My prime motivation in starting this blog, was and remains to espouse my enthusiasm for plants as medicines. However, some say food is the best form of medicine, and fruits, berries, vegetables and nuts (all from plants), are certainly healthy foods. Food availability and quality are also dependent on the condition of the soils and waterways where they are grown, as is human health related intrinsically to the health of the planet Earth.

In 2016, environmental sustainability and climate change are critical issues facing humankind. A recent study by a formidable team of scientists suggests the impact of global warming will be quicker and more catastrophic than generally envisaged⁽¹⁾. The environmental effects of human agriculture, which contribute more than a quarter of all greenhouse gas emissions, therefore warrant more debate.

Growing evidence highlights the likely dual health and environmental benefits of reducing the proportion of animal-sourced foods in our diets⁽²⁾. Recent evidence from large prospective US and European cohort studies and meta-analyses of epidemiological studies, shows an association of long-term consumption of substantial meat and particularly processed meat, with an increased risk of total mortality, cardiovascular disease, colorectal cancer and type 2 diabetes^{(3,4 ,5)}.

Two modelling studies published recently by sustainability researchers at Oxford University, now provide a compelling case that reducing red meat intake could also dramatically reduce greenhouse gas emissions and the rate of climate change^(6,7).

The Oxford researchers used a region-specific global health model to analyse the environmental and health impacts of four dietary scenarios in the year 2050. A reference scenario was developed based on current projections from the UN Food and Agriculture Organisation (FAO). The second scenario, assumed the implementation of global dietary guidelines on healthy eating (the healthy global diet), and that people consume just enough calories to maintain a healthy body weight. The healthy global diet included a daily intake of at least five portions of fruits and vegetables, less than 50g of sugar, a maximum of 43g of red meat, and an energy content of 2,200-2,300 kcal. Other scenarios also assumed a healthy energy intake but were based on diets that were vegetarian (six portions of fruit and vegetables) or vegan (seven portions of fruits and vegetables, and one portion of pulses). For the first time, the Oxford team also attempted to estimate the economic value of different dietary choices, through their effects on health and the environment.

For the health analysis, they built a comparative risk assessment model to estimate age and region-specific mortality associated with changes in dietary and weight-related risk factors known to influence mortality in a dose-related manner. For the environmental analysis, they linked regional and scenario-specific food type consumption levels to greenhouse gas emissions. The economic analysis placed a monetary value on changes in greenhouse gas emissions by using estimates of the social cost of carbon and explored monetizing the health consequences using the value of statistical life, and projections of health-care expenditure by cause of death.

The findings from this analysis were that by 2050 less than half of all global regions are projected to meet dietary recommendations for the consumption of fruit, vegetables and red meat, and would also exceed the optimal total energy intake. To achieve the healthy global diet scenario, a 25% increase in global fruit and vegetable consumption would be required, moreso in Sub-Suharan Africa and South Asia. Global red meat consumption would need to decrease by 56%, and in Western high-income and middle-income countries, by a staggering 78% and 69% respectively.

The modelling study shows that moving to diets with fewer animal-sourced foods would have major health benefits, and reduce global mortality by 6-10%. Compared to the reference scenario, the authors projected that adoption of the healthy global dietary guidelines would avoid 5.1 million deaths per year, the vegetarian diet 7.3 million deaths a year, and the vegan diet 8.1 million deaths a year. More than half of these avoided deaths would be attributable to decreased red meat consumption, with 23-35% to increased fruit and vegetable consumption, and 19-30% to less over-eating. Shifting diets toward more plant-based and less animal-based foods, could reduce global mortality by 6-10% and food-related greenhouse gas emissions by 29-70% compared with a reference scenario in 2050. These benefits were calculated to be achievable even without any allowance for the beneficial impacts of dietary change on land use through avoided deforestation, meaning the theoretical reduction in greenhouse gases could be even higher.

The monetized value of adoption of the healthy global diet would also be comparable with, or exceed, the value of the environmental benefits. Overall, the economic benefits of improving diets were estimated to be 1-31 trillion US dollars, which is equivalent to 0.4-13% of global gross domestic product (GDP) in 2050.

In New Zealand, our animal-based agricultural sector is responsible for the bulk of our greenhouse gas emissions.  An estimated 80% of agricultural emissions of greenhouse gas arise from the livestock sector, in particular from ruminants such as cattle. One cow’s annual output of methane is about 100kg, equivalent apparently to the emissions generated by a car burning 890 litres of petrol, each year.

With growing concerns about the economic viability of the dairy industry even without any allowance for the many negative and historically under-estimated environmental impacts of its intensive model⁽⁸⁾, it is time for a serious re-evaluation of New Zealand’s current agricultural sector.

However, food is both emotional and political, especially in agriculturally based economies such as New Zealand, where many have an unquestioning belief that red meat is a necessary dietary component, and that ‘more is good’. The negative reaction from the North American Meat Institute to the Oxford studies, is about as predictable as that of the American Rifleman’s Association to every attempt made to tighten gun laws there. Proponents of a largely vegetarian-based diet tend to gain more airtime in the U.K., but this has undoubtedly been catalysed by the Thatcher era mad cow disease scare, and the subsequent foot and mouth outbreak in 2001.

These types of regional differences and ingrained dietary and farming practices, will be no easy task to change, a fact acknowledged by Springmann and others^(6,9). Clearly, massive political, industrial and cultural changes would be required to produce a 25% increase in fruit and vegetable consumption and 56% less meat consumption on a global level. Nevertheless, with climate change and the growing toll of diet-related premature deaths reaching crisis levels, it is time to seriously digest the growing amount of compelling research supporting horticulture as the basis of both foods and medicines. What we eat greatly influences our personal health and the environment we all share, and growing plants rather than farming methane-producing animals is a powerful way to mitigate climate change and to prevent many deaths.

Refs:

1. Hansen James: https://www.aip.org/history/climate/impacts.htm
2. Tilman D, Clark M Global diets link environmental sustainability and human health. Nature 2014; 515(7528):518-522.
3. Battaglia Richi E et al, Health risks associated with meat consumption: A review of epidemiological studies. Int J Vitamin Nutr Res 2015; 85(1-2):70-78.
4. Lippi G et al, Meat consumption and cancer risk: a critical review of published meta-analyses. Crit Rev Oncol Hematol 2016 Jan; 97:1-14.
5. Wang X et al, Red and processed meat consumption and mortality: dose-response meta-analysis of prospective cohort studies. Public Health Nutr 2016 Apr; 19(5):893-905.
6. Springmann M et al, Analysis and valuation of the health and climate change cobenefits of dietary change. Proc Natl Acad Sci USA 2016; Mar 21. pii:201523119 (epub ahead of print).
7. Springmann M et al, Global and regional health effects of future food production under climate change: a modelling study. Lancet 2016 Mar 2. Pii:S0140-6736(15)01156-3.
8. Foote KH et al, New Zealand Dairy Farming: Milking Our Environment for all its worth. Environ Manage 2015; 56(3):709-720.
9. Marsh D. J Water resource management in New Zealand: jobs or algal blooms? Environ Manage 2012; 109:33-42.