In developed countries, too much protein is a much bigger health threat than too little. Excess protein leads to kidney overload and mineral deficiency diseases, such as osteoporosis. Vegetarianism is too complicated. To get quality protein, one must carefully mix and match foods. Research has proven this unnecessary.
Bananas have complete protein.
Check any official food chart listing for amino acid content. Dairy products are necessary for calcium. Excess protein actually inhibits calcium absorption. The less protein you eat, the less calcium you require. Most greens are abundant sources of calcium.