Yoga, when done properly and for some time, strenghtens and cleanses body and mind in the way you wouldn't believe. I know a guy, who is over 50 years old, who has been doing yoga for over 20 years on regular basis - every morning for at least 30 mins. When you lok at him you can tell his age (he's got wrinkles and white hairs) but when you se what he's capable of you can't believe it. No one I know can outrun him (no mater how much younger they are). No one is as flexible as he is. No ne can work hard physical work longer than him. And he doesn't get tired. I've never seen him with low energy. I also do not remember whan he was sick the last time.
He's also been doing meditation, for just as long. Combination of the two gives marvelous results. You can hear many stories, but you'll benefit only if you do it. I believe meditation is very powerful because it removes our blockages and frees our powers (not laser beams, like in power rengers 
). However it has to be done with purpose and not just for its own sake.
I am also one of those guys who never gets sick. This winter, for example, there was terrible flu virus, and everyone who caught it was sick for at least 7 days. Everyone in my family got it, but I did not. I did have a headache and felt drowsiness one day, but that was it, and it only lasted for couple of hours. Strong immunity? Sure, but why? Could it be because I'm 'helping' my organism to fight disease? You see, every time I feel bad (getting sick) I do what can be called meditation - I lie down and let go everything so I can observe my body fully concentrated. No effort, no grinding your teeth. Just relax and observe. In a matter of hours that 'bad' feeling leaves my body and I feel as healthy as before. I've been doing it since I know for myself, and long before I found out about meditation. It's my natural way to deal with disease. If only I could find a way to fight carries naturally .
You might be suprised to hear this but I've read/heard it in many places - vitamins in pills are not nearly as effective as natural (e.g. fruit). Human organism does not absorb them well, which means that most of what you put in goes to waste (I can not tell you for sure exact percentage, but I think it was about 90%).
