Shifting protein ratios in four European countries: Dietary substitution modelling with plant and novel proteins

Transitioning diets towards more plant and novel protein sources is essential for achieving environmental goals but may pose nutritional challenges. This study evaluated the nutritional and environmental impacts of shifting dietary protein ratios by substituting meat and dairy products with analogues based on alternative proteins – including plants, crickets, microalgae and microbial mass – in four diverse European dietary contexts. Using nationally representative dietary data from Finland, Germany, Italy and Serbia, linear programming was applied to model 1:1 substitutions that maintained existing meal structures. Diets were optimized to reach protein ratios of 50:50 and 30:70 (animal:plant/novel), while minimizing the number of product substitutions. A median of 0.0–0.5 and 0.5–3.0 substitutions per day were needed to achieve the respective targets, resulting in average reductions of 3–29% and 19–50% in both greenhouse gas emissions and land use. Average utilizable protein intake exceeded requirements in the modelled diets, but declined to >93% of the dietary reference value in the 30:70 scenarios relying solely on plant-based analogues. Changes in nutrient intakes showed both benefits (increased fiber, mono-unsaturated fatty acids, vitamin E, iron and magnesium and decreased saturated fatty acids) and drawbacks (decreased vitamins A, B2, B6, B12 and D, calcium, iodine, potassium, selenium and zinc and increased sodium), with some inadequacies mitigated by fortification. These findings demonstrate that shifting dietary protein ratios through modest and realistic substitutions with analogues can yield notable environmental gains. However, potential inadequacies in nutrients primarily provided by animal products should be addressed by establishing fortification and reformulation strategies for analogues.