I've had a lot of luck with this brand: https://www.amazon.com/Dr-Mercola-Complete-Probiotics-Supplement/dp/B001GFBC7S https://www.amazon.com/Dr-Mercola-Complet

I've had a lot of luck with this brand: https://www.amazon.com/Dr-Mercola-Complete-Probiotics-Supplement/dp/B001GFBC7S https://www.amazon.com/Dr-Mercola-Complete-Probiotics-Supple.... Take 2 each AM. By "luck" I mean I haven't got the common cold in over 2 years since I started taking them. I'm sure there are other variables I'm not taking into account, e.g., exercise and healthy eating, my age (35), etc. but they're inexpensive and I don't see any reason not to take them. EDIT: here are the strains that this brand includes (notably Lactobacillus plantarum, as mentioned in the study): Lactobacillus acidophilus DDS-1, Bifidobacterium lactis, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus brevis, Bifidobacterium longum, Lactobacillus salivarius, streptococcus thermophilus, and Bifidobacterium bifidum