Iron plays an integral role in such processes as DNA synthesis and adenosine triphosphate (ATP) production, which provides energy for cells. Therefore, it’s important to maintain iron homeostasis, or balance.
Iron in excess amounts may contribute to a host of diseases, including diabetes, diabetic retinopathy, age-related macular degeneration (AMD), glaucoma, Parkinson’s disease and even heart disease. Why? Because when we have excess iron, it may cause free radicals, which results in breakdown of DNA and tissues, the very things that iron homeostasis tends to preserve.
There are two main types of ingestible iron: heme and nonheme iron. Dietary heme iron primarily comes from red meat and is easily absorbed into the gut. Dietary nonheme iron comes from other sources, such as plants and fortified foods, which are much more difficult to absorb.
By focusing on the latter source of dietary iron, you may maintain homeostasis, since the gut tends to absorb 1 to 2 mg of iron but also excretes 1 to 2 mg of iron through urine, feces and perspiration.
Not only does it matter what type of iron we consume but also the population ingesting it. Age and gender are critical factors. Women of reproductive age, patients who are anemic and children may require more iron.
However, iron overload is more likely to occur in men and postmenopausal women because they cannot rid the body of excess iron easily, other than through blood donation.
Impact on diabetes
In a meta-analysis of 16 studies and 45,000 patients, results showed that both dietary heme iron and elevated iron storage (ferritin) may increase the risk of type 2 diabetes. When ferritin levels were high, the risk of diabetes increased 66 to 129 percent.
With heme iron, the group with the highest levels had a 39 percent increased risk of developing diabetes. Ferritin was measured with a simple blood test.
Diabetic retinopathy is a complication of diabetes when glucose levels are not tightly controlled. Iron excess and its free radicals can have detrimental effects on the retina, or the back of the eye, resulting in retinal tissue damage.
How does iron relate to uncontrolled glucose levels? In vitro studies suggest that high glucose levels may perpetuate the breakdown of heme particles and subsequently raise the level of iron in the eye.
Those with diabetic retinopathy tend to have iron levels that are 150 percent greater than those without. Diets that are plant-based and nutrient-dense are some of the most effective ways to control glucose levels and avoid diabetic retinopathy.
Age-related macular degeneration (AMD)
Excessive dietary iron intake also may increase the risk of AMD, according to the Melbourne Collaborative Cohort Study. AMD is the number one cause of blindness for people 65 and older. People who consumed the most iron from red meat increased their risk of early AMD by 47 percent.
I am frequently asked if unprocessed red meat is better than processed meat. This study showed that both types of red meat were associated with an increased risk.
In the Japan Collaborative Cohort study, men who had the highest amount of dietary iron were at a 43 percent increased risk of stroke death, compared to those who ate the least.
Overall risk of cardiovascular disease death, which includes both heart disease and stroke, was increased by 27 percent in men who consumed the most dietary iron.
In conclusion, we should focus on avoiding heme iron, especially for men and postmenopausal women. Too much iron creates a plethora of free radicals that damage the body.
Significantly decreasing red meat consumption and donating blood quarterly, assuming that one is not anemic, may be the most effective strategies for not falling into the trap of iron overload.