Sidenote on older adults (which means all of us, we’re either there or going there) protein reqs are also lifestyle related - way more nuanced than standardized protein intake prescriptions that ignore many key factors such as frequency of eating, frequency of fasting, weight bearing activity, spices used, and whether an elder is low carb or not. As we know, the body is magnificent and has mysterious ways of optimizing when various factors come into play, such as:
Degree/frequency of fasting - the fasted state reduces protein reqs for the sedentary, though elders who do strength training may have a higher req. Eating less is pretty common in elders due to a variety of reasons often related to ill health in this culture - but sometimes its from natural fasting and a well formulated LCHF/keto way of eating! Keto researcher Cristi Vlad in his book Periodic Fasting reports on the connection between fasting and time-restricted eating and longevity with good health in historic cases, including the self-experimenters Luigi Cornaro and Upton Sinclair.
Joy in life. Enjoying one’s food - joie de vivre - and living a little. Spices stimulate the brain, and eastern science holds that the 5 tastes (chinese) or 6 tastes (ayurveda) vastly enhance digestion & health. In ancient times, the use of spices was largely local and nowhere near as complex as it is for modern foodies. Also, certain spices with buttery veg can trigger positive memories (indian veg food does that w/ me every time, for example) that enrich life/digestion.
(But sadly in the SAD context, many adults have artificially stimulated/dumbed-down palates and/or palates affected by medications (the famous metallic stench tasted on the palate and smelled in bodily excretions). Often this “requires” high amounts of sugar, MSG, and fast food formulas to thus “enjoy” food. So by the elder years, there can often be very little taste enjoyment in any food. Without taste and gusto/digestive fire, it’s very hard to do anything but decline, as nourishment gets even dicier).
Happily in the non-SAD context, elders tend to be lucid till their last days, and also maintain gusto/digestive fire or take herbals specific to helping elder circulation (such as Ginger). Even with a bit o’ SAD as long as it’s limited to OMAD, esp when elders regularly consume adaptogens and rejuvenators which also include garlic, chillis, green tea, oolong tea, chai, etc.
Hoever, elder health in the SAD context nowadays is usually a state of illness - as those who are entering their 70s now have more SAD in their histories, and often are highly medicated just to cope. But with tasty LCHF/keto food, and/or strength training every 7-10 days (as shown by Doug McGuff’s reports on controlled studies w/ elders) there is such a thing as elder rejuvenation & healing. Good fats, nourished muscle mass, and joy in life can do great things.
What is tastiest and most nourishing & satiating varies among us - and in the elder years there are several paths to health using nutrient-dense foods, fasting, and/or strength training. So, I wouldn’t aim for generalized prescriptives on protein reqs without taking into consideration multifactorial realities 
