Do the math for a potato-only diet. 1 baked potato is 171 calories. 2000/171 is 11.7 potatoes. 11.7*4.3 = 50.3. That's sufficient for a 62.5 kg individual by your 0.8 g/kg standard.
Potatoes are also lower protein than a variety of grains and vegetables (which are low in macronutrients in general).
Men on a 2,000 calorie diet are recommended a minimum of 56 grams of protein.
0.8 per kg is for a generic sedentary lifestyle, with increased activity your needs go up. 2000 calories on a 62.5 kg person is a non sedentary lifestyle.
Moderate levels generally shows up as low albumin levels on a blood test aka Hypoalbuminemia a type of Hypoproteinemia, and is associated with a huge range of symptoms. Westerners generally only get this due to Malabsorption.
> Westerners generally only get this due to Malabsorption
Exactly. It's not really a "protein deficiency" as much as it is a "nutritional deficiency". You can easily get enough protein even if you just eat vegetables (for example) as long as you get enough calories.
Can does not mean will. People do dumb things like get 10+% of their calories from sodas.
The tendency to over eat, eat lots of meat, and have a very sedentary lifestyle are the main reasons it’s uncommon in the west. However, it does still occasionally happen to people due to very poor diets combined with active lifestyles. Healing and inflammation related heath issues can also increase people’s needs for protein.
PS: People also very rarely get scurvy via avoiding or over cooking all their sources of vitamin C for months. Occasionally taking a multi vitamin covers most nutritional issues except for macro nutrients.
Legumes tend to have a surprisingly balanced macronutrients at 21g carbs, 8g protein, 0.6g fat, vs a baked potatoes 37 g carbs, 4.3g protein, 0.2 fat.