Iron is an essential nutrient and one that is vital for the oxygen-carrying capacity of red blood cells. It is not only important for blood formation, but it is also necessary for optimal bone health. Iron helps convert vitamin D into its active form and therefore is involved in calcium absorption. Iron is also important for normal osteoblastic activity and the formation of strong collagen fibers, the foundation of bone.
Low hemoglobin and iron-deficiency anemia can result from inadequate iron intake; poor absorption due to celiac disease and other GI disorders; or chronic bleeding from excessive menses, ulcers, bleeding hemorrhoids, or cancer. Without iron, or even in low iron anemic states, bone mineral density suffers and fracture risk increases.
On the other end of the spectrum, iron overload can be just as detrimental to a person's health. The two most common causes of iron overload are excessive iron intake (usually from over-supplementing) and hemochromotosis (a hereditary condition where the body absorbs too much iron). Excess iron can deposit within the tissues and organs of the body leading to liver disease, diabetes, heart disease, arthritis, and other maladies. It is also toxic to bone health.
We have known for years that excessive iron loads can have damaging effects to the bone metabolism of animals. But there were no clinical studies to show this effect in humans. Now, for the first time, we have clinical evidence that excessive iron levels can reduce bone density and bone strength in women. In a study by Kim et al. (2013) published in Osteoporosis International, women over the age of 45 with elevated serum ferritin (a blood test for iron levels) were associated with lower bone mineral density and greater risk for fracture. While iron is important for osteoblast function, excessive amounts can be toxic to osteoblasts, reducing their ability to form bone.
It is not unusual for me to see patients with osteoporosis who are consuming excessive amounts of iron. Red meat, liver, fortified cereals, and molasses are all sources high in iron. Take this into consideration if your supplements include iron. Also, while menstruating women may need to supplement with iron to avoid becoming anemic, most postmenopausal women should avoid iron-containing vitamin/mineral supplements.
To avoid inadvertently ingesting too little or too much iron, make sure you are reading labels.
Kim B.J., S.H. Lee, J.M. Koh, G.S. Kim. 2013. The association between higher serum ferritin level and lower bone mineral density is prominent in women ≥45 years of age (KNHANES 2008-2010). Osteoporosis International 24(10):2627-37.