What is the best formula to supplement a breastfeeding mother?

All equal: All the standard formulas are equal but you really shouldn't need to supplement with formula. If you are having milk supply problems increase the frequency of breast feeding and pumping to produce more milk. You can also talk with a lactation consultant or contact la leche league for ways to boost your milk supply.

About the same: Every formula will tell you why theirs is great and the other guys' stuff is poison. However, they are all remarkably close. I tend to like carnation good start with the probiotics (green can) because it has a more liquid protein that is a bit closer structurally to breast milk, and the probiotics help with digestion. However, we used enfamil most of the time for ours because it was on sale.