If you freeze yogurt does it kill the active cultures, the good bacteria?

Despite medication, diet control, and exercise, I still have a ratio problem regarding HDL/LDL. What foods would you suggest to boost HDL, while reducing LDL?

I've been trying to diet for over two years. My goal is to lose about 25 pounds, but the most I've been able to get is 15, and I can hardly keep it off. I concentrate on eating very little and since exercise is so hard to keep up, I pretty much starve myself to death. I manage to maintain the weight for a month, and then I lose control again. I've been thinking about the various diet products in the market, such as diet teas, herbs, meal- substitution shakes, and other medical products. I'd like to know what kind of side-effects they have, and how effective they are. (Some boast a seven-day plan, but that seems hardly believable.) Also, I'd like to know how well-researched the information is on these products (i.e., are they long-term enough to cover all the side-effects?) As for aspartame, is it really harmless, or is it just not researched yet?

How much calcium do college-age women need in order to avoid osteoporosis and other such problems in later life? What's the best way to get it? (Calcium, I mean, not osteoporosis.)

Can you explain the difference in healthiness of breads and grains? Are all darker grains better for you than lighter counterparts? Why? If all bread is low in fat, how can it be bad for dieters, etc.?
Thanks!