Veganism is a way of living which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose. - The Vegan Society
You could just simply say that you want to adopt a vegan diet because of the health benefits. Or maybe you don't just care about your self and say you would also do it for the animals or for our environment.
All of the above are great reasons.
Humans are designed to be herbivorous, due to the fact that we can develop atherosclerosis (clogged arteries) by eating animal products. This is proven in a study by Dr. William Clifford Roberts , the editor of the American Journal of Cardiology: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1312295/
Also a video proving this claim: (I do not own any rights to this video content, only used for explanation)
Research supporting that vegan diets are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy,
childhood, adolescence, older adulthood, and for athletes:
Video: (I do not own any rights to this video content, only used for explanation)
Video: (I do not own any rights to this video content, only used for explanation)
Video: (I do not own any rights to this video content, only used for explanation)