With all due respect to our colleagues who follow the vegan or a modified vegetarian lifestyle, meat / poultry / fish is high quality protein. Protein = survival.
Every cell in the human body MUST have protein on a regular, ongoing frequency for viability, cellular renewal and reproduction. If you do not get enough protein, you will eventually waste away and die as your body consumes lean muscle mass for it's protein content. This is even more critical when you are putting your body under the stress of walking weeks or months carrying weight on your back.
To clarify, I am NOT preaching, merely sharing what I have learned from direct experience.
I KNOW you all know all of this intellectually. But, on Camino, it may mean having to eat things you would not ordinarily choose to eat, for whatever reason. If you decide to forego commonly available (in Spain) sources of protein, like red meat, poultry, fish, or dairy (cheese, eggs, milk), the only viable choice for obtaining enough quality protein is likely to be toting along supplies of protein supplement powder or protein bars. Here is an aside on that option...
Because I have a bariatric lap band on my stomach (since 2005), I cannot eat enough conventional protein to satisfy my body's need for quality protein. So, I am on a medically supervised lifelong diet of supplemental protein powder. I must add about 60 grams of medical quality protein to my diet daily to supplement whatever else I might be able to consume.
Fortunately, this powder (brand = UNJURY) is available in single-serving pouches. Unfortunately, one pouch weighs about one ounce and contains 20 grams of high quality protein. Extrapolating, based on 2-3 pouches daily, two week's worth of protein pouches weighs about one kilo.
So, I must mail caches ahead for resupply every two weeks. In the caches, I also include the prodigious amounts of nutritional supplements I must take for general health as well as joint health. It is a nuisance, but beats weighing 150 kg.
When the weight of the nutritional supplements is added to the weight of the protein pouches, the weeks total added weight for my special needs is about 1.5 kilos, or 3 kilos per two weeks. This is also why it is practically impossible for me to attain an all-in-rucksack weight of 10 kg. If I can get it to 12 kg, I consider myself lucky.
I hope this helps.