It depends on whether this is a recent, recurrent or odd episode issue. If you have recently changed your dog's food, is likely just to be that, as some foods are more easily digested than others, and therefore they might need to go more frequently to the toilet.
However if you think that the faeces are slightly loose, that's already considered diarrhoea, and therefore you might need to do something about it. Some dogs with gastrointestinal issues feel like they need to go to the toilet more often despite there is very little to pass.. which is also an indication of an issue.
Might be worth trying some probiotics. I really like the Purina Pro Plan Fortiflora :)