I have been vegan for about 15 years. I am much healthier than the 19 years I spent (Yes, I feel I litterally "Spent" in relation to this time and suffering) on a standard american diet. I have always paid attention to my overall health in relation to eating vegan. I take into consideration my times of feeling lethargic or dizzy or any other strange experiences. I have my nutrition tested by my medical doctor yearly. I always receive the same results-Healthy and sustaining good nutrition. I credit my lifelong allergies and the side affects of the medications for them to my lethargy. I also get dizzy. My doctor says my diziness is most likely related to sinus allergies and perhaps the caffeine from my daily consumption of coffee. I also know that I could be exercising more (or at all) to build up my energy. These things cold be related to a number of possibilities, it's just easier to blame them on a new and different diet. Please see that life long nutrition is more obtainable on a vegan diet rather than a standard american diet. A standard american diet is proven to be a one way ticket to an early and miserable death.