I have been using cranberry supplements for many years for urinary tract issues, and recommended them to clients. I have also warned them off believing that cranberry juice (the sweetened version from the grocery store) is a good answer. It has always been best to take it as a supplement, as drinking unsweetened cranberry juice can pucker you – up it is so tart! The sweetened juice has so much sugar in it that it counters the good effect of the mannose in the cranberry juice.

Dr Mercola has addressed this in detail – nice article: From Mercola.com

D-Mannose is not a drug. This nutritional supplement occurs naturally in cranberries, peaches, apples, other berries, and some plants.

At some time in their lives, one out of every five women will experience less-than-optimal urinary tract health. And, it’s not just women who are concerned with urinary tract health – men are, too.

It’s entirely possible that your urinary tract health could be less than optimal… and you don’t even know it. You’ve probably heard of a number of ways to promote optimal urinary tract health naturally. And I bet cranberry juice is one of the things you think can do it the best…

Cranberry juice has long been thought to help boost your urinary tract health. And, you’ll be happy to know that studies do indeed show that drinking cranberry juice can help support a healthy urinary tract.

But, this will come as a surprise to many, drinking blueberry, peach, or apple juice could theoretically have the same beneficial effects, too.

However, there’s a BIG problem with cranberry juice as well all of these other juices: SUGAR.

To be more specific, these juices, including cranberry juice, are loaded with fructose, a monosaccharide (simple sugar) that can potentially cause many health problems, including impacting the normal way your urinary tract functions.

You see, if you eat sugars and grains (which also rapidly break down to sugars), it becomes more difficult to maintain a healthy balance of flora. As a result, you’re much more likely to experience less-than-optimal urinary tract health.

So, although cranberry juice can assist your efforts, I would not advise using it in its juice form. It simply has far too much sugar in it.