I have also had an increasing problem with cold hands - in fact it got to the point last year that I thought I would have to give up winter hiking unless the temps were going to be in the 30's! I was always hiking with hand warmers (right on my skin) and they still didn't keep my hands from getting very cold. Taking off my mittens (with glove liners on - the best are smart wool ones) to put on snow shoes or crampons or even just to have a snack meant that my fingers would be so COLD that they wouldn't come close to warming up for nearly 1/2 hour after.
Since last January, however, I have been taking a whole food nutritional supplement that has made an incredible difference! Now I occasionally end up taking my gloves off because my hands overheat!!! This isn't a cure, by any means, and my fingers and hands still get cold - but it is not like it used to be. Now if I take my mittens off to eat a snack or put on snowshoes, it only takes about 5 minutes for my hands to warm back up. When I am moving and generating a lot of body heat, I am often bare-handed - at least until I stop.
If anyone is interested in learning more - PM me.