PDX stands for Polydextrose, a dietary fiber that feeds beneficial bacteria throughout the large intestine. It supports the balance of the gut system by stimulating growth and activity of beneficial bacteria (gut flora)6, which benefits your child's immune system7.
PDX and GOS (Galactooligosaccharide) work together to foster the growth of good bacteria and promote digestive health. The unique blend of PDX and GOS promotes frequent and softer stools in children, and thus may help reduce the risk of occasional constipation8.
 
References:
6.Scalabrin DM, Mitmesser SH, Welling GW, Harris CL, Marunycz JD, Walker DC, Bos NA, Tölkkö S, Salminen S, Vanderhoof JA. New prebiotic blend of polydextrose and galacto-oligosaccharides has a bifidogenic effect in young infants. J Pediatr Gastroenterol Nutr. 2012;54:343-52.
7.Ouwehand A, Isolauri E, Salminen S. The role of the intestinal microflora for the development of the immune system in early childhood. Eur J Nutr. 2002;41 Suppl 1:I32-7.
4.Ribeiro TC, Costa-Ribeiro H Jr, Almeida PS, Pontes MV, Leite ME, Filadelfo LR, Khoury JC, Bean JA, Mitmesser SH, Vanderhoof JA, Scalabrin DM. Stool pattern changes in toddlers consuming a follow-on formula supplemented with polydextrose and galactooligosaccharides. J Pediatr Gastroenterol Nutr. 2012;54:288-90.