18–65 years will be randomized to one of four dietary patterns: a vegan diet, a vegetarian diet, a reduced-meat diet aligned with Danish dietary guidelines, or a habitual mixed diet.

Participants will undergo screening and baseline assessments prior to the intervention, followed by a dietary intervention period of three months and a follow-up assessment at the end of the intervention. Assessments include dietary measurements, anthropometry, and collection of biological samples to evaluate micronutrient status and cardiometabolic health markers.

Participants will receive oral dietary counselling from dietitians, written guidance (including recipes and lists of allowed and non-allowed foods), and selected food products free of charge to support adherence to the assigned dietary pattern. Dietary supervision and product collection will take place on a regular basis throughout the intervention period.

The environmental impact of the dietary patterns, including carbon footprints, will be evaluated using life cycle assessment based on Danish food data.

Recruitment is expected to begin at the end of 2026.

Consumer Survey

To assess feasibility and acceptability, a consumer survey will be conducted in the Danish population building upon deeper insights to already obtained consumer data.

The survey will investigate dietary habits, perceptions, barriers, and facilitators related to healthy and sustainable diets with varying levels of animal- and plant-based foods.

The survey will provide insights into consumers’ willingness to adopt dietary changes and the cultural and behavioral factors influencing adherence to more sustainable dietary patterns.