TL;DR: At least 2g per kg of your desired weight, every day, mostly from animal sources.
This is a really old question that never really goes away. There are many different answers, and depending on which philosophy you follow, which agendas you have, and which books you read, you can end up with very different recommendations. There are some authors who recommend a really low intake of protein, about 10% of total calories. Those recommendations are well below the RDA (recommended daily allowance) issued by the U.S. government, which is 0.8g per kg of “reference body weight”. At the high end of the spectrum you have the body building community, traditionally recommending intakes well above 2g per kg.
So there is this wide range of intakes which people can survive on, ranging between about 5-50% of calories from protein. What is ideal? Does it depend on your goals, your age, your gender? The average intake in modern “westernized” societies is around 14-15%. The average intake in modern hunter-gatherer populations is about 25%.
My suggestion: >30% protein, or >2g per kg of desired body weight, mostly from animal sources!
I’m a big fan of Ted Naiman, who has recently given a great talk on protein intake. He goes through various arguments for and against high protein intake, and basically shows that a) higher protein intakes (above 30%) are not unhealthy and b) improved body composition (more muscle, less body fat) may be easier to achieve on such higher intakes. This is in line with most of the literature I’ve read and agree with. The take-away message is: It’s better to eat too much protein than too little.
There are many books and studies which I could refer you to, but I’ve settled on just linking to this well-respected (and often cited) paper:
The paper recommends a lower limit of 1.2g per kg of body weight for active people, and 1.5g for those who suffer from acute or chronic disease. That is at least 50% above the RDA (0.8g per kg).
Advantages of Higher Protein Intake From Animal Foods
- Increased satiety (you stay fuller longer)
- Positive nitrogen balance (minimal muscle loss, maximum muscle gain)
- Delicious meals (meat, fish and eggs should be the center-piece)
- Improved digestion (less bulky plant-matter, more nutrient-dense food)
- “Automatic low-carb” (more meat/fish means less carb-heavy plant food, if total calories stay the same)
So What Does This Mean Practically?
The easiest way to implement this principle is to incrementally change your diet, replacing low-protein/high-carb foods with high-protein/low-carb animal foods. Like I outlined a while ago in my post about changing one’s diet one swap at a time.
For example, If you really like salads, add a nice serving of meat and in exchange, have less or no bread with the salad. Maybe add eggs and reduce beans/corn.
Extreme Example: Cake vs. High-Protein Yogurt
As a treat, I used to have cheesecake. As it turns out, a little bit of full-fat yogurt, some salt and vanilla whey protein powder emulates the taste nicely. I add some frozen blueberries, and that combination is really, really satisfying and tastes like a combination of blueberry cheesecake and ice cream. According to Cronometer, one serving of Baskin Robbins blueberry cheese cake ice-cream is 273 Calories, with 7% protein, 46% carbs (28g sugar) and 48% fat. This is the worst combination possible: low-protein (5g) plus a 50:50 mix of carbs/sugar and fat.
Here’s my combination of yogurt, salt, protein-powder and blueberries: 31% protein, 18% carbs and 51% fat. 11g of sugar. 21g of protein. So compared to the ice-cream, on an equal-calories basis it contains only 30% of the sugar and carbs, but 4 times more protein. And almost the same amount of fat.
Why Not Use Plant-Based Sources Of Protein?
Typical plant-based sources of protein include low-starch vegetables like broccoli or even kale, and beans/legumes. These foods come with big disadvantages:
- Low-Starch vegetables surely contain a lot of protein in terms of percent of total calories, but you would have to eat several pounds to get meaningful absolute amounts of protein.
- Beans/legumes contain a decent amount of protein per calorie, but also a lot of energy in the form of carbohydrates.
- Both contain a lot of fiber and anti-nutrients which can cause gastro-intestinal distress in many people.
- The protein in plants is generally less bio-available than that in animals, the human body typically absorbs only 70% of it. So you would have to eat even more of these sources.
This does not mean you have to stop eating those foods – you just don’t need to eat them for the protein.