Jessica -- I think the conventional wisdom is a minimum of 30g of fiber per day. I personally need more than that for things to run smoothly, as they say

possibly due to the large proportion of protein that I eat in my diet. Veggies and my bowl of oatmeal aren't enough for me, so I supplement with SF Metamucil or I'll eat some Fiber One or homemade chili.
I looked on the label of the Benefiber and it is indeed soluble fiber (guar gum) so if anyone has trouble tolerating insoluble fibers, like those in Fiber One, bran cereals, and Metamucil, try the Benefiber. I've been putting it in fruit smoothies for DS, but it would also work in our beloved protein shakes. The label says you can put it in soup, soft foods, and hot and cold drinks.
http://www.benefiber.com/index.jsp
Meg