As people consider options for modifying their diet and significantly reducing meat consumption, it is important to consider how to eat a balanced nutritious diet. Meat is high in protein, vitamins, and minerals, which are needed in the human body. These can be easily replaced in a vegetarian diet, but it is important to deliberately choose a variety of healthy plant-based foods, such as whole fruits and vegetables, legumes and nuts, and whole grains. Soy products and seeds are high in protein, so these can be used to replace the protein found in meats. Meats and animal derived products are also good sources of some of the B vitamins, especially B12, but fortified foods, such as many breakfast cereals, can provide many of the B vitamins in a predominantly plant-based diet. Other vitamins and minerals commonly found in meats also need to be deliberately replaced in a completely vegetarian diet, and people will need to consider replacement sources that work with their food preferences.
Some useful information on nutrition in a vegetarian diet, can be found in the links below:
https://nal.usda.gov/legacy/fnic/vegetarian-nutrition
https://www.healthline.com/health/food-nutrition/19-high-protein-vegetables
https://www.hopkinsmedicine.org/bariatrics/_documents/nutrition_protein_content_common_foods.pdf
https://www.todaysdietitian.com/pdf/webinars/ProteinContentofFoods.pdf