Iron Info and FAQs: What You Should Know

Nutrition 101 Iron FAQs

I have gotten some really good questions about nutrition lately from my friends at the Get Back UP Today Team. Read about the great work they do here! Many of the questions overlapped into similar themes and so I have broken the answers into groups of similar topics. The first set of questions and answers involve iron and iron status. I thought I would share the answers to their questions here in this lengthy iron info post, so I hope you find the information helpful.


What does iron do in the body?

Iron plays several of important roles in the body:

  • It is needed to make new red blood cells
  • Iron is part of hemoglobin, a protein in the blood that carries oxygen from the lungs to all of the cells in the body
  • It plays a role in the immune system
  • Iron is involved energy producing reactions
  • It is involved in DNA synthesis


Iron Info: What are the signs and symptoms of iron deficiency?

Symptoms of iron deficiency include:

  • Fatigue or fatigue with exertion
  • Dizziness
  • Headaches
  • Shortness of breath
  • Frequent infections
  • Irritability
  • Pale appearance

Who is at risk for iron deficiency?

There are three general categories to explain iron deficiency. Individuals who fit into more than one category are at increased risk of iron deficiency.

Individuals with Increased Physiological Demand:

  • Young children, adolescents, pregnant women in periods of growth
  • Endurance athletes who engage in intense physical training

Individuals with Increased Iron Losses:

  • Endurance athletes who may damage red blood cells during training, may experience heavy sweat loss of iron or increased loss through foot strike hemolysis
  • Females of child bearing age who experience blood loss with menstruation

Individuals with Inadequate Iron Intake Due to Diet or Poor Absorption:

  • Individuals with intestinal disorders that affect nutrient absorption such as celiac disease or Crohn’s disease may be at risk. Surgical removal of parts of the GI tract where nutrients are absorbed can also lead to nutrient deficiencies including iron.
  • The Elderly
  • Vegetarians (including vegans) tend to have lower iron stores than meat eaters and are potentially at risk because of the poor iron availability or non-heme iron.

*Individuals with chronic health conditions such as cancer, kidney, heart failure or liver disease may be at risk for Anemia of Chronic Disease, a multifactorial condition that may not be related to an absolute deficiency and may not be appropriate for iron supplementation.*


Iron Info: How can I get iron from my diet?

Dietary sources of iron come in two forms: heme and non-heme iron. Heme iron is found in animal products, such as red meats, fish, and poultry. Non-heme iron is found in plant foods such as lentils and beans, as well as in iron-enriched and iron-fortified foods. Non-heme iron is less efficiently absorbed into the body than heme iron.

Good sources of heme iron:

  • Lean cuts of meat (venison, beef, lamb, pork, skinless dark meat chicken or turkey)
  • Oysters, clams, mussels, octopus
  • Tuna (dark flesh), mackerel


Good sources of non-heme Iron:

  • Beans (white, kidney, navy, pinto, black, adzuki, garbanzo, edamame, lima beans, black eyed peas)
  • Tofu, Tempeh, Seitan
  • Dried Fruits (prunes, raisins, apricots)
  • Cooked Greens (spinach, swiss chard, beet greens, collards, turnip greens)
  • Whole Grains (amaranth, bulgur, quinoa, teff, oats, buckwheat groats, spelt)
  • Flours (rye flour, chickpea flour, amaranth flour, teff flour)
  • Iron enriched or fortified breads, cereals or grains (Cream of Wheat, Cream of Rice, Cheerios, Whole Grain Total, Raisin Bran, Frosted Shredded Wheat, Fiber One Honey Clusters, enriched corn grits, fortified oatmeal, enriched macaroni or pasta products)
  • Vegetables (canned tomato products, asparagus, baked potato with skin, canned pumpkin, canned beets)
  • Nuts & Seeds (cashews, almonds, hazelnuts, macadamia, pistachios, walnuts, pecans chia seeds, toasted sunflower seeds, dried sesame seeds, pumpkin seeds)
  • Other (Blackstrap molasses, fresh parsley, dried spirulina, toasted wheat germ, dark chocolate, dried thyme)


How much iron do I need each day?

