what causes lowered amounts of melanin
1 Vitamin E - It doesn't directly reduce melanin production but it is effective in reducing hyper pigmentation caused by melanin over production.  Use a good SPF protection to all the exposed parts before going out in the sun and keep ypurself covered (It may get hot though...so upto you!!)
There are 4 vitamins that can be used to reduce melanin production. Vitamin C: Popularly known as ascorbic acid, Vitamin C is a water soluble vitamin which has anti-oxidant properties. When applied topically, vitamin C seeps deep into the skin where the melanin producing cells are located and inhibits their production.
Dark circles caused due to excessive melanin production are also removed when Vitamin K is used. Besides taking Vitamin D supplementation, you can opt for foods enriched with this vitamin. Foods enriched with vitamin D are fortified cereal, fortified milk products, cod liver oil, soy and soy products and fishes.