The topic of protein adequacy should be a mainstay because it impacts every tissue in our bodies. Instead, it seems to experience episodic popularity in the area of weight loss and muscle mass building, overshadowing other important aspects of our health , such as soft tissue resilience and integrity.
All of our soft tissues are predominantly built on amino acids. What complicates matters is that collagen proteins require a higher percentage of some amino acids that are not well represented in our standard diet, even some protein rich diet: proline and glycine being the most important ones.
Proline and glycine are found in lower concentrations in vegetarian sources of protein, and in higher concentration in flesh protein. Thus vegetarian diets, even if supplemented with vegetarian protein powders like rice and peas, can be lacking the rate limiting amino acids to build strong tendons and ligaments. ( they will be usually adequate to build muscle mass however, but a bulkier muscle anchored by a weaker tendon can actually spell more soft tissue trouble). Moveover, not all animal protein is high in proline, which is not primarily found in muscle meat, but in the connective tissue of the animal you eat. Compared to even a generation ago, the standard American diet animal protein is very muscle based and contains little bone-in, skin, tendons, joints: chicken breast, steak, chops etc… All muscle meat. Contrary to their reputation for being lower quality, meat products such as sausages will often reclaim those “lower cuts” in ground form and give you a better amino acid mix for collagen building. Unless you eat your animal “nose to tail”, as humans have for most of their omnivore history, and continue to do so in many places in the world, you may need to consider a little proline/glycine and collagen support. Thankfully, collagen supplementation has been pretty readily available on the shelves and many patients have empirically found that their frame functions better when they take them, not just because collagen helps articular cartilage, but because proline ang glycine helps shore up tendons and ligaments
