Plant-based diets can improve human and planetary health

Changing eating habits holds the potential to undo damage from unsustainable food production

Picture Credit: KALLIOPÉ ANVAR MCCALL/THE VARSITY

Food production systems on earth are struggling to feed its 7.7 billion inhabitants. This is likely to continue: the United Nations projects food production would have to increase by 70 per cent, compared to 2009, in order to feed an estimated global population of 10 billion people by 2050. 

Not only does food production use a considerable portion of natural resources, it has also been identified as a contributor to climate change. The grand total of global greenhouse gas (GHG) emissions from food systems is estimated to account for 35 per cent of all human-made GHG emissions. GHG emissions from food production lead to changes in environmental conditions. Overall, such dramatic GHG emissions decrease agricultural yields, which makes certain regions in the world more vulnerable to food insecurity. 

So, how should humanity mitigate and reverse harms to the environment caused by food production? One option is to change our diets. Switching to plant-based diets in particular may do the trick, since most plant-sourced foods are known to be less resource-intensive than animal-derived foods. 

Quantifying greenhouse gas emission from animal-based foods 

A recent study by University of Illinois researcher Xiaoming Xu and their colleagues has attempted to estimate global GHG emissions from plant- and animal-based food in 2010. The researchers set out to quantify the GHG emissions from production and consumption of all foods — particularly, emissions of the gases carbon dioxide, methane, and nitrous oxide.

In addition to production-related emissions, GHG is also emitted from food consumption. High demand for plant-based commodities such as coffee, tea, bananas, palm oil, sugar cane, and grazing feeds translate into a conversion of tropical land into agricultural land. International trade, namely food imports and exports, is responsible for transfer of approximately 17 per cent of GHG emissions between regions worldwide. 

That’s why changing diets to be more plant-based holds great potential for reducing GHG emissions. Although these estimates are not definitive and have a large uncertainty range, they still provide policymakers with a framework to formulate strategies around combatting climate change caused by human food production and consumption. 

In total, the GHG emissions from 171 crops and 16 animal products were included in this study. This study was significant, since the researchers took several key factors of food GHG emission into consideration by factoring in conditions that previous studies hadn’t, like carbon dioxide emissions from natural and human-made changes to land use. 

It also considered a diverse set of farming practices that change agricultural land management. To properly tabulate GHG emissions from plant- and animal-based food production, the study also explicitly estimated emissions from both cropland and grazing land. 

The results from this comprehensive data analysis do indicate that plant-based foods are much more environmentally friendly than animal-derived foods. Overall, animal-based food production accounts for 57 per cent of total food-related GHG emissions — twice as much as that of plant-based foods. The data, which was collected from more than 200 countries around the world, delineates observable trends in global food productions. For example, the leading emitters of GHG are populous countries like China, Brazil, the US, and India. 

The common factor between all these regions is that they all have large herds of cattle dedicated to the production of meat and dairy. To support these cattle, many of these regions are converting land into cropland and grazing grounds, which further exacerbate farmland carbon dioxide emissions. 

The correlation between unregulated agricultural land use and carbon dioxide emission highlights a dire need for global action. Regulators around the world can refer to the data framework established in this study for guidance on how to mitigate the environmental impact of food-related GHG emissions. 

Tracking the water footprint of foods

How much more eco-friendly are plant-based food products in comparison to their equivalent animal-based counterparts? That’s a question that Ertug Ercin, a senior water and climate expert at the University of Twente in Netherlands, decided to investigate. 

Previous studies have concluded that, in developed countries, the average meat eater consumes 1.6 times more water a day than people on vegetarian diets. Freshwater scarcity is becoming more problematic in many regions around the world. Since 86 per cent of the earth’s water is used to grow food, it’s important that we prioritize tracking the ‘water footprint’ of food production. Instead of only measuring the amount of water withdrawn from sources, the water footprint metric comprehensively tracks allocation of freshwater resources from its source to becoming wastewater. 

Ercin set out to quantify and compare the water footprint of soy milk and soy burgers with cow’s milk and beef burgers. His results show that cow’s milk and beef burgers leave a much larger water footprint than plant-based alternatives. The global average of water footprint for a 150 gram beef burger is 2,350 litres, compared to only 158 litres for soy burgers. Similarly, one litre of cow milk takes 1,050 litres of water to produce, compared to 297 litres for soy milk.

