COPLANT Study: What Happens When You Go Plant-Based?
What happens when you switch to a plant-based diet? It’s a question that more and more people are trying to answer for themselves as growing numbers reduce or eliminate meat and other animal products from their diets. Their motivations range from concerns about animal welfare and the climate to hopes of improving their health. But while the shift toward plant-based eating is gaining momentum, sticking with it isn’t always easy. Many people eventually return to their previous diets, often because maintaining a healthy, balanced plant-based lifestyle can be challenging without proper planning and supplementation. In some cases, nutritional gaps can lead to health issues, particularly when key nutrients such as vitamin B12 or iodine are overlooked. Germany’s largest-ever nutrition study, the COPLANT Study, is now set to explore exactly what happens when people adopt plant-based diets and how those choices affect their health over time.
Plant-based eating often relies heavily on ultra-processed foods and supplements
In the latest episode of the “Risiko” science podcast by the German Federal Institute for Risk Assessment (BfR), Professor Cornelia Weikert, a distinguished researcher at the BfR specialising in nutrition and public health, emphasises that cutting out meat alone doesn’t automatically lead to a healthier diet. She explains that plant-based eating can still be unbalanced, particularly when it relies heavily on ultra-processed foods that are rich in sugar, salt, or fat but low in important nutrients such as vitamins and trace minerals.
Meat and fish are rich sources of several essential nutrients, so eliminating them can increase the risk of deficiencies. One key nutrient to watch is vitamin B12, which is typically absent from plant-based foods. This vitamin plays a crucial role in blood formation and various metabolic functions. For this reason, individuals following a vegetarian or vegan diet should be especially mindful of maintaining a well-balanced diet and consider taking supplements, ideally after consulting a healthcare professional, to ensure they’re meeting their nutritional requirements.
Significant gaps in understanding how plant-based eating truly affects long-term health
Research by the BfR has found that individuals following a vegan diet have low iodine levels, an essential mineral important for growth, bone development, and brain function. They also tended to have lower scores related to bone health, supporting previous studies that linked vegan diets to reduced bone density. Interestingly, B12 deficiency is currently more common among vegetarians than vegans. “It’s encouraging that many people who follow a vegan diet are now well aware of the importance of getting enough vitamin B12,” says Professor Weikert. Vulnerable groups, such as children, teenagers, pregnant and breastfeeding women, and the elderly, should be especially careful to ensure their diets are well-balanced and meet all their nutritional needs to prevent deficiencies.
However, there are still significant gaps in understanding of how plant-based eating truly affects long-term health, as much of the existing scientific data on vegetarian and vegan diets comes from studies conducted decades ago, long before the rise of plant-based sausages, burgers, and ready-made meals. “One challenge,” explains Professor Weikert, “is that many of the existing studies were carried out in the 1980s and 1990s.” Since then, the availability of vegan meat alternatives and ultra-processed plant-based products has increased dramatically. Yet, how these newer foods influence diet quality and health over time hasn’t been thoroughly explored.
The COPLANT Study explores the long-term health effects of plant-based diets
To help fill these gaps, the COPLANT Study (Cohort on Plant-Based Diets) is underway, led by the BfR and Professor Weikert as the principal investigator. This study is a large-scale research project, one of the most ambitious ever launched in the German-speaking world, aimed at exploring the long-term health effects of plant-based diets.
Researchers will collect data on nutrition, lifestyle, and health from approximately 6,000 adults aged 18 to 69 from across Germany and Austria to investigate how different dietary patterns —vegan, vegetarian, pescetarian (including fish but no meat), and mixed diets —impact health. Participants must have been following their chosen diet for at least one year, and researchers plan to track them for at least 20 years. The goal is to gather detailed data not only on nutrition but also on lifestyle, body composition, bone health, metabolic markers, and even environmental contaminants, recognising that diet is more than just an individual health choice; it’s deeply connected to the wider world. For this, the study includes blood tests, urine and stool samples, saliva analysis, bone density scans, physical performance measurements, and comprehensive lifestyle questionnaires.
People, students and researchers based in Germany can participate
To record what participants are eating, researchers use a dedicated app called NutriDiary, which tracks daily food intake, including the growing variety of modern plant-based and meat-substitute products now available on the market. Interestingly, even pregnant or breastfeeding women can participate, and eventually, researchers also plan to study their children to understand how diet influences early development. People based in Germany who follow one of the diets under study may be eligible to participate and can sign up. This new study will provide up-to-date, science-based insights that will help to shape future dietary guidelines and public health recommendations, influencing how we understand the relationship between food, health, and sustainability for years to come.