When cooking and you have leftovers, should they be put in the refrigerator while hot? Or should you cool them first?

I have a weird problem that happened to me once when I was maybe 8 years old (I'm 20 now). I woke up one morning and all dairy products tasted horrible. They tasted as though they had gone bad. I'm not sure how long it lasted back then because I just stopped eating all dairy products for a couple of years — I was afraid they would taste bad, but it definitely lasted several months. When I started to have them again they tasted fine. It seems to have started again. What could possibly be the cause of this?

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?

1) What's the deal with monosodium glutamate (MSG)? What exactly is it, and how bad is it for you really?

2) I have recently been told I have a strong intolerance to MSG. But I am having trouble in working out what it is in. Is there any chance you could give me a list of items of food in which MSG is present in? I would be extremely grateful for any help.

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!

Can you tell me what are the uses of artificial preservatives and additives? Also, can you tell me info on the different types of preservatives and additives and why food manufacturers use them? Can you give examples for those??

Thank you very much!!!