Vitamin D helps my skin. I take 2000 IU/day.
There are other supplements which I believe also help my psoriasis:
1. Anti-oxidants. A number of chemical reactions in the body produce free radicals, which cause inflammation in our bodies. More inflammation = worse skin. I take: vitamin C (250 mg), selenium (100 mcg), and alpha lipoic acid - a natural antioxidant the body makes in small amounts (300 mg). Occasionally I substitute a capsule of coenzume Q10. In addition I try to eat plenty of colorful fruits and veggies, which are also good sources of antioxidants.
2. fish oil and borage oil. The white cells in our skin produce chemicals (prostaglandins and leukotrienes) that cause our skin cells to multiply too fast. Fish oil (containing EPA) and borage oil (containing GLA) interfere with the production of these chemicals. I take 2 fish oil and 2 borage oil capsules most every day. Each capsule contains only 1/4 tsp of oil, so this is not a great amount. I also use olive oil for cooking as much as I can, since the oleic acid in it is anti-inflammatory.
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A high blood glucose level promotes inflammation in the body. I do better when I cut back on my sugar and flour intake.
I don't know about you, but I discovered that several foods cause an inflammatory reaction in my body, and my skin has improved since I cut them out of my diet: whole wheat (containing wheat germ), legumes (starchy beans, peas, and peanuts), and the inside "seedy part" of tomatoes.
The key, I believe, is to figure out what is causing iflammation in your body, then work to reduce the causes. If you can achieve success with this, perhaps you won't feel the need to take drugs all your life.
Good luck, DottieD