Another study shows that Vitamin D lowers breast cancer risk; this time if you start young

Researchers from the Samuel Lunenfeld Research Institute at the Mount Sinai Hospital in Toronto show that increased Vitamin D levels during youth may reduce the risk of breast cancer by 30% later in life. 972 women newly diagnosed with breast cancer were compared to 1,135 cancer free women. Vitamin D obtained through exposure to sunlight, from food, or from supplementation, all decreased the risk significantly. Sources ranged from dairy, to sunlight, to cod liver oil. The study is published in the March 1st, 2007 issue of Cancer Epidemiology, Biomarkers, and Prevention, a journal of the American Association for Cancer Research.

Lacking iron, or worse, being anemic, strongly impacts cognitive function and task speed

At any time of life, a lack of iron affects mental function and behavior. Women of reproductive age are among the most vulnerable to iron deficiency which can lead to cognitive decline.
In this blinded, placebo-controlled study, 113 women between the ages of 18 to 35 were randomly assigned to receive iron supplements or placebo in a random fashion for 16 weeks. Cognitive function was assessed using 8 cognitive performance tasks which represented a broad range of tasks.

At the start of the study, iron sufficient women performed better on cognitive tasks and completed them faster than women who were iron deficient but not to the point of anemia, and these women in turn did better than the women with full-blown iron deficiency anemia. After treatment with an iron supplement, a significant improvement in iron status as measured by ferritin levels was associated with a 500% to 700% improvement in cognitive performance. A significant improvement in hemoglobin was related to improved speed in completing the task. The research was performed at the Department of Nutritional Sciences, Pennsylvania State University, and is published in the March 2007 issue of the American Journal of Clinical Nutrition.