While the impact of food production on the climate is well documented, the reverse influence is discussed far less often: how climate change affects nutrition and food security on a global scale. Yet, the degradation of food systems linked to climatic variations poses a concrete threat to the health of millions of people, especially in the most vulnerable regions, where nutritional deficiencies and diet-related diseases are on the rise.
According to the World Health Organization (WHO), in 2023 nearly 2 billion people lacked access to safe drinking water, and around 600 million suffered from foodborne illnesses each year, with 30% of related deaths occurring in children under five.
In this first article of a two-part series, Alcimed explores how global warming jeopardizes food security and its consequences on population health worldwide, emphasizing the critical need for both public and private health stakeholders to fully grasp these issues. The second article will focus more specifically on the challenges these stakeholders face and the strategies needed to adapt to these impacts.
Climate change reduces access to healthy food through several interconnected mechanisms. Rising temperatures, in particular, lead to increased atmospheric CO₂ concentrations, creating a feedback loop that further intensifies global warming.
Numerous studies have shown that global warming causes agricultural production losses directly linked to higher temperatures, varying across regions of the world1Zhao, C., Liu, B., Piao, S., Wang, X., Lobell, D. B., Huang, Y., Huang, M., Yao, Y., Bassu, S., Ciais, P., Durand, J., Elliott, J., Ewert, F., Janssens, I. A., Li, T., Lin, E., Liu, Q., Martre, P., Müller, C.,. . . Asseng, S. (2017). Temperature increase reduces global yields of major crops in four independent estimates. Proceedings Of The National Academy Of Sciences, 114(35), 9326 9331. https://doi.org/10.1073/pnas.17017621142INSERM (Press Room). (2025, September 24). “Junk food”: Really a cause of depression? INSERM Press Room [in French]. https://presse.inserm.fr/canal-detox/la-malbouffe-une-cause-de-depression-vraiment/. According to IPCC projections, in the Sahel region, without appropriate adaptation measures, cereal production could drop by 20% to 50% by 20503Intergovernmental Panel on Climate Change (IPCC). Sixth Assessment Report (AR6). Yield losses are also worsened by the growing frequency of extreme weather events such as droughts, floods, and cyclones that destroy crops and agricultural infrastructure.
Beyond quantity, the nutritional quality of crops is also compromised by climate change. Increased atmospheric CO₂ directly affects soil composition and therefore, the composition of food. This leads to lower concentrations of protein, zinc, and iron in foods that account for two-thirds of global nutrition (wheat, rice, and maize).
Studies on rice have shown a decrease of up to 30% in folate and other B vitamins when exposed to elevated CO₂ levels. Moreover, this condition increases toxin levels in certain staple crops and in hundreds of seafood species, posing new risks for food safety.
Rising temperatures also contribute to biodiversity loss and dramatically increase virus transmission between animal species, drastically raising the risk of emerging new pathogens in human populations. In addition, pathogens spread more easily, increasing the frequency of foodborne diseases.
Climate change can also alter fungal distribution, heightening human exposure to certain mycotoxins and worsening their health effects. Meanwhile, harmful insects currently consume between 5% and 20% of major grain crops (wheat, rice, and maize), and researchers estimate these losses could increase by 10% to 25% per degree of warming. This encourages greater pesticide use regardless of their toxic or even carcinogenic effects, as in those linked to pancreatic cancer.
Climate change directly affects the availability, quality, and diversity of food, worsening two distinct nutritional challenges:
Unhealthy diets contributed to 11.2 million deaths globally in 20214Romanello, M. et al. The 2024 report of the Lancet Countdown on health and climate change: facing record-breaking threats from delayed action. Lancet (London, England) 404, 1847–1896 (2024)., while approximately 750 million people suffered from hunger, mainly in Africa. These situations lead to an increased incidence of certain diseases.
Worldwide, declining agricultural yields and soaring food prices drive many households toward unbalanced diets, often poor in essential nutrients but high in ultra-processed foods. This increases the risk of cardiometabolic diseases such as obesity, hypertension, type 2 diabetes, and cardiovascular comorbidities. These pathologies are now the leading cause of death worldwide, affecting both lower-income populations in developed countries and those in vulnerable regions, with over 17 million premature deaths every year (WHO).
As discussed earlier, wheat, rice, and maize (providing nearly two-thirds of global calories) face severely threatened production due to climate change. This weakening of food systems heightens population vulnerability, particularly among children exposed to wasting and nutrient deficiencies.
According to UNICEF (2023), 45 million children under five suffer from wasting, and 149 million experience stunted growth. These deficiencies compromise physical and cognitive development while increasing childhood morbidity and mortality.
Micronutrient deficiencies, such as those in iron and zinc, weaken the immune system and increase susceptibility to anemia, diarrhea, and other infections, including respiratory illnesses. Each year, diarrheal diseases cause about 525,000 deaths among children under five, often worsened by poor nutrition (WHO, 2022). Respiratory infections, such as pneumonia, are also more frequent and severe in malnourished children, particularly in regions with high food insecurity.
Additionally, intensified heat and humidity conditions promote the spread of pathogens and the development of mycotoxins in food, amplifying the risks of food and water contamination. For example, outbreaks of leptospirosis and hepatitis A linked to contaminated water regularly affect vulnerable populations. Chronic exposure to mycotoxins in certain cereals can also cause kidney damage and other health complications. These conditions often require specialized care that is difficult to access in affected regions.
Undernutrition directly affects the brain by disrupting the production of key hormones such as serotonin and promoting neuroinflammation, which can lead to gradual cognitive decline. Diets poor in essential nutrients are associated with increased depressive and anxiety disorders, while balanced diets—especially those rich in omega-3 fatty acids—play a protective role in supporting mental and cognitive health.
Rising temperatures and CO₂ emissions on our planet indirectly impact human health through our diets, by altering the quality and availability of food resources.
Global warming intensifies a dual nutritional imbalance: the overconsumption of ultra-processed products in industrialized countries and the worsening of undernutrition in low-income regions. Even minor deficiencies weaken the immune system and increase the risk of infectious and metabolic diseases.
As is often the case in environmental crises, the most vulnerable populations (economically or geographically) bear the heaviest burden, facing limited access to healthy food, inadequate healthcare, and increased exposure to health risks.
Given these challenges, it is urgent to rethink public health policies and food resilience strategies through both a local and systemic approach.
In our next article, we will explore the repercussions of global warming on the agri-food industry and healthcare systems, to better understand the adaptations needed to address these new realities.
If you would like to explore how climate change impacts health through nutrition, our specialized teams in healthcare and agri-food can support you. Don’t hesitate to contact us!
About the author,
Elise, Senior Consultant in Alcimed’s Healthcare team in France
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