Iron overdose, Toxic effects of excess intake
Large doses of iron can cause deterioration of the gut lining, vomiting and diarrhea, liver damage, abdominal and joint pain, weight loss, fatigue, excess thirst and hunger. Immediate medical attention is necessary. It is important to keep iron supplements out of reach of children as doses as low as 3 g can cause death in children and every year there are a few cases of fatal poisoning.
Constipation is the most common side effect associated with iron supplements, although diarrhea can also occur. Side effects can be reduced if the iron supplements are taken in small divided doses with meals. Doses of 25 to 75 mg per day have been taken without side effects, although those with iron overload or kidney disorders might develop symptoms at lower doses, In most people iron absorption becomes less efficient as blood levels reach optimum and dietary excesses pass out in feces. Accumulation is possible; however, as excesses are not easily excreted once absorbed. Heme iron absorption may be less affected by the iron status of the individual than nonheme iron absorption, making it easier to overdose on diets high in animal foods.
Hemochromatosis is the term used to refer to iron overload disorders. It may be hereditary, due to excessive intake or due to chronic alcoholism. Hereditary hemochromatosis is an inherited condition of defective iron metabolism in which the body lacks the ability to limit iron absorption from the diet and stores greater than normal amounts. This iron is stored in the liver, heart, pancreas, skin and other organs and can generate free radicals which cause serious damage. In the US, the disorder is known to affect 1.5 million people. Many experts believe hemochromatosis is under-diagnosed and may occur in as many as one in 200 people. The effects are usually seen in men over 50 years of age as the disease can often go undetected until mid-life when iron levels reach five to 50 times normal amounts. The initial symptoms are fatigue, achy joints and weakness. Other symptoms include heart disorders, joint pain, cirrhosis of the liver, diabetes and excessive skin pigmentation.
Researchers involved in the Framingham Heart Study have found high iron intakes to be common in elderly people with around 91 per cent of study participants having intakes above the recommended dietary levels. Only one per cent of the people had iron deficiency anemia.
Iron accumulation can contribute to a variety of disorders such as cancer, heart disease, arthritis, osteoporosis, diabetes and psychiatric illnesses. The liver is particularly susceptible to the toxic effects of iron as it is the major site of iron storage in the body. Treatment for hemochromatosis involves repeated bleeding (phlebotomy) to remove excess iron. Therapy for hemochromatosis may also involve a diet rich in bread and cereals, and fruit and vegetables. The amount of meat and alcohol should be limited. Tea or coffee may be drunk with meals as this will reduce iron absorption. Foods and supplements rich in vitamin C, such as fruit and fruit juice, should be avoided with meals.
Early therapy is very important to prevent complications and increase the chance of normal life expectancy. A test is advisable for those with a family history of hemochromatosis.
The evidence from many scientific studies suggests that high iron levels (above 200 mcg per liter blood ferritin), may lead to an increase in the risk of cardiovascular disease. The increased risk may be due to oxidative damage to the heart and blood vessels and increased oxidation of LDL cholesterol. A study published in 1998 in the American Journal of Epidemiology suggests that men and women, particularly those over 60, are at increased risk of heart disease if they have high levels of iron in their diets. The study, which was conducted in Greece, involved 329 patients with heart disease and 570 people of similar age who were admitted to hospital with minor conditions believed to be unrelated to diet. Results showed that for every 50 mg increase in iron intake per month, men over 60 were 1.47 times more likely to have heart disease than their peers. In women over 60, the risk was even higher, with a 3.61 -fold risk for every 50 mg increase.
In a paper published in 1997, Austrian researchers involved in the Bruneck study investigated the links between serum ferritin concentrations and the five- year progression of carotid atherosclerosis in 826 men and women aged 40 to 79 years old. Serum ferritin was one of the strongest risk predictors of overall progression of atherosclerosis, probably due to increased oxidation of LDL cholesterol. Changes in iron stores during the follow-up period modified atherosclerosis risk, in that a lowering was beneficial and further iron accumulation exerted unfavorable effects. High serum ferritin and LDL cholesterol also increased the risk of death from cardiovascular disease.
Another study published in 1998 in the American Heart Association journal (Circulation suggests that men with high levels of stored iron in the body have nn i ncreased risk of heart attack. The Study, which was done in Finland, involved 99 men who had had at least one heart attack and 99 healthy men matched for background and age. The results showed that those men with the highest iron levels had almost three times the risk of heart attack when compared with those with the lowest levels.
Donating blood may help prevent a heart attack according to a 1998 study reported in the American Journal of Epidemiology. The results of a Finnish study showed that middle aged men who gave blood had an 88 per cent lower risk of heart attack than those who had not donated. In a group of 2862 men, less than 1 per cent of the blood donors had heart attacks compared with 12.5 per cent of the non-donors.
Some studies have shown that iron can inhibit tumor development while others have shown that it might enhance it. Iron may increase the risk of cancer through its effect on free radical formation. In some population studies, high iron levels have been associated with an increased risk of throat and gastrointestinal cancers while others have not shown links. Results from a study assessing the links between body iron stores and cancer in 3287 men and 5269 women participating in the first National Health and Nutrition Examination Survey (NHANES I) found an increased risk with high iron levels. Some experts believe that the findings of increased risk are due to causes such as defects in iron metabolism, rather than diet alone.
High iron levels may also worsen the joint inflammation associated with rheumatoid arthritis. High iron levels may also lead to an increased risk of infection as iron is necessary for bacterial growth. Vitamin A supplementation may help to control the adverse effects in areas where infections are prevalent.
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