BKB: Check my updated post January 25, 2010 for an updated recommendation after reading the basics here.  I've written before about digestive health issues and the best fiber therapy.  The other major piece of the digestive health story is probiotics: dietary supplements of live microorganisms thought to be healthy for the digestive system*. "Good" bacteria populate our digestive system, and help regulate bowel function and immune health. Probiotics help intestinal bacteria perform their tasks more
efficiently. They take over when your intestinal bacteria have too much
work or are weakened or even destroyed by antibiotics, stress, poor
nutrition or any other factors. Probiotics have been heavilty marketed recently in functional foods like Activia and Danactive, but probiotic supplements have been around for years, and many supplement manufacturers produce them.  The key here is live micoorganisms.  Five or fifty billion cell counts are irrelevant if they're dead by the time you take them.  They have to be live when they hit your gut in order to be effective.  I've tried many different probiotics, and can recommend two: Bio-K+ CL1285** and Garden of Life Primal Defense Ultra. BioK+ live organism count is guaranteed at time of consumption, and the capsule formula is enteric coated, to deliver the organisms through your stomach acid.  It's the gold-standard of probiotic efficacy, and is also available in liquid fermented milk and dairy-free versions.  Garden of Life Primal Defense only guarantees their organism count at time of manufacture, but includes a broader range of organisms and also uses proprietary packaging technology to help assure efficacy.  Neither is inexpensive, but I can personally vouch for their superior efficacy.   Buy both at your local Whole Foods Market; or order BioK+ online from the manufacturer; order Primal Defense Ultra from the amazon.com marketplace.

This
information is not intended to replace the advice of a physician. Ask
your doctor before starting any dietary supplementation program.

*A whole new frontier of beneficial microbial supplementation may soon emerge. The NIH have begun studying the presence of microbes on human skin, where a surprisingly broad number of microbes have been found to grown in surprisingly specific locations: the bacteria on your forearm (home to the greatest bacterial diversity on our bodies) is more similar to the bacteria on my forearm than it is to the bacteria under your arms. Interesting!

**My sample of BioK+ was provided by bzzagent.com, a word-of-mouth marketing company.