That's a good question, Mary!
I also have reynaud's and suffer from it pretty bad. I can lose all feeling in my hands, feet, legs, even my arms which is pretty scary. I also turn pretty shades of red, blue and purple in the cold, as well. I absolutely hate winter here! Since I walk all over the place and don't drive, dressing properly for the weather is essential! I've even been known to carry a small gel heat pack with me that I can use just so I can tolerate standing at a bus stop long enough for a bus. Most restaurants seem willing to toss it in their microwaves for you, as well, or you can just run it under hot water, too. I usually dress in three layers in the winter, too. People think I'm nuts that I wear everything in layers but I have to or I come close to passing out in the cold weather.
I think vitamin-wise the main thing we need is iron which also needs vitamin C in order to be absorbed properly, along with calcium and magnesium. I think the "B" vitamins are also helpful but I have a hard time tolerating the "B" ones...I have no idea why! Anemia also seems to be an issue for me, as well, so that really affects me, so it's important to get enough iron in supplements and in your diet. I hope that helps.
Dini