Best gut & digestive supplements, ranked.

A single well-characterized studied strain (B. coagulans GanedenBC30) fully disclosed at 120 million CFU per chew with FOS, from an NASC brand that owns its cGMP plant, at a low price; the catch is the strain has weak canine evidence and 120 million CFU sits below the studied effective dose.

A single studied strain from a manufacturer that owns its plants, but no NASC seal or independent testing and a high cost per day; lands Mixed.

The feline twin of FortiFlora: one studied strain from an owner-operator manufacturer, but no NASC seal, no independent testing, and a high cost per day; Mixed.

A four-strain probiotic with prebiotics, NASC-sealed and well priced, but the combined 6 billion CFU hides each strain's dose behind a proprietary blend, so it lands Limited.

A 7-strain probiotic that names its strains but discloses only a combined 7.5 billion CFU, so we cannot confirm an effective per-strain dose and the Active Dose score is capped; the marketing also reaches past the acute-diarrhea evidence into allergy, immune, and behavior claims. Well made and inexpensive per day, but the hidden per-strain dose and claim breadth land it low.

A seven-strain probiotic from a batch-testing maker at the studied strain set, well priced; the multi-strain evidence is modest and per-strain CFU is hidden behind a proprietary blend, so it lands Limited.

Names three Bacillus strains and discloses FOS and GOS at 100 mg each, but hides the per-strain CFU behind a single 3 billion total so the probiotic dose cannot be verified, and at one chew a day it runs about 1.25 per day; NASC-sealed with a clean recall record.

The studied De Simone (former VSL#3) multi-strain formulation, NASC-sealed, but it discloses only a combined 112.5 billion CFU rather than per-strain amounts, so under our rules it is a proprietary blend (Active Dose capped) and at over a dollar a day it lands in Limited.