- No consensus in the literature on strain, strength, or dose.
- Commonly used species with individual evidence include:
- Lactobacillus rhamnosus GG (most evidence)
- Lactobacillus casei
- Lactobacillus acidophilus
- Kefir (Expert opinion, 1 cup BID-TID, avoid in diabetics)
- Saccharomyces boulardii
- Mixed strain formulations (often proprietary blends)
Pooled results of different strains still show benefit, indicating that positive effect may be seen regardless of strain.