Moving from shortfall towards adequacy: improving the protein quality of New Zealand vegan diets through optimisation modelling
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Background
Poorly planned vegan diets may incur deficiencies in indispensable amino acids (IAAs) and certain micronutrients. Targeted dietary modifications are necessary to improve nutrient adequacy for optimal health.
Objective
Optimisation modelling was applied to identify combinations of plant-based foods within an individual’s existing diet to address protein and IAA shortfalls in a sample of New Zealand vegans grouped into three clusters with varied daily dietary patterns.
Methods
Shortfalls for protein and IAAs were calculated by comparing daily intakes to individual requirements. An energy-tailored optimisation using linear programming was used: diets with lower energy intake had foods added while those with excess energy had energy-dense and low-protein foods replaced with protein-rich alternatives. The modified diets had to 1) meet protein and IAA shortfalls, 2) respect serving size constraints for added foods, and 3) remain within individual energy boundaries while minimising the weight of food added. Post-optimisation analysis assessed changes in intake of protein, amino acids, dietary fibre and selected micronutrients with results compared across clusters.
Results
Protein and IAA shortfalls were more prevalent in cluster 1 (85% of daily diets) compared to clusters 2 (61.1%) and 3 (30.8%). Legumes and pulses contributed most to total protein and lysine with lower energy costs, while nuts and seeds contributed most to methionine and leucine, but with higher energy. Optimisation resolved shortfalls in 93.2% of the daily diets. The remaining 52 diets - mainly from clusters 1 and 2 - could not reach adequacy due to large protein and IAA deficits and limited energy capacity. Post-optimisation micronutrient analysis showed continued risks of shortfalls for calcium, vitamin B12 and iodine.
Conclusion
Mathematical optimisation can enhance the protein adequacy of vegan diets while preserving individual acceptability. However, full nutritional adequacy remains challenging in energy-constrained diets with large nutrient deficits.
