For some, the idea of never eating meat, milk or eggs again might seem like an impossible challenge.
But there's been a huge rise in the number of people willing to give it a go, including several celebrities.
In 2014 around 3,000 people signed up to take part in Vegan January, or 'Veganuary' as it's known. This month, more than 20,000 people have signed up already.
The key reasons people give for taking part are animal welfare, health and the environment.
A GP in Strood says in order to be healthy, vegans need to have a varied diet, because some nutrients from plant-based foods are absorbed by the body less well than from meat.
Watch Emma Wilkinson's report:
Interviewees: Keiko Goto (Chef at Itadaki Zen), Emilija Pimpyte (waitress at Itadaki Zen), Clea Grady (Marketing manager, 'Veganuary'), Dr Julian Spinks (North Kent GP).