In most cases however, constipation while on a protein rich diet is likely the result of a lack of good fiber in your diet.
It's very unlikely that hemp protein powder would cause constipation. This is due to the higher than normal fiber content of hemp protein powder.
While soy protein itself does not cause constipation, it can increase the occurrence of constipation in those with a low fiber diet.
Yes, whey protein powder can cause constipation, but only when used excessively and without sufficient fiber and hydration in your diet.
Constipation is unlikely with casein protein powder alone, but more often is due to excessive use of protein supplements without sufficient fiber or hydration.
It is fairly uncommon to suffer from constipation when using pea protein powder, however there are a couple of exceptions to this.