Soy: The Surprising Protein Dividing Vegans and Omnivores

Soy: The Surprising Protein Dividing Vegans and Omnivores

An egg contains all the essential amino acids needed to grow a whole chicken. Soy, a byproduct of oil extraction, is ranked by a nutritionist as the best protein. The ranking has sparked a debate where science, interests, and dogmas clash.

Egg or Soy? The Battle for Complete Protein
Egg is considered the gold standard: it contains all amino acids, fats, and trace elements. Soy lacks methionine, though it can be complemented with rice. Pea protein is also low in methionine. Some argue that plant protein can be complete by combining sources, such as a 70-30 mix of pea and rice.

The Dark Side of Soy: Phytoestrogens and Antinutrients
Soy contains isoflavones, phytoestrogens that can reduce testosterone if consumed in large quantities. In addition, textured soy is an ultra-processed byproduct, leading some to call it 'feed'. There is also debate about digestibility: well-cooked meat stimulates digestion, while textured soy contains compounds that hinder it.

The Price of Protein: Meat or Tofu?
A block of silk tofu in China costs 0.23 euros. In Spain, 500 grams of tofu at 1.60 euros works out to 3.20 euros/kg, comparable to economical cuts of meat. Liquid egg whites are another cheap option (about €3/liter). Textured soy is positioned as an economical alternative, although some consider it an inferior substitute.

With such disparate data, the final decision likely has more to do with personal ethics than the amino acid table. Is soy the best protein? It depends on what is measured: price, nutritional profile, or environmental impact.