Seb Bowden ANutr is an associate registered nutritionist with the Association for Nutrition (AfN) and a member of the British Dietetics Association. Seb holds a Master's in human nutrition and a post-grad diploma in nutrition with exercise physiology.

‍Climate change has a two-fold effect on global nutrition: extreme weather can destroy crops, livestock and impact food supply. Rising carbon dioxide in the atmosphere can also reduce the nutrition available in some crops.

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Most of us are now aware of the climate emergency and its impact on weather patterns. Floods, droughts, wildfires and hurricanes destroy crops, devastate local economies and interrupt the food supply chain.  

Global warming is also impacting the growing season. These effects are both positive – as evidenced by lengthening growing seasons in certain areas – and negative, as seen in areas where heat already limits production, as well as in increasing soil evaporation.  

But climate change has even more impacts on our food, many of which are yet to hit the headlines.‍

Evidence shows that the changing climate can affect the nutritional composition of foods:

• A large international study found that increased carbon dioxide in the atmosphere had both a positive and negative impact on vegetables.
  
  On a positive note, more carbon dioxide does promote the yield of vegetables; sugars, total antioxidant capacity, flavonoids, vitamin C and calcium levels all appeared to increase with higher levels of atmospheric carbon dioxide. But this was at the expense of protein and minerals such as magnesium, iron and zinc.
  

• In 2019, a report from the United Nations suggested that climate change has a negative impact on the nutritional value of staple crops such as wheat and rice, which are vital to basic nutrition across the globe. 
  
  The studies that form the basis of this report found that there is a careful balance between the carbon dioxide plants take from the atmosphere and the nutrients they absorb from the soil. Proteins are nitrogen based, which many plants get from the soil. If they take up less nitrogen (as nitrates), then the plant will yield less protein in its structure.
  

• Several studies funded by the Bill Gates Foundation suggest that rising carbon dioxide in the atmosphere could lead to global protein deficiencies, as an estimated 76% of the world’s population depend on plants for protein. 
  
  Furthermore, the reduction in minerals could exacerbate an already increasing problem of iron and zinc deficiency in vulnerable populations in Asia and Africa, where most of the world’s population reside.
  
  However, whilst some studies do suggest that there is a decline in the nutritional values of some foods we consume, there is a word of caution.

Are we comparing apples and pears?

Dr Paul Finglas, Head of the Food Databanks National Capability at the Quadram Institute in Norwich, suggests that there are methodological problems in comparing the nutritional values of food today with those in the past, due to measuring techniques used to evaluate the compositions of foods.

Today, highly sophisticated computer-based instrumentation is available to more accurately measure proteins, vitamins and minerals. Comparing datasets across time periods could therefore be prone to error. This might explain why, historically, studies found that the nutritional status of some foods declined or were diluted over time.

That said, studies looking at the change in carbon dioxide in the atmosphere are not comparing nutrient composition historically but have been conducted in controlled experiments using varying atmospheric carbon dioxide levels.

A global shift in the way we eat is vital

There is mounting evidence to suggest the adverse nutritional effects of climate change should warrant government attention. In 2019 the fourth UN Environmental Assembly tabled the topic of food systems and climate change. 

This initiative called for a global food system geared towards healthier diets, characterised by plant-based dietary patterns. But if the protein and mineral composition of plants is decreasing, will encouraging populations to shift from animal to plant-based nutrition have unintended consequences? 

Like everything, there is a balance to be struck. Especially when you consider that the global consumption of highly processed foods – high in salt, sugar and calories but low in fibre, vitamins and minerals – is a far bigger problem. (UNSCN, 2019)

There are many links between climate change, agricultural production, food security and nutrition; they’re also bi-directional. The food we consume is affected by climate change and the systems that produce them create climate change.

In the UK, the British Dietetics Association (BDA) has come up with a toolkit to help professional nutritionists and dieticians advise on diets that are good for health and environmental sustainability.  

The toolkit, titled One Blue Dot, was released in 2019 and can be accessed here for anyone to read.

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