Micronutrient deficiencies are a serious global health problem, affecting up to 5 billion people today1. Deficiencies in zinc, iron, folate, and vitamin A contribute to stunted growth, birth defects, poor cognitive development, and increased vulnerability to disease. Soils poor in essential minerals are widespread, and this geological variation has likely shaped human diets for much of evolutionary history. But the role of these micronutrients as a selective pressure on human populations has been less well studied than other dietary factors, such as lactose intolerance. Rees et al. (2025)2 present the first study to examine micronutrient-related genetic adaptation systematically across multiple populations worldwide, moving beyond isolated case studies in an attempt to identify a broader evolutionary impact.
The authors analysed whole-genome data from 913 individuals across 40 populations in the Human Genome Diversity Project. They focused on 276 genes linked to the uptake, regulation, or metabolism of 13 dietary micronutrients, including iron, zinc, iodine, selenium, and calcium. To detect signals of positive selection – genetic changes that rose in frequency because they provided a survival or reproductive advantage – they applied two approaches: F_ST, which measures allele frequency differences between populations, and Relate, which reconstructs genealogical trees to infer allele frequency changes over time. SUMSAT was also used to test for gene set enrichment, which can indicate polygenic adaptation.
The study found that nearly all micronutrients showed evidence of driving genetic adaptation in at least one population. Most signals were local and oligogenic, affecting a handful of genes. Strong examples included selenium adaptation in East Asian populations, iodine adaptation in the Maya, and zinc-related adaptation in 28 of the 40 populations studied. Iron and calcium genes also showed signatures of selection, with timing analyses suggesting adaptation is linked to both early migrations into new environments and dietary changes during the Neolithic period.
The Evolutionary Imprint of Micronutrients
This study supports the theory that nutrition has been a persistent evolutionary pressure. Cases such as iodine adaptation in the Maya or selenium adaptation in East Asia align with known deficiencies in those regions, linking geology and diet directly to genetic change. For iodine, the authors suggest that adaptation may have influenced phenotypes such as reduced goitre incidence or shorter stature in some populations, while selenium-related changes may have moderated the risk of some regional diseases, like Keshan or Kashin-Beck. Zinc-related signals, detected in most non-African populations, point to a more global pattern of adaptation, suggesting that this micronutrient may have been a widespread constraint during human dispersal.
The findings also highlighted how adaptation to micronutrients differs from other well-known dietary adaptations, such as lactose intolerance. Rather than a single mutation sweeping through a population, most micronutrient-related signals involve small numbers of genes in specific groups. This oligogenic pattern reflects the complexity of traits like metabolism and nutrient transport, where changes in multiple pathways can provide local advantages.
However, the authors caution against over-interpretation. Distinguishing adaptive change from background noise is difficult, particularly when signals are weak or polygenic. Evidence for broad genome-wide adaptation is limited, and some signals may reflect demographic history rather than selection. Timing estimates add further uncertainty, since the same genetic changes could have arisen during early migrations into new environments or later dietary changes, like the Neolithic shift to cereal-based diets.
In all, the study points to a model where micronutrients acted as local, often subtle, selective pressures. While not all findings are definitive, the overall pattern suggests that nutrition has shaped human diversity more deeply than previously recognised.
This study suggests that nutrition has exerted a selective pressure throughout human history, but adaptation has not eliminated the risks of nutritional deficiency. Populations developed local genetic changes in response to low levels of iodine, zinc, or selenium, but conditions such as goitre, anaemia, and growth disorders persisted. This suggests that evolutionary change can alter susceptibility but does not provide protection against the broader health burden of micronutrient scarcity.
Some of the genes highlighted in this study, including HFE3 and TMPRSS64, are also known to influence iron status and responses to supplementation in modern populations. Carriers of certain variants exhibit differences in baseline iron levels or supplement efficacy, although researchers caution that diet, infection, and inflammation may also play significant roles. Together, these findings suggest that evolutionary history may help explain variation in nutritional health today, even if it interacts with wider social and environmental factors.
The study also highlights how evolutionary change may alter risks in the future. Over-farming5 and climate change6 are depleting soils of essential minerals, reducing the nutritional value of crops in many regions. If populations have historically adapted to local conditions, rapid shifts in soil chemistry and diet could create new mismatches between genetic background and nutrient availability. Such mismatches may exacerbate health disparities, particularly where access to supplementation is limited.
Another lesson lies in research priorities. Nutritional adaptation has received far less attention than other forms of dietary evolution. Yet, this work suggests that essential minerals have shaped the human genome on a global scale. Integrating genomic, ecological, and nutritional data may offer new ways to understand disease risks that vary across populations and help explain why some groups respond differently to interventions.
Rees et al. (2025) frame nutrition as both an ancient and ongoing evolutionary pressure. Just as past environments left traces in our DNA, current changes in agriculture and climate may influence health outcomes for future generations. Recognizing this link may help guide strategies for food security, public health, and equitable research investment.