14 Roles of Protein: The Power House

Protein, often referred to as the building block of life, plays a crucial role in maintaining our health and well-being. 

In this guide, we will delve deep into the world of protein, exploring its various benefits, sources, and answering frequently asked questions.

What is Protein?

Protein is an essential macronutrient found in almost all tissues in the body.
Our bodies repair cells, grow, and sustain life due to proteins. 

Proteins are composed of hundreds or even thousands of smaller units known as amino acids, linked together in lengthy chains. 

There exist 20 distinct types of amino acids, which can be combined in different ways to create a protein. The precise order of these amino acids in the chain establishes the unique three-dimensional structure of each protein and its particular function. The code for amino acids is determined by sets of three DNA building blocks called nucleotides, as the genetic sequence dictates.

What are proteins made of?

Proteins are macromolecules composed of smaller building blocks known as amino acids. These amino acids are organic compounds consisting of: 

• carbon (C), 
• hydrogen (H), 
• oxygen (O), 
• nitrogen (N), 
• and sometimes sulfur (S). 

The basic chemical structure of an amino acid can be represented as follows:

RCH(NH2)COOH

In this structure, the central carbon (C) atom is bonded to four different groups:

Amino Group (NH₂): The amino group consists of a nitrogen atom (N) bonded to two hydrogen atoms (H). It is typically found at one end of the amino acid molecule.

Amino acids fall into three categories:

• Essential Amino Acids: These cannot be synthesized by the body and must be obtained from dietary sources. They do not require consumption with every meal; their daily intake is more critical.

• Nonessential Amino Acids: The body can produce these amino acids either from essential amino acids or during the routine breakdown of proteins.

• Conditional Amino Acids: These amino acids become essential during illness or heightened stress when the body’s demand for them increases.

Essential amino acids	Non-essential amino acids
Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine	Alanine Arginine Asparagine Aspartate Cysteine Glutamate Glutamine Glycine Proline Serine Taurine Tyrosine

Carboxyl Group (COOH): The carboxyl group consists of a carbon atom (C) double-bonded to an oxygen atom (O) and single-bonded to a hydroxyl group (OH). This group is usually found at the other end of the amino acid molecule.

Hydrogen Atom (H): One hydrogen atom is bonded directly to the central carbon.

R-Group (Side Chain): The fourth group, represented as “R,” varies among different amino acids. It is called the side chain and can be any of various chemical structures. The specific R-group determines the identity and properties of the amino acid.

20 amino acids can be found in proteins with a unique R-group. These amino acids can link together through a peptide bond formation chemical reaction. When amino acids join together, they form a chain known as a polypeptide, and when the polypeptide chain folds into a specific three-dimensional structure, it becomes a functional protein.

The sequence of amino acids in a protein, determined by the genetic code encoded in DNA, dictates the protein’s unique structure and function. Proteins have a wide range of bodily functions, including enzymes that catalyze biochemical reactions, structural proteins that provide support and shape to cells and tissues, antibodies that play a role in the immune system, and many others essential for life processes.

Protein roles in the human body

Proteins play numerous vital roles in the human body, contributing to its structure, function, and overall health. Here is a list of some of the key roles that proteins perform:

1. Enzymes

Proteins act as enzymes, biological catalysts that accelerate chemical reactions in the body. Enzymes are involved in digestion, metabolism, and various biochemical processes, facilitating essential reactions such as breaking down food molecules, synthesizing new compounds, and regulating metabolic pathways. They carry thousands of chemical reactions in cells and assist in creating new molecules by reading DNA.

2. Structural Proteins

Structural proteins provide support and shape to cells, tissues, and organs. Examples include collagen in skin and connective tissues, keratin in hair and nails, and actin and myosin in muscle fibers.

3. Transport Proteins

These proteins help transport molecules throughout the body. Hemoglobin, for instance, transports oxygen from the lungs to tissues, while various carrier proteins move nutrients, hormones, and ions across cell membranes.

4. Hormones

Some proteins serve as hormones, acting as chemical messengers that regulate various physiological processes. Insulin, for example, regulates blood glucose levels, and growth hormone influences growth and development.

5. Immune Proteins

Antibodies (immunoglobulins) are specialized proteins the immune system produces to recognize and neutralize pathogens such as bacteria and viruses. They play a crucial role in defending the body against infections. They bind to viruses, bacteria, and foreign bodies to help protect the body 

6. Cell Signaling 

Signaling proteins transmit signals within and between cells, helping to coordinate various cellular activities. Examples include protein kinases and G proteins involved in cell communication.

