Although human beings have not had time to evolve to do dairy or kefir, kefir was evolved to be healthy for human beings, unlike apples that were evolved to be tasty for human beings, and grains that were evolved to provide calories for young working human beings and forget about the older people.
Although early man did evolve to eat lame apples, our current apples and other sweet fruits have WAY too much fructose. So a good strategy with fruit is to limit them.
But what about kefir? Kefir was carefully nurtured to be healthy for human beings by sweet mothers in the Caucasus Mountains. I have had no problems whatsoever and base a lot of my eating on kefir, but I want your collective wisdom.
Fermented dairy is ok, especially from goat/sheep/buffalo, for those not intolerant. And even for those intolerant, kefir is known to build up tolerance, in addition to many other health benefits. Personally, I ferment my goat kefir between 24 and 36 hours (sour, less lactose).
As for fruits, they are not the devil. Fruits have monosaccharides, which are easily digested by the human body, before the gut bacteria get to them. Fruits should be a bit limited only by those who want to lose weight, everyone else should be eating fruits.
To be frank, I think this whole notion that sweet fruits are the devil incarnate is a little over the top, and presenting it as a matter of fact is as misquided as the saturated fat is evil argument. That means I also embrace kefir wholeheartedly.
It depends on the person. Some people do fine with cultured dairy. Genes for lactose tolerance did appear in Northern European and Near Eastern populations several thousand years ago. (although not universally.) The affect on insulin levels needs to be considered for people who have metabolic problems, since dairy increases insulin production.
Fruit is much the same - fine for thin, active people who don't have metabolic problems, but requiring limits or removal from the diet in others.
Kefir is a fermanted food which makes it a very worth while food to include. I don't believe diary is a sin if it is real diary- Raw if possible in your State. I don't believe in drinkiong multiply glasses of any milk every day but using a kefir or yogurt or cheese a few times a week is a good thing as long as it is a real honest old style food.