Recommended Dietary Allowance (RDA) is the average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals.

The recommended daily iron intake is:

  • Males 19+ years of age: 8 mg per day
  • Females 19-50 years of age: 18 mg per day until menopause
  • Females 51+ years of age: 8 mg per day
  • Pregnant females: 27 mg per day
  • Lactating females <18 years of age: 10 mg per day
  • Lactating females 19+ years of age: 9 mg per day

*The RDAs for vegetarians are 1.8 times higher than for people who eat meat. This is based on the fact that non-heme (plant) sources of iron are less bioavailable than heme (animal) sources of iron.

*Endurance athletes involved in regular intensive training can quickly deplete iron stores and be at risk for developing iron deficiency anemia. These athletes, and in particular female adolescent athletes have higher iron requirements than non-athletes. Because of this, iron requirements for endurance athletes—especially distance runners—are increased by 30-70% of non-athletes.


What impacts absorption of iron?

The iron absorbed from food or supplements is driven to some degree by the amount of body stores of iron (ferritin). Iron absorption is variable, but in general between 10% and 35% of the iron in any given food is actually absorbed. That said, there are a number of things that can interfere with the absorption of iron, including:

  • Phytates found in foods like grains and legumes.  Phytates are a component of plant foods capable of forming insoluble complexes with calcium, zinc, iron, and other nutrients and interfering with their absorption by the body.
  • Polyphenolic tannins found in coffee and tea.
  • Calcium and Zinc. Consuming calcium rich foods or beverages, calcium supplements or zinc supplements with iron rich meals or supplements can interfere with iron absorption.
  • Oxalates found in foods like dark green leafy vegetables, berries, some nuts, beans and grains.
  • Antacids interfere with iron absorption


Is there anything I can do to improve iron absorption?

Yes. There are a number of things you can to improve the bioavailability and absorption of iron in your food:

  • Consume a good source of vitamin C with iron rich foods.
  • The oxalate content of some foods is diminished with cooking. Read more about oxalate content of foods here.
  • The effects of phytates in grains and beans nuts and seeds can be diminished somewhat with soaking, sprouting and/or fermenting.
  • Consuming heme and nonheme iron foods together can improve iron absorption.
  • Avoid coffee, tea and milk with iron rich meals or supplements.
  • Be aware of timing if you take calcium supplements, zinc supplements, antacids or other substances that impact iron absorption. Take two hours apart.
  • Use cast iron cookware.


Can I get too much?

Iron toxicity in an otherwise healthy individual is rare and very unlikely from food sources. However, overloading the body with iron can be dangerous because excess iron accumulation can damage your liver and cause other complications.

The Tolerable Upper Limit is the highest level of nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As intake increases above the TUL, the risk of adverse effects increases. The TUL for iron is:

  • Males and Females 19+ years of age is 45 mg/day
  • Pregnant females 19+ years of age: 45 mg/day
  • Lactating Females: 45 mg/day


Iron Info: Supplements

Should I take an iron supplement?

Iron supplementation is indicated when diet alone cannot restore deficient iron levels to normal within an acceptable timeframe. Iron supplementation may be contraindicated with some health conditions and iron supplements interact with numerous medications. As a result, you should not take an iron supplement unless recommended by your physician. It would be best to determine your iron status as well as the cause for a possible iron deficiency.

If you feel you may be deficient, have your blood tested. Common tests for iron status include:

  • Hemoglobin: measures the level of hemoglobin, the iron containing oxygen transportation protein in red blood cells. Normal range for men: 14.6-17.5 g/dL. Normal range for women: 12.1-15.6 g/dL
  • Hematocrit: determines the percentage of red blood cells in the blood. Normal range for men: 41-51%. Normal range for women: 34-45%.
  • Ferritin: The amount of ferritin in the blood shows how much iron your body is storing. If the stores are low you may be at greater risk for deficiency. Normal range for men: 30-320 ng/dL. Normal range for women: 12-150 ng/dL.


