Everything You Need to Know About Iron

Oct 14, 2022 | BY First & Foremost Clinical Team

Everything You Need to Know About Iron

Iron is a trace mineral, and is absorbed in the small intestines. Iron is used in the production of new red blood cells, which carry oxygen from the lungs to all parts of the body and muscles. Iron is also required for the production of some hormones. As such, it is essential for the body to obtain from the diet for growth and development.

Heme iron vs. non-heme iron

In food, iron is provided in two different forms, heme and nonheme iron. Heme iron — think hemoglobin and myoglobin — is from animal sources, while nonheme iron is from primarily plant sources and iron-fortified food products. Heme iron is easily absorbed, with a 14-18% bioavailability in mixed diets. Meanwhile, nonheme iron has a bioavailability of 5-12%, and is better absorbed with a source of vitamin C, to help reduce from ferric iron to ferrous iron. [1] This is especially important for vegetarians, as their only food source of iron is nonheme (ferric) iron. [2] 

Within the body, iron is provided in various oxidation states, depending on the chemical environment. The only states that are stable in the body’s aqueous environment and in food are the ferric and ferrous forms. In supplements, ferrous iron is more bioavailable than ferric iron. [3] In First & Foremost supplements, we provide iron in the form of Iron-Bisglycinate Chelate, a ferrous iron that is chelated for optimal bioavailability with few gastrointestinal tract side effects. [4, 5]

What is the recommended daily allowance for iron?

Your specific daily iron needs depend on your age, sex, lifestage and diet. Iron needs vary dramatically over your lifespan, especially for women. That's why we include your full RDA of iron in the afternoon occasion, tailored to your specific stage of life. 

Recommended Dietary Allowance for Iron [1]
Birth-6 months
0.27 mg
0.27 mg
Infants 7-12 mo
11 mg
11 mg
1-3 years
7 mg
7 mg
4-8 years
10 mg
10 mg
9-13 years
8 mg
8 mg
14-18 years
11 mg
15 mg
27 mg
10 mg
19-50 years
8 mg
18 mg
27 mg
9 mg
51+ years
8 mg
8 mg

What is the best way to get iron?

Dietary iron is found naturally in many foods and is added to some fortified food products. Some people are more likely than other to have trouble getting enough iron: 

  • Teen girls and women with heavy periods
  • Pregnant women and teens
  • Infants
  • Frequent blood donors
  • People with cancer, gastrointestinal disorders, or heart failure
  • Vegetarians

The RDA amounts for iron are determined for non-vegetarians. The RDAs for vegetarians are approximately 1.8 times higher than for people who eat meat, because the nonheme iron in a vegetarian diet is poorly absorbed compared to the heme iron in meat, poultry, and seafood. [1]

Consuming plant source iron along with meat, poultry, seafood, and foods that contain vitamin C (citrus fruits, sweet peppers, tomatoes, broccoli) helps your body absorb the nonheme iron. 

If you’re taking an iron supplement, it’s best absorbed on an empty stomach, either 1-2 hours before or after meals due to potential interactions that affect bioavailability (discussed more below, and also why First & Foremost features iron in the afternoon occasion). If necessary to consume with a snack, choose one that won’t inhibit iron absorption, such as a fruit or vegetable that is low in polyphenols and phytic and oxalic acid, and avoid caffeine. 

How does iron react with other nutrients?

Iron has a few “friends” within the body. Iron and copper work together to make new red blood cells. Meanwhile, vitamin C is known to enhance the intestinal absorption of nonheme iron most likely by reducing iron ferric (Fe3+) state to a ferrous (Fe2+) state. It is commonly suggested that individuals, especially iron deficient ones, consume vitamin C-rich foods (offering at least 25 mg vitamin C) such as orange juice when ingesting nonheme iron-rich foods to promote the iron's absorption. First & Foremost provides our iron as Iron Bisglycinate Chelate, which is already in the ferrous state; therefore, vitamin C is not needed. 

Calcium from dietary sources (like milk) as well as from supplements (in doses of 300-800 mg or more) can decrease iron absorption. The inhibitory effect, however, appears to be of short duration, that iron status is not negatively impacted. [3] In addition, vitamin A, zinc and manganese also interact with nonheme iron and may negatively affect absorption [3]. 

Polyphenols or polyphenolic compounds, when consumed with a source of nonheme iron, can reduce iron absorption by over 50%. Coffee consumption, with or just after a meal, may reduce iron absorption by 40%. 

