Here’s how the study worked: Forty-three college-age women were divided into two groups. One group ate three ounces of beef at lunch, while the other ate a non-beef protein lunch (like chicken, pork, cheese, pasta, or rice) three times a week.  Why the focus on beef? Red meat is a good source of iron that the body can easily absorb, says study author Cynthia Blanton, PhD, RD. And because the study’s goal was to determine if increasing iron intake would improve cognitive function (iron deficiency is associated with memory and attention problems), beef was a good fit. On average, the beef and non-beef groups consumed 19% and 13% of their RDA of iron, respectively, at the meal.  After four months, something surprising happened: Both groups had increased blood levels of iron, and the women—particularly those with low iron levels to start—experienced improvements in working memory, speed, and attention. Iron helps produce neurotransmitters like serotonin and thyroid hormones essential in brain function, explains Dr. Blanton, who is an assistant professor of dietetics at Idaho State University. Here’s what’s funny: In both groups, the women’s total daily iron intake didn’t increase during the study. What mattered was that they were eating a better diet overall because of the lunches (many college-age women less than ideal diets). “It could be that the total nutrient package of the lunches improved the diets of these women and thus improved their iron status,” says Dr. Blanton. Translation? To up your body’s iron level, it’s not just about eating more iron-rich foods, but about eating a more nutritious diet overall. In general, women 19-50 years old need 18 mg of iron a day, while those 50+ need only 8 mg daily. (After your period stops, you need less of the mineral.)  If you suspect you may be low on iron, ask your doc to measure your levels. To bump up your stores, fill your diet with a variety of iron-rich foods, such as beef, turkey, spinach, lentils, tuna. Don’t start an iron supplement unless you have an iron deficiency and your doctor says you need one, since iron at higher levels (taken through supplements) can be damaging to the body. More from Prevention: Your Brain On Junk Food