Indi wanted me to "write about yoghurt". This is a broad sort of request! I will deal with it with a heap of observations and if there is anything people want to expand on we can deal with that later.
Yoghurt is a fermented milk product where the bacteria convert the lactose in the milk to lactic acid. The lactic acid gives the yoghurt the sour taste and ‘sets’ the milk by coagulating the proteins. The acidity also helps prevent other, possibly harmful, bacteria growing.
As the lactose in the milk is largely converted to lactic acid, yoghurt is usually well tolerated by people who are lactose intolerant and is easy to digest generally.
I am not a big fan of the fruit yoghurts, usually too sweet for me, but there is nothing wrong with them.
I like Jalna yoghurts but, for the one pictured above, take philosophical exception to the idea that (1) the product is fat free, it isn’t, (2) that fat free milk is in anyway natural, it isn’t. Not from the cows I know, anyway. Sadly, I don’t think they make full fat plain set yoghurt any more but their Swiss Custard Yoghurt is far too nice.
That hard white stuff you find on the top of ‘health’ bars might be called yoghurt but it isn’t. It is yoghurt flavoured fat, mostly saturated fat.
Probiotic yoghurt drinks probably do no harm (though they are twice as sweet as Coca Cola) but it is a open question as to whether they do any good. While the bacteria used will pass through the stomach into the intestines, they are not self sustaining and disappear from the system in a few days if not constantly replenished. I do not see their value and take the view that the flora that has thrived in the intestines over the eons are probably the best ones to have there.
Greek yoghurt has a higher fat level (10% cf normal yoghurt of 3%) and hence is more creamy.