Kefir is not made by cultures but by kefir grains, and it is very different from yogurt in that it has a lot more lactic acid bacterias than yogurt and also several yeasts and acetic acid bacterias along with a higher nutrient profile, in particular protein (amino acids and peptides) and enzymes. Since kefir includes many more lactose and casein digesting bacterias and yeasts the lactose/carb content is quite lower than in yogurt. Kefir then is better for those who are lactose intolerant or suffer from milk (casein) allergy.

The yogurt bacterias used as starter culture is lactobacillus bulgaricus and streptococcus thermophilus, and not "acidophilus and/or bifidus". These bacterias are not part of our intestinal flora and therefore don't colonize our intestines, something which the bacterias in kefir does. However, the bacterias in yogurt does the body good as long as they are consumed regularly.

Have fun :-)

VriL