Iron: Benefits, Immune Support and How Much You Need

Iron is the mineral that helps your blood carry oxygen to every part of your body [1]. It's also one of the most talked-about nutrients in the world, because iron deficiency is the most common nutritional cause of anemia [2]. With iron, getting the amount right matters, because both too little and too much can cause problems [1].

What is iron?

Iron is a mineral your body needs for growth and development [1]. An adult body holds about 3 to 4 grams of it, and most of that is found in hemoglobin, the protein in your red blood cells that carries oxygen [1].

The iron in the foods we eat comes in two forms. Heme iron comes from meat, seafood and poultry, and your body absorbs it easily. Nonheme iron comes from plants and iron-fortified foods, and it's absorbed less well [1]. Meat, seafood and poultry actually contain both forms, which is part of why they're such good sources [1].

What does iron do for the body?

Iron's best-known job is helping your red blood cells carry oxygen from your lungs to the rest of your body [1].

Iron is important to four things inside the human body: the blood, the muscles, growth and the brain, and the immune system. Let's take each one individually.

• The blood: Iron sits at the core of hemoglobin, the protein that carries oxygen in your red blood cells [1].
• The muscles: Iron is part of myoglobin, a protein that stores oxygen and delivers it to your muscles when they're working [1].
• Growth and the brain: Iron is needed for normal growth, brain development, everyday cell function and making certain hormones [1].
• The immune system: And the last one. Your immune cells need iron to multiply and do their jobs, especially when they're responding to a threat [3] [4].

Why is iron important for the human body?

Without enough iron, your body can't make enough healthy red blood cells. Over time, that can lead to iron deficiency anemia, which can leave you tired, weak and short of breath [1] [2].

This is a big deal around the world. Anemia affects an estimated half a billion women ages 15 to 49 and 269 million young children, and iron deficiency is its most common nutritional cause [2]. Here in the United States, low iron isn't unusual either, especially among young children, women under 50 and pregnant women [1].

But iron is a double-edged nutrient. Research links two processes to declining health with age: increased oxidative stress, which is damage from excess free radicals, and chronic inflammation [5]. Free iron that isn't safely bound to proteins can drive up free radical production, which is why too much iron is a concern [6]. That's also why your body tightly controls iron, absorbing more when your stores run low and less when they're full [1].

So with iron, the goal isn't simply more. It's the right amount for you.

How does iron support immune function?

Iron supports immune function by fueling your immune cells, especially T cells and B cells, so they can multiply and respond to threats [3] [4]. At the same time, your body deliberately holds iron back from germs during an infection, because they need iron to grow, too [7] [8].

Think of your immune system as having two jobs: responding strongly when a threat shows up, and calming back down once the job is done. With iron, there's a twist: keeping it away from the invaders. Let's look at how it all fits together.

• First-line (innate) defense: This is your body's rapid-response team. Iron helps regulate macrophages, neutrophils and natural killer cells [4]. During an infection, your body also hides iron away so germs can't use it, a defense scientists call nutritional immunity [7] [8].
• Targeted (adaptive) defense: This is the part of your immune system that learns and remembers specific threats. When T cells switch on, they rapidly ramp up how much iron they take in. Within 24 hours, each one makes about a million new iron receptors [3]. When iron runs low, T-cell and B-cell responses and antibody production can weaken [3].
• Balance matters: More isn't better here, either. Research suggests that while low iron holds T cells back, extra iron beyond normal levels doesn't make them work any better [9].

The takeaway is simple: your immune system works best when your iron levels are in a healthy range, not too low and not too high.

Getting the most from iron

Iron is one nutrient where one size doesn't fit all. Here are four things the research points to.

• Know your own needs: Iron needs vary more than almost any other nutrient. Women ages 19 to 50 need 18 mg a day, more than twice the 8 mg that adult men need, mainly because of monthly blood loss [1].
• Help your body absorb plant iron: Eating vitamin C-rich foods, or some meat, seafood or poultry, alongside plant sources of iron helps your body absorb more of it [1].
• Space out iron and calcium: Calcium can interfere with how well you absorb iron, so if you take both as supplements, take them at different times of the day [1].
• Check before you supplement: Healthcare providers usually use more than one blood test to tell whether you're low in iron, because a single measure can be thrown off by inflammation [1].

Frequently asked questions about iron

Why some comprehensive formulas leave iron out

You might notice that not every multivitamin contains iron, and sometimes that's on purpose. Some research-based micronutrient formulations, including Micro Daily EMF, leave iron out entirely [6] [10]. Here's the reasoning. Your body does need small amounts of iron for its own antioxidant enzymes. But a slight excess of free iron can increase free radical production, especially when it's combined with vitamin C, which antioxidant formulas contain in generous amounts [6]. Leaving iron out puts the focus on getting it from food, and adding it separately only when you actually need it. That said, some people truly do need more iron than food alone provides. This includes pregnant women, people with heavy menstrual periods and anyone diagnosed with iron deficiency [1]. For them, an iron supplement chosen with a healthcare provider may be exactly the right call, and it can be taken alongside an iron-free formula.

How much iron do I need each day?

Adult men and women over 50 need 8 mg a day. Women ages 19 to 50 need 18 mg, and during pregnancy that rises to 27 mg. Children need 7 to 10 mg, and teens need 11 mg (boys) or 15 mg (girls) [1]. If you're vegetarian, you may need about 1.8 times these amounts, because plant iron is harder to absorb [1]. The upper limit is 45 mg a day for anyone 14 and older, and 40 mg for younger children [1].

What foods are high in iron?

Iron-fortified breakfast cereals can provide 18 mg in a single serving. Three ounces of cooked oysters have about 8 mg, a cup of canned white beans about 8 mg, and three ounces of beef liver about 5 mg. Half a cup of lentils or cooked spinach gives you about 3 mg [1].

What's the difference between heme and nonheme iron?

Heme iron, from meat, seafood and poultry, is absorbed better, and other foods in your meal don't affect it much. Nonheme iron, from plants and fortified foods, is absorbed less well and depends more on what you eat with it [1]. Spinach, for example, contains plenty of iron, but natural compounds called polyphenols make it harder to absorb [1].

Who is most likely to be low in iron?

The groups most at risk are young children, women under 50 and pregnant women. People who don't eat meat, poultry or seafood, people who lose blood, and people with digestive conditions that affect absorption are also at higher risk [1].

What are the signs of low iron?

Common signs of iron deficiency anemia include tiredness, weakness and shortness of breath, along with less energy for physical activity [2]. Because these signs are so common, a blood test is the only way to know for sure [1].

Can you take too much iron?

Yes. High doses from supplements can upset your stomach and cause constipation and nausea, and very large doses can be dangerous [1]. Accidental iron overdose is a serious risk for young children, so keep iron supplements out of their reach. People with hemochromatosis, an inherited condition that causes iron to build up, should avoid extra iron unless their doctor advises it [1].

Explore more micronutrients

Iron works alongside other nutrients. Folate and vitamin B12 also help your body make healthy red blood cells. Learn more about vitamin D, magnesium, calcium, zinc and potassium.

Key sources: NIH Office of Dietary Supplements, Iron Fact Sheet for Health Professionals [1]; World Health Organization, Anaemia fact sheet [2]; Ni S, et al., "Iron Metabolism and Immune Regulation," Frontiers in Immunology, 2022 [4]. Every numbered citation links to its full entry on our References page.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Talk with your healthcare provider before starting any supplement, especially if you are pregnant, nursing, taking medication or have a medical condition.