How much protein do I need? If you ask a dietitian this question, you’ll likely be told that you need to consume about 0.8 grams of protein per kilogram of bodyweight per day (the Recommended Dietary Allowance (RDA)) to meet your requirements and make sure your body has the building blocks it needs to function properly. You may also be told that as long as you eat a “balanced diet” – whatever that is – your protein intake will be sufficient.
However, if you ask a scientist who does research on protein or a nutritionist who is involved in the emerging field of Darwinian medicine, such as myself, you’ll probably get a very different answer. He/she may tell you that human protein requirements most likely have been underestimated and that the vast majority of people will benefit from intakes that are significantly higher than the RDA of 0.8 g protein/kg/day.
Over the past several years, research data supporting these non-conventional notions have started to accumulate, and some scientists now make the case that there is an urgent need to reassess recommendations for protein intake in adult humans.
Recent research suggests that human protein requirements may have been significantly underestimated
Earlier this years, a paper entitled Recent developments in understanding protein needs – How much and what kind should we eat? was published in the journal Applied Physiology, Nutrition, and Metabolism (1). The authors of this article make the case that minimum protein requirements have been underestimated by as much as 30-50%. In support of this statement, they present data derived from studies that have used a technique called Indicator Amino Acid Oxidation (IAAO) – a method validated by comparison with the “gold standard” nitrogen balance – to determine protein requirements.
The authors put forth the following take-home points at the end of the article:
- Recent evidence indicates the current RDAs substantially underestimate minimum protein requirements throughout the lifespan.
- The AMDR [Acceptable Macronutrient Distribution Ranges] of 10% to 35% of calories from protein for adults allows considerable flexibility to recommend protein intakes above the current RDA.
- In practice, 1.5 to 2.2 g/(kg·day) of high-quality protein constitutes a reasonable recommendation for adults as part of a complete diet.
- High-quality animal proteins require far less energy intake to meet essential amino acid needs than lower quality plant proteins.
Other researchers have also made the case that human protein requirements have been significantly underestimated (2). That said, one should be very cautious about drawing firm conclusions about diet and health from just looking at a couple of studies or research papers. Before we jump to conclusions, we have to consider the evidence as a whole…
The power of protein
It’s important to distinguish between the minimal level of protein intake needed to avoid a deficiency, which is what the nitrogen balance approach seeks to determine, and the optimal or desired level of protein intake, which is what I’m most concerned with. You won’t necessarily experience symptoms of protein deficiency if you only take in 0.8 g protein/kg/day, but that doesn’t mean that you are eating enough protein to achieve and maintain good health. It’s therefore problematic that the RDA is often interpreted as a target for the desired level of protein intake.
You don’t have to look far and wide to find a systematic review or meta-analysis that supports the idea that most people will benefit from protein intakes above the RDA of 0.8 g protein/kg/day. Actually, I would say that the weight of the evidence from systematic reviews, meta-analyses, and Randomized Controlled Trials (RCT) suggests that the recommendations put forth by the authors of the paper above – which are aligned with the recommendations I’ve been making her on the site – are more appropriate for the general population than recommendations based on nitrogen balance studies (3, 4, 5).
Protein has a higher thermic value than the other macronutrients, promotes satiation and fullness, may enhance sleep quality, and can improve leptin sensitivity in the central nervous system, among other things. Furthermore, research looking into the protein-leverage hypothesis has shown that humans (as well as many other animal species) who are instructed to adhere to a so-called high-protein diet tend to consume less total calories than individuals who are instructed to eat a low-protein diet (4). It’s therefore not surprising that numerous studies have shown that high-protein diets are effective in the prevention and treatment of obesity and the metabolic syndrome.
Darwin’s theories need to be incorporated into nutritional science
It’s somewhat comical that scientific findings such as the ones highlighted in the paper by Pencharz et al. are viewed as revolutionary, novel discoveries. This wouldn’t have been the case if all dietitians and nutritional scientists used a conceptual framework based on evolutionary biology to guide their understanding of diet and health.
Most of the time, nutritional research doesn’t provide us with new and novel insights about food and health; rather, it just confirms what we already know, namely that we humans, as well as all other animals on this planet, are best off adhering to a diet that is similar to the types of diets that conditioned our genome.
If there’s one thing we know about hunter-gatherers – both contemporary and ancient – it is that they generally eat more protein than modern, industrialized people (6, 7). This isn’t surprising, as they don’t have access to dense sources of fat (e.g., butter), starch (e.g., bread), or sugar (e.g., ice cream), but rather have to rely on meat and wild, fibrous plants as their primary sources of calories.
The Paleolithic diets that sustained our species for millions of years and supported the evolution of the large human brain were fairly high in protein; hence, it shouldn’t come as a surprise that modern scientific research has shown that humans do best on a diet that contains solid amounts of lean protein.
I want to make it clear that this doesn’t mean that stuffing yourself with red meat, eggs, and other protein-rich foods all day long is a good idea. You don’t need massive amounts of protein; a moderate amount at every meal is sufficient, preferably derived from animals that have had a good life. Those who eat an ancestral diet will naturally tend to consume more protein than individuals who eat a diet that contains more refined grains and/or processed food, as they usually include protein-rich foods such as meat, fish, and/or eggs in every meal.
