That the food we put into our bodies today is making us unhealthy is not news. We know of the dangers of processed food – instances of artificially dyed greens, adulterated oils, and hormone-ridden milk make news often. Organic food is no longer niche, as more people learn of the downfalls of chemical agriculture. The move towards artificially treated, processed foods is said to be largely driven by consumers, by our growing appetites for perfectly shaped, blemish- and pest-free fruits and vegetables, better transportability, and year-round availability.

But there is a less well-known phenomenon that may be leaching nutrients out of our food, one that we are equally complicit in. Climate change or, more specifically, a rise in global atmospheric carbon dioxide from anthropogenic activities, is affecting the nutritional quality of the foods we eat, say scientists working at the intersection of agriculture, human health and climate change. In India, climate change has been associated with agricultural crises brought about by extremes of rainfall and erratic weather, but a handful of studies reveal that there’s more to the relationship between climate change and food than we’ve known so far.

Mathematician and biology enthusiast Irakli Loladze was first alerted to this link during a lab experiment to boost food supply to zooplankton by feeding them additional quantities of algae. To speed up the growth of algae, scientists shone more light on them. However, what they found was not what they’d expected: the zooplankton that should have thrived as a result of increased food supply and nutrition began struggling to survive.

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What happened was this: the additional light they received made the algae grow faster but they were not nutritious enough for the zooplankton to survive and flourish. Essentially, scientists had sped up the algae’s growth and turned them into junk food in the process. Food that filled the zooplankton up but fell short of providing them the necessary nutrition and offered too much of a nutrient, like glucose, that was bad for them.

This made Loladze curious about whether this experience could be extended to understand the relationship between humans and the plants we eat – all of which are becoming more and more exposed to increased atmospheric carbon dioxide. He asked a question much overlooked by agriculture and medicine: if more light results in faster-growing, less nutritious algae whose ratio of sugar to nutrients was out of balance, then isn’t it logical to assume that increased CO2 might do the same to the plants humans and animals feed on? It seems counter-intuitive at first. Since plants synthesise CO2 to produce food, shouldn’t elevated CO2 levels produce a greater volume of food of better quality?

Loladze and others like Harvard University doctor and environmental researcher, Samuel Myers studying this nutritional collapse found that staple crops such as rice, wheat, barley and potatoes exposed to CO2 levels of 546-586 ppm had significantly lowered concentrations of iron, zinc and protein. Grown in elevated CO2 conditions, wheat had 9% less zinc, 5% less iron, and 6% less protein; in rice, zinc fell by 3%, iron by 5% and protein by 8%. Maize registered similar falls in zinc and iron concentration. Even legumes grown under conditions of elevated CO2 had lower concentrations of protein. Loladze’s research on plants collected over three decades also showed a drop in calcium and potassium. He attributes this erosion of nutritional content to “carbohydrate dilution”, which is what happens when plants experience accelerated growth in the presence of rising CO2, causing them to become carbohydrate dense at the cost of other important nutrients. Myers and his team explain it as the result of a combination of processes including slower uptake of nitrogen by plant roots resulting from increased CO2 levels.

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Foods deficient in vitamins, minerals and protein have become more commonplace over the last few decades as fruits and vegetables are bred for higher yields, larger size, and better pest-resistance rather than for richer nutrition value. Which is why hybrids are considered far less nutritious and lower in phytonutrients than heirloom varieties which retain much of their original characteristics. However, we are only just learning of the extent to which climate change impacts our food.

Until the last two centuries, CO2 concentration had never exceeded 280 ppm. Its current concentrations are about 390 ppm – higher than at any time during the last 650,000 years – largely owing to human activities following the Industrial Revolution. It is estimated that, at the current growth rate, CO2 levels will reach 550 ppm in the next five decades, endangering global food supplies, and making the risk of nutrient deficiencies and associated diseases a serious problem. India is the world’s third largest CO2 emitter when measured on the basis of annual gross emissions.

Myers’s study reveals that more than 2 billion people worldwide receive a majority of their dietary zinc and iron from grains and legumes. In India, 70% and 60% of the population respectively depend on grains and legumes for dietary zinc and iron. We are already the world leader in iron-deficiency anaemia and associated risks: lowered immunity, impaired cognitive functioning, maternal mortality, and low productivity. Lowered protein concentration in cereal crops, in a country where much of the rural population is already protein-deficient, will have serious knock-on effects on public health, besides intensifying the problem of hidden hunger. Globally, 150 million people will join the hundreds of millions of people who already suffer protein deficiency, and will have their deficiencies exacerbated, Myers warns.

If Loladze’s claim that we are witnessing “the greatest injection of carbohydrates into the biosphere in human history” is true, then there’s another consequence of the changing nutritional profile of cereals which, in India, contribute about 53% to rural and urban calorie intake. With obesity and diabetes already on the rise with our growing consumption of refined starches and sugar, do we need more carbs in our diet?

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Climate change affects all aspects of agricultural productivity and consequently, the availability and access to nutritious food. If current levels of CO2 emissions continue unabated, lowered yields are predicted for rice and wheat in India, the worst victims of which will be its poor and marginalised.

As an immediate response to this nutritional deficit, Myers and Lalodze suggest breeding bio-fortified grains whose micronutrient concentrations are less vulnerable to atmospheric concentration of CO2, and nutrition supplements, but they warn of the risks and limitations of such measures.

Any long-term agricultural solutions must include targeted adaptation strategies that straddle climate change, farming and consumption behaviour by way of crop diversification, amelioration of diets with a wider basket of local, climate-resilient foods, and adoption of location-specific, natural farming practices, along with a reduced dependence on intensive animal agriculture.

This article first appeared on Eartha, a digital publication focused on environment, development and sustainability.