About 30 years ago, I had severe Reynaud's. It got progressively worse for about 10 yrs. I was experimenting with vitamins and stumbled on niacin. Niacin dilates capillaries. I had immediate relief. I took it daily for about a year and found that I no longer had Reynaud's. In the subsequent years, if I sense poor circulation or if I find my body is slow to react to changes in temperature, I'll take it again for a week and I am back to normal.