We completely understand the need to know about every ingredient that's in your probiotic and supplements. The hydroxypropyl methyl cellulose (HPMC) is an inert substance which does not get digested or absorbed into the system, but rather - excreted out. However, if you're not comfortable with the capsules, there's also the option to purchase GutPro powder. Whereas Organic3 need the benign fillers (cellulose and the amino acid L-leucin) for the encapsulation process in the capsules, GutPro Powder is pure and condensed... this is why Organic3 formulated the powder - for people who are hyper-sensitive!
Just a reminder about both GutPro powder and capsules... they're free of common allergens. All strains are grown on a dairy-free, soy-free, vegetarian, non-GMO culture. They do not contain milk/casein, eggs, fish, shellfish, wheat/gluten, peanuts, tree nuts, yeast, corn or soy.