Diets that draw upon evolutionary history (like the Paleo-Diet) tend to emphasize the role of meat protein in an individual’s diet. How necessary, however, is protein in an individual’s diet, and, in modern times, are we consuming enough of it? To be sure, a protein is considered a macronutrient because, ideally, it represents one of the three chemical compounds that provide us with the bulk of our energy (the two other macronutrients are carbohydrates and fat). Not all people, however, get enough of this macronutrient (protein) and consequently suffer from protein-energy malnutrition (PEM).
A bright student in my lecture asks: “It is true that consuming too much protein can cause bodily harm?”
That’s a great question! Thanks: we will tackle that question here, in addition to protein deficiency.
What are Proteins and How are they Used?
In addition to being a macronutrient, proteins are also macromolecules or “big molecules.” These macromolecules can be thought of as a chain of amino acids (the elements that make up an amino acid include carbon, hydrogen, nitrogen, and oxygen) that are responsible for building and repairing muscle and tissue. As explained by the American Diabetes Association (nd), “protein is one of three major sources of calories in the diet. It provides the body with material for building blood cells, body tissue, hormones, muscle, and other important substances. It is found in meats, eggs, milk, beans, legumes, vegetables, starches, and nuts.”
As a source of energy, our body tends use protein as a source of anaerobic fuel only when carbohydrate levels are low. In other words, anaerobic activities like weight training, for example, will use carbohydrates as the main source of fuel while working out. Similarly, protein is only used as an aerobic fuel when lipids (fats) are depleted. For instance, long distance running will use fat as the main source of fuel rather than protein. This is why many weight loss programs suggest that people who want to lose weight increase their protein consumption and decrease carbs and fat. While exercising, your body will burn fat rather than the food you have just consumed. Furthermore, because meat-proteins do not contain carbohydrates, they do not raise blood glucose levels.
Daily Protein Intake
A recent summit on protein – proceedings published by the American Journal of Clinical Nutrition – has arrived at a consensus that Americans are not getting enough daily protein to maintain adequate health. So what are the daily dietary requirements for protein? The Recommended Dietary Allowance (RDA) states that for every kilogram a person weighs, they need 0.8 grams of daily protein (0.8 x total kg or .36 x total pounds). If you weigh 81.6 kilograms (180 pounds), your daily minimum is approximately 65 grams of protein per day (81.6kg x 0.8g = 65.28 grams of protein per day).
Our bodies, however, are different. Some people have more muscle mass than others. Some people engage in more strenuous physical activity than others. Keeping human variation in mind, we need to understand that our RDA for protein also varies between people. According to Pendick (2015), while 0.8 grams of daily protein may be adequate for someone who lives a sedentary life, it is not adequate for active individuals. Keeping that in mind, experts have suggested that active individuals can safely increase their RDA of daily protein to 1.6-2 grams per kilogram of body weight without causing bodily harm (see the assigned readings at the end of this unit).
Excess Protein and the Global North
“Bodily harm?” you exclaim. Absolutely, at least according to some research. According to Wu (2016), chronic high protein intake (>2 g per kg BW per day for adults) may result in digestive, renal, and vascular abnormalities and should be avoided. Similarly, as explained by the American Heart Association (2001, para. 1),
individuals who follow high protein diets [such as the Atkins Diet] are . . . at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall. . . . Extra protein is not used efficiently by the body and may impose a metabolic burden on the kidneys and liver. High-protein diets may also be associated with increased risk for coronary heart disease due to intakes of saturated fat, cholesterol, and other associated dietary factors.
