This review synthesises current research findings and modelling approaches to explore the impact of elevated atmospheric carbon dioxide (eCO) concentrations on crop productivity, water and nutrient use efficiency, plant nutritional quality, and the implications for global food security. Over recent decades, rising atmospheric CO levels have sparked significant concern due to their role in driving climate change. While some studies highlight the potential benefits of eCO, such as increased crop yields and improved water-use efficiency, many recent investigations reveal a concerning decline in crop nutritional quality. eCO has been shown to reduce concentrations of key nutrients, including nitrogen, minerals, vitamins, polyphenols, and other non-nutrient compounds, as well as alter gene expression. These changes are further complicated by interactions with heat stress and drought, presenting significant challenges in predicting sustainable future crop productivity. These nutritional declines exacerbate the global crisis of malnutrition and hidden hunger, threatening the achievement of Sustainable Development Goal 2 (SDG2), which aims to end hunger and ensure food security. Addressing these challenges requires further research, interdisciplinary collaboration, and innovative approaches to mitigate the adverse effects of eCO on crop physiology and nutritional content while maximising agricultural sustainability. This review aims to provide insights into the complex mechanisms governing crop responses to eCO using wheat as a model and proposes pathways for future research and agricultural practices. These strategies are critical for tackling the intricate dynamics of climate variability, ensuring nutrient-rich food production, and securing food security in the face of a rapidly changing climate.