You can say "Maintains..." or "Helps maintain..." They have a slight difference in meaning though. Just for the sake of an example, I'll assume you're talking about a pill. If you said this pill helps maintain digestive health, I will assume that it is not completely responsible for digestive health on its own but will offer an improvement or else works in conjunction with a healthy diet, etc. However if you say this pill maintains digestive health, I'm going to assume that all I need to do is take this pill and I will have great digestive health, regardless of what else I do.

Out of those two, 'Maintains digestive health' is correct but I would rather use "Helps maintain..."