I'd be interested in your recipe also, RCW. I recently began drinking kefir (Lifeway from the grocery store) just to see if I'd like it before I got into making my own. I know the grocery store stuff isn't supposed to be as effective, but I'm already seeing some benefits. And I just found out about the water kefir which I think I'd be more inclined to make since I'd like to get away from dairy.
I take a multi-vitamin, flax seed oil, calcium, and acidophilus daily. If I do feel a cold coming on, I start taking zinc tablets and drink hot ginger tea, and that usually heads it off. I don't get sick often though.
eta: I also drink either green or white tea throughout the day and have been doing so for the past several years. I think that's made a big difference too.