When Robert Downey Jr. played Tony Stark, aka Iron Man, from 2008 ("Iron Man") to 2019 ("Avengers: Endgame"), he stormed the world shielded by iron armor.

Ironically, that's not the best use of iron if you want to protect yourself.

According to the American Medical Association, the more than 10 million people in the U.S. with iron deficiency (half have iron deficiency anemia) need to increase intake of heme iron from animal sources and non-heme iron from plants.

Animal sources include fish and poultry. Non-heme sources are green, leafy vegetables, beans, and nuts, as well as tofu, dates, figs, and raisins.

Non-heme iron is less well-absorbed, but you can increase absorption by eating citrus fruits or taking a vitamin C supplement along with your iron-rich foods.

Low levels of iron lead to fatigue and lightheadedness because there's a lack of oxygen-transporting red blood cells throughout your body. Iron is also needed to produce various hormones and for brain development.

Severe deficiency is associated with a fast heartbeat, shortness of breath, brittle nails, a sore tongue, extreme fatigue, and cold hands and feet.

Do you think you have low iron levels? Don't take supplements on your own. Excess iron can cause liver, heart, and brain damage as well as other complications.

Get diagnosed and discover precisely how much to take.

And don't take iron supplements with whole grains, dairy product, blacks tea, antacids, or proton-pump inhibitors — they interfere with absorption.