What Is Iron & Why Do You Need It?

Jessica Ball, M.S., RD
·6 min read

Pictured recipe: Rosemary-&-Garlic-Basted Sirloin Steak

Chances are, you've probably heard of the nutrient iron before. As a kid, you may remember the not-so-pleasant finger pricks at the doctor's office to check your iron levels, and as an adult, iron levels may have come up in conversations as a reason for low energy levels. But exactly what is iron? What does it do and why do you need it? Here we take a deep dive into why this nutrient is so important for your health, as well as the best food sources of iron, so you can make sure you're getting enough.

cast iron skillet with steak
cast iron skillet with steak

What Is Iron?

Iron is a mineral that can be found in foods, fortified products and supplements. Iron is an essential component of hemoglobin, or red blood cells, and it's what allows the red blood cells to shuttle oxygen from the lungs to the rest of the body. It's also part of other proteins in our body that support muscle metabolism, healthy connective tissue, neurological development and other components of healthy cell function.

Heme vs. Nonheme Iron

There are two types of dietary iron: heme iron and nonheme iron. The biggest difference between the two is that heme iron is a type of iron that can only be found meat like beef, poultry and certain seafoods. "Heme" essentially means it's iron that's attached to red blood cells, or hemoglobin. Nonheme iron is the type of iron found in plant foods and iron-fortified foods.

While both are usable forms of iron in our bodies, heme iron is about twice as bioavailable to our bodies, meaning you can absorb more of the iron from heme-iron food sources. Fiber and other nutrients found in plant-based foods (like like phytates and tannins, both of which are antioxidants) bind with the nonheme iron, making it harder for us to absorb it. This is why vegetarians and vegans need to be strategic about eating enough iron-rich food sources.

Thankfully, vitamin C can help boost iron absorption, so be sure to pair iron-rich foods with sources of vitamin C, like bell peppers, broccoli, citrus, leafy greens, pineapple and more.

Iron Deficiency vs. Iron-Deficiency Anemia

Iron deficiency can be mild, which means your iron stores are marginally low but hemoglobin levels are within the normal range. When iron stores are completely exhausted and your hemoglobin levels decline is when it becomes iron-deficiency anemia. Especially if you are following a vegan or vegetarian diet, you have probably heard of iron-deficiency anemia. Iron-deficiency anemia can result from a variety of causes, including diet, and requires medical treatment to manage.

Iron Deficiency Symptoms

Some moderate or mild forms of iron deficiency might not have any symptoms. However, as deficiency progresses to iron-deficiency anemia, symptoms can become more pronounced. Some common signs of iron deficiency include the following:

  • Fatigue

  • Feeling cold when others aren't

  • Shortness of breath

  • Dizziness

  • Headache

  • Hair loss

  • Brittle nails

  • Swollen or sore tongue

  • Irritability

If you think you might have iron deficiency or even iron-deficiency anemia, reach out to your doctor to see if getting a blood test to determine your iron levels is right for you.

Foods High in Iron

Red meat might be the first thing that comes to mind, but rest assured there are plenty of foods with more iron than beef. It's recommended that women shoot for 18 milligrams of iron per day and men aim for 8 mg of iron per day. Here are a few good food sources of heme and nonheme iron, and we've listed how much a serving of each contributes to the recommended daily intake levels (or Daily Value):

  • Fortified cereals: 18 mg per cup (100% DV)

  • Oysters: 8 mg per 3 ounces (44% DV)

  • White beans: 8 mg per cup (44% DV)

  • Dark chocolate: 7 mg per 3 ounces (39% DV)

  • Beef liver: 5 mg per 3 ounces (28% DV)

  • Lentils: 3 mg per ½ cup (17% DV)

  • Spinach: 3 mg per ½ cup cooked (17% DV)

  • Tofu: 3 mg per ½ cup (17% DV)

  • Sardines: 2 mg per 3 ounces (11% DV)

  • Beef round steak: 2 mg per 3 ounces (11% DV)

  • Chickpeas: 2 mg per ½ cup (11% DV)

  • Potato: 2 mg per 1 medium (11% DV)

5 Health Benefits of Iron

Now that we have covered what iron is and food sources of iron, let's take a look at the health benefits of getting enough iron.

1. Increased energy

While iron deficiency can lead to feeling fatigued, the inverse is also true. Getting enough iron can help boost your energy by making sure hemoglobin is able to carry plenty of oxygen throughout your body. Research has shown that adding in diverse sources of iron to your diet can help reduce risk of deficiency and help keep you feeling at your best.

2. Healthier pregnancy

During pregnancy, one's blood volume and red blood cells increase to meet the needs of the fetus and the placenta. For this reason, pregnant people have higher iron needs than those who are not pregnant, at about 27 mg per day. It's important for pregnant people to get enough iron, not only to help meet their needs during pregnancy but also because iron is crucial for the growth and neurological development of the fetus.

3. Improved muscle endurance

Your muscles need adequate levels of oxygen to contract, which is a reason why muscle weakness is one of the common signs of iron deficiency. Beyond oxygen needs, iron is important for healthy muscle metabolism. Making sure you're meeting your iron needs can help keep your muscles functioning at their best and improve your muscle endurance.

4. Better brain health

Iron is an important nutrient for brain health, neuron health and cognitive function. When iron levels drop, so does the ability to concentrate and be mentally sharp. Getting enough iron supports a healthy nervous system as a whole and is important for keeping your brain healthy.

5. Stronger immune system

Iron's ability to carry oxygen to our cells directly influences how cells can heal from damage and fight off infection. For this reason, having enough iron is important for healthy immune function. Research has shown that people with lower levels of iron are more susceptible to illnesses, including several foodborne illnesses. Studies have also found that those with adequate iron stores can fight off bacterial infections more quickly.

Bottom Line

Iron and iron deficiency are hot topics in nutrition. Our bodies need iron for a variety of reasons, from neurological function to muscular endurance and more. Getting enough iron is important for staying energized and feeling your best, and there are plenty of ways to meet your needs. Eating iron-rich foods is a great first step. (Consult your health care provider to get your levels checked, if needed, and don't start taking iron supplements without professional advice.) For more, check out the 12 Best Food Sources of Iron.