Iron

Iron is the fourth most common element on earth and is a critical component of all living organisms

Close to 75% of body iron is in the hemoglobin of circulating red cells and in the muscle protein myoglobin. Both proteins act as oxygen transport and storage molecules,  shuttling oxygen throughput the body to maintain normal function.

Iron levels in the body are tightly regulated. Significant consequence arise both in the setting of iron deficiency and iron overload.

Iron deficiency reduces physical activity and increase susceptibility to infection, while iron overload increases the production of free radicals that contribute to oxidative stress and chronic inflammation.

Iron, like many essential vitamins and minerals have an optimal range that promotes overall well being.

Musculoskeletal Benefits of Iron

1. Iron May Boost Bone Health

Iron plays a key role in collagen synthesis. Approximately 90% of bone protein is collagen.  Iron modifies sub units of collagen, allowing them to bond together and form their characteristic  triple helix structure. This unique architecture helps make bone strong.

Additionally, enzymes that require iron catalyze chemical reactions that activate vitamin D. Vitamin D stimulates calcium absorption from the gut for storage in bone and constrains excessive inflammation in bone, both of which are essential for bone well being.

Finally, iron is critical for normal functioning hemoglobin. Hemoglobin carries oxygen to cells for use in energy production. Iron deficiency may lead to insufficient oxygen, literally suffocating bone cells and promoting bone resorption. Excessive bone resorption increases the risk for osteoporosis and fracture.

Researchers at the University of Arizona examined the association of dietary iron and bone mineral density. The investigators concluded that greater bone mineral density was associated with greater calcium intake in the range of 800 mg-1200 mg/day. Underscoring, iron’s positive benefit only within a certain range of daily consumption.(Harris MM et al. Dietary iron is associated with bone mineral density in healthy postmenopausal women. J Nutr. 2003 Nov;133(11):3598-602.)

2. Iron Promotes Muscle Health

Muscle has a spectacularly high energy demand compared to other body tissue,  even your brain. Muscle meets its energy needs through three mechanisms: the phosphocreatine pathway, anaerobic complex sugar breakdown (glycolysis), and aerobic oxidative phosphorylation(breakdown of sugar and fat for fuel in the setting of ample oxygen). The particular energy pathway used depends on the amount of oxygen available and the duration/intensity of the activity.

Iron is fundamental to both oxygen storage (myoglobin) and optimal activity of mitochondria, the cell’s main power generator. Iron deficiency compromises muscle’s ability to store oxygen and utilize aerobic oxidative phosphorylation, the cell’s most efficient energy pathway.

This has a dramatic negative effect on muscle well being and results in a decrease in overall physical work capacity, decreased aerobic capacity, decreased endurance, loss of muscle mass, and mitochondria dysfunction.

Researchers at Amsterdam University examined the association of dietary iron and sarcopenia(extreme muscle loss and weakness). The investigators found dietary iron intake was associated with better physical performance in older adults.(van Dronkelaar C et al. Minerals and Sarcopenia; The Role of Calcium, Iron, Magnesium, Phosphorus, Potassium, Selenium, Sodium, and Zinc on Muscle Mass, Muscle Strength, and Physical Performance in Older Adults: A Systematic Review. J Am Med Dir Assoc. 2018 Jan;19(1):6-11)

Other Health Benefits 

There are other conditions that iron may assist, although more research is needed and for some conditions results to date have been mixed. Those include:

  • Supports heart health
  • Reducing the risk of anemia, especially due to menstrual bleeding
  • May reduce feelings of fatigue
  • May reduce symptoms of depression
  • May improve symptoms of restless leg syndrome
  • May increasing energy levels

Rich Sources of Iron

Iron from animal and fish sources is frequently attached to heme proteins (think hemoglobin) and referred to as heme iron. Heme iron tends to be more readily absorbed by our digestive tract compared to non heme iron. The richest sources of heme iron in the diet include lean meat and seafood.

Non heme iron is derived form plant foods. Dietary sources of non heme iron include nuts, beans, vegetables, and fortified grain products.

