Recently I attended a workshop relating to a project which I am currently completing as volunteer, developing a food and drink strategy for the East Lancashire Hospitals NHS Trust. This strategy is subdivided into multiple elements, including patient nutrition, patient hydration, catering services, healthy eating, and sustainability. The matter of sustainability was a considerable aspect of discussion during this workshop; however, initiatives to enhance sustainability were dominated by food waste alone.

Food waste is certainly a significant concern. According to Love Food Hate Waste, approximately 7 million tonnes of food and drink are being wasted from UK homes every year, costing around ~£12.5bn, and if we stopped such wastefulness it would save the equivalent of at least 17 million tonnes of carbon dioxide. However, waste isn’t the sole culprit in affecting measures of sustainability in relation to food and drink.

Indeed, a matter which stakeholders within the NHS are willing to neglect, dietary choice exhibits considerable influence on sustainability, with the potential of a synergistic relationship with another element of the aforementioned strategy: healthy eating.

I partially approached the topic of sustainable diets in an earlier post, ‘The Answer is Change: Diet & Climate’, however, my intention this time is to provide practical evidence of how a healthy diet is beneficial and may be closely related to sustainability, particularly via comparison of the Western diet (“unhealthy”) versus the Dietary Approaches to Stop Hypertension (DASH) diet (“healthy) – a dietary pattern which seemingly fits the description of being protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable, nutritionally adequate, safe and healthy.

Global agriculture and food production release more than 25% of all greenhouse gases, pollute fresh and marine waters with agro-chemicals, and use approximately half of the ice-free land area of Earth as cropland or pastureland (Tilman & Clark 2014). The sustainability of livestock is not as viable as that of crop production: production of livestock accounts for 30% of land use globally, and 70% of all agricultural land; the livestock industry is a major contributor to global warming, emitting 18 percent of total greenhouse gas emissions, contributing 65% of anthropogenic nitrous emissions (mainly from manure), 37% of anthropogenic methane (mainly from enteric fermentation and manure), 9% of anthropogenic carbon dioxide emissions (mainly from land use changes including deforestation), and 64% of anthropogenic ammonia emissions; livestock also negatively impacts on the replenishment of freshwater, through compacting soil (thereby reducing infiltration), contributing to deforestation (thereby increasing runoff), degrading the banks of watercourses, lowering water tables, and reducing dry season flows (Joyce et al. 2012).

Furthermore, the inevitable increase in demand for food, linked with the increase in global population and its affluence, will only exacerbate current concerns regarding agriculture and food production. One recent study highlights the inefficiency of livestock products: livestock globally consume 4.6 PgCyr-1 (biomass carbon/year) as feed (1.2 PgCyr-1 of crop products, 0.7 PgCyr-1 of crop residues and 2.7 PgCyr-1 of pasture forage). The main outputs, meat and dairy, contain only about 0.12 PgCyr-1 or 2.6% of that carbon mass, before losses, confirming both the trophic energy inefficiency and the land-intensiveness of animal-based food products. Subsequently, if the demand for inefficient pathways of food supply disproportionately increases (e.g. an increasing global acceptance of the Western diet), the whole system becomes not only larger, but also less-efficient. Interestingly, future scenarios involving “healthy diets,” in comparison to current trends in yields and yield gap closures, appear most permissible, alleviating land-intensiveness by reducing the area necessary for cropping by ~5%, pasture by ~25% and facilitating reductions in total greenhouse gas emissions by ~45% – savings that are largely associated with livestock reductions (Bajzelj et al. 2014).

The Western diet is characterised by frequent consumption of processed and/or red meat, refined grains, sweets, desserts, eggs and high-fat dairy products. Such a diet has been suggested as unsustainable with respect to environmental impact, with the production of protein from meat taking 11 times the amount of fossil fuel use compared to a vegetable-based protein (specifically corn) and the production of the equivalent amount of animal protein taking 100 times more water than for vegetable protein. Furthermore, in assessing the impact of single food items, it’s suggested that beef has the largest environmental impact, followed by fish, cheese, and milk, with sources of stress coming from land use, fossil fuel use and water use e.g. in Australia the dairy industry is the highest user of irrigated water in the Murray-Darling Basin (Joyce et al. 2012).

