Iron is a dietary requirement, women aged 19-50 needing the most, routinely around 18mg/day, moreover all adults need at least 8mg/day. Pregnant women need even more. Dietary sources include, but are not limited to, meats, nuts, grains and broccoli. Despite these potential dietary sources, iron deficiency anaemia (IDA) was estimated to be the 7th leading cause of disability worldwide by the World Health Organization (WHO) in 2017.
Some forms of iron deficiency have a genetic basis and are refractive of dietary changes. Iron deficiency may account for 60% of anemia cases globally. In particular, anemia is a serious problem in sub-Saharan Africa, with an estimated 40% of the population suffering from the condition, which may have a genetic basis.
Susana Campino of the London School of Hygiene & Tropical Medicine, UK, and colleagues, conducted a review of the literature to identify genetic variants known to be associated with iron imbalances, particular emphasis was placed on research for SNPs in TMPRSS6, HAMP, TF, TFR2, SLC40A1 and HFE genes. The rural Gambian Keneba Biobank and the 1000 Genomes Project were sources of data. The results were published in the journal PLoS One.
The majority of the studies (59/64) under review took place in Europe, Asia or the USA. Of the remaining African studies two were in Rwanda, one in Zimbabwe, one in South Africa, and there was one meta-analysis including Kenya, Tanzania and South Africa. In total, 50 SNPs were noted in six genes (TMPRSS6, HAMP, TF, TFR2, SLC40A1 and HFE).
The gene with the most frequent (n = 23) SNPs was TMPRSS6. The majority of the SNPs were associated with iron-refractory iron deficiency anaemia (IRIDA), iron deficiency or indicators of low iron status. The transferrin (TF) gene had the second highest frequency (n = 18) of SNPs.
Of the available SNPs, corresponding to the 50 identified in other studies, in the Gambian Keneba Biobank and the pan-African populations in the 1000 Genomes project, few differences in the frequency of the primary SNP allele were observed. The minor allele frequencies (MAFs), however, were greatly different in the African datasets.
Surprisingly, compared to other populations, the frequency of risk alleles for low iron in the Gambian and overall African populations were significantly lower. Gambians in the Keneba Biobank and pan-African populations also have the lowest number of combined risk alleles for high iron. These surprising findings may be due to a lack of data, as the available arrays did not cover all the identified risk SNPs. Certainly the available genetic data does not explain the prevalence of anemia in sub-Saharan Africa.
“In conclusion, this study identified a substantial disparity in allele frequencies of genetic variants associated with iron, between Africans and other populations. We also identified the scarcity of data on the genetic influences of iron status in Africa. Given the high burden of iron deficiency in sub-Saharan Africa, particularly in child-bearing women and children, comprehensive mapping of the genetic influences on iron status may help lay the foundation for future studies and assist in developing future iron intervention strategies,” stated the authors.