By Eirik Garnas
Official dietary guidelines generally recommend that everyone should get between 10-20% of their daily energy from protein, and some health authorities even argue that high protein diets (>20%) have adverse effects on health. Even though people who are very physically active have higher protein needs, the recommendations still apply as these individuals usually consume more total calories. However, if we look at the human dietary patterns throughout our evolutionary history, it’s clear that the average protein intake in most countries today is on the low side. While this doesn’t mean that high protein diets are necessary optimal, the mismatch between the typical protein intake in the western diet and the average protein intake in ancestral diets, in combination with the scientific evidence showing the benefits of “high” protein diets for weight loss, muscle growth, and prevention of several types of chronic diseases, suggests that the official recommendations are lower than optimal for many people. This is especially true for strength trainees and other physically active people who want to maximize protein synthesis and gain muscle and strength.
When discussing intake of the different macronutrients, the most common practise is to either present the percentage of daily energy intake or grams per kilogram or pound of bodyweight per day. For the average female eating around 2000 kcal per day, a protein intake of 15% equates to 75 grams of protein, and for a male eating 2500 kcal the same percentage gets him about 93,5 grams of protein.
Dietary protein recommendations, such as the RDA in the U.S. of 0.8 g protein per kg bodyweight per day, are largely based on nitrogen balance studies. While these studies indicate the amount of protein that is needed to avoid loss of protein from tissue, they don’t say much about the level of protein intake that will optimize body composition, gene expression, and health.
Human evolution: Dietary patterns characterized by declining levels of protein intake
Hunter-gatherer diets are generally (not always) high in protein
Although there’s a lot we don’t know about the diet of our paleolithic ancestors, it’s believed that preagricultural human diets generally were higher in protein than the typical western diet. While macronutrient intake in hunter-gatherer diets varied/vary greatly beetween different tribes, estimates show that protein intake in ancestral-type diets is generally much higher (19-35%) than that of the typical western diet (15%) (1). These numbers have later been questioned by other reesearchers, but it’s widely accepted that the diet of ancient humans contained more protein than the levels consumed in industrialized nations today. Since the prehistoric human diets in many ways represent the default human dietary pattern, it could be argued that a protein intake of 20% or more is actually within the normal range, while 15% could be considered a low protein diet.
It’s important to note that protein intake in the diet of hunter-gatherers and other non-westernized populations varied/varies depending on geographical location, season, climate, etc., and while the traditional diet of some populations, such as the Maasai and the Inuit, contain a fairly high percentage of protein, other cultures have/had a fairly low intake. Regardless, the fact that subsistence data from 229 hunter-gatherer societies shows an average intake that is well above today’s recommendations highlights the discrepancy between the average protein intake in modern diets and protein intake in the diets we’ve been eating throughout most of our evolutionary history.
Just imagine the stereotypical image of a group of hunter-gatherers sitting around a fire at night and gorging on meat from today’s hunt. We know this definitely wasn’t the case for all ancient humans, as some paleolithic tribes likely subsided on mostly plant food. However, we do know that periods of fasting, large meals eaten at night, and a high (compared to today) intake of animal source foods was a common feature of the hunter-gatherer diet.
One of the reasons I think it’s important to learn more about the lifestyle of prehistoric humans is because their dietary practises involve many of the factors that modern science has shown are healthy for us. I don’t think we have to try to emulate the diet of paleolithic humans, and I don’t think 10000 years is too little time to adapt to neolithic foods. However, there’s no denying that periods of food shortage (fasting), consumption of nutritious whole foods, a relatively high protein intake compared to today’s standards, and other aspects associated with the ancestral dietary pattern are beneficial to humans in the modern world.
We have to remember that this ancestral environment is where our human genome was forged, and although there have been some adaptations since then, we clearly haven’t adapted to many aspects of the modern, western lifestyle. Using this default human environment as a framework when determining the optimal diet and macronutrient intake in the 21st century is therefore a good idea. However, we do have to remember that hunter-gatherers didn’t aim for a targeted protein intake or necessarily did what was optimal, they typically just ate the most palatable and calorie-dense foods available. Also, they clearly didn’t perform goal-oriented training in the way bodybuilders, weight lifters, and other athletes do today.
Agriculture led to the dilution of protein in favor of carbohydrate and/or fat
Let’s take a look at the macronutrient content and energy density of foods that were available before the neolithic revolution. One striking characteristic of the food items that were available prior to agriculture is that most foodstuff which are high in carbohydrate and low in protein, such as fruits, vegetables, and tubers, have a low energy density and high fiber content (Some exceptions exist). However, with the advent of agriculture, domestication of cereal grains and new processing techniques led to a dramatic change in the human diet. To be clear, I don’t think foods that were introduced after the agricultural revolution are necessary bad for us. However, grains have a high carbohydrate content (unless they’ve been fermented or processed in some way), a low content of high-quality protein, and a relatively high calorie density and poor micronutrient profile compared to fruits and vegetables. Is this problematic? Not necessarily. However, if we eat a grain-based diet, high quality protein is often diluted in favor of carbohydrate.
