Background: Agricultural activities occupy a significant part of the world’s land area and the food systems are comprehensively reliant on fossil fuels, resulting in that the sector is responsible for a large percentage of the world’s greenhouse gas emissions. Changes are needed in order to meet the challenges of developing sustainable food systems. One change strategy would be to replace parts of animal proteins with greener plant substitutes. This thesis is part of a four-year transdisciplinary research project with the aim to, within four years, develop domestically produced products based on Swedish legumes. This paper will focus on exploring significant components affecting health-conscious consumers’ attitudes and purchase intentions regarding legumes-based products. By the thesis, valuable information and insights regarding legumes as a protein substitute will be gathered amongst the growing consumer group of health-conscious consumers.  Purpose: The purpose of this study is to explore the attitudes regarding legumes, and underlying key components affecting health-conscious consumers purchase intentions towards legume-based products. Additionally, two research questions have been developed to reach valuable findings for this investigation.

The traditional treatment for phenylketonuria (PKU) is a phenylalanine (Phe)-restricted diet, supplemented with a Phe-free/low-Phe protein substitute. Pharmaceutical treatment with synthetic tetrahydrobiopterin (BH4), an enzyme cofactor, allows a patient subgroup to relax their diet. However, dietary protocols guiding the adjustments of protein equivalent intake from protein substitute with BH4 treatment are lacking. We systematically reviewed protein substitute usage with long-term BH4 therapy. Electronic databases were searched for articles published between January 2000 and March 2020. Eighteen studies (306 PKU patients) were eligible. Meta-analyses demonstrated a significant increase in Phe and natural protein intakes and a significant decrease in protein equivalent intake from protein substitute with cofactor therapy. Protein substitute could be discontinued in 51% of responsive patients, but was still required in 49%, despite improvement in Phe tolerance. Normal growth was maintained, but micronutrient deficiency was observed with BH4 treatment. A systematic protocol to increase natural protein intake while reducing protein substitute dose should be followed to ensure protein and micronutrient requirements are met and sustained. We propose recommendations to guide healthcare professionals when adjusting dietary prescriptions of PKU patients on BH4. Studies investigating new therapeutic options in PKU should systematically collect data on protein substitute and natural protein intakes, as well as other nutritional factors.