This fascinating BBC Radio 4 programme last night can be heard here. It refers to the fact that we only understand/know of a small fraction of the microbial species living in our gut, and what they do. It states that diet has a large effect on our gut microbiota. It states that our gut microbiota have a large effect on our immune systems. It therefore stands to reason that our diet has a significant effect on our immune system. Although the programme does not dismiss the value of probiotics, the fact that we know so little about our gut microbiota has long made me believe that introducing a relatively small range of 'beneficial' bacteria is naive. The programme refers to faecal transplants, which makes more sense although instinctively yucky. However, someone else's gut flora may not suit the recipient, and as the programme states, it would make more sense for us all to 'donate' a little of our own when healthy, for potential use if our flora become unbalanced. (This causes me some amusement, as when I used to be a blood donor, a colleague and I used to joke during our habitual nervous dash to the loo beforehand that it was a shame we couldn't donate that!) But I have also come to the view since last year that the gut may be enabled to regain the right balance given the right diet and/or supplements. This seems to be supported by the programme. Food for thought - and for health!