Recommended Dietary Allowance (RDA)

The Food and Nutrition Board has developed a table of recommended dietary allowances (RDAs) of iron, based on age and gender: 

  • Infants under six months: 0.27 mg
  • Babies under a year: 11 mg
  • Children under three years: 7 mg
  • Children between three and eight years: 10 mg
  • Tweens between nine and 13: 8 mg
  • Males between 14 and 18: 11 mg
  • Females between 14 and 18: 15 mg
  • Adult males: 8 mg
  • Adult females up to 50 years: 18 mg
  • Adult females over 50 years: 8 mg
  • Pregnant people: 27 mg
  • Lactating people up to 18 years: 10 mg
  • Lactating people over 18 years: 9 mg

It is estimated that eight million women who are over 14 suffer from anemia or iron deficiency. This can cause significant risk to a baby during pregnancy, so it is especially important that women of childbearing age monitor iron levels.

Precautions

Iron from natural foods is generally well tolerated. RDA amounts can be obtained from a balanced, healthful diet. 

The FNB has published an upper limit value of 45 mg /day. 

Excessive intake of supplemental iron may cause gastrointestinal upset, such as nausea and vomiting.

Any consideration a supplementation should be discussed with a qualified health professional familiar with your unique medical history.

References

Toxqui L, Vaquero MP. Chronic Iron Deficiency as an Emerging Risk Factor for Osteoporosis: A Hypothesis. Nutrients. 2015;7(4):2324-2344. doi:10.3390/nu7042324.

Stugiewicz M et al. The influence of iron deficiency on the functioning of skeletal muscles: experimental evidence and clinical implications. 2016 Jul;18(7):762-73.

Ohira Y, Hegenauer J, Strause L, Chen CS, Saltman P, Beinert H. MitochondrialNADH dehydrogenase in iron-deficient and iron-repleted rat muscle: an EPR and work performance study. Br J Haematol 1982;52:623–630.

Thompson CH, Green YS, Ledingham JG, Radda GK, Rajagopalan B. The effect of iron deficiency on skeletal muscle metabolism of the rat. Acta Physiol Scand1993;147:85–90.

Zick M, Rabl R, Reichert AS. Cristae formation—linking ultrastructure and function of mitochondria. Biochim Biophys Acta 2009;1793:5–19.

Hagler L, Askew EW, Neville JR, Mellick PW, Coppes RI Jr, Lowder JF Jr. Influence of dietary iron deficiency on hemoglobin, myoglobin, their respective reductases, and skeletal muscle mitochondrial respiration. Am J Clin Nutr1981;34:2169–2177.

Lee, K.S.; Jang, J.S.; Lee, D.R.; Kim, Y.H.; Nam, G.E.; Han, B.D.; Do Han, K.; Cho, K.H.; Kim, S.M.; Choi, Y.S.; et al. Serum ferritin levels are positively associated with bone mineral density in elderly Korean men: The 2008–2010 Korea National Health and Nutrition Examination Surveys. J. Bone Miner. Metab. 2014, 32, 683–690.

Buyukbese, M.A.; Cetinus, E.; Cetinkaya, A.; Aras, S. Ferritin levels in postmenopausal women do not seem to play a significant role in osteoporosis. South. Med. J. 2005, 98, 845.

Medeiros, D.M.; Stoecker, B.; Plattner, A.; Jennings, D.; Haub, M. Iron deficiency negatively affects vertebrae and femurs of rats independently of energy intake and body weight. J. Nutr. 2004, 134, 3061–3067.

Katsumata, S.; Katsumata-Tsuboi, R.; Uehara, M.; Suzuki, K. Severe iron deficiency decreases both bone formation and bone resorption in rats. J. Nutr. 2009, 139, 238–243.

Harris, M.M.; Houtkooper, L.B.; Stanford, V.A.; Parkhill, C.; Weber, J.L.; Flint-Wagner, H.; Weiss, L.; Going, S.B.; Lohman, T.G. Dietary iron is associated with bone mineral density in healthy postmenopausal women. J. Nutr. 2003, 133, 3598–3602.

https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/

http://www.umm.edu/health/medical/ency/articles/iron-in-diet

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenium, Nickel, Silicon, Vanadium, and Zinc. Washington, DC; National Academies Press; 2001. PMID: 25057538 www.ncbi.nlm.nih.gov/pubmed/25057538.

Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 218.

Parks EP, Maqbool A, Shaikhkhalil A, Groleau V, Dougherty KA, Stallings VA. Nutritional requirements. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 44.