Food-based dietary guidelines vary greatly from one country to the next – and as a result, so do the carbon footprints of these guidelines, according to new research published in Nutrition Journal (1).

Researchers from Tulane University in the United States, looked at the greenhouse gas emissions associated with the national dietary guidelines of seven countries (Germany, India, the Netherlands, Oman, Thailand, Uruguay, and the United States). They also took into account food consumption patterns for each country.

Key findings:

• Sustainability messages, such as eating more plant-based foods, have not been integrated into the majority of official dietary guidelines around the world.

• The United States (US) guidelines had the highest carbon footprint.

• The Indian guidelines had the smallest carbon footprint (at around 5.2 times less than the US guidelines).

• The carbon footprint of the main US dietary guidelines (the ‘Healthy US-style Dietary Pattern’) was more than twice that of the US vegetarian guidelines (the ‘Healthy Vegetarian Dietary Pattern’). The US vegetarian guidelines are almost identical in recommendations to the main US guidelines, except for the protein group – which recommends legumes, soy, nuts, and seeds, as well as eggs and dairy.  

• Previous single-country studies, including in Australia, largely suggest that if populations shift away from the average (or ‘typical’) national diet, and instead move more towards their country’s dietary guidelines, greenhouse gas emissions would reduce.

The research considered the impact of dietary guidelines on greenhouse gas emissions, but not other environmental impacts, such as land and water use.

How do dietary recommendations differ?

Although the dietary guidelines from all seven countries are designed to meet the nutritional needs of adults, recommendations within the six main food groups (protein foods, dairy, grains, fruits, vegetables, and oils/fats) vary.

• The main difference is in the amount recommended for each food group, particularly the protein and dairy groups. Protein food recommendations range from 75g per day in India to 156g per day in the US guidelines, for instance.

• The type of foods included in the food groups also differ. For example, the protein group in Germany’s guidelines only includes animal proteins, the US recommends a full spectrum of plant and animal protein foods, and the Indian guidelines recommend just plant proteins.

The findings, including such differences, offer insights for future development of dietary guidelines.

According to the researchers, dietary guidelines of countries with a higher carbon footprint due to their protein or dairy groups could:

• Reduce the recommended daily amount of these groups
• Create sub-groups of plant proteins within the larger ‘protein food’ group
• Encourage plant-based substitutions for animal-based foods

Global guidelines: EAT-Lancet

The EAT-Lancet Commission’s Planetary Health Diet (developed by 37 leading scientists across 16 countries) provides global guidelines, designed with environmental sustainability in mind (2).

It emphasises a plant-forward diet where whole grains, fruits, vegetables, nuts and legumes comprise a greater proportion of foods consumed. Meat and dairy constitute important parts of the diet, but in significantly smaller proportions than whole grains, fruits, vegetables, nuts and legumes.

The EAT-Lancet Commission concluded that 11 million deaths worldwide could be prevented if our current diet moved towards a more plant-based diet, including greater nut intake.

Protein food sources: Does it matter?

A major study, published in 2021, found eating more plant protein, and substituting animal protein with plant protein, was linked with a lower risk of all-cause mortality, cardiovascular disease mortality and dementia mortality in post-menopausal women (3).

Among the key findings was that substituting total red meat, eggs and dairy products with nuts was associated with a lower risk of death from all causes.

As a result, the authors of this large prospective cohort study state that protein sources need to be considered when developing future dietary guidelines.

The bottom line

Future dietary guidelines must strike the right balance between nutrition and sustainability, say the Tulane University researchers.

Addressing sustainability in food based dietary guidelines will become critical as the global population continues to grow towards an estimated 9.8 billion people by 2050, and as climate change threatens the world’s food supply and global food security.

Understanding the different carbon footprints of dietary guidelines can assist in decision-making for future dietary recommendations.

Food for thought as Australia embarks on the huge task of updating the 2013 Australian Dietary Guidelines!