12. Mindful that many women under 50 are iron-deficient, you’re beefing up on iron-rich spinach.

Result: You may get lots of nutrients—but not much iron.

Iron is important for energy because it helps deliver oxygen to every cell in your body, but it’s tricky to get because it comes in two types. Spinach and other plant sources are rich in what is called non-heme iron. Only about 2% to 20% of non-heme iron is absorbed, versus 15% to 35% of the heme iron found only in animal foods, specifically meat. Chicken liver has the most (13mg), followed by oysters (4.5mg), and beef (about 3mg).

What to do: Vitamin C helps increase your body’s uptake of non-heme iron from foods. Pair iron-fortified breakfast cereal with a glass of OJ, or add grapefruit segments to that spinach salad.