Probiotic Yogurt

I've been eating yogurt with added cultures of Bifidobacterium lactis in the last little while, and it's supposed to have a good effect on the immune system and digestive system.

I was just wondering if anyone has noticed and differences in their health from eating normal yogurt (without added cultures) and probiotic yogurts.

I myself don't eat much yogurt, if I've ever eaten any, but my cousin eats yogurt, and has been recently eating probiotic yogurt, and says it's made a big difference in her health, saying she just feels better when she eats this stuff. I dunno why, though.