Dark circles under your eyes are caused by lack of sleep, genes, nasal congestion, alcohol and aging. Vitamin K is naturally found in spinach. This nutrient is needed for blood clotting and to strengthen blood vessel walls, which helps diminish dark circles. It also keeps your skin clear, reduces skin inflammation and enhances blood circulation. The adequate intake of vitamin K for men is 120 micrograms and for women 90 micrograms. One cup of spinach gives you almost 900 micrograms of this nutrient.
Info found on: http://www.livestrong.com/article/517233-what-does-eating-a-lot-of-spinach-do-for-my-skin/