You can go to any tackle store and look at the articifial worms they sell. Alot of the them are impregnated with garlic and/or salt. You can also buy garlic extract for bait. I have never used them for fishing because with LMB you don't try to attract them to the bait you put the bait in thier faces to try and trigger a "strike instinct". I would imagine that if you go in to dicks, cabelas, or gander mountain and get the brand name for a fish attractant you will get a link to their websites that show it being used in test aquariums.
Fish need vitamins as well, baby vitamins contain no phosphates. You pay a ton of money for these fancy pelletized foods that pretty much just have vitamins added to them, and most of them are ground up fish, shrimp, and then a whole lot of fillers. Also NLS sells Thera-A which has garlic in it. Supposed to improve the fishes appetite and boost their immune systems. The thing with Thera-A is that it has a ton of garlic in it.
If the worm is alive it will breath garlic water through its skin. If you leave the worm in the tank long enough it may leach out. But in my experience it is usually in the fish's belly as soon as they see what it is.
This is a link to the NLS site, they discuss nutrition and know a great deal about fish nutrition and nutrition in general. In this document they talk briefly about vitamins. I looked at their vitamin list on a package and compared it to store bought vitamins and found that baby vitamins have the same composition.
http://nlsfishfood.com/index.php?option=com_content&task=view&id=29&Itemid=63&limit=1&limitstart=0
This is a link to the NLS forum that discusses garlic as a health benefit. I add a little garlic to my worms (oh yeah, and shrimp) but these guys put great gobs of garlic extract into their food. They say that it can increase palatability, but is not the intent of their Thera food. For me I use just a touch of garlic to make the fish keep the food in their mouths longer.
http://www.newlife.ipbhost.com/forums/index.php?showtopic=256
banana oil is also supposed to work as an attractant and appetite stimulant as well, but I don't grow bananas in the back yard.