Protein per 100 calories of selected foods

broccoli: protein 8.3 g; carb 19.5 g; fat 1.1 g; fiber 7.6 g

mustard greens: protein 10.4 g; carb 18.9 g; fat 0.8 g; fiber 12.7 g

tenderloin steak: protein 6.6 g; carb 0 g; fat: 8.0 g; fiber 0 g

chicken (white meat): protein 20.4 g; carb 0 g; fat 1.4g; fiber 0 g

salmon (sockeye): protein 12.7 g; carb 0 g; fat 5.1 g; fiber 0 g

If you play with the math, these are the amounts of food you need to eat of each food to get 10 grams of protein: kale 303 g, broccoli 357 g, steak 55 g, chicken 43 g.

You can get adequate protein with green vegetables alone, except that you need to eat a lot of it. There are a lot more micronutrients per calorie (i.e., vitamins, minerals, antioxidants) in vegetable than in animal sources.

Perhaps the often-heard need for more animal protein as one ages (from a protein/bioavailability standpoint) is really a function of how much volume (of greens) our digestive system can take as we age. There is no doubt one can take in the necessary amount of protein via vegetables, although some may personally argue that they can’t just handle that amount of food volume. (However, if you add nuts and seeds to the equation, then you solve the “volume” problem, since these are compact sources of high quality proteins and fat.)

I personally think the mix (vegetable vs animal source of protein) has to be determined on an individual basis. Some experts have advocated that the percent of calories contributed by animal sources should be in the ten percent range, as a maximum.

In real time, optimal nutrition becomes very difficult not because we don’t know what to eat, but rather because we have the social, emotional, and behavioral ball of wax that prevent us from sticking to an ideal diet.