Are You Getting Too Much Iron?

Our bodies need iron; it’s a mineral that we must obtain in our diet because it is essential to human life. Because iron is crucial for the transport of oxygen and carbon dioxide by hemoglobin throughout the body, a deficiency of iron can cause anemia and fatigue. In addition to oxygen transport, iron is essential for the proper function of several enzymes and other proteins. Iron defiency can also cause compromised immunity, and in children can negatively affect brain development. But iron excess is also a problem, and the standard American diet makes excess a real concern.   

Plant Food vs. Animal Food Sources of Iron

There are two types of iron your diet can supply: Heme iron which is found in animal foods and nonheme iron which is found in plant foods. Many multivitamin supplements also contain nonheme iron. Heme iron from animal foods is more readily absorbed than nonheme iron from plant foods.  Heme iron is absorbed even when the body does not need the iron, however nonheme iron absorbtion is curtailed when the body’s iron stores are adequate.

A diet composed primarily of vegetables, beans, nuts, seeds, and fruit provides adequate iron for most people. Iron-rich plant foods include dark leafy greens, beans and lentils, and pumpkin seeds. Although plant food contains phytate which inhibits iron absorption, plant food also contains vitamin C and carotenoids which enhance iron absorption. Including colorful vegetables and fruits in meals containing iron-rich legumes and seeds enhances the body’s absorption of iron from those foods, counteracting the effects of phytate.¹

If you eat a standard American diet containing iron-rich red meats, pork and poultry, you are getting a lot of heme iron, which could lead to excess. Heme iron can accumulate in the body over time becoming problematic for older adults who have eaten meat-heavy diets their whole lives.

What are the Harms of Excess Iron?

The human body’s capability to store excess iron helped early humans to carry out iron’s vital processes in case of extreme conditions like blood loss or famine, but today, this survival mechanism may put us in danger. Iron accumulation over time can become detrimental later in life, largely because iron also drives chemical reactions that produce free radicals or reactive oxygen species (ROS).²

Excessive production of ROS causes progressive oxidative damage to cellular components such as DNA and proteins, and this damage contributes to chronic diseases and aging. High heme iron intake or high iron body stores have been linked to heart disease, type 2 diabetes, and the neurodegeneration associated with Alzheimer’s disease.^3-7

Oxidation of LDL cholesterol promotes the development of atherosclerotic plaque in our arteries. Because the brain uses more oxygen and produces more energy than any other organ, it is the most vulnerable to oxidative damage. Too much iron in the brain makes it even more vulnerable to oxidative stress.⁸ The pancreas is also especially susceptible to oxidative stress, because beta cells do not have strong antioxidant defenses.⁴

Heme iron from meat has unique dangers that are not shared with nonheme iron from excessive supplementation. In processed meat for example, nitrite from preservatives reacts with heme iron to produce N-nitroso compounds (or NOCs), which are carcinogenic.⁹ An excess of meat overall poses a risk, since the heme iron is packaged with additional harmful components: high animal protein intake elevates circulating insulin-like growth factor 1 (IGF-1), which is linked to increased cancer risk;^10-12 carnitine from meat is metabolized by gut bacteria into a pro-inflammatory compound called TMAO, which promotes heart disease;^{13, 14} carcinogenic heterocyclic amines and polycyclic aromatic hydrocarbons are formed in meats cooked at high temperatures.¹⁵ Many long-term studies have found an association between greater meat consumption and a greater risk of premature death.^16-18

When Supplemental Iron is Appropriate

To avoid the potential pro-oxidant effects of excess iron, supplements should only be taken in cases where there is a deficiency or an increased iron requirement, such as in pregnancy.

Not every woman should be taking iron during pregnancy, however. Both too much and too little can be a problem, and research supports the idea of personalized iron recommendations for pregnant women.¹⁹ During pregnancy, a woman’s iron needs increase; adequate iron stores are essential for early infant brain development and are needed to support the large increase in blood volume.²⁰ On the other hand, iron excess can lead to increased oxidative stress, elevated blood pressure, and low birthweight.^{19, 21-24}

I have developed a formula based on blood ferritin and/or hemoglobin levels to help pregnant women determine whether they should take supplemental iron, and how much.  --. Found Here (link)

Because of the differences in absorption between plant and animal sources of iron, menstruating females following plant-based diets, and women with heavy menstrual bleeding may be low in iron and require supplements. If you are uncertain about your need for extra iron, it is wise to monitor your iron levels with a ferritin blood test. Based on your blood test results, you may or may not need a supplemental source of iron.

