The last couple of times I've spoken to Jeff B. on the phone our conversations has returned to the same topic.
That being, worms may be more beneficial to garter snakes than just a food source.
Worms may be mostly water but what's left is some good stuff, especially the dirt that the worms have eaten.
I think for the most part this dirt is a benefit to the snakes rather than a problem. I understand there would be some exceptions to this statement.
Not only have the worms consumed many good minerals but Jeff and I both believe that the soil possesses beneficial bacteria that especially help the babies develop.
Gut flora, gives the young a jump start to their immune system.
I know that the Plains garters(T. radix) in my area feed mostly on night crawler and grow quickly and big.
Gut flora - Wikipedia, the free encyclopedia

Thanks Jeff for the great conversation. Always a pleasure.