Those who observe the vegan diet or are vegetarians do not eat meat for various reasons. Some think it is immoral to kill animals for food. Others think they can be healthier without eating meat. It is likely in both cases that they supplement their vegetables with vitamins and minerals. There are several degrees of being a vegan or vegetarian. Some eat no meat at all or any other creature. Others compromise and say that they are willing to eat fish and/or chicken.
But let’s see what the Bible says about this regiment. All through the book of Genesis God instructed mankind to eat meat. In Exodus and Leviticus God instructed believers to eat meat, sacrifice meat on altars, and give the remnant of offering meats to the priest. Several times before and after his resurrection Jesus ate meat with his disciples. The early church practiced eating meat together. The apostle Paul dealt with the question of meat that had been offered to idols. In most cases the only source of meat was what was offered to idols. This is the only case of a person using their conscience whether to eat meat or not. That situation concerned a weaker Christian that might be questioning a another Christian if they ate meat offered to idols.
In Acts 23 God told Peter to eat meat when he had a vision of a sheet lowered before him with many sources of meat some of which were ritualistically clean and unclean according to Jewish customs. God told Peter that what he called clean, Peter should not call unclean. In this situation two things resulted. First, God instructed Peter to eat meat. Second, God used the vision as a means to prepare him as a witness to the Gentiles that they should not be rejected as unclean.
In the story of the prodigal son, he wasted all his inheritance and returned to his father asking to be a servant. The father killed the fatted calf and celebrated at the return of his wayward son. Here again meat was eaten as part of their practice. The elder son was jealous. He did not object to the eating of meat. He objected to the celebration for the returning brother.
Nowhere in the Bible other than in the Garden of Eden were humans instructed to eat plants alone. Afterwards, it was part of daily living to either raise or hunt animals, fish for food out of the waters, or incorporate any other kind of meat into their diet.
Regardless of a person using supplements, this is unlikely to be approved by God. In fact, it is almost hypocritical to use supplements for what was missing from eating plants. If the vegetarian diet was so great, why would supplements be needed to replace what a person lost by not having meat in their diet? Besides this, some people have been negatively affected by using supplements.
Should a person want to follow Scripture, they should have a well-balanced diet of various plants and meat. This is an example of how we can easily ignore the practices within Scripture, following what other humans say instead. Regardless of all the diet fads, such extreme eating is not supported by the Bible.