Example ingredients list for a high-qulity probiotics:

Lactobacillus species
5.0+ billion CFUs*

Lactobacillus rhamnosus

Lactobacillus casei

Lactobacillus paracasei

Lactobacillus gasseri

Lactobacillus salivarius

Bifidobacterium species
5.0+ billion CFUs

Bifidobacterium bifidum

Bifidobacterium longum

Bifidobacterium breve

Bifidobacterium infantis

Bifidobacterium lactis

Other Ingredients: None.

All of those ingredients are microorganisms. That’s what probiotics *are*, by definition: beneficial bacteria. Organisms need to eat something, which means sugar, and that usually means glucose, either exclusively from corn or from mixed sources that could be corn. If there is a probiotic out there that is grown on a corn-free medium, I would LOVE to know about it.

 

Your best bet is to make your own probiotics, if you can tolerate the ingredients required. 

But to my understanding, if you for some reason need to take a probiotic supplement rather than making your own, the best you can do is no inactive ingredients, that way the only corn you’re getting is what the probiotics ate, and whatever wasn’t filtered out from the medium when they were being harvested. 

My thinking on it is that if you are going to be getting some corn exposure, you’d best pick the highest quality, most pure supplement out there, so you’re getting the most benefit in return.

Edited 2012-04-12: Apparently there are some probiotics that are grown on inulin, a sugar from chicory, that may be corn free. I have yet to contact any of these companies to be positive that they always uses only inulin and never add corn glucose, but that sounds hopeful.

Update 2013-05-09: I had my naturopath look into two products that seemed promising:
http://www.klaire.com/prod/proddetail.asp?id=V084-02

http://kirkmanlabs.com/ProductKirkman/702/1/Acidophilus%20Probiotic%20Powder%20-%20Hypoallergenic/

I am struggling to remember exactly what she told me, but it wasn’t promising. I think she said Klaire wouldn’t tell her what it was grown on, just said “no corn protein” over and over, which basically means corn. I think Kirkman said microrystalline cellulose, but that doesn’t sound right as does that really have enough sugar in it to feed a probiotic beastie? They also said it is not possible to grow probiotics only on inulin, something else is required.

Based on that I decided to stick with the Gutpro becuase I already have it, it is higher quality than the other options, and the other options don’t sound safer.