7. Neurotransmitters 

Neurotransmitter proteins enable communication between nerve cells (neurons) in the nervous system. They are critical in transmitting signals and controlling bodily functions like muscle contraction and sensory perception.

8. Storage Proteins 

Some proteins serve as storage depots for essential molecules. For instance, ferritin stores iron in the liver, and casein stores calcium in milk.

9. Antioxidant Proteins

Antioxidant enzymes, such as superoxide dismutase and catalase, help protect cells from damage caused by oxidative stress and free radicals.

10. Blood Clotting 

Clotting factors, including fibrinogen and thrombin, are proteins responsible for the blood clotting, preventing excessive bleeding after injury.

11. Transport of Lipids 

Lipoproteins transport lipids (fats) in the bloodstream. High-density lipoprotein (HDL) and low-density lipoprotein (LDL) are examples involved in lipid metabolism and cardiovascular health.

12. Receptors 

Receptor proteins on cell surfaces or within cells bind to specific molecules (ligands), such as hormones or neurotransmitters, initiating cellular responses. For example, insulin receptors respond to insulin to regulate cell glucose uptake.

13. Enzyme Inhibitors

 Some proteins regulate enzyme activity by inhibiting or blocking their function. Examples include protease inhibitors in the immune system.

14. Energy Source

In times of need, proteins can be broken down into amino acids for energy, although this is not their primary role, and it is generally a less efficient energy source than carbohydrates and fats.

Protein Sources for Human Nutrition

To reap the benefits of protein, incorporate a variety of sources into your diet. Here are some excellent protein-rich foods:

Lean Meats: Chicken, turkey, and lean cuts of beef are rich in protein and low in fat.

Fish: Salmon, tuna, and cod are delicious but packed with protein and healthy omega-3 fatty acids.

Dairy Products: Milk, yogurt, and cheese are excellent protein sources and provide calcium for strong bones.

Plant-Based Proteins: Beans, lentils, tofu, and tempeh are great options for vegetarians and vegans.

Eggs: Eggs are a versatile protein source and contain essential amino acids.

Nuts and Seeds: Almonds, peanuts, chia seeds, and hemp seeds are nutrient-dense protein sources.

Protein Supplements: For those with specific dietary needs, protein supplements like whey or plant-based protein powder can be beneficial.

Protein Turnover and Nitrogen Balance

Proteins in the body are continually being broken down and synthesized. During physical activities like resistance training, protein breakdown accelerates. 

During periods of rest and feeding, the body synthesizes more proteins. This ongoing cycle is vital for assessing protein needs. 

Nitrogen balance, which is the difference between nitrogen intake (primarily from protein intake) and nitrogen loss (due to protein breakdown), is a key metric for determining the adequacy of protein intake. 

When intake equals loss, it signifies a state of nitrogen balance sufficient for maintaining existing muscle mass. However, to stimulate muscle growth, nitrogen intake must surpass nitrogen loss, creating a positive nitrogen balance.

Recommended Protein Intake

Recommended Dietary Allowance (RDA) for protein is set at 0.8 grams per kilogram of body weight per day, roughly equivalent to 0.36 grams per pound of body weight. 

However, this amount is insufficient for individuals engaging in regular physical exercise, let alone athletes with specific fitness goals.

Recreational athletes and those seeking moderate muscle gains may aim for the lower end of the range.

Bodybuilders and strength athletes, whose goals are substantial muscle growth, would target the higher end of the range.

Ultra Endurance Athletes: despite their lean appearance, may require high protein intakes at certain points in their training cycle. This need arises from:

• High-volume training: During phases of intense training with long-duration sessions, such as long-distance running or cycling, there’s a significant increase in protein breakdown.
• Protein as an energy source: As these athletes engage in prolonged activities, they tap into protein as an energy source to sustain their efforts, leading to a higher demand for protein intake.

Individual Variability: the ideal protein intake is not universally fixed. It varies among individuals due to genetics, metabolism, and unique physiological responses. Therefore, experimentation may be necessary to find the optimal protein intake that aligns with one’s goals and needs.

Safety Considerations 

Excessive protein intake leads to ammonia buildup as a byproduct of protein breakdown. While intakes up to 2.5 grams per kilogram are generally considered safe, exceeding this limit may lead to potential toxicity issues due to the body’s limited capacity to convert ammonia to urea, a less toxic compound.

Is there a difference between animal and plant-based proteins?

