The Cohort on Plant-based Diets (COPLANT) study is a multi-centre cohort study that starts baseline recruitment from 2024 to 2027 with approximately 6,000 participants in Germany and Austria. The COPLANT study focuses on vegan (no animal products), vegetarian (no meat and fish, but dairy products and eggs), pescetarian (no meat, but fish) and omnivorous (mixed diet including all possible animal products) diets. The aim of the COPLANT study is to gain new insights on health benefits and risks as well as social, ecological and economic effects of different plant-based diets in comparison to a mixed diet. In addition to a detailed dietary survey using an app adapted to the needs of this study, the baseline examination includes measurements of body composition, bone health, cardiovascular risk factors, diabetes risk, contaminants and lifestyle. For the basic laboratory program, fasting blood, 24-hour urine collection and a stool sample are taken from all study participants. Furthermore, specific aspects of dietary behavior, physical activity and other lifestyle factors are collected via questionnaires. Follow-up studies are planned at intervals of 5, 10 and 20 years after the baseline visit.

The multicenter Cohort on Plant-based diets (COPLANT) study, aims to investigate the health benefits as well as short-term and long-term risks of different plant-based diets (vegan: no animal products, vegetarian: no meat and fish, but dairy products and eggs, pescetarian: no meat, but fish) compared to a mixed diet among 6,000 participants aged 18 to 69 years across German speaking countries. Currently the impact of different diets not only on health effects, but also on social, ecological and economic factors is becoming increasingly evident in areas of social justice, climate change and animal welfare. For this reason, a sustainability analysis (social, ecological and economic effects) together with findings on health effects will be included in the COPLANT study. As plant-based diets, especially vegan diets, are associated with specific risks and benefits for certain population groups such as pregnant women, breastfeeding mothers and children, COPLANT will also establish appropriate research structures for these groups and include them in the study.

The detailed consumption survey of all study participants is one of the main pillars of the planned study. Of particular importance is the dietary assessment of novel vegan and vegetarian foods, thus an app adapted to the needs of this study was developed. The characterisation of external and internal intakes of nutrients and contaminants within a particular diet will be examined. Large epidemiological projects currently underway in Germany, such as the NAKO Health Study, are unable to answer these questions. In order to prospectively investigate links between diet and the later occurrence of common diseases such as type 2 diabetes, cardiovascular diseases and cancer, the study participants should be followed up for at least 20 years if third-party funding is successfully acquired.

The study is to be conducted in study centers at the Federal Institute for Risk Assessment (BfR), Berlin, the Max Rubner-Institut (MRI) in Karlsruhe, the Rheinische Friedrich-Wilhelms University in Bonn, the Friedrich Schiller University Jena, the Research Institute for Plant-Based Nutrition in Giessen, in cooperation with the Justus Liebig University Giessen and at the universities of Heidelberg, Regensburg and Vienna. Furthermore, the basic examination includes measurements of body composition, bone health, cardiovascular risk factors, diabetes risk, contaminants and lifestyle. Specific aspects of dietary behavior, physical activity and other lifestyle factors will be assessed using questionnaires. For the basic laboratory program, fasting blood, 24-hour urine collection and a stool sample are taken from all study participants.

Participants will be recruited for the baseline study from 2024 to 2027. Follow-up visits are planned at intervals of 5, 10 and 20 years.

Inclusion Criteria:

• age between 18 and 69 years at recruitment (age-stratified recruitment in four age groups (18 to 29, 30 to 39, 40 to 49 and 50 to 69 years) which should be equally distributed across the four diets)
• following their current diet for at least one year
• health insured
• are willing to have blood taken (adults)
• are willing and able to complete questionnaires
• only at Berlin, Jena, Giessen and Karlsruhe sites: pregnant and breastfeeding women were recruited (shortened examination programm)
• only at the Regensburg, Heidelberg, Bonn and Vienna sites: are neither pregnant nor breastfeeding at the time of recruitment
• only at Berlin and Karlsruhe sites: children of adult participants (shortened examination programm without collection of blood, urine, and stool)
• are able to give informed consent to participate in the study
• have given their consent to participate in the COPLANT study

Exclusion Criteria:

• who can no longer be contacted
• who withdraw their consent to participate in the study

We plan to include proportions of women and men (ratio 1:1), whereby a proportion of women of up to 60 % is accepted.

Vegans - no consumption of animal products (less than one exception per month)

Vegetarians

• no consumption of meat and fish (less than one exception per month)
• consumption of eggs and/or dairy products (at least once a month)

Pescetarians

• no consumption of meat (less than one exception per month)
• consumption of fish (at least once a month)
• consumption of eggs or dairy products possible

Omnivores/ mixed diet - group of non-exposed persons or control group

- consumption of meat or sausage (at least once a month).

In accordance with the informed consent of the COPLANT participants, pseudonymised study data could be provided to external researchers upon request for cooperation or data-use purposes. In this case, a cooperation or data use agreement must be concluded in advance. The use of COPLANT study data is therefore only possible with a detailed prior justification of its scientific purpose and after agreement of the steering commitee of the COPLANT study.