Analysis: are you Culturally Sustainable, Nutritionally Sustainable or Unsustainable when it comes to your diet?

By Sinéad McCarthyTeagasc

The foods that we produce and eat have received much attention in recent years, not just because they contribute to our health but also because of the impact they have on our environment. It is reported that food production and consumption in the EU is responsible for as much as 30% of EU greenhouse gas emissions. Therefore, our food choices have the potential not only to substantially influence our health, but impact on the environment we live in. 

Is it possible to consume a diet where we can achieve both healthy eating guidelines and have minimal environmental impacts? This is a difficult question to answer because not all healthy foods have low carbon footprint, just as not all foods with a low carbon footprint are considered healthy. 

For example, carbonated beverages and milk both have the same carbon footprint of 400g of CO2 per 200ml glass of beverage. However, the HSE food pyramid for healthy eating recommends three servings per day from the dairy shelf with less than 3 serving per week from the shelf containing carbonated beverages so choosing a drink on just carbon footprint alone could result in a less healthy food choice. Similarly a beef lasagne will have a carbon footprint of 3.9kg per portion while a vegetarian pizza has approximately 1.2kg per portion, but the pizza will result in higher calorie intake compared to the lasagne.

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As individuals, we consume a range of foods that constitutes our overall diet and one single food does not result in our diet being more or less healthy/sustainable. If we consider the way in which we consume all of our foods over a given day, it is the combination of foods that determines whether our diet overall is healthy and sustainable or not. 

Researchers in Teagasc and UCC used the national food consumption survey of 1,000 Irish adults to determine if there were patterns of food consumption that were both sustainable and healthy and to profile the foods contributing to these patterns. The survey is one of the best food consumption surveys in Europe and collects a significant amount of detail on all of the foods consumed in a representative sample of the population.

Using this survey, we multiplied each food consumed by a carbon conversion factor specific to each food group to generate the carbon footprint associated with the amount of food or drink consumed by each individual, using published conversion data from the UK and Ireland. Statistical analysis identified three very distinct consumer groups whose patterns of consumption varied according to health and sustainability credentials. 

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The first of the three groups, which accounted for one-quarter (25%) of the population, were termed Unsustainable. Their diets resulted in the lowest level of compliance with dietary guidelines as well as the highest carbon footprint arising from the pattern of foods they consumed. The highest food intakes for this dietary pattern were from processed meats, alcohol and savoury snacks with low intakes of fruit and vegetables resulting in a carbon footprint of 9 kg per day for men and 6 kg per day for women. 

The second group were the Nutritionally Sustainable and accounted for one-quarter of the population. They achieved compliance with the most dietary guidelines and they were characterised by high intakes of fish, fruit & vegetables, and dairy foods, and moderate to low intakes of red meat resulting in a carbon footprint of 7.7 kg per day for men and 5 kg per day for women.

The third and largest group at half of the population were the Culturally Sustainable group.  They were characterised by a traditional and culturally-derived diet of red meat, dairy and potatoes and achieved fewer dietary guidelines compared to the nutritionally sustainable group. Despite the fact that this group had the highest intake of red meat, they did not differ from the nutritionally sustainable group (with lower meat intake) in their overall carbon footprint at 7.4 kg per day for men and 5 kg per day for women.

We are faced with many challenges when we attempt to change our food preferences

In general, plant-based foods have a lower carbon footprint, whereas foods from animal sources are higher, especially from ruminant animals. However, it cannot be overlooked that foods from animal sources provide many essential nutrients necessary for good health and therefore are an important part of a healthy diet. It has been clearly outlined above that a healthy and nutritionally sustainable diet does not have to be devoid of animal products such as red meat and dairy. Similar research on dietary related emissions using national food consumption surveys from UK, France, Australia have also shown that a sustainable diet which meets requirements for health and lower emissions can be achieved without eliminating meat or dairy products from the diet.

Nevertheless, there has been increasing calls for consumers to adopt more plant based diets and to abandon our carnivorous habits. Given how difficult it is to get consumers to include the rainbow of five portions of fruit and vegetables for personal health benefits, can the call to exclude a significant and frequently consumed food group realistically be achieved? More importantly, will the substitutions/replacements be more healthy and suitable for all consumers?

For many, changing behaviour is often undesirable and delayed to some far off time in the future (I will start the diet on Monday!). We are also faced with many challenges when we attempt to change our food preferences. These habits have been developed and established over many years and generations reflecting the multidimensional nature of eating from social aspects, habits, preferences, cultural and social norms.

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Recommendations to change our current consumption habits should be evidence based and consider the prevailing cultural food consumption patterns of a population. Guidelines developed for sustainability reasons should be holistic in nature, take many parameters into consideration especially health and nutrition, rather than concentrating on one food group or one measure such as emissions. 

The study was funded by the Department of Agriculture Food and the Marine through the Food Institutional Research Measure (FIRM) funding instrument (ReVisData 13/F/365).

Dr Sinéad McCarthy is a researcher at the Teagasc Food Research Centre

The views expressed here are those of the author and do not represent or reflect the views of RTÉ