Yes, there are significant differences between animal-based and plant-based proteins:

	Animal Based Proteins	Plant Based Proteins
Source	Come from animal sources such as meat, poultry, fish, dairy products, and eggs	These proteins are derived from plant sources like legumes, beans, lentils, tofu, nuts, seeds, and certain grains.
Protein Content	Generally, animal-based proteins are considered “complete proteins” because they contain all the essential amino acids in sufficient quantities. They tend to have high protein content.	Plant-based proteins can vary in amino acid composition; some may lack one or more essential amino acids. However, combining different plant protein sources (e.g., beans and rice) can create complete protein profiles.
Fat Content	Animal proteins often contain higher amounts of saturated fats, which can contribute to heart disease and other health issues.	Plant proteins are typically lower in saturated fats and can provide healthier fats, such as unsaturated fats and omega-3 fatty acids
Cholesterol	Animal products like meat, eggs, and dairy contain cholesterol, which can raise blood cholesterol levels.	Plant-based proteins are naturally cholesterol-free.
Fiber and Nutrients	Animal products generally lack dietary fiber and may be lower in certain vitamins and minerals found abundantly in plant foods, such as fiber, antioxidants, and phytochemicals.	Plant-based proteins often come with the added benefit of dietary fiber and a wide range of vitamins, minerals, and antioxidants that promote overall health.
Environmental Impact	The production of animal-based proteins, especially beef and lamb, is associated with higher greenhouse gas emissions, land use, and water consumption than plant-based proteins.	Plant-based proteins, on average, have a lower environmental footprint, making them a more sustainable choice.
Health Implications	Excessive consumption of certain animal-based proteins, particularly processed meats, has been linked to an increased risk of chronic diseases like heart disease, cancer, and diabetes.	Plant-based diets are associated with lower risks of chronic diseases and can support better overall health.

Both animal-based and plant-based proteins can be part of a balanced diet. The choice between them often depends on dietary preferences, nutritional needs, and ethical or environmental considerations. Incorporating various protein sources from both animal and plant origins can help ensure a well-rounded intake of essential nutrients.

Protein and Human Health

The Harvard Chan School of Public Health research reveals several important findings regarding the relationship between dietary choices, particularly red meat consumption, and cardiovascular health, diabetes, cancer, bone health, premature death, weight control, and more. 

Protein and heart health

Red Meat and Cardiovascular Risk: Regular consumption of even small amounts of red meat, especially processed red meat, is associated with an increased risk of heart disease, stroke, and the likelihood of dying from cardiovascular disease or other causes.

Healthy Protein Sources: Replacing red and processed red meat with healthier protein sources like beans, soy foods, nuts, fish, or poultry reduces the aforementioned risks. Plant-based proteins are rich in unsaturated fats, which can lower LDL cholesterol, a known risk factor for heart disease. Moreover, plant sources contain no cholesterol.

Statistical Evidence: One study that followed a large group of individuals over two decades found that the more unprocessed red meat participants consumed, the higher their risk of cardiovascular disease death. Processed red meat showed an even stronger link to cardiovascular disease mortality.

Lifesaving Potential: Cutting down on red and processed red meat intake could significantly reduce cardiovascular disease deaths. The research suggests that if study participants had reduced their red meat consumption to less than half a serving a day, it could have prevented many cardiovascular disease deaths.

Protein Source Matters: Another study found that while total protein intake had a minimal association with heart disease risk, protein from red meat was linked to a higher risk. Replacing red meat with healthy plant proteins led to decreases in risk factors for cardiovascular disease.

Impact on Cholesterol: Diets high in red meat did not show significant differences in total cholesterol, lipoproteins, or blood pressure compared to other diets. However, diets rich in high-quality plant protein sources, such as legumes, soy, and nuts, resulted in lower levels of both total and LDL (“bad”) cholesterol.

High-Protein Diets: Evidence suggests that a relatively high-protein diet can benefit heart health, provided the protein comes from healthy sources. Low-carbohydrate diets high in plant-based sources of fat and protein were associated with a 30% lower risk of heart disease in a 20-year prospective study of women.

Diet Quality Matters: The type of carbohydrate and protein sources in the diet is crucial. Healthy protein replacements for carbohydrates can lead to better blood pressure and LDL cholesterol levels, whereas diets high in animal fat or protein may not offer the same protective benefits.

Contradictory Findings: Occasionally, studies may produce conflicting results. For instance, a study of Swedish women suggested that low-carbohydrate, high-protein diets were associated with higher rates of cardiovascular disease. However, this study did not consider the types of carbohydrates or sources of protein consumed, and most of the protein, in this case, came from animal sources.

