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We'd recommend that you talk

We'd recommend that you talk to your vet about this; they may know how/if baking soda can react with dogs internally; if it might help/hinder IBD; and if it is safe, what the recommended dosage and frequency would be for your dog's health condition, size, age, and breed.

As for humans, the American Cancer Society says this about baking soda and cancer:

http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/herbsvitaminsandminerals/sodium-bicarbonate