Hey K.,
Sorry, this is really lengthy, I actually copied and pasted it from an older post I answered:
We tried Good Start w/natural cultures after our 5 week old son was fussy and crying all the time. We switched to the Enfamil Gentlease and that seemed to help some, but then I had read by a Doctor in the "Baby 411" book that a study was done that said the good bacteria (probiotics) in the cultures could help with colic, digestion and mimic the immune system boosters in breast milk. Since I stopped breastfeeding at about 3 1/2 weeks, I thought I'd try it. It could be a coincidence, but I think it made a big difference. Even his poopie turned more yellow like it was when I was breastfeeding.
It was extremely expensive however (about $30.00 a can), so we decieded to see if maybe we could switch to a formula half the price since he was a little older. We went to Target's version of the Enfamil Gentlease (about $14.00 a can), but then he did get a little more fussy and a little consitpated. (He is now 10 weeks old). Then I looked back at the Baby 411 book where the Doctor also said you could add a certain probiotic powder to regular formula. I tried that and within a day or two, his poop was back like it was on the Good Start w/ cultures and he seems a lot better....and its a much more affordable option.
If you're interested, the powder is called Primadolphilus Reuteri by Nature's Way (the same one the Dr. in the book sells in her practice). The VitaminShoppe carries it. It was about $14.00 for a 5oz tub of it, but it should last a while since you only use a 1/2 teaspoon for the whole day. (It even said on the package you can add it to infant formula.) We just mix it in one bottle of formula a day.
I'm not a doctor, but on our last visit, our Doctor said he was fine with us giving him the Good Start with Cultures, so I didn't actually ask before doing this with the other formula and powder, but like I say, he's doing great with it. I really feel that it's good for them, just like all these new Yogurts like LiveActive are for adults digestion and immune system.
Hope this helps!