My question is about nutritional supplements, specifically androstenedione and its closely related cousins. I have a five-day-a-week workout routine, and I have been searching for a supplement that will give me the greatest benefit for all of that hard work. I am, however, very concerned about the negative effects of some of these unregulated supplements. My question then is, what kind of side effects can I truly expect from using one of the male hormone precursors like androstenedione? And, in your opinion, is it safe?

For as long as I can remember, I've been using my back muscles when I did sit-ups. In fact, I distinctly remember the first time we did them in second grade. After a few reps, it was already so painful that I was having trouble breathing properly. Being eight years old, however, I didn't realize this was a warning sign and assumed it was normal.

Flash forward ten years, and I have almost no strength in my abdominal muscles. I've tried to teach myself to do curl-ups properly, but no matter how hard I try, I can't even lift my head without using my back muscles. Exercise balls are no help either. Even when I concentrate on using my abs to keep myself steady, my back is still doing 95% of the work.

So, in short, I have two questions: Am I at risk for having damaged my back from years of abuse, and how can I work on strength training my abs now?

Almost every place that I go to, I see stores and stores just devoted to selling vitamins and more vitamins, and I was wondering what the benefits are of a normal healthy person taking vitamins daily. Are there any risks for a normal healthy person who doesn't take vitamins? Will the person taking vitamins' health be improved or have longer longevity? Will the person not taking any vitamins be as healthy as the person who is taking them? And also, what will happen if a person takes more than he or she should consume every day?

A friend of mine takes laxatives to keep her weight under control. The directions on the box say that you should only take two a day for no more than a week. She has been taking two to six a day for two months now. I was wondering what possible physical side effects might result from this kind of activity.

1) Which foods, if any, have negative calories?

2) I have recently started a weight loss plan and after doing some research I learned about calorie burning foods. My question is, are there really calorie burning foods or is it just another diet fad?

I have been a lacto-ovo vegetarian for three years now. I want to stop and get back to eating meat. I do not know the proper way of doing this, so I would love feedback on how to plan my meals.

I eat lots of different kinds of lentils but don't know much about their individual nutritional properties. Are certain kinds of lentils healthier than others? What are the different calorie and protein figures for different kinds of lentils?

Is milk good or bad for you?

I read on someone's blog about drinking seltzer water if you're trying to quit drinking soft drinks but still need that fizz. Are there any good/bad side effects to drinking seltzer water?