Processed, westernized food is often low in protein
These changing macronutrient patterns have become even more apparent over the last centuries, as new products with an “unnatural” macronutrient composition have made their way into the human diet. While highly processed foods often are high in both carbohydrate and fat, foodstuff available to our prehistoric ancestors didn’t contain this potent combination. Yes, nuts provide a fair amount of both of these macronutrients, but they are generally considered low in carbohydrate. Also, the amount of work that goes into making nuts edible suggests that they’ve never been a substantial part of the human diet.
One of the characteristics of many westernized foods, such as potato chips, pastries, and baked goods, is that they are calorie-dense and high in carbohydrate and/or fat, not protein. Unless they had access to tubers and other plant-based foods that are relatively rich in calories, our ancient ancestors had to subside on animal source foods, which are often (not always) high in protein, to get enough energy. However, today we can quickly meet our daily energy requirements by eating food that is high in calories and low in protein.
If we take a closer look at the western dietary pattern, there’s no surprise that the average protein intake is so low compared to ancestral diets. Highly palatable and calorie-dense foods are typically high in fat, starch, sugar, salt, glutamate, and/or other highly rewarding food ingredients, and protein is therefore diluted in favor of the other two macronutrients. It’s well established in the scientific literature that protein has a potent effect on satiety, and it’s therefore no surprise that food manufacturers deliberately engineer products that are fairly low in protein; one of the strategies that keep us buying and eating more of that specific food.
The fact that quality sources of protein are far more expensive than sources of carbohydrate and fat is another reason many food manufacturers deliberately keep the protein content of their products low. Also, since grass-fed meats, eggs, and seafood are relatively expensive compared to sources of the two other macronutrients, there’s no surprise that so many people end up with a less than ideal protein intake.
Essentially, when we eat these types of “westernized” foods, we have to consume more total energy throughout the day to meet our daily protein requirements.
I’ve previously discussed the benefits of high protein diets for weight loss, which basically bowls down to these primary factors:
- Protein has a very strong thermic effect
You can basically eat more calories on a high protein diet than you can on a low protein diet, since the thermic effect of macronutrients is about 2-3% for lipids, 6-8% for carbohydrates, and 25-30% for proteins (2).
- Protein has a potent effect on satiety
- Studies suggest that a low percentage of protein in the diet leads to a higher total energy intake
The protein-leverage hypothesis suggests that protein intake is prioritized over fat, carbohydrate, and total energy intake. The idea that humans prioritize protein when regulating food intake is interesting in terms of the western dietary pattern as it probably means that we’re not only diluting protein in favor of the other macronutrients, but that one of the reasons so many people eat more food than they need to sustain body weight is that they’re trying to reach a targeted protein intake. There’s no compelling evidence showing this type of leverage for any other nutrients in the human diet. Some researchers have proposed that we keep eating in an attempt to reach a targeted intake of certain micronutrients, but this has not been scientifically shown. If you substitute some of the protein in your diet for carbohydrate or fat, you’ll probably feel the effects of this protein leverage pretty quickly.
- High-protein diets potentially improve leptin sensitivity in the central nervous system (3)
High-protein diets seem to be especially beneficial for resistance-trained athletes who want to preserve lean body mass during a prolonged calorie deficit. For this population, consuming as much as 2.3-3.1 g/kg of lean body mass per day of protein (depending on the severity of caloric restriction and leanness) will likely maximize muscle retention (4,5). This elevated protein need largely stems from the high levels of muscle mass these athletes carry and the energy deficient diet (absolute protein intake required to achieve nitrogen balance is generally higher when you eat a low-calorie diet).
Strength development, muscle growth, and athletic performance
Generally, bodybuilders and most experienced strength trainees tend to consume a much higher percentage of protein than the average Joe. A high protein intake in this population primarily stems from conventional wisdom linking high protein diets to enhanced muscle growth. The notion that we need to consume a lot of protein is so ingrained in the fitness community that some trainees seem to think that more is always better. However, not everyone feels this way. Dietary recommendations from “official” sports institutions rarely advocate a protein intake that is higher than 1.4-1.7 g/kg/day, and while this protein intake might seem high to a layman, many strength trainees and bodybuilders consume a lot more than this. And this is where there’s a lot of controversy; how much protein do you really need to optimize athletic performance? Let’s have a look at the literature:
Total intake: Most studies indicate that a protein intake of 1.6-2.0 g/kg/day is sufficient to maximize muscle protein synthesis and optimize strength gains and hypertrophy (6,7,8.9) Dr. Stu Phillips, one of the world’s leading researchers on protein consumption and hypertrophy, revealed in a recent interview with Bret that his most recent study shows that about 1.8 g/kg is enough to maximize muscle protein synthesis (10). However, more protien is not going to have adverse effects, and some studies indicate that a higher intake (2-3 g/kg) could enhance hypertrophy- and strength-related adaptations (11).
