Sweet potatoes are often sold under the name "yam" in America.  However red
garnet and jewel "yams" are actually sweet potatoes.  White sweet potatoes
(aka jersey sweets), and Japanese sweet potatoes, are also sweet potatoes.
True yams are not sweet, nor are they rich in betacarotene.

Glycemic index charts I've seen list sweet potatoes as having a moderate
glycemic index.  On a chart put out by Bio Foods, sweet potatoes are at 48
(around the level of non instant oatmeal, and just under dried peas).  Yams
are at 51. They are not as high as bananas, rice, potatoes, corn, or honey.

Also, if eaten with protein and/or fat, the glycemic index will be lower
than if the carb is eaten on its own.  I know of an obese diabetic man who
adopted a paleo diet, loved sweet potatoes, and chose to eat one almost
every day.  This did not prevent him losing 10 pounds of fat a month in the
first 5 months, getting off several diabetic meds, and experiencing other
benefits.  Of starchy carbs, sweet potatoes are one of the most nutrient
rich.  There are various opinions about whether this or that vegetable is
paleo.  The answer depends upon which group of primitives you use as the
standard for paleo diet.  In the broadest context, a question to ask might
be:  is it a nutrient rich food?  Does it confer more benefits than
drawbacks?

Rachel Matesz