How common are high iron levels?
It is important to remember that you can have high iron or ferritin levels without it being unhealthy. Unless you have extremely high levels of iron (more than 9 mg per pound of body weight), you are not in danger of iron poisoning.
Dangerously high levels of iron can occur as the result of multiple blood transfusions, iron injections, lead poisoning, liver disease, or kidney disease. It can also be due to the genetic disease hemochromatosis, which causes a person's body to absorb too much iron.12 Other than people with hemochromatosis, dangerously high iron levels are rarely seen in adults. The most common occurrences are in children who accidentally swallow a parent's iron supplements. People with high levels of iron usually show no signs of their illness until their iron stores have reached a level of about 20 g. The most common symptom is pain as iron accumulates in your body, usually in your joints. Other symptoms include fatigue and lack of energy, abdominal pain, loss of sex drive, and heart problems. Some people, however, have no symptoms.12
Studies looking at iron levels and heart disease refer to higher than normal levels, usually defined as blood levels of ferritin greater than 200 micrograms per liter of blood (µg/L) for women and 300 µg/L for men. Iron levels regularly spike after a meal or after taking iron supplements. Ferritin, just like C-reactive protein, is an inflammatory marker, so an elevated ferritin level may be an indicator that the body is dealing with some sort of injury. It is not clear how common excess iron is in the population as a whole. Several studies in women suggest that 10% to 12% of healthy postmenopausal women have elevated ferritin levels. 6, 13, 14 Iron stores are related to a person's weight. In one large study, overweight and obese women were more than 3 to 5 times as likely to have elevated ferritin levels than women of normal weight.6
Do high iron levels affect my risk of heart disease?
Excess iron may interact with free radicals—highly reactive molecules that can damage cells—causing inflammation and the buildup of fatty plaques in your arteries.9 It may also increase your risk of developing type 2 diabetes or the metabolic syndrome—a group of risk factors including a large waistline and higher than normal blood pressure or blood sugar levels.15, 16 However, it is not clear whether high iron levels increase your risk of heart disease; some studies have shown an association between high iron levels and heart disease while others have not.
In a Canadian study of nearly 10,000 men and women, those who had the highest iron levels (175 ?g/dL or more) had an increased risk of dying from a heart attack. The risk increase was greater for women than for men.17 In a study of more than 12,000 women, those carrying the genetic defect causing hemochromatosis were 2 to 3 times more likely to die from heart disease than women with normal iron absorption.18
Does donating blood reduce my risk of heart disease?
Studies conducted mostly in men have found that lowering iron levels in your body by donating blood may lower the risk of developing heart disease or experiencing a heart attack.19, 20 Men who donated blood were found to have iron levels similar to those of premenopausal women. In a study of more than 3,800 people (almost half were women), blood donation was associated with a reduced risk of heart attack in men but not in women.21 One explanation for the gender difference is that the study didn't give separate results for premenopausal and postmenopausal women; according to the iron hypothesis, only postmenopausal women would see the benefits. More studies are needed before any definite conclusions can be reached about the effects of blood donation on heart disease risk.