Future dietary paradigms should add diverse recipes to tally exact carbon emissions, study suggests

15 Apr 2024 --- Most food studies assess the impact of diets on human health and the environment by looking at them from the food group level. However, scientists from the University of Tokyo switched this up with an optimization modeling approach that looks at diets from a nuanced dish level. The results show that this new approach can help people make more informed choices and improve industry practices.

The researchers argue that the approach can complement guidelines like the EAT-Lancet Commission Report with more comprehensive information on sustainable diet composition in specific geographic contexts. Roughly 100 countries have developed dietary guidelines to optimize the economic, environmental and social aspects of diets. Still, the ecological implications of the dietary practices are often not thoroughly considered.

“In considering the improvements needed in the current diet paradigm, it is essential to address two primary areas: clarity in food choices and practicality of dietary guidelines. Current popular diets, such as low-carb, Mediterranean and vegetarianism, often focus on specific objectives like weight loss or minimal intake of sugars and salts,” Yin Long, lead author of the study and associate professor at the University of Tokyo’s Graduate School of Engineering, tells Nutrition Insight.

“However, they can leave individuals perplexed about what specific foods to eat. A practical solution would be the introduction of tailored recipe suggestions that align with various dietary habits, making it easier for people to adhere to these diets.”

“Moreover, many diet recommendations present daily intake metrics in grams, which can be challenging for the general public to translate into actual meals. Future dietary paradigms should consider offering diverse recipe suggestions that not only specify what to eat but also take into account the time, cost and environmental impact of adopting these diets,” she stresses.

“Providing comprehensive, easy-to-understand and actionable diet suggestions will make it more feasible for individuals to follow and benefit from healthier dietary practices.”

Data assessed dishes
The study, published in Science Advances, identified trade-offs in nutrition, carbon footprint and price for individual dishes with multiple ingredients rather than broad food categories such as red meat, fish or vegetables.  

Data from 45 popular dishes of Japan consisting of multiple ingredients were analyzed, each with different cooking times. The analysis was conducted using algorithms that optimize specific parameters in the datasets. 

“A mixed diet typically signifies an eating pattern that incorporates a variety of foods without restrictions, including both plant-based and animal-based items. This approach provides a comprehensive array of nutrients and ensures the intake of essential amino acids and micronutrients often found in animal foods,” Long explains.  

“The essence of a mixed diet lies in its balance and moderation, which help minimize health risks and environmental impacts associated with excessive consumption of animal products. By embracing diversity in food choices, a mixed diet avoids overly selective eating habits and promotes a well-rounded nutritional intake.”The researchers believe dish-based approaches better inform food planning consumption.

The study shows that diets with more plant-based ingredients tend to have lower carbon footprints but fail to meet the daily nutrient requirements. Mixed diets are more balanced between good nutritional value and carbon footprint. 

Food intake guides
The scientists believe providing direct food intake recommendations at an individual level is essential because some prioritize consuming high-protein and low-calorie, low-salt or low-cholesterol diets to prevent health problems such as obesity, cardiovascular disease and other non-communicable diseases. 

Broad dietary scenarios can be implemented differently in different cultural contexts. According to the study, a vegetarian or pescatarian diet can have different impacts because it is not the same across countries due to differences in the availability or preferences for ingredients.

Long notes: “Take Japan’s Oyakodon. The main ingredients of this dish include chicken thighs, onions, cress, eggs and rice. Nutrient content was calculated using the information provided by the Dietary Reference Intakes for Japanese (Ministry of Health, Labor and Welfare).” 

“Each ingredient has its specific nutritional content, such as chicken thighs, which are rich in protein and vitamin B complex. Eggs provide high-quality protein and a variety of micronutrients. Although our study area is only Japan, it can also reflect certain food cultures, such as preferences for specific meats (not eating pork, etc.) or pure vegetarianism.

“Regarding carbon footprint, from a supply chain perspective, carbon dioxide emissions are generated during the cultivation, transportation, processing and cooking of food ingredients. Based on the computational model proposed in this study, the carbon footprint of each dish can be assessed, including all links from production to table. The production of chicken legs and eggs involves carbon emissions, especially during the raising process,” she explains.

Carbon emission intensity
According to the scientists, dish-based approaches better reflect how food is prepared and consumed in a given local context. It mirrors cultural preferences for specific tastes, cooking methods and the acceptability of food items. The relative availability of the foods can also be seen based on the local varying environmental conditions.

“We should stress that we do not believe impact analyses based on food groups and dishes are mutually exclusive. Instead, we believe they are highly complementary. We believe dish-based approaches can better inform the day-to-day organization of food consumption at the national and local levels by acting as a reality check to convey feasible and acceptable ways to steer dietary habits toward sustainable directions,” says Alexandros Gasparatos, co-author of the study and professor at the University of Tokyo’s Institute for Future Initiatives.

The study results show that beef-based dishes had the highest average carbon footprint, followed by chicken- and seafood-based dishes, while pork- and vegetable-based dishes had lower carbon footprints than the rest. Pork-based dishes in Japanese cuisine generally contain smaller meat portions, include many vegetables and require a shorter cooking period.

Long adds: “This culinary tradition offers a balanced mix of nutrients and showcases the potential for diverse food choices. We advocate for balanced dietary practices and emphasize the importance of education in raising awareness about the nutritional value of these meats when integrated with vegetables and their environmental impact. Such initiatives can contribute significantly to more sustainable dietary habits in the future.”

In addition, the results revealed that direct emissions from cooking had a much lower contribution to the dishes’ overall carbon footprint than indirect emissions. Generally, direct emissions only account for 1.6 to 12.1% of the overall carbon footprint, depending on the type of dish. 

By Inga de Jong