The effect of iron fortification of the diet on clinical iron overload in the general population.

The gene coding for idiopathic hemochromatosis is prevalent in Sweden, the country with the highest iron fortification of food (42%) in the world. We wanted to study if this highly iron-fortified diet had negative effects on the iron situation in carriers of the iron-loading genes. Iron stores averaged 6.7 grams in male homozygotes who were mainly identified through laboratory screening. It was 3.4 grams in female homozygotes. By HLA typing of family members of these homozygous probands, 39 additional homozygotes and 172 heterozygotes were detected. Serum ferritin averaged 620 micrograms/l in 20 male and 168 micrograms/l in 19 female homozygotes in the family screening. Storage iron as measured by serum ferritin concentration was slightly but significantly higher in male heterozygotes than controls (117 micrograms/l versus 87 micrograms/l, p less than 0.02). There was no further increase in serum ferritin concentration with age after 40 years. Heterozygotes showed no clinical signs of iron damage. These findings do not indicate that carriers of the iron-loading genes in Sweden have been adversely affected by the highly iron-fortified diet of the country.

The effect of withdrawal of food iron fortification in Sweden as studied with phlebotomy in subjects with genetic hemochromatosis.

OBJECTIVES: The iron fortification of food in Sweden, the highest in the world, was withdrawn 1st January 1995, because the effect upon target groups was considered to be uncertain. We wanted to study the effect of such a dietary experiment. DESIGN: Comparative cross over study. SETTING: Out patient service and Blood Bank. SUBJECTS: Sixteen men aged 24-73 y on maintenance phlebotomy after treatment for iron overload. One was excluded because of inflammatory disease. INTERVENTIONS: Quantitative phlebotomy with serial measurements of Hb conc., % transferrin saturation and serum ferritin concentration. MAIN OUTCOME MEASURES: Iron absorption was measured by phlebotomy during two periods, with and without iron fortification. 1 g Hb = 3.4 mg Fe. RESULTS: Iron absorption was significantly reduced (P < 0.001) when iron fortification was withdrawn from a mean of 4.27 +/- 1.2 to 3.63 +/- 1.1 mg/d. The difference of 0.65 mg/d (95% c.i. 0.32-0.97) corresponds to the fraction of iron derived from fortification. Intervals between donations had to be extended from 59 +/- 15 to 69 +/- 17 d (P < 0.01) to avoid induction of iron deficiency anemia. The iron content of the fortified diet averaged 15.4 mg/d, of which the fortified fraction constituted 4.1 mg/d (27%). The relative bioavailability of carbonyl iron used as fortificant was 38%. CONCLUSIONS: The relative bioavailability of carbonyl iron used as fortificant was higher than previously reported. Target groups such as menstruating females will probably be affected by a higher prevalence of iron deficiency when food is no longer fortified. People with genetic hemochromatosis will accelerate into clinical disease at a slower rate.

Studies on iron stores built up by an iron-poly (sorbitol-gluconic acid) complex, Ferastral, in man. Preliminary report.

The characteristics of iron stores built up by a new parenteral iron-poly (sorbitol-gluconic acid) complex, Ferastral, have been studied in iron depleted non-anemic blood donors. The results from studies on the first three subjects are presented. The availability of this storage iron for the chelator, desferrioxamine, was found to be in the same range as normal iron stores. The pattern of distribution in reticulo-endothelial cells of the bone marrow could not be differentiated from natural storage iron. No visible iron could be detected in liver parenchymal cells 40 days after iron administration. The results from these preliminary studies suggests normal bioavailability of this material for Hb-synthesis. The absence of iron in liver parenchymal cells might be explained by the short time interval between the iron administration and the fine needle aspiration biopsy.

Liver affection in iron overload studied with serum ferritin and serum aminotransferases.

Liver dysfunction as measured by S-ALAT activity was present in 72% of patients over 40 years of age with HLA-related iron overload, mainly detected by laboratory screening. Liver dysfunction was correlated to the amount of iron stored (r = 0.54, p less than 0.001). When iron was removed by phlebotomy, liver function returned to normal. S-ALAT activity was closely correlated to serum ferritin concentration (r = 0.73, p less than 0.001). Even a mild iron excess can affect hepatocytes and result in increased levels of ferritin and aminotransferases in serum. Patients with "transaminitis" should be investigated for iron overload.

Preclinical hemochromatosis in a population on a high-iron-fortified diet.

