Key Takeaways
- Plant protein requirements are 10-15% higher than general guidelines due to lower digestibility scores (PDCAAS/DIAAS) of most plant sources compared to animal proteins.[3]
- Lysine is typically the most limiting amino acid in plant-based diets. Legumes (lentils, beans, soy) and pea protein are the richest plant sources.[2]
- Complementary protein pairing — combining legumes with grains — ensures a complete amino acid profile across the day. These foods do not need to be eaten in the same meal.[2]
- The Institute of Medicine recommends a baseline of 0.8 g/kg for sedentary adults, scaling up to 1.6-2.0 g/kg for intense training and muscle building.[1]
Why the +10-15% Adjustment?
The Protein Digestibility Corrected Amino Acid Score (PDCAAS) and the newer Digestible Indispensable Amino Acid Score (DIAAS) measure how efficiently your body can use protein from different food sources.[3]
Most plant proteins score between 0.5 and 0.9 on the PDCAAS scale (compared to 1.0 for animal proteins like whey and eggs). This means that if you eat 100g of plant protein, your body may utilize only 50-90g effectively.
The calculator applies a flat 12% adjustment to account for this, which aligns with the recommendation by Mariotti & Gardner (2019) for mixed plant-based diets.[2]
Meeting Your Lysine Target
Lysine is the amino acid most likely to be insufficient in a plant-based diet, particularly if your protein comes primarily from grains, nuts, and seeds. The WHO recommends 38 mg of lysine per kilogram of body weight per day.
The best plant sources of lysine are legumes: lentils, black beans, chickpeas, and soy products. A single cup of cooked lentils provides roughly 1,250 mg of lysine. Pea protein powder is also exceptionally high in lysine.
Frequently Asked Questions
Sources & References
- Dietary Reference Intakes for Protein and Amino Acids. Institute of Medicine. National Academies Press (2005)
- Dietary Protein and Amino Acids in Vegetarian Diets — A Review. Mariotti F, Gardner CD.. Nutrients (2019)
- Dietary Protein Quality Evaluation in Human Nutrition. FAO Expert Consultation. FAO Food and Nutrition Paper No. 92 (2013)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.