Athletes, particularly those in endurance sports, depend on efficient oxygen delivery to working muscles. Iron deficiency, which is especially prevalent in female athletes, prevents the body’s cells from getting enough oxygen, causing fatigue, dizziness, headaches and even decreased immunity.
Furthermore, when you sweat, you actually lose a bit of iron with each drop. If you’re looking to build muscle or boost endurance, it’ll be a tough road without adequate iron intake.
In the following video, Liz Applegate, Oakland Raiders team nutritionist and director of sports nutrition at UC Davis, explains why iron is so crucial in an athlete’s diet.
Below are Recommended Daily Amounts of iron for females. If you are unsure of your own needs, consult your doctor.
14 to 18 years old — 15mg/day
19+ years old — 18mg/day
Many foods are rich in this essential energizing mineral. Check out these top sources—with their iron content (in milligrams) and calorie count:
Clams
3 oz — 14mg, 126 calories
Lean Meats
½ cup — 1-3mg, varying numbers of calories
White Beans, Lentils and Soybeans
½ cup white beans — 3.9mg, 153 calories
½ cup lentils — 3.3mg, 115 calories
½ cup soybeans — 4.4mg, 140 calories
Grains
½ cup of fortified breakfast cereal — up to 18mg, varying numbers of calories
½ cup oatmeal — 10mg, varying numbers of calories
Spinach
½ cup spinach — 2-3mg, approx. 20 calories
Pumpkin Seeds
1 oz — 4.2mg, 148 calories
Also, consuming Vitamin C with your meals enhances the absorption of iron into your system.
Sources:  Office of Dietary Supplement, firstendurance.com