Protein, protein where art thou? And how much of thee shall I ingest on a regular basis? We often ask ourselves what the origins of dietary protein requirements are, what are the best proteins for men and women, and how much of it should we aim to consume.
To begin with, proteins are organic molecules that are essential for human life. Proteins not only operate enzymatic reactions in most living cells, but are also tasked with controlling the entire cell process. Proteins comprise of sequences of smaller subunits called amino acids. Our genes dictate amino acid sequence, while amino acid sequence and structure determine individual proteins. The biological activity of the protein, as well as its stability and shape, is defined by the distinct chemical properties of various amino acids. Amino acids are therefore critical components of normal protein synthesis. The body uses 20 amino acids in various sequences and configurations in order to make all the proteins men and women require for cellular function.
Why Dietary Protein?
For normal protein synthesis to take place, 20 amino acids are required. The body can only make 10 of the 20 amino acids required. The rest, which we call “essential amino acids”, have to be obtained from dietary protein intake. This is why high-quality protein is required in a healthy diet, even for women. These can come from both plant and animal sources; however, plant sources sometimes do not always contain all of the essential amino acids. Vegetarians may have to calculate their protein requirements more specifically to ensure they have an adequate intake of high-quality protein. In the absence of proper protein intake, the body resorts to breaking down tissues. Symptoms of protein deficiency include edema or swelling, failure to thrive in children, poor musculature, as well as dull skin and brittle thin hair. People suffering from severe protein deficiency may experience muscle wasting, poor immune function, psychosis, and even organ failure.
Meaty (and Variable) Requirements
In order to calculate protein requirements, scientists monitor nitrogen, which is present in all protein. By using nitrogen balance studies, scientists have determined that on average, a person requires approximately 0.8 grams of protein per every kilogram of weight. If we consider that the average height for a man and woman in the United States is roughly 5’9” and 5’4”, respectively, this is about 58 grams of protein per day for men, and 44 grams of protein per day for women. It is also important to note that weight is estimated by ideal body weight. Ideal body weight typically lies between a healthy BMI of 18.5-24.9. Even with these calculations, protein requirements are unique for individual men and women depending on age, environment, physical activity level, and even current health status. Simply put, protein intake cannot be stored for future energy. It is either used for normal bodily function or excreted.
Optimal intake of protein has been highly debated because a person’s nitrogen needs and protein needs have been shown to change across the lifespan. For example, certain populations such as athletes, pregnant/lactating women,the elderly, and those who are critically ill require more protein due to their various metabolic needs.
Most recently, scientists have also examined the impact of optimal protein intake for men and women in regards to other metabolic processes. A review presented by the Canadian Nutrition Society in 2015 advocated for a protein intake range of 1.2-1.6 grams per day citing numerous health benefits. These include appetite regulation, weight management, and healthy aging across the lifespan. The American College of Sports Medicine has also cited that even people with mild and moderate levels of activity could benefit from an increased intake of protein ranging from 1.0-1.7 grams per day. For a more convenient number, this defines the best optimal range of protein between 73-123 grams of protein per day for men, and 54-92 grams of protein per day for women.
Defining “High Protein” Intake
Can there be too much of a good thing? A high protein definition continues to be debated, as scientists cannot seem to agree on a set number. There have been recent concerns about high-protein intake (1.8 grams per kilogram of weight and greater) being associated with increased insulin resistance, particularly in people with diets largely comprised of animal protein alone. To paint a clearer picture, this would be more than 130 or 98 grams per day for men and women.
Kidney and bone health have also been concerns, but studies are not conclusive or have been refuted. Optimal protein studies indicate health benefits, but more studies need to be designed for higher than optimal intakes. A review published in Nutrition and Metabolism illustrated this point quite succinctly.
Protein Strengthens Your Overall Health
Credit: Dean Ryan
With that being said, people cannot live on bread alone. Optimal protein intake contributes to overall health and wellness, and can be found in numerous forms. Your skin, your hair, and your internal organs will all thank you for continuing to invest in them with protein-rich animal and plant-based foods. As always, I encourage all men and women who may want to best optimize their protein intake to consult with a licensed physician for proper supervision of their current health status.
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