A new study has further revealed how climate change is reducing yields and sucking the nutrients from our vegetables and legumes, raising serious questions over the future of food security and public health around the world.

The study is apparently the first of its kind to methodically examine to what extent environmental changes such as water scarcity, increases in temperature and a greater concentration of carbon dioxide could impact the nutritional quality and yield of crops vital to our everyday nutrition.

Read more: Sustainable food for everyone? The challenge of our century

Previous research into the impact of environmental change on food has mostly focused on the yield of staple crops such as wheat, rice and corn. However, there has been comparatively little discussion on how climate change is affecting nutritious foods that are considered more important to a healthy diet.

The 'junk food effect'

The phenomenon of crops being stripped of their high nutritional qualities due to environmental factors has become known as the "junk food effect." 

For some time now, researchers have been aware that many of our most important plant-based foods are becoming less nutritious. Studies have shown how the mineral, protein and vitamin content in fruits and vegetables has decreased over the past few decades, although until recently this had been explained away by the fact that we had been prioritizing higher yields over nutrition. 

"Vegetables and legumes are vital components of a healthy, balanced and sustainable diet, and nutritional guidelines consistently advise people to incorporate more vegetables and legumes into their diet," says lead author Pauline Scheelbeek.

"However, our new analysis suggests that this advice conflicts with the potential impacts of environmental changes that will decrease the availability of these crops."

The carbon dioxide factor

Alongside water scarcity and increasing temperatures, higher levels of carbon dioxide are being blamed for stripping crops of their nutritional value.

But carbon dioxide is good for plants, so why should we be worried about rising CO2 levels? While it's true that plants do require carbon dioxide in order to grow and thrive, it's possible to have too much of a good thing.

Rising carbon dioxide levels ramp up the process of photosynthesis — which is what allows plants to transform sunlight into food. While this certainly helps plants grow, it has the side effect of causing them to produce more simple carbohydrates such as glucose.

And this comes at the expense of other important nutrients we need in order to stay healthy including protein, zinc and iron.

Food security a growing concern

The latest findings, published in Nature, have alarming implications for food security and raise some disconcerting questions about the future of our planet's food supply.

Hotter regions such as Southern Europe, Africa and South Asia are most at risk, where higher temperatures are already expected to reduce crop yields by about 31 percent.

But Scheelbeek says the total crop yield is not necessarily the most important factor to consider.

"I think we have shifted from food intake being the biggest problem in terms of global food security to the issue of nutrition," she told DW.

Tim Benton, a visiting fellow at Chatham House and a specialist in food security and sustainability, agrees that the issue of food security — at least from a global perspective — needs to be looked at through the lens of public health and nutrition rather than focusing on the amount of crops that we grow.

"It's a developed world problem and a developing world problem," he told DW. Benton, who was not involved in the new study, doesn't see the world heading toward starvation due to not being able to grow crops. "But we are going to be in a situation where public health gets worse."

Potential for a nutritional crisis

The reduced nutritional quality of important crops could mark the beginning of a looming health crisis.

One of the biggest concerns addressed by the report is the potential increase of micronutrient deficiencies. Around 1.5 million deaths per year are already linked to low vegetable intake, according to the Global Burden of Disease (GBD) study. The worldwide per capita daily consumption of fruit and vegetables is already from 20 to 50 percent below the minimum recommended levels.

A paper published in Nature in 2014 highlighted how rising carbon dioxide levels are leading to lower nutrient concentrations in staple crops, like wheat and rice. 

But Benton stresses that at this stage, we should be more worried about the non-staples. A focus on cash crops is part of the problem, he added.

"We currently grow three times as much grain and about a third of the amount of fruit and vegetables that we need," he told DW.

Scheelbeek says various issues need to be considered if the consumption of legumes and vegetables drops as a result of environmental changes.

"For example, what would people eat instead? What would be their substitution for a less-available or more expensive legume on the market? It's certainly something we need to address."

Adaptation key to crisis

Experts say the best way to alleviate the threat to crops in the future is to prioritize changes in agricultural production.

Benton believes looking toward growing new crop varieties is "absolutely necessary" if we wish to avoid a crisis.

Read more: Gene editing: The key to food security in a warmer world?

Scheelbeek says the results of the study represent a "business-as-usual scenario," assuming very little action is taken over the next few decades.

"We hope of course that the [results] of this study are a bit of an eye-opener, and that this is a gap that we need to bridge to make sure that there is enough nutritious food until the end of the century."