Unfortunately there isn't any research that has directly looked at the impact of personal lubricants on encouraging the growth of yeast, and promoting yeast infections. So there isn't a simple answer to this question but here's what lubricant manufacturers, and health conscious sex store owners, say about it.
Most water based lubricants contain glycerin which is a sugar alcohol with a sweet taste. Those who suspect that lubes cause yeast infections usually believe that glycerin is the culprit because the yeast feed on sugar, and they assume that having more sugary liquid in the vagina could encourage more yeast. This is why many sex stores tell customers that using lubricant with glycerin could encourage a yeast infection.
On the other hand, there is actually no proof that this is the case, and women use water based lubes with glycerin all the time without getting yeast infection. In fact the makers of Astroglide (your lube of choice) point out that glycerin is sometimes an ingredient in yeast infection medication. But they also say on their website that if you already have a yeast infection, glycerin could make it worse. And they now offer a glycerin free version of their product. And finally it's worth pointing out that just because a drug contains something that doesn't mean it should!
For me the bottom line is that yeast infections are so annoying, why not take preventative action? There are plenty of glycerin free lubes that are water based lubricants, and all silicone based lubricants are glycerin free. So it's not that hard to avoid.
That said, if you aren't prone to yeast infections, and haven't had a problem with a lubricant you love, there's no reason to switch just because it contains glycerin.
