Iron: 7 things you need to know before you take supplements

Before you buy iron supplements, read this.

by Kate S. Petersen
Originally Published: 

Iron is one of the most popular mineral supplements, accounting for a significant portion of the total mineral supplement market. According to one market-research site, the global mineral supplements market size was estimated at $10,753 million in 2019 and is expected to reach$11,193.4 million in 2020.

According to the National Institutes of Health, between 14 and 18 percent of Americans use some form of iron supplement on a regular basis. The reason why it is so popular is to do with the function of iron in our bodies — the mineral is critical to transporting oxygen in the blood. Too little iron results in anemia, a condition which may be so mild you may not even know you have it, or so severe it endangers your life.

But before you reach for the pill bottle, consider these seven factors which could help you decide whether iron supplements are right for you.

What is iron?

Iron is a mineral that is required for normal development, growth, and bodily processes. According to the National Institutes of Health (NIH), everyone needs iron, but the daily requirement depends on various factors, including one's age and sex.

The recommended daily dietary allowances ranges from .27 milligrams for an infant to 27 milligrams for a pregnant person. Men require less dietary iron than women require to have adequate levels in the blood — 8 milligrams per day as opposed to 18 milligrams, respectively.

Scanning electron microscope image of red blood cells

Steve Gschmeissner/Science Photo Library /Getty Images

What does iron do in the body?

Iron is used to create the proteins hemoglobin and myoglobin.

Red blood cells are rich in hemoglobin, and it these cells which transport critical oxygen throughout our bodies. But to accomplish this task, these cells need iron.

The reason why is to do with the hemoglobin protein itself, which is composed of four subunits. Each of these contain an iron center. The iron binds to oxygen molecules, securing them in place like a safety belt for the trip though our bloodstream. Bone marrow needs iron to produce hemoglobin — and some people just don't have enough of it.

Iron is also required to create hundreds of enzymes as well as to build certain connective tissues and hormones.

Why do you need iron?

Iron is crucial to producing the proteins that keep your muscles, organs, and other tissues working. Too little iron in the blood can result in anemia, a condition that affects almost one in every four people on Earth, according to the World Health Organization.

If you don’t ingest enough iron, your body tries to compensate for the lack by using up stores of iron reserved in bone marrow, muscles, and organs. But when these stores are used up, iron deficiency or anemia sets in. Red blood cells become less adept at moving oxygen though the body as hemoglobin abundance decreases and the cells shrink and distort in shape.

Six key symptoms of anemia are:

  • Fatigue
  • Problems concentrating and poor memory
  • Immune system disfunction
  • Cold hands and feet
  • Chest pain and heart palpitations
  • Fainting or weakness

According to the NIH, iron deficiency is common among people living in the United States. Poor diets tend to be the cause, but for some groups, regular loss of blood may be a more likely culprit. These can include frequent blood donors and menstruating women. Certain diseases and medications affect nutrient absorption, like cancer or ulcers, can also cause iron deficiency.

People with iron deficiency may be tired and have difficulty concentrating

Dowell / Getty Images

A 2018 study published in the World Journal of Psychiatry suggested iron plays a critical role in our mental health, too. This study compiled a list of nutrients essential for combating depression symptoms, including iron.

“If you suspect you are iron deficient or have iron deficiency anemia, your doctor can order a blood test," Paul Thomas, a nutrition scientist who works with the National Institutes of Health Office of Dietary Supplements, tells Inverse. "Hemoglobin concentrations lower than 12 g/dL in teens and adults suggest anemia."

“For people with iron deficiency or iron deficiency anemia, a doctor might recommend taking higher than recommended amounts of iron for a time to raise blood levels of this mineral to normal levels.”

What are the best ways to get iron from your diet?

OK. There is no two ways about this: The best food to eat to boost your iron intake without supplements is meat and seafood. There are two forms of iron found in food, heme and non-heme iron. Non-heme iron, which is found in plants and fortified foods, is more difficult for our bodies to absorb.

