It will not be helpful for lions. If you have any health problems at all, you should check with your doctor before altering you diet. In fact, even if you're in better shape than Carl Lewis, you should tell your doctor that you've become a vegan, simply because it's always good to tell your doctor these sorts of things. Before you make a wise-ass remark, realize that this obvious step can be quite difficult. Not to worry, we're here to help.
Many people like to eliminate animal products from their diets in stages.
For example, you might want to stop eating pigs and cows the first week, birds the second week, fish the third week, etc. After six weeks or so you'll have run out of categories and you'll find that you're a vegan. We very strongly recommend this method of conversion. It has been our experience that the transition to veganism is easier and more likely to last if you use this method. On the other hand, some folks prefer the grandness of a sudden conversion and want no part of our gradual method.