For many baby boomers, former president Bill Clinton among them, vegetarian diets — including vegan ones, which eschew all animal products — have become a way of life. Much of the reason for that, doctors say, is that this demographic group is heading into prime time for health issues and sees vegetarianism as a way to protect their bodies. Yet for boomers these diets can carry some risks that don’t concern those in their 30s or 40s. As we age, our nutritional needs change and are harder to meet.