Climate Change and Food Nutritional Quality: A Global Synthesis of Crop Nutrient Changes and Human Health Implications—A Review

Climate change is emerging not only as a threat to global food production but also as a major driver of declining nutritional quality in food crops. Throughout this review, terms such as nutrient decline, imbalance, and nutritional quality changes are used to describe relative changes in the nutritional attributes of edible crop tissues, as reported in the source studies. Elevated atmospheric CO2, altered rainfall patterns, shifts in solar radiation, and rising temperatures influence soil processes, plant metabolism, and genotype × environment interactions that determine nutrient composition and density. Evidence from controlled experiments, free-air CO2 enrichment (FACE) studies, field trials, and meta-analyses suggests a recurrent tendency toward reduced concentrations of essential macronutrients and micronutrients, including protein, iron, zinc, and selected B-vitamins in a range of cereals, legumes, and horticultural crops, while responses remain context-dependent and are not universally observed across all nutrients, cultivars, or production systems. These reductions raise serious concerns for populations already experiencing widespread micronutrient deficiencies. This review synthesizes the current knowledge on the extent and mechanisms of climate-driven nutrient decline across major crops, highlighting variability among species, cultivars, and production environments. We also evaluate the potential health consequences, particularly heightened risks of anemia, impaired immunity, developmental challenges, and other deficiency-related disorders. Regions such as South Asia, Southeast Asia, and Sub-Saharan Africa are identified as highly vulnerable due to their strong dependence on nutrient-poor staples and existing burdens of hidden hunger. Furthermore, we assess key mitigation and adaptation pathways, including agronomic innovations, climate-smart agricultural practices, biofortification, advanced breeding strategies, and the emerging use of microbial and cyanobacterial biostimulants to enhance nutritional resilience in cropping systems. Finally, this review provides an integrated synthesis of climate-induced nutrient decline, its health implications for vulnerable populations, and priority actions needed to protect global food and nutrition security in the face of accelerating climate change.