What are the various forms of iron supplements? What is the difference? Which is best?

There are multiple iron formulations e.g., amino acid chelates, carbonyl iron, polysaccharide-iron complex, extended release products, enteric coated products etc. But most provide non-heme iron. Heme iron polypeptide is considered a medical food rather than a supplement, and therefore requires medical supervision and a prescription. Most iron supplements vary in the amount of elemental iron they contain as well as the physical form they come in. They also vary in their side effects. GI side effects including diarrhea, constipation, and abdominal discomfort are one of the biggest deterrents to iron supplements.

There is no one “best” iron supplement to choose, since people and their iron needs also vary. Some things to consider include:

  • Extended release and/or enteric-coated iron may come with less side effects but may not completely dissolve and be absorbed before passing through the duodenum (where iron is absorbed) meaning less than optimum absorption.
  • Syrup or elixr preparations may contain ingredients to make them more palatable that impact their absorbability (fruit juices with high polyphenol content) Others contain ingredients that enhance absorption but may contribute to side effects. (sorbitol).


The “best” iron supplement will be an individualized choice and is the one that you can tolerate, improves iron your stores and/or reverses anemia.


Are more expensive brands better than cheaper alternatives? How do you know if a brand is good? Is there a resource for knowing which supplement brands are more recommended than others?

The cost of a supplement does not necessarily correlate with the quality. Independent third party testing of supplements at present is voluntary at present but I encourage everyone to refer to USP Verified Dietary Supplements or ConsumerLab to research supplement claims and or ingredients prior to use


I’m a vegetarian…what options do I have for gel-caps? Are most gel-caps vegetarian friendly?

Gel caps, as with all gelatin products, are derived from animal collagen. Vegetarian alternatives to gelatin based capsules are often made with cellulose, which will be indicated on the label.


How do I know if my body is absorbing iron?

If you are absorbing adequate iron, your symptoms should begin to improve. Blood tests can confirm improved iron status.


Takeaway message about iron:

It is possible to meet iron needs with diet whether you eat meat or are a vegetarian, but variety is the spice of life! Focus on eating a variety of iron rich foods everyday, and consult with your doctor if you feel as if you may be iron deficient. In addition, consult with your doctor, pharmacist or registered dietitian to help select the iron supplement best suited for your needs.



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  • Clark, N. Nancy Clark’s Sports Nutrition Guidebook, Fifth Edition. Human Kinetics, Champaign Il. 2014.
  • Gropper S, Smith J, Groff J. Advanced Nutrition and Human Metabolism, Fifth Edition. Wadsworth, Belmont CA. 2009.
  • National Institute of Health Office of Dietary Supplements. Iron: Dietary Supplement Fact Sheet.
  • Pronsky Z. Food Medication Interactions, 15th Edition. Birchrunville, PA 2008.
  • Rodriguez NR, DiMarco NM, Langley S. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the American Dietetic Association. 2009;109:509-27.
  • Vegetarian Nutrition Dietetic Practice Group, Academy of Nutrition and Dietetics. RD Resources for Consumers: Iron in Vegetarian Diets.
  • US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 27 (revised). Version Current: May 2015.
  • Zariwala MG, et al. Comparison Study of Oral Iron Preparations Using Human Intestinal ModelScientilla Pharmaceutica. 2013;81:1123-1139.


I am a Registered Dietitian Nutritionist living in Greensboro, North Carolina. I help people overcome nutrition obstacles and help them meet their nutrition and wellness goals.

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Hi, I’m Mona. I have been living with Relapsing Remitting Multiple Sclerosis (RRMS) for over ten years. As a registered dietitian nutritionist (RDN) I help others with MS to navigate the nutrition superhighway and make sustainable progress toward their unique wellness goals.

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