The differences in quantification of obligatory losses of iron made by various expert groups is possibly explained by differences in environmental sanitation and the prevalence of diarrhoea. The presence of dietary components that affect bioavailability differs between and within a given ecological setting.
The concern about iron excess may be greater in places where anaemia is no longer an issue (e.g. in northern Europe), but in other areas iron deficiency is significant.
Genetics is the study of genes, genetic variation, and heredity in living organisms. A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins.
The Human Genome Project has estimated that humans have 20,000 - 25,000 genes. Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but less than 1% of genes are slightly different between people. Poplar tree genome suggests more than 45,000 genes.