The research underscores the importance of dietary choices, emphasizing the potential cardiovascular benefits of reducing red meat consumption and replacing it with healthier protein sources, particularly plant-based options. The quality of protein and carbohydrate sources also plays a critical role in heart health.

Protein and Diabetes 

The research on diabetes risk and dietary protein sources highlights the importance of the type of protein consumed rather than just the quantity:

Red Meat and Type 2 Diabetes Risk: Studies have consistently shown that a higher intake of red meat, particularly processed red meat, is associated with an increased risk of developing type 2 diabetes. For example, one study from 2011 found that for each additional daily serving of red meat or processed red meat, the risk of diabetes increased by 12% and 32%, respectively. In contrast, replacing a serving of red meat with healthier alternatives like nuts, low-fat dairy products, or whole grains was linked to a 16% to 35% lower risk of type 2 diabetes.

Change in Red Meat Consumption: Another study observed that individuals who increased their red meat consumption had a 50% higher risk of developing type 2 diabetes over the next four years. Conversely, those who reduced their intake of red meat experienced a 14% lower risk of type 2 diabetes over a 10-year period.

Cooking Methods and Diabetes Risk: How meat is cooked also affects diabetes risk. A study involving a large sample of over 289,000 individuals found that those who frequently consumed red meats and chicken cooked at high temperatures had a 1.5 times higher likelihood of developing type 2 diabetes than those who ate this meat less often. 

Additionally, frequent users of high-temperature cooking methods were more likely to experience weight gain and develop obesity, which may contribute to diabetes risk. Importantly, this research suggests that cooking methods can influence diabetes risk beyond the effects of meat consumption alone.

Low-Carbohydrate Diets: A 20-year study examined the relationship between low-carbohydrate diets and type 2 diabetes risk in women. It revealed that low-carbohydrate diets rich in vegetable sources of fat and protein were associated with a lower risk of developing type 2 diabetes. However, diets high in animal sources of protein or fat did not offer the same benefit.

In summary, the findings emphasize that the source of dietary protein is critical in determining the risk of type 2 diabetes. Red meat, particularly when processed or cooked at high temperatures, is linked to an increased risk, while healthier protein sources like nuts, legumes, and poultry are associated with a lower risk. Additionally, the type of carbohydrate and protein sources in the diet can influence diabetes risk, with vegetable-based sources being more beneficial than animal-based ones. These studies provide valuable insights into the relationship between dietary choices and diabetes risk, highlighting the significance of making informed food selections to reduce the likelihood of developing type 2 diabetes.

Proteins and Cancer 

Research on cancer risk and dietary protein sources highlights that the type of protein consumed may be more critical than the quantity:

Red Meat and Cancer Risk: Multiple studies, including the Nurse’s Health Study and the Health Professionals Follow-Up Study, have shown a clear association between higher red meat and processed red meat consumption and an increased risk of cancer-related deaths. Specifically, each additional daily serving of red meat or processed red meat was associated with a 10% and 16% higher risk of cancer death, respectively.

World Health Organization (WHO) Findings: In October 2015, the WHO’s International Agency for Research on Cancer (IARC) declared that processed meat is “carcinogenic to humans” and that red meat is “probably carcinogenic to humans.” These conclusions were drawn from an extensive evaluation of over 800 studies by a working group of 22 scientists from 10 countries. While the primary evidence focused on colorectal cancer, positive associations were also observed between processed meat consumption and stomach cancer and between red meat consumption and pancreatic and prostate cancer.

Adolescent Diet and Breast Cancer: A 2014 study found a noteworthy connection between high consumption of red meat during adolescence and premenopausal breast cancer. In contrast, higher intakes of poultry, nuts, and legumes were linked to a lower risk of breast cancer. 

Analyzing data from 89,000 women followed over 20 years, the study revealed a 22% higher risk of breast cancer among those who consumed 1.5 servings of red meat daily during high school compared to those with only one serving per week. Each additional daily serving of red meat was associated with a 13% increase in breast cancer risk.

Cooking Methods and Cancer Risk: The way meat is cooked can also influence cancer risk. High-temperature grilling, for instance, generates potentially carcinogenic compounds in meat, including polycyclic aromatic hydrocarbons and heterocyclic amines. These substances have been linked to an elevated risk of cancer. Proper grilling techniques and precautions can help mitigate these risks.

In summary, the research underscores the importance of considering the source of dietary protein in relation to cancer risk. Red meat and processed meat consumption have been associated with a higher risk of various cancers, while healthier protein choices like poultry, nuts, and legumes are linked to a reduced risk. Additionally, how meat is cooked can introduce additional cancer-related risks due to