Definitely not the yogurt - it's high in sugar.

When considering for a probiotics supplement, you need to make sure the bacteria is still alive when they go into your digestive system. The whole point is to let them breed and grow in your guts.

Generally speaking, you should consider taking one with prebiotics. Prebiotics are foods for probiotics. They help the probiotics to survive and thrive in your stomach.

If you prefer just probiotics, I normally recommend cald'ophilus by Natural Factors. The tablet is coated with calcium, which helps to protect the probiotics from the stomach acid. The price is quite affordable.

If you don't mind paying a bit more, Bio-life has an extensive range of probiotics (some have to be kept in the fridge).

Finally there is GI Flora Plus by Celllabs which has 11 strains of good bacteria with prebiotics. It's quite pricey though.

Anyway, PM me if you would like a detailed consultation on whether you need probiotics at all or not.