Predetermined dietary patterns vs optimisation
One of the differences is that the EAT-Lancet Commission starts from a number of predetermined dietary patterns, such as semi-vegetarian (‘flexitarian’), pescatarian, vegetarian and vegan. This means that the amounts of the different types of foods are fixed in advance. In our studies we chose an ‘optimisation’ approach in which we look for an optimum dietary pattern derived from nutrient needs and sustainability targets. This method ensures that an optimised dietary pattern always meets nutritional requirements, such as the right number of calories and a sufficient intake of vitamins and minerals. It leads to different results because there are more degrees of freedom, and it even generates a dietary pattern with a lower environmental impact than an approach based on a predetermined reference dietary pattern. .
Whole life cycle of food products taken into account
Another important difference is that we critically examined the whole life cycle of the food products, whereas the Lancet study focused on agricultural production. This means that the Lancet study underestimates the environmental impact of some foods, because for some foods the bulk of impacts are not caused during primary production, but elsewhere in the life cycle, such as the manufacture of the packaging or the preparation of the meal by the consumer.
Moreover, unlike the EAT-Lancet Commission, we did not use production and export figures to describe current dietary patterns. Our calculations are based on the Dutch National Food Consumption Survey, so the amounts reflect real consumption by consumers. The difference in the outcome is well illustrated by the product group ‘oils’. The Lancet study assumes that all the vegetable oils available in a country are consumed, but that is not a sound assumption (frying oils being a case in point).
Feasibility of new dietary patterns
Finally, a further aspect in our approach is that new dietary patterns diverge as little as possible from the current (average) dietary pattern in a country, making them more accessible to consumers. A healthier and more sustainable diet can be achieved simply by making relatively small adjustments.