Complex sentence: This was all suggested benefits of probiotics, but later on a study actually tested this with the probiotics Bifidobacterium longum and Lactobacillus helveticus on both rats and humans.
Split into simpler sentences: This was all suggested benefits of probiotics, but later on a studies actually tested this with different probiotics. In addition, the probiotics of Bifidobacterium longum and Lactobacillus helveticus were looked at using both rats and humans.