Not all researchers, however, agree. For example, as Manninen (2004, p. 45) in the Journal of the International Society of Sports Nutrition writes (addressing the AHA Statement on Protein), which is also supported by Rodriguez (2015):
There is no scientific evidence whatsoever that high-protein intake has adverse effects on liver function. . . . [and] such public warnings should be based on a thorough analysis of the scientific literature, not unsubstantiated fears and misrepresentations. For individuals with normal renal function, the risks are minimal and must be balanced against the real and established risk of continued obesity. (p. 45)
As we have already learned, though, humans have always benefited from a varied diet – generally speaking, dietary diseases tend to emerge when populations rely on a limited dietary variety. I think that there is a simple rule here that can help us out: Too much of anything can be harmful. With that said, we understand that protein is necessary for our muscles, tissues, and bones to develop. Too much protein, however, may cause problems, especially if it is associated with higher levels of animal fat. As explained by Pendick (2015, np), then,
Don’t read “get more protein” as “eat more meat.” Beef, poultry, and pork (as well as milk, cheese, and eggs) can certainly provide high-quality protein, but so can many plant foods — including whole grains, beans and other legumes, nuts, and vegetables. . . . It’s also important to consider the protein “package” — the fats, carbohydrates, vitamins, minerals, and other nutrients that invariably come along with protein. Aim for protein sources low in saturated fat. . . . If you increase protein, dietary arithmetic demands that you eat less of other things to keep your daily calorie intake steady. The switches you make can affect your nutrition, for better or for worse. For example, eating more protein instead of low-quality refined carbohydrates, like white bread and sweets, is a healthy choice — though how healthy the choice also depends on the total protein package.
Protein Deficiency and the Global South
Inadequate protein consumption can lead to a variety of ailments such as kwashiorkor. When people do not get adequate protein in their diet, they can suffer from a condition referred to as protein-energy deficiency or PEM. As pointed out by the WHO (2016), while overconsumption of food characterizes the dietary pattern of many countries around the world, food insecurity and starvation continue to plague people around the world. In areas of Africa, kwashiorkor, for example, emerges as a result of inadequate protein consumption. In Ghana, for instance, “kwashiorkor” is literally translated as the “evil spirit that infects the first born child when a second child is born” (Insel, Ross, Bernstein, and McMahon, 2016, p. 216). It is the disease of the displaced child.
Historically, post-partum sex taboos (a taboo that generally stipulates no intercourse until the newborn has finished weaning) have been practiced around the world as a matter of increasing a child’s chance of survival. These taboos, then, help ensure adequate spacing between breastfeeding and weaned children. When post-partum sex taboos are not practices, and a second child is born while the first born child is still breastfeeding, the first born must be weaned immediately. As a result, the first born child no longer benefits from breastfeeding and the vital nutrients contained in breast milk. Consequently, the first born child must begin to consume “adult foods.”
Adult diets, however, are characterized by high carbohydrates and starches, and low levels of dietary protein. As explained by Insel et al. (2016), low levels of proteins in the individuals’ blood causes fluid loss and edema (bodily fluid leaks into tissues and tissue swells). Second, low levels of protein cause fat to accumulate in the liver. This causes a distended abdomen or “bloated belly.” Left unattended, kwashiorkor will lead to dehydration, anorexia, renal failure, shock, coma, and death.
Statement of the AHA Nutrition Committee. (2001). American Heart Association.
Conrad, L. (nd). Kwashiorkor. Centers for Disease Control.
Insel, P., Ross, D., Bernstein, M., McMahon, K. (2016). Discovering Nutrition. Burlington, MA: Jones and Bartlett.
Manninem, A. (2004). High-protein weight loss diets and purported adverse effects: Where is the evidence? Journal of the International Society of Sports Nutrition, 1(1), 45-51.
What is the role of dietary protein in the body? American Diabetes Association. https://www.sharecare.com/health/protein-body-impact/what-role-dietary-protein-body
The deal with protein. The SciShow. https://www.youtube.com/watch?v=Chbm84sCBAw
Pendick, D. (2015). How much protein do you need everyday? Harvard Health Publications. Harvard University. http://www.health.harvard.edu/blog/how-much-protein-do-you-need-every-day-201506188096
Wu, G. (2016). Dietary protein intake and human health. Food Function, 7(3):1251-65. doi: 10.1039/c5fo01530h.