In addition to its presumed negative relation with sustainability, the Western diet is suggested to adversely impact health. Although several meta-analyses relating dietary patterns to different cardiovascular disease (CVD) events have failed to demonstrate a direct association between adherence to unhealthy dietary patterns, such as the Western diet, and CVD incidence (Rodríguez-Monforte et al. 2015), it has been indicated that adopting the Western dietary pattern is significantly associated with almost all CVD risk factors (Aljefree & Ahmed 2015).

A study published in 2015 found that a Western-type dietary pattern was associated with an increased risk of coronary heart disease (CHD), indicating that red meat and processed meat consumption are greatly associated (Zhang et al. 2015). Accordingly, past studies have highlighted that high consumption of red and processed meat is associated with raised total cholesterol, LDL-cholesterol and blood pressure, and greater BMI. And, furthermore, it’s suggested that high temperature commercial cooking or frying, commonly used in preparing processed meats, may generate heterocyclic amines or polycyclic aromatic hydrocarbons, which may increase the risk of CHD and type 2 diabetes mellitus; processed meats also contain a high content of salt, nitrates and their by-products (e.g. peroxynitrite), again associated with an increased risk of CHD (Zhang et al. 2015).

Red and processed meats aren’t the only concerns. The intake of refined grains, sweets (especially sugar-sweetened soft drinks), desserts and high-fat dairy products increases the amount of saturated fat, trans fatty acids, dietary sugars and salt consumed (Rodríguez-Monforte et al. 2015) – all of which are indicated as exhibiting potential roles in heightened disease risk (including hypertension, obesity and metabolic syndrome, diabetes, and cardiovascular disease) (de Souza et al. 2015; Te Morenga et al. 2014; Taylor et al. 2011). Coincidentally, the potential role of the Western diet in relation to disease risk was recently studied among adults in the Middle East and North Africa region. Findings of this review indicated that adopting the Western dietary pattern is significantly associated with risk of obesity, blood lipids, hypertension, diabetes and metabolic syndrome in the reference populations e.g. in Iran, the Western dietary pattern was significantly associated with an increased risk of dyslipidemia and hypertension (Aljefree & Ahmed 2015).

The DASH diet encourages a high intake of whole grains, fruits, vegetables, and low-fat dairy products, while limiting sodium intake and the consumption of all meats, poultry, fish, and eggs (Shirani et al. 2013; Yu et al. 2014). In relation to its plant-centered characterisation, it’s suggested that the DASH diet may have positive implications on environmental impact.

As modelling studies have previously suggested that reducing the consumption of meat and other animal-derived foods can simultaneously reduce the greenhouse gas (GHG) impact of the diet, it’s appropriate that adherence to the DASH diet has shown a negative association with GHG impact e.g. Monsivais et al. found that adults with the closest degree of accordance (quintile 5; Q5) with the DASH diet consumed diets with a mean GHG impact that was 16% lower than diets exhibiting the lowest level of accordance (quintile 1; Q1). However, the benefits of this diet towards mitigating climate change aren’t equally distributed. Accordance with 4 of the 8 food groups (fruit, whole grains, red and processed meat, and dietary sodium) showed a negative association with emissions. Alternatively, the vegetable, low-fat dairy, and foods high in sugars categories were positively associated with greenhouse gas impact, partially offsetting the environmental benefits related to the diet’s guidelines for fruit, whole grains, red and processed meat, and dietary sodium: Q5 for red and processed meat guidelines had an associated GHG impact that was 49.5% (4.3 kg CO2eq/d) lower than the GHG impact associated with Q1 diets; Q5 diets for vegetables and foods high in sugars both showed a GHG impact approximately 16% (1 kg CO2eq/d) greater than diets in Q1 (Monsivais et al. 2015). Presumably, this beneficial impact on GHGs, and thus sustainability, is supported by the finding that, in regards to meat and soy products, an equivalent amount of meat protein requires 6 to 17 times the amount of land than soy protein. Also, meat production requires 4.4 times the amount of water through intensive irrigation, and 26 times the amount of water through rainfall alone, compared to soy. Meat production also requires between 2.5 and 50 times (depending on the intensity of agriculture) more use of fossil fuels than soy protein requires (Joyce et al. 2012). Thus, limitations on meat consumption simultaneously limit environmental impact.

