Store shelves are packed with products boasting of their protein content. Cereals, protein bars and protein supplements are among the many products highlighting their levels of this macronutrient. We are often told by those around us, and sometimes even our doctors, that we need to make sure we are getting enough protein to power us through the day. However, what do the findings by nutrition researchers tell us about the true importance of getting enough protein in our diet?
To help us better understand what these researchers are finding, we must ask what, exactly, is protein? Proteins are macromolecules which are extremely common in every living organism. They are the molecules that carry out the instructions of our genes and make nearly every process of our bodies possible. To make these proteins, our bodies use building blocks called amino acids. Out of the 20 standard amino acids, our bodies can only make 11. The rest we need to get from food, so we need to eat foods containing proteins because they include amino acids that we can’t generate ourselves.
An important aspect to understand about protein from food is that every essential amino acid is made either by microbes or plants, and every plant has every essential amino acid, although in varying amounts.1 Misconceptions have led to the myth of “complete proteins,” which says that certain plants must be eaten in combination (e.g. beans and rice) during a single meal to achieve a balanced variation of amino acids, when in reality our bodies store amino acids to be used when needed.2 A varied diet of plant foods will contain sufficient amounts of every essential amino acid.3
In light of the previously-described societal obsession with protein, protein must be the holy grail of nutrition, health and longevity, right? It seems as though there must have been an epidemic of protein deficiencies in the past to merit the continued discussion of getting as much as we can. Although neither of these cases are true, these beliefs have led to what has been called the “great protein fiasco.”
A single researcher during the 1930s described a condition called kwashiorkor which occured in starving children in Africa.4 This form of malnutrition is commonly believed to be caused by a deficiency of protein in the diet during adolescence despite adequate calorie intake. Although this disease is found only in cases of extreme starvation, it was incorrectly generalized and applied to the other forms of malnutrition throughout the developing world. This generalization led to the United Nations declaring protein deficiency as “the most serious and widespread nutritional disorder known to… science” in the 1950s.5 This declaration sparked what ultimately led to the “great protein fiasco” in which protein became incorrectly thought of as the most important macronutrient.6
Is protein really the magic nutrient which fuels our growth, and should we strive to maximize it in our diet? Our primary fuel source during a period of rapid growth and development, human breast milk, has the lowest concentration of protein of any animal on the planet: less than one percent protein by weight.7 Additionally, high-protein diets are associated with higher mortality in those under 65, though the ideal ratio of protein in the diet increases as we age.8 Since the aforementioned fiasco, researchers have limited the recommended daily intake of protein for adults to 0.8 to 0.9 grams of protein per kilogram of body weight per day,9 although it is increasingly common to far exceed that range.10
More recent data suggests that rather than not getting enough protein, it is far more likely that people in Western countries are getting too much protein.11 Excess protein is not able to be stored in the body and increases acidity in the blood, which may strain the body, leading to disease such as kidney and bone calcium disorders.12
Ideal protein intake may be as high as 1.2 to 2.0 grams protein per kilogram of body weight per day during periods of intense athletic training, which is considered easily achievable by food intake.13 However, foods commonly described as being protein-rich (e.g. meat, eggs and dairy) are also the main dietary sources of saturated fat, trans fat and cholesterol, which all have a negative impact on kidney function as well as many other chronic diseases.14 Protein quality may be as or more important than quantity, as this same paper noted that the same negative effect is not seen in equivalent protein consumption from plant sources.15 Plant proteins contain base precursors (lowering acidity), while animal proteins contain only acid precursors (raising acidity)16 creating a negative effect on kidney function seen with the consumption of meat,17 eggs and dairy.18
Protein is a macronutrient which has received a lot of attention over the years, and public understanding of the nutrient has, and continues to have, an attitude of “more is better.” However, research has been telling us for decades that although protein in an essential macronutrient of which we must maintain sufficient dietary levels, more is not always better, and too little is very rare with a calorie sufficient diet. In fact, overconsumption puts strain on your body and may lead to diseases such as kidney disease, which is on the rise in the U.S.19 Research also tells us that the source of protein is an important factor, as protein from varied plant sources will contain all of the amino acids needed in sufficient amounts, minus the negative effects seen with the consumption of animal sourced dietary proteins.