Serum ferritin concentrations in Africans with low dietary iron.

In the setting of high dietary, several studies have provided evidence for a strong effect of both high dietary iron and an unidentified genetic locus on iron stores in Africans. To investigate whether these effects are discernible in the setting of low dietary iron, serum ferritin concentrations were measured in 194 Zimbabwean men >30 years of age and 299 postmenopausal women who consumed a non-iron-fortified diet and who did not drink iron-rich traditional beer or other alcoholic beverages. Comparisons were made with non-alcohol drinking African-Americans studied in the third National Health and Nutritional Examination Survey (NHANES III) who consume an iron-fortified diet. As stratified by age and sex, serum ferritin concentrations were significantly lower in the 493 Zimbabweans studied than in 1,380 comparable African-Americans (P < 0.0005). Nevertheless, nine Zimbabwean subjects (1.8% of all cases) had modestly elevated serum ferritin concentrations not associated with evidence of inflammation or hepatic dysfunction. These data suggest that mild serum ferritin concentration elevations may occur among Zimbabweans not exposed to high dietary iron and that iron fortification of the diet may have substantial effects on serum ferritin concentration.

Iron status in black persons is not influenced by haptoglobin polymorphism.

Iron status in man is influenced by environmental and genetic factors. The molecular variation of haptoglobin is one of the genetic factors influencing iron status in Caucasians. Differences in iron metabolism between blacks and whites have been reported. We wanted to investigate the effect of haptoglobin polymorphism on iron status in blacks. We studied 300 African subjects who were apparently healthy with normal erythrocyte sedimentation rate and with no increase in dietary iron because of traditional beer consumption. We determined haptoglobin (Hp) phenotypes using starch gel electrophoresis and measured indirect iron status indices using standard methods. We compared iron status indices according to haptoglobin type. Ninety two individuals (31%) had Hp 1-1, 114 persons (38%) had Hp 2-1, 20 subjects (7%) had Hp 2-1(Modified) and 54 individuals (18%) had Hp 2-2 type. Haptoglobin was not detectable in 19 subjects and Hp 2-1(Johnson) was found in one subject. In both males and females, serum iron concentration, total iron binding capacity, transferrin saturation and ferritin concentration were not different with regard to Hp phenotype. These results suggest that haptoglobin phenotypic variation may not be a factor which influences iron status in black persons.

Effect of transferrin polymorphism on the metabolism of vitamin C in Zimbabwean adults.

BACKGROUND: Transferrin is the major iron binding protein in human plasma. In black persons, the transferrin CD phenotype has been associated with alterations in certain markers of iron status. OBJECTIVE: We studied vitamin C status in a Zimbabwean population according to transferrin phenotype because vitamin C metabolism is influenced by iron-driven oxidative stress. DESIGN: The study population consisted of 150 black African adults, 90 of whom were at risk of iron overload on the basis of high dietary iron content in the form of traditional beer. Transferrin phenotypes, indirect measures of iron status, and leukocyte ascorbic acid concentrations were determined. The in vitro rate of L-ascorbic acid depletion in sera from different transferrin phenotypes was investigated. RESULTS: The transferrin phenotype frequencies of transferrin CC and CD were 0.893 and 0.107, respectively. The iron status of transferrin CC and CD subjects was similar. After adjustment for traditional beer consumption, baseline leukocyte vitamin C concentrations were significantly higher in 16 transferrin CD subjects ( +/- SE: 2.10 +/- 0.34 and 2.61 +/- 0.28 fmol/leukocyte in men and women, respectively) than in 134 transferrin CC subjects ( +/- SE: 1.65 +/- 0.11 and 1.99 +/- 0.11 fmol/leukocyte in men and women, respectively; P = 0.024). Oral administration of ascorbic acid (2.0 g every 24 h for 48 h) led to slower rises in leukocyte vitamin C concentrations in subjects with the transferrin CD phenotype than in subjects with the transferrin CC phenotype (P = 0.028). After in vitro supplementation of serum with 570 micromol vitamin C/L, the rate of L-ascorbic acid depletion was significantly lower in subjects of a transferrin CD phenotype than in subjects with the transferrin CC phenotype. CONCLUSION: Transferrin polymorphism may affect vitamin C status in blacks.