Night Shift Sleep

I definitely understand the importance of sleep, especially in between the hours of 10 pm and 6 am as you have prescribed. However, my current job requires me to wake up at 3 am and work until noon. I feel that my health is faltering greatly, though I am attempting to get at least 7 hours of sleep a night, eat well, and get exercise. I feel that it is negatively affecting my moods and memory as well as my physical well-being. I can’t change the hours I work at this point – what can I do within this situation to work towards optimum health?