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Harvard Commentaries
35320
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Food for Thought Food for Thought
 

Iron -- There's Nothing Small About
This Micronutrient


August 28, 2012


By Jenna B. Damareck, B.S.
Brigham and Women's Hospital

Vitamins and minerals from A to Zinc are vital to a healthy body. Thanks to public health initiatives, such as fortification of breads and cereals, deficiencies are not as common as they once were. But they still exist. Getting the right amounts of these nutrients, however, can still be a challenge.

This article will take a closer look at what iron does for you and how to get the right amount.

Why Do I Need Iron?

About two-thirds (65%) of the iron in our bodies is found in hemoglobin. Hemoglobin is a protein in red blood cells that holds onto oxygen molecules and delivers them to all organs and tissues. Even though you breathe in oxygen all the time, you need iron to help make sure it circulates through the body.

Iron deficiency can lead to anemia. This is a condition in which the blood doesn't have enough hemoglobin or healthy red blood cells. This means that oxygen does not reach your tissues as well as it should. There are many different causes of anemia, such as chronic disease, genetics, and deficiency of folic acid or vitamin B12. However, iron deficiency is the most common cause.

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Signs and Symptoms of a Deficiency

Not all iron deficiency leads to anemia. Around 20% of the iron in our bodies is not in use but stored for back up. So iron deficiency starts by depleting our stores of iron, and symptoms get worse as time goes on. Anemia occurs when the deficiency becomes severe enough to effect the production of hemoglobin. Symptoms of iron-deficiency anemia include:

  • Fatigue
  • Pale complexion
  • Weakness
  • Headache
  • Brittle, thin, concave nails
  • Poor cognitive function and slow reaction
  • Decreased immune function
  • Inflamed tongue

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How Much Iron Do I Need?

The amount of iron you need depends on your age, lifestage and gender. Here are the recommended dietary allowances (RDAs) from the Institute of Medicine:

 

Milligrams Per Day

Infants
 
7 to 12 months
11
Children
 
1 to 3 years
7
4 to 8 years
10
9 to 13 years
8
Males
 
14 to 18 years
11
19 and older
8
Females
 
14 to 18 years
15
19 to 50 years
18
50 and older
8
Pregnant women
27
Lactating women
 
Younger than 18 years
10
19 to 50 years
9

Pregnant women need the most iron to support the growth of a baby. While inside the womb, babies store enough iron for the first six months after birth.

Children and adolescents need enough iron to support their rapidly growing bodies.

Menstruating women in particular have increased iron needs because of regular blood loss, which results in iron loss. After menopause, women have the same iron needs as men.

Endurance athletes may also experience an increased need for iron due to the level of intense exercise, but this should be addressed with a physician.

People with certain diseases may also need to increase their iron intake. Many diseases can affect the gastrointestinal tract and cause poor iron absorption from food into the body. So some people may need to increase their iron intake.

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Food Sources

There are two food sources of iron:

  1. Meat or "heme"
  2. Plants or "non-heme"

Meat contains iron in a form that is most easily absorbed by your body. Your body can absorb non-heme iron but not as efficiently as heme iron.

The trick to absorbing as much iron as possible from non-heme sources is to eat them with a source of vitamin C. That does not mean taking a vitamin C supplement with your meals. It means, for example, squeezing lemon juice on your broccoli. The acid from the lemon juice helps to free up the iron so the body can absorb it.

Food

Amount (milligrams)

Clam, canned, drained, 3 ounces
24
Cream of wheat, 1 cup
10.3
Rice, white, long-grain, enriched, dry, 1 cup
9.7
Soybeans, cooked, boiled, 1 cup
8.8
Beans, white, canned, 1 cup
7.8
Lentils, cooked, boiled, 1 cup
6.6
Spinach cooked, boiled, drained, 1 cup
6.4
Beans, kidney, red, cooked, boiled, no salt, 1 cup
5.2
Potatoes, baked, skin, no salt, 1 skin
4.1
Turkey, meat only, cooked, 1 cup
2.5
Beef, round, lean, cooked, braised, 3 oz
2.4
Pork, fresh shoulder, lean, cooked, braised, 3 ounces
1.7

From the USDA National Nutrient Database for Standard Reference, Release 21

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When Is a Supplement Necessary?

Most people don't need a iron supplement unless they have an iron deficiency, anemia or other diseases that impair the function of the intestines.

Vegetarians and vegans who do not eat any meat as well as menstruating and pregnant women who think they may not be getting enough iron from their diet might consider a multivitamin that includes iron.

In most cases, it is best to speak with a physician before taking iron supplements.

Excessive iron intake can be toxic. Iron is not regularly excreted from the body in large amounts, so it can easily build up.

Increased iron intake is associated with the risk for increased free radicals, compounds in the blood that damage cells and tissues. Although more research is needed, too much iron may also be associated with heart disease as well.

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The Bottom Line

Be conscious of what you eat and appreciate the importance of the nutrients in your food. You don't have to eat like a lion to get enough iron. Just follow a healthy, balanced diet and chances are you'll get enough.

Iron deficiency is the most common nutrient deficiency. If you fall into one of the high-risk groups and think you may not be getting enough iron in your diet, call your physician. He or she can determine if your iron levels are safe. A registered dietician can teach you more about incorporating iron into your diet.

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Jenna B. Damareck. B.S. is a Dietetic Intern at Brigham and Women's Hospital. She received her B.S. In Dietetics and Nutrition from the University of Vermont

 

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