The best and cost-effective protein source is Soyabean. There is a myth that if you eat soybean that you will suffer from Man boobs (Gynecomastia) and also it is very underrated in the health industry but if you will check its nutrition values than you will find if you eat 100g of soya than you will get 52grams of protein in a very cost-effective manner.
Even it is cheaper than eggs, chicken, and good protein brands too. But its Bioavailability is quite low [BIOAVAILABILITY – It is the fraction of a food/drug or any digestible matter reaches the systemic circulation for its effect or in simple terms how much nutrients you will absorb from a substance while digesting it.] E.g. Bioavailability of whey protein is 100% so if you consume 30g of whey protein than the system will absorb max portion of it. Bioavailability of soybean is very low which is 74% e.g. if you eat 100g of soybean (must not eat this much QTY. will explain further.) then you will digest only 74g but it is a quite good number which is a very good deal, considering its cost.
If you are a vegetarian or you don’t want to invest in supplements then you should add this to your diet. There is a difference between plants and animal protein, Animal protein is considered good because it contains all profiles of an amino acid (the base ingredient of a protein) but soybean is a plant product in which you will get almost all amino acids. It means it is a good protein source for vegetarians, it is not a lean protein source like chicken you will get some carbohydrates from soybean. E.g. You will consume 30g of carbs if you have 100g of soya but in this 30g, you will digest 13g of fiber too, which improve our digestion. From this you are getting protein, complex carbs, and fiber but it is underrated in the fitness industry because our protein brands wrong advertise it by publishing that if you consume soybean than you will get man boobs but it not the complete truth. If you are consuming a significant amount of soya then you will not create a hormonal imbalance.
Soybean contains an enzyme known as Phytoestrogen( female hormone, Testosterone, and Estrogen are two hormones which are majorly responsible for male and female characteristics respectively). Both male and female body contains receptors for both enzyme, in vary amount we all contain these to hormones but in different proportions. So if you eat soybean then the enzyme in soybean will attach to its receptors with very weak force( because estrogen receptors in the male body are less sensitive than it is for testosterone and vice versa for females). Which will not cause an imbalance in you but if you consume it in huge QTY. then it will affect you.
Researches suggest that if you consume 30-50g of protein from soya which is 100g of soybean max limit in a day then you are safe from Gynecomastia( Man boobs). So overcall soybean is quite good so we should include it in our diet.