For athletes involved in endurance training, getting between 1.3-1.8 g protein per kilogram of body weight seems to be a good general guideline (12).
Although there’s now plenty of research on protein intake and athletic performance, there are some limitations to these studies. Two of these are: 1) Studies showing benefits of a very high protein intake (e.g., 3 g/kg/day) typically compare the high protein group to a control group eating well below recommendations for strength/power athletes (e.g., 1.2 g/kg/day). It’s therefore no surprise that the high protein group see greater resistance training induced muscle and strength gains. It would be interesting to see more studies comparing a high intake (e.g. 1.8-2 g/kg/day) to a very high intake (2.5-3.0 g/kg/day).
2) Studies on protein intake and athletic performance typically look at protein synthesis, hypertrophy, and strength gains.
High protein diets have been linked to increased satiety, elevated thermogenesis, and a lower absolute energy intake, indicating that simply looking at protein intake from the perspective of maximizing protein synthesis could be too narrow.
Protein timing: When should you be getting these essential building blocks into your body? I recently wrote an article where I took a closer look at protein timing and strength training, and the conclusions from the most recent meta-analysis suggest that the so-called post-workout window doesn’t close 30-60 minutes after a workout, and that your results won’t suffer from waiting a couple of hours after training before you consume food.
When it comes to protein distribution throughout the day, a general recommendation is to eat 3-5 protein rich meals. If you eat less than 3 meals, you’ll have problems getting enough total protein into your diet. However, contrary to what many people think, there’s no advantage to eating 6-8 meals a day if the goal is to maximize protein synthesis. Actually, studies indicate that 4-5 large meals are superior to 6-8 when it comes to protein synthesis and muscle repair, given the same daily total protein intake (13,14). The notion that eating every other hour is the optimal way to go for muscle growth is one many lifters still cling to. However, it has scant support in science, and from an evolutionary and physiological perspective it makes little sense
I’m not going to talk a lot about protein quality in this article, as I think this is common knowledge for most folks reading this blog. Personally I find that there is a significant advantage to eating red meat on a regular basis if the goal is to build muscle and strength (No, unlike what you’ve been told, high-quality meats don’t give you colon cancer or heart disease). This beneficial effect largely stems from the amino acid profile and high creatine content in red meat, but there could also be other factors that are important. Scientists often refer to the red meat factor when discussing the benefits of red meat on absorption of nutrients such as iron, and this “unknown” factor definitely also extends to other areas.
Wrapping it up
Optimal protein intake depends on several factors, such as activity levels, goal, and the amount of lean mass you carry. Since a lot of data suggest that the body has its own hard-wired mechanisms for regulating protein intake (the protein-leverage hypothesis), it could be argued that protein consumption takes care of itself. However, these mechanisms were forged in the ancestral natural environment and evolved to deal with a diet rich in simple, whole food. When you eat a diet with a low percentage of protein (as so many modern humans do), reaching this target level could mean eating more calories than you need to sustain body weight. This is especially true for athletes and strength trainees who have higher protein needs.
The idea that high protein diets are harmful has little support, neither from an evolutionary nor scientific point of view (15,16,17). However, getting your protein from quality sources, such as grass-fed meats, free-range organic eggs, traditionally fermented dairy products, and seafood, as opposed to for example processed meat, is clearly important.
In the end I want to emphasise that although “high” protein diets are very effective for a wide variety of purposes – especially for weight loss and muscle growth – this doesn’t mean that everyone should eat these types of diets. Many healthy populations have thrived on diets that contain only 10-15% protein, and those who aren’t working out and just want to stay relatively healthy don’t really need that much protein. However, I would argue that keeping protein fairly high (compared to the average intake in the western diet) is often beneficial, as an increased intake of high-quality protein often leads to a lower intake of other inferior sources of energy. Also, protein’s effect on satiety, weight regulation, and a wide range of health markers suggests that getting at least 15-20% of your calories from protein is beneficial, regardless of your goals.
About the author
Name: Eirik Garnas
Besides studying for a degree in Public Nutrition, Iíve spent the last couple of years coaching people on their way to a healthier body and better physique. I’m educated as a personal trainer from the Norwegian School of Sport Sciences and also have additional courses in sales/coaching, kettlebells, body analysis, and functional rehabilitation. Subscribe to my website and follow my facebook page if you want to read more of my articles on fitness, nutrition, and health.