The researchers indicated that the numbers they obtained in their investigation are only a global average — which means more in-depth analysis of the local environment would be necessary to properly assess the water footprint of food production in specific geographic areas. The researchers emphasized that food companies should conduct detailed assessment of the water footprint from their entire food production supply chain if they want to effectively reduce water consumption and pollution. 

One other noteworthy discovery in this study is how organic farming practices are harvesting positive environmental impact. Growing organic crops spares groundwater from pollution via synthetic pesticides and fertilizers. Instead, organic farmers implement strategies such as crop rotation, which involves growing crops that either complement or compensate each other on one land. This farming practice helps to improve soil fertility and break known pest cycles. Because of this, organic and plant-based food production leaves a lower ecological and water footprint. 

The take-home message is that “[humans] need to produce food groups that are good for health in ways that are restorative to the planet, rather than extractive,” according to Corrinna Hawkes, the director of the Centre for Food Policy at City, University of London. 

Health benefits of vegetarianism and veganism 

In addition to benefiting the environment, well-balanced plant-based diets are associated with numerous health benefits. A 2017 review article by Hana Kahleova outlines the various benefits of vegetarianism, including the prevention and treatment of heart and metabolic diseases. 

Kahleova and colleagues indicate that certain eating habits, such as consuming a lot of processed meat products and not enough fresh produce, can lead to a higher risk of cardiometabolic death, such as heart diseases. There are also other ways that eating plant-based diets can contribute to improving human health: if you eat more plant products, you take in more fiber, less cholesterol and saturated fat, and more antioxidants and micronutrients. 

Fibre is known to reduce plaque formation in blood vessels, which decreases the risk of developing cardiovascular diseases. Fibre is also known to be very filling as the human body cannot break down this particular class of molecules.  

Vegetarians tend to have a lower body mass index (BMI) than non-vegetarians. Although the current scientific literature is moving away from using BMI as the primary indicator of healthy body weight, it is still considered a risk factor for cardiometabolic diseases. Participants in 15 clinical trials of vegetarian or vegan diets lost an average of approximately 4.6 kilograms in a meta-analysis. Since obesity is a significant risk factor for cardiovascular illnesses, a lower BMI may play an important role in lowering blood lipid levels and reducing risk of heart diseases. 

Moreover, vegans tend to consume more whole grain, soy, and nuts than people on omnivorous diets. These whole foods are beneficial to maintaining heart health. 

Growing evidence suggests vegan diets are even more advantageous and cause even less of an environmental impact than shifting current eating habits to an ovolactovegetarian diet: one that supplements plant-based foods with egg and dairy products. A completely vegan diet increases the body’s access to plant-derived chemicals that may protect against cancer development. 

Further studies are still needed to definitively establish other long term health benefits of vegan diets. However, people who follow vegan diets may consume insufficient amounts of calcium and vitamin D, which can lead to concerns of increased risks of bone fractures. To ensure adequate nutrition, the researchers recommend that vegans regularly consume calcium- and vitamin D-fortified foods to maintain bone health. 

That being said, when a person adopts an entirely plant-based diet, the rich nutrients in whole plant food in their new diet may cause more pronounced positive effects than the isolated supplements they would consume while on an omnivorous diet. 

Should humanity voluntarily evolve into herbivores? 

The short answer is yes. An international group of scientists have proposed a meal plan called EAT-Lancet that could theoretically accommodate the estimated 10 billion people on earth by 2050, but it requires humans to cut down on meat consumption directly and increase their intake of fruits and vegetables. Such a dramatic shift in humans’ eating habits would bring about a huge reduction in water pollution and GHG emissions. 

However, there are economic challenges to adopting the EAT-Lancet diet. Currently, as many as 1.6 billion people would not be able to afford the recommended mix of foods proposed under the EAT-Lancet model. Implementing the EAT-Lancet diet would increase food costs by 60 per cent compared to the cheapest alternative diets that still provide essential nutrients. 

Even if the world is financially able to support the full implementation of the EAT-Lancet diet, meat consumption is seen as a symbol of high social status and holds a lot of significance in different cultures around the world. The combination of valued social status in various cultures compounded with the spread of Western eating habits — characterized by high amounts of processed food and red meat — is expected to exacerbate damage to the environment caused by food production and consumption. 

One of the lead scientists who proposed the EAT-Lancet model, Johan Rockström from Stockholm University, has admitted that the model has its shortcomings. The emphasis on the plant-based components of the EAT-Lancet diet can still serve, however, as an inspiration for future efforts to build sustainable, affordable, and healthy eating habits for the planet and its people. 

Article Credit: thevarsity