But vegetarians and vegans do not despair — iron-rich plant-based foods exist and can, if consumed in adequate quantity, provide enough dietary iron to ensure you don't become iron deficient.

The best foods to eat for iron are:

  • Meat, poultry, and seafood: The 2018 study highlights oysters and other seafood as particularly beneficial sources of iron. The NIH finds 3 ounces of oysters contain 44 percent of your daily intake.
  • Pulses: White beans, kidney beans, and lentils all contain a form of iron called non-heme iron. A cup of white beans stacks up to oysters when it comes to percent of daily intake.
  • Nuts and raisins: A serving of 18 cashew nuts will provide you with 11 percent of the daily recommended value, according to the NIH.
  • Fortified bread and cereal: Cereals like cornflakes are often fortified to provide 100 percent of the daily recommended intake in just one serving.
  • Chocolate: Dark chocolate contains a surprisingly high amount of iron. Three ounces can add 7 milligrams, or 39 percent, of your daily intake to your diet.
  • Spinach: Popeye was not wrong. But you will need to really enjoy this leafy green to get enough iron from it. A serving contains just 3 milligrams of iron, and like pulses, this iron is non-heme iron — which is harder to absorb.

You can help your body absorb non-heme iron more effectively if you also eat foods high in Vitamin C, such as berries, citrus fruits, tomatoes, broccoli, or sweet peppers.

Meat is a good source of the highly absorbable heme form of iron

The Picture Pantry / Getty Images

What are the best ways to supplement iron?

Nearly one in five Americans take iron supplements, and iron supplements are widely available in pill and capsule form. But be wary: Different supplements may contain different forms of iron, and many are combined with Vitamin C to help absorption.

The different forms of iron found in supplements include: ferrous sulfate heptahydrate, ferrous sulfate monohydrate, ferrous gluconate, and ferrous fumarate.

According to the Harvard T.H. Chan School of Public Health, iron supplements' labels tend to list two values for iron amounts. The higher number refers to the amount of iron in the supplement plus the molecules it is bound to — the fumarate in the ferrous fumarate, for example. The lower number on the bottle refers to the amount of elemental iron in the supplement. This is the value you want to pay attention to, because it represents the actual absorbable amount of iron in the supplement.

According to a 2005 paper published in the journal Clinical Toxicology, ferrous fumarate is 33 percent elemental iron by weight. Ferrous sulfate contains some 20 percent elemental iron by weight.

What is the best time to take iron supplements?

Iron supplements are usually taken with a meal, Thomas says.

Another word of caution: You have to be careful if you are taking other supplements alongside iron. The NIH recommends taking calcium and iron supplements at different times of the day, because calcium can negatively affect iron absorption. High doses of iron can also affect zinc absorption.

Iron supplements can also affect the efficacy of drugs used to treat cancer, hypothyroidism, and Parkinson’s disease. Likewise, certain medications, can inhibit iron absorption.

It is also possible to take too much iron. Going beyond your recommended daily amount of this mineral can cause fainting and gastrointestinal problems, including painful constipation. Extremely high doses of iron can even cause organ failure and death, but to do this, a person would need to overdose on hundreds or thousands of milligrams of iron in a single go.

Because of the potential for unwanted drug interactions or overdose, the NIH recommends discussing iron supplementation with a healthcare provider.

How long does it take iron supplements to work?

The good news is this: If you need more iron, then once you start taking supplements you will notice a difference.

“If you are iron deficient, and especially if you have iron-deficiency anemia, you will probably notice within days that the extra iron is beginning to make you feel better, have more energy, and improving your mental focus,” Thomas says.

Strategies for correcting iron deficiency can vary depending on the severity of the deficiency. Ask your healthcare provider for guidance on whether you need iron supplementation and how much you should take to combat any deficiency you might have.

Correction: An earlier version of this article incorrectly stated premenopausal women required 11 mg of iron per day. The correct figure is 18 mg or iron, according to the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine. We apologize for the error.

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