From my own experiences,I found it fine to supplement my babies breastfeeding,however on advice from our plunket here, nurses specialising in baby care, i ended up putting my son on the bottle, as they were telling me he just was not getting enough via breast, to this day i think they were wrong, i had no trouble feeding my daughter and did so for 16 mths, way longer than i ever anticipated i would do,anyhow to cut a long story short both are healthy young adults now, so i don't think either of them suffered because of it.

So if you intend to add a supplement i would think it would work fine.,it is your personal choice, however if the feeding is going well, maybe the others are right you should just continue with that, breast is best,good luck.