Here is the science on soy: http://nutritionfacts.org/video/how-much-soy-is-too-much/
I tried "Natura Nuova Bio Tofu naturale 100% vegetale" from esselunga and it was very bad. I haven't found any good tofu here in Italy. @yepes
: When there is a protein deficiency in the body, protein synthesis halts in the hair follicle(s) and then the hair falls out when protein demands of the hair follicle aren't met by the diet. A person will know they need protein when they are loosing more hair than normal.
The truth is that people require more protein to stimulate protein synthesis because they are deficient in the fat soluble vitamins(Vitamin A/D/K); a lot of people are. The fat soluble vitamins are like hormones and are a lot more potent at stimulating protein synthesis than a high protein diet and are a lot healthier for the body in the long run.
Best protein source: Raw leafy greens(Vitamin A & K) with sunshine (Vitamin D).
Best fat source: Nuts, olives, seeds.
Best carb source: Ripe fruit.@MillaD
: More protein is required when there is a lack of fat soluble vitamins as I mentioned above and when insufficient calories are eaten. Protein is the basically the bricks(mattoni) of the house(your body), so when daily calories aren't fulfilled from either the intake of carbs and fat, the body breaks down muscle(protein/bricks/mattoni) to produce fuel(sugar).
Protein requirements for a sedentary individual: http://it.wikipedia.org/wiki/Amminoacidi_essenziali
We don't know how much protein you need or if you even need a protein powder. You can do a simple test by doing bodyweight deep squats until you can't do anymore reps. If you gain muscle and don't loose your hair; you don't need anymore protein. If you don't gain muscle and start loosing more hair than normal; you need more protein. Don't let me stop you from experimenting with protein powders because at the beginning of the day, it is your path of life that you have to walk down.
Nuts do contain protein however I mean't that they contain the essential fatty acids(omega 3 & 6's). We need the essential fatty acids for cell membranes, brain health, muscle growth and other physiological functions. Fats are best eaten as the last meal of the day because they make us tired.
Here is a good read on an Omega 6: http://en.wikipedia.org/wiki/Arachidonic_acid#Arachidonic_acid_in_the_body
Too many fats are only a problem if we eat foods which irritate our intestine by poking holes in it, such as gluten sensitivity
and for certain individuals, other grains like legumes and rice.