MEDICINE / HEART DISEASE : Study Links Iron Level, Risk of Coronaries
In a study that could lead to revised thinking about heart attacks and diet, Finnish researchers have linked excess amounts of iron in the body to an increased risk of heart attacks in middle-aged men.
The study, published in the September issue of the American Heart Assn.’s journal Circulation, is the first of the hundreds of statistical studies of heart disease risk factors to implicate iron.
According to the report, men with high amounts of iron in their bodies had twice as much risk of heart attacks as men with lower amounts of iron--after known heart disease risk factors, such as cholesterol levels and smoking, were taken into account.
Experts caution that the results need to be confirmed in other studies before recommendations can be made about the wisdom of lowering body iron.
In addition, they note that many people have iron concentrations substantially lower than those associated with an increased risk of heart attacks in the report.
“The study represents the first direct empirical evidence in support of . . . the conjecture that stored iron promotes (heart disease),” Dr. Jerome L. Sullivan of the Medical University of South Carolina in Charleston wrote in an editorial for the medical journal.
A decade ago, Sullivan theorized that women are protected against heart attacks until after menopause because of the large amounts of iron they lose each month in menstrual blood. Despite the exclusion of women from the Finnish study, Sullivan called the findings “especially relevant” to his theory.
The Finnish researchers, led by Dr. Jukka T. Salonen and Riitta Salonen said their findings raise the question of whether current dietary recommendations for iron intake should be revised for men and possibly for post-menopausal women.
Iron is a vital component of hemoglobin, the protein in blood that carries oxygen to the tissues. It is found in liver, meat and leafy green vegetables.
Current dietary recommendations are designed to ensure that the body has sufficient iron. Low concentrations of iron lead to the development of anemia, a decrease in the number of red blood cells. Anemia can cause weakness, pallor and fatigue.
Sullivan suggested that, based on the findings, the level of iron considered normal may need to be lowered.
No one is certain how excess iron might contribute to heart attacks. One theory, cited in the report, is that iron can catalyze biochemical reactions that can contribute to the progression of atherosclerosis, the buildup of fatty deposits in arteries. A heart attack occurs when a heart artery becomes blocked, causing heart muscle tissue to die.
The study of 1,931 men was conducted at the University of Kuopio in eastern Finland between 1984 and 1989. At the beginning of the study, the men were age 42, 48, 54 or 60 and were free of heart disease. They were followed for an average of three years. Fifty-one men suffered heart attacks.
The amount of iron in the body was determined indirectly by measuring the concentration of ferritin, an iron-storage protein. The normal concentration of ferritin is 20 micrograms or more per liter of blood. A ferritin value greater than 400 is considered excessive. The typical ferritin value of study participants was 166, which is higher than typical for adult men.
The study found that men with serum ferritin values of more than 200 micrograms per liter had 2.2 times the heart attack risk of men with lower ferritin values, after adjustment for other risk factors. A substantial number of heart attacks also occurred in men with the lower ferritin values, the report said.
