In my expereince, I would say that it does help – but ‘quantifying’ the effect is far from easy.
Ref other parts of this thread: I’ve managed to quit the macrogol (or any other chemical laxative), with the help (apparently at least) of a combination of kefir, linseeds and water, and a diet predominantly of cheese, fruit and vegetables. I’ve also largely cut out wheat products — subsituting corn crackers to eat with the cheese (I miss bread and wheat biscuits a lot, but don’t miss the effects — so make them an occasional treat).
It’s therefore difficult to tell how much the kefir is individually responsible for benefit. I’ve also taken on board Michael Mosely’s advice about welcoming the right kind of bacteria generally rather than shunning them (eg, I’ve been making a point of eating somewhat over-ripe fruit and cheese… er, not licking the pavement…)
That said, I use the macrogol when travelling – and frankly I still find the whole thing a bit of an unpredicatble mystery…
Hope this helps!