Thanks again, folks. Being a vegan, I already eat huge amounts of green (and other coloured) veg. I don't add sugar to anything (except brown sugar in coffee) and drink huge quantities of tea (ordinary, Earl Grey, fruit). I hardly eat anything from a tin, cooking everything from raw, so as fresh as possible. My tongue looks OK. I think the answer is not in what I am putting in my body, but in strengthening either my breathing gear or my body's overall resistance to infection (or both) - in other words, overcoming my own individual physical weakness.

I will look into pilates and the Hay diet.

Thanks all. Any more?

Ian