Three hundred forty-seven (96.4%) of all persons aged 30 to 39 years were screened with serum iron and iron binding capacity measurements to determine the incidence of hemochromatosis in a population. No women had signs of iron overload; however, nine men (5%) had persistenly elevated serum iron levels. In four men (2%), increased iron stores was found with a distribution like that in the early stages of hemochromatosis. In combination with recent findings of clinical hemochromatosis at our hospital, this study suggests that this condition is not as rare as has been reported earlier.

HLA as a marker of the hemochromatosis gene in Sweden.

The frequency of HLA-A3 and HLA-B14 antigens was found to be significantly (P = less than 0.0001) higher in a series of 50 unrelated and unselected Swedish patients with idiopathic hemochromatosis (IH) than in controls, being 66% and 32% for A3 and 22% and 2% for B14. The haplotype A3B14 was associated with the highest risk in this material (relative risk 23.4). One family with this haplotype was traced back to the end of the seventeenth century. The pattern of HLA antigens associated with IH in Sweden shows remarkable similarity to those reported from England and Brittany.

Prevalence of iron overload in central Sweden.

An increase in the iron content of food may be harmful to people with genetic hemochromatosis. We studied the prevalence of this disorder in Sweden, which is the country with the world's highest iron fortification of food. Serum ferritin and transferrin (TIBC) saturation levels were used as initial screening methods. Three (0.5%) of 623 males aged 30-39 years were found to have genetic hemochromatosis. Family studies revealed 10 additional homozygotic family members. A prevalence of 0.5% of homozygotes (q2) implies a gene frequency (q) of 6.9% or a heterozygote frequency (2 x Q) of 13.8%. The high gene frequency may be explained by a possible genetic advantage of heterozygotes in the past. We conclude that idiopathic hemochromatosis is not as rare as previously thought. Affected persons should be detected and treated before irreversible organ damage occurs. This study demonstrates that serum ferritin levels together with TIBC saturation levels are adequate methods for screening populations.

Screening for iron overload using transferrin saturation.

People with parenchymal iron overload exhibit an elevated serum iron concentration and a raised transferrin (TIBC) saturation early in the course of the disease. They can therefore be detected by simple laboratory tests before organ damage has occurred. In this study running for 2 months, 10512 samples from approximately 8750 patients and blood donors were examined in a county hospital in Central Sweden. Abnormal TIBC saturation (greater than 70%) was found in 1.7% of the samples. This abnormality was caused by physiological fluctuations in serum iron in 44%, liver disease in 22%, blood disorder in 10%, iron therapy in 10.5% and parenchymal iron overload in 11.5%. The diagnosis of iron overload was confirmed by measuring the serum ferritin concentration and by performing the desferrioxamine test, liver biopsy, quantitative phlebotomy and family studies including HLA typing. We found a prevalence of iron overload of 0.24%. This figure is almost certainly too low because some affected patients were probably lost because of TIBC desaturation induced by inflammatory conditions.

Iron deficiency and iron overload in Swedish male adolescents.

OBJECTIVES: The present study was undertaken to confirm or reject recent findings indicating a high prevalence of iron deficiency in Swedish male adolescents; a second aim was to study the prevalence of genetic iron overload. DESIGN: The diagnostic criteria were: anaemia: Hb < 130 g L-1 (a): iron deficiency: serum ferritin (SF) < 12 micrograms L-1 + transferrin saturation (TS) < 16% (b): iron deficiency anaemia a + b. Iron overload: SF (90th percentile) + TS (90th percentile) in repeat tests. SETTING: Central Sweden. SUBJECTS: A total 3975 men aged 18 years studied on enrollment into military service. RESULTS: Serum ferritin averaged 36.8 micrograms L-1. Anaemia was present in 0.5%, iron deficiency anaemia in 0.17% and iron deficiency in 0.4%. If iron deficiency is defined as SF < 16 micrograms L-1, as was recently suggested, the prevalence would be 2.8%. Such a cut-off value would include 73% normal people (false positives). Iron overload had the same prevalence as iron deficiency, 0.4%. CONCLUSIONS: Iron stores, as measured by serum ferritin, are small in young men studied at the end of their growth spurt. However, iron deficiency is rare. Therefore, the present study has not been able to confirm the high prevalence of iron deficiency recently reported. A prevalence of genetic haemochromatosis of 0.4%, confirms earlier findings and would mean that 12.6% of the population are heterozygotic carriers of the iron-loading genes. These findings give no support for a proposed, more effective iron-enrichment of food. It is not needed and can be harmful.