Phytic and oxalic acids also compete with iron absorption. Phytic acid is a substance found in plant seeds that also has antioxidant effects; oxalic acid is an organic compound found in many plants, including leafy greens, vegetables, fruits, cocoa, nuts and seeds. As these food sources have many benefits for the human body, it is best to consume them, but separately from your consumption of an iron supplement to avoid reduced iron absorption. [6]

Iron Interactions with Medicine

Consult your primary care provider if you are taking any of these medications or any other medications not listed.

  • Levodopa (Sinemet® and Stalevo®)
  • Levothyroxine (Levothroid®, Levoxyl®, Synthroid®, Tirosint®, and Unithroid®)
  • Proton Pump Inhibitors, such as lansoprazole (Prevacid®) and omeprazole (Prilosec®)

What happens when you’re deficient in iron?

Insufficient iron within the body is also called iron deficiency anemia (IDA). Without enough iron, your body cannot produce enough hemoglobin in red blood cells. Hemoglobin is what enables the cells to carry oxygen throughout the body. Symptoms of anemia include fatigue and shortness of breath. 

Other deficiency symptoms associated with IDA include gastrointestinal disturbances, weakness, impaired cognitive function, decreased immune function, and poor body temperature regulation. [3]

Can you take too much iron?

Unless you have a condition that alters your body’s ability to regulate iron stores — like hemochromatosis, which causes increased absorption of iron in your digestive tract — iron overconsumption from diet alone is not a concern. 

However, acute iron toxicity, which can be lethal, is typically an accidental iron overload, usually occurring with the excessive ingestion of iron-containing supplements. Therefore, regulations are put in place on labels warning consumers of accidental iron overdoses — it’s important to pay attention to the amount of iron-containing supplements you are taking each day.

First & Foremost provides your RDA amount, so you do not need additional iron supplements unless your physician prescribes it — you should always speak to your primary care doctor about all supplements you take. 

The FNB established Tolerable Upper Intake Levels for iron from food and supplements based on age, lifestyle, and associated gastrointestinal effects following supplemental intakes of iron salts. Physicians sometimes prescribe intakes higher than the UL for people with Iron Deficiency Anemia. 

Tolerable Upper Intake Levels (ULs) for Iron [1] are as follows.

Age Male Female (No change for pregnancy or lactation)

14-18 years

45 mg/ day

45 mg/ day

19+ years

45 mg/ day

45 mg/ day

How can I get the right amount of iron?

Following a healthy diet each day including a variety of vegetables, fruits, grains, dairy, and healthy oils will provide a robust array of essential nutrients, including iron. Seek out a variety of protein-rich foods like lean meats, beef, cashews, poultry, eggs, seafood, beans, peas, lentils, nuts and seeds. It’s also recommended to limit alcohol consumption, as well as foods and beverages with added sugars. 


  1. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
  2. Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010;91(5):1461S-1467S. doi:10.3945/ajcn.2010.28674F https://pubmed.ncbi.nlm.nih.gov/20200263/
  3. Advanced Nutrition and Human Metabolism; 7th edition; S. Gropper, J. Smith, T. Carr. Page 479-499.
  4. Abbas AM, Abdelbadee SA, Alanwar A, Mostafa S. Efficacy of ferrous bis-glycinate versus ferrous glycine sulfate in the treatment of iron deficiency anemia with pregnancy: a randomized double-blind clinical trial. J Matern Fetal Neonatal Med. 2019;32(24):4139-4145. doi:10.1080/14767058.2018.1482871 https://pubmed.ncbi.nlm.nih.gov/29843553/
  5. Bumrungpert A, Pavadhgul P, Piromsawasdi T, Mozafari MR. Efficacy and Safety of Ferrous Bisglycinate and Folinic Acid in the Control of Iron Deficiency in Pregnant Women: A Randomized, Controlled Trial. Nutrients. 2022;14(3):452. Published 2022 Jan 20. doi:10.3390/nu14030452 https://pubmed.ncbi.nlm.nih.gov/35276810/
  6. L ayrisse M, GarcĂ­a-Casal MN, Solano L, BarĂłn MA, Arguello F, Llovera D, RamĂ­rez J, Leets I, Tropper E. Iron bioavailability in humans from breakfasts enriched with iron bis-glycine chelate, phytates and polyphenols. J Nutr. 2000 Sep;130(9):2195-9. PubMed PMID: 10958812.
  7. Murray-Kolbe LE, Beard J. Iron. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:432-8.

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