1. Hunt JR. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. Am J Clin Nutr 2003, 78:633S-639S.
2. Brewer GJ. Risks of copper and iron toxicity during aging in humans. Chem Res Toxicol 2010, 23:319-326.
3. Hunnicutt J, He K, Xun P. Dietary iron intake and body iron stores are associated with risk of coronary heart disease in a meta-analysis of prospective cohort studies. J Nutr 2014, 144:359-366.
4. Bao W, Rong Y, Rong S, Liu L. Dietary iron intake, body iron stores, and the risk of type 2 diabetes: a systematic review and meta-analysis. BMC Med 2012, 10:119.
5. Zhao Z, Li S, Liu G, et al. Body iron stores and heme-iron intake in relation to risk of type 2 diabetes: a systematic review and meta-analysis. PLoS One 2012, 7:e41641.
6. Tuomainen TP, Punnonen K, Nyyssonen K, Salonen JT. Association between body iron stores and the risk of acute myocardial infarction in men. Circulation 1998, 97:1461-1466.
7. Brewer GJ. Iron and copper toxicity in diseases of aging, particularly atherosclerosis and Alzheimer's disease. Exp Biol Med 2007, 232:323-335.
8. Kidd PM. Neurodegeneration from mitochondrial insufficiency: nutrients, stem cells, growth factors, and prospects for brain rebuilding using integrative management. Altern Med Rev 2005, 10:268-293.
9. Herrmann SS, Granby K, Duedahl-Olesen L. Formation and mitigation of N-nitrosamines in nitrite preserved cooked sausages. Food Chem 2015, 174:516-526.
10. Levine ME, Suarez JA, Brandhorst S, et al. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metab 2014, 19:407-417.
11. Key TJ, Appleby PN, Reeves GK, Roddam AW. Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies. The lancet oncology 2010, 11:530-542.
12. Rowlands MA, Gunnell D, Harris R, et al. Circulating insulin-like growth factor peptides and prostate cancer risk: a systematic review and meta-analysis. Int J Cancer 2009, 124:2416-2429.
13. Koeth RA, Wang Z, Levison BS, et al. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med 2013.
14. Tang WH, Wang Z, Levison BS, et al. Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk. N Engl J Med 2013, 368:1575-1584.
15. National Cancer Institute. Chemicals in Meat Cooked at High Temperatures and Cancer Risk. In [http://www.cancer.gov/cancertopics/factsheet/Risk/cooked-meats]
16. Wang X, Lin X, Ouyang YY, et al. Red and processed meat consumption and mortality: dose-response meta-analysis of prospective cohort studies. Public Health Nutr 2016, 19:893-905.
17. Pan A, Sun Q, Bernstein AM, et al. Red Meat Consumption and Mortality: Results From 2 Prospective Cohort Studies. Arch Intern Med 2012.
18. Sinha R, Cross AJ, Graubard BI, et al. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med 2009, 169:562-571.
19. Pregnancy: Does every pregnant woman need daily iron supplements, and what are the possible adverse effects? PubMed Health 2010.
20. Dietary Supplement Fact Sheet: Iron. In Office of Dietary Supplements National Institutes of Health, [http://ods.od.nih.gov/factsheets/iron]
21. Scholl TO. Iron status during pregnancy: setting the stage for mother and infant. Am J Clin Nutr 2005, 81:1218S-1222S.
22. Pena-Rosas JP, De-Regil LM, Dowswell T, Viteri FE. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev 2012, 12:CD004736.
23. Song QY, Luo WP, Zhang CX. High serum iron level is associated with an increased risk of hypertensive disorders during pregnancy: a meta-analysis of observational studies. Nutr Res 2015, 35:1060-1069.
24. Pena-Rosas JP, De-Regil LM, Garcia-Casal MN, Dowswell T. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev 2015:CD004736.