sustainable diet

Sustainable healthy diet

What is the definition of a sustainable diet?

According to the FAO Biodiversity and Sustainable Diets symposium (Nov. 2010, Rome, Italy), Sustainable diets are defined by as “diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations”.

“Sustainable diets are:

protective and respectful of biodiversity and ecosystems;
culturally acceptable, accessible;
economically fair and affordable;
nutritionally adequate, safe and healthy;
while optimizing natural and human resources (1).”

Sustainable foods or diet isn’t just about environment. There are many different views as to what constitutes a sustainable food system, and what falls within the scope of the term sustainable food or sustainable diet:

Environment
Health
Economics

Characteristics required for a sustainable food

How to be sustainable with food?

In order to adopt an eco-friendly diet, the key is to consider a food’s nutritional value, affordability and accessibility within the landscape of its impact on environmental and social factors such as land use, animal welfare, labor and market conditions and economics of food supply (2, 3).

According to this approach, the consumer can be confronted to a dilemma:

Nutrient-rich foods tend to be more expensive, whereas foods that provide “empty calories” are usually cheaper
Nutrient-rich foods typically have a higher environmental impact and are consequently costlier in terms of environmental footprint. Meat and dairy foods that have a high nutrient density also have higher greenhouse gas emissions (GHGEs). Yet, sugar and some grains that have low GHGEs, have fewer nutrients.

The key of a healthy sustainable diet is to identify those foods, which are high in nutrient density, have a low environmental footprint whilst also being affordable and culturally accepted.

Is eating meat and other animal-sourced foods (fish, egg, dairy) sustainable?

The growing worldwide population challenges global food supplies and nutrient-dense foods are crucial to support nutrient security in the future.

Eating meat or other animal-sourced foods sustainably is mainly a question of balance between nutrition and sustainability. The easier way to analyze it is to look at dairy products and milk.

Milk and dairy products are recognized as a nutritious foods (2), providing numerous keys essential nutrients. Consequently, the demand for yogurt and milk products is rising and the Food & Agricultural Organization (FAO) estimates that the demand for milk will increase from currently 700 to over 1000 billion kg in 2050. Indeed, cows are efficient convertors of human-inedible resources (low-quality proteins in grains and soy) into nutrient-dense milk and yogurt, containing essential micro-nutrients and high-quality proteins. However, food production, distribution and storage create greenhouse gas emissions and milk production contributes to the production of greenhouse gas emissions, which impacts environment.

So what is the overall result of eating a yogurt or drinking one glass of milk?

Plant-based foods have a lower environmental footprint than animal-sourced foods (on a unit-weight basis), but this is offset by their lower nutrient density. The environmental impact of dairy farming has to be weighed against the high nutrient density of milk, yogurt and cheese compared with plant-based foods. A Danish research team took into account human health impacts of food and diets. For one portion of milk, they compare the nutritional impacts to environmental impacts (such as global warming), and their consequences for human health. The model showed that adding one serving of milk in the diet, without substituting other healthy foods such as fruits and vegetables, could result in health benefits (6,7,10). The net health benefit was even further increased when substituting less healthy foods (such as sugar-sweetened beverages) on an iso-caloric basis.

Carbon cost by food category: mean greenhouse gas emissions (GHGE) per 100 g

Is flexitarian diet sustainable?

A flexitarian diet gives more place to plant-based foods in the global diet and less meat and animal-sourced foods.

It differs for vegetarian and vegan diets, as it is more flexible and still allows to eat meat. It may be an interesting compromise for a balanced and sustainable diet. There is no specific rules for a “good flexitarian diet” but the main approach is to:

Promote the consumption of fruits, vegetables and whole grains.
Limit the consumption of processed foods
Limit the consumption of sugar and sweets
Add meat and animal-sourced foods occasionally

The flexitarian diet can be considered as a way to build a sustainable diet: As it reduces the part of animal-sources foods consumption, it may help decrease the greenhouse gas emissions, as well as land and water use and has a lower impact on the environment. However, the occasional consumption of animal-sourced foods assure the nutritional needs and limits the risk of nutrient deficiency.

In this situation, nutrient-dense foods such as yogurt and dairy products may be particularly of interest (6,7,10).

Can yogurt be part of sustainable food choices?

Yogurt is commonly viewed as a healthy food and is part of the diet of many people worldwide and the yogurt consumption is even seen as a marker of an overall healthy diet and lifestyle (11)!

The specific manufacturing and fermentation process of the yogurt give it a high amount of micronutrients (vitamins B, calcium, potassium, zinc and magnesium). Yogurt is a nutrient-dense food with low energy density.

Based on the greenhouse gas emissions, related to food production, processing, transporting, and retailing of different foods, yogurt appears to be an eco-friendly food. The carbon footprint of yogurt production is low to moderate, compared with other foods .

According to the FAO, one of the components of a sustainable diet includes reference to the health and well-being of the population. This explains that sugar and sweets, despite their little effect on the environment, cannot be considered to be part of a sustainable diet, while yogurt can perfectly fit.