My son was on the NAN 1 HA Gold formula. Does ...

My son was on the NAN 1 HA Gold formula. Does anyone know what the "HA" stands for? I know there is another 1 Gold variety, but don't know the difference between the two. I must admit because it's more expensive I immediately think it's a better formula! Then I discovered Bellamy's Organic formula. He had a few tins of that, but found he got constipated. He didn't poo for 4 days and when he did it came out solid! Has anyone else tried the Bellamy's? Did this happen to your baby?