Besides apparent sustainability enhancements, the design of the DASH diet, rich in plant foods and low-fat dairy products and relatively low in fats and sugar, was originally predicted to benefit health, specifically lowering blood pressure in persons with hypertension and pre-hypertension (Monsivais et al. 2015). However, it is now recommended as an ideal eating pattern for all adults (Shirani et al. 2013).

As a result of its emphasised constituents, the DASH diet, in comparison with usual diets, provides lower amounts of total fat, saturated fat, and dietary cholesterol, while providing higher amounts of potassium, calcium, magnesium, fibre, and protein (Salehi-Abargouei et al. 2013). Previous studies have found that greater adherence to dietary patterns categorised as “healthy,” similar to the DASH diet, could be favourably correlated with reductions of the incidence of lipid abnormalities, hypertension, arrhythmias, diabetes and obesity through the amelioration of insulin sensitivity and their anti-inflammatory and antioxidant actions (Li et al. 2015). Accordingly, it has been found that the DASH diet can significantly reduce fasting insulin concentration [compared with a control diet] (Shirani et al. 2013), and that imitating a DASH-like diet can significantly reduce risk for CVDs, CHD, stroke, and heart failure by 20%, 21%, 19%, and 29%, respectively (Salehi-Abargouei et al. 2013).

Explanations for the health benefits associated with the DASH diet are varied. According to epidemiological research data, there is a beneficial effect of increased dairy, whole grain and nuts on diabetes risk. High intakes of calcium and magnesium are associated with improvement in insulin sensitivity (Shirani et al. 2013). Inflammatory markers, such as C-reactive protein, are associated with an increased risk of developed type 2 diabetes; however the DASH diet has been shown to result in a statistically significant decrease in mean C-reactive protein [compared to a control group] (Nowlin et al. 2012). And, greater intakes of fibre, especially soluble fibre; folate, vitamin C, and phytochemicals such as flavons, flavonons, carotenoids, and phytoesterol in the DASH diet may result in augmentation of antioxidant capacity, may have a blood pressure-lowering effect and a beneficial effect on lipid profile insulin sensitivity, and reduction in oxidative stress (Salehi-Abargouei et al. 2013).

Ultimately, evidence suggests that wide-scale adoption of a plant-based diet would reduce human impact on the environment and improve some of our most serious environmental problems such as climate change and fresh water scarcity (Joyce et al. 2012), whilst being associated with a lower risk of mortality outcomes for men and women (Reedy et al. 2014).

Fortunately, the DASH diet was designed to be largely congruent with US norms of food consumption (Monsivais et al. 2015), therefore implying potential social acceptance (especially as the diet limits, rather than omits, animal-derived foods). Thus, in an effort to alleviate current health epidemics, such as that of obesity, and mitigate climate change via a promising synergistic relationship between healthy diet and sustainability, it would seem prudent to focus our attention on transitioning away from the current Western dietary pattern to a plausible alternative such as the DASH diet – hopefully deviating from forecasts estimating that the 2050 diet composition may shift to having 61% more empty calories, 18% fewer servings of fruit and vegetables, 2.7% less plan protein, 23% more pork and poultry, 31% more ruminant meat, 58% more dairy and egg and 82% more fish and seafood (Tilman & Clark 2014).

So…thinking of changing your dietary habits?

Maybe you want to be healthy enough that you’re physically capable of attempting to escape a future natural disaster?

Well, a quick and simple suggestion: make healthy, sustainable eating a theme, such as Meat-Free Monday or Sustainable Sunday. After all, small changes make a difference: “shifting less than one week’s worth of calories from red meat and dairy products to chicken, fish, eggs or a vegetable-based diet achieves more greenhouse gas reduction than ‘buying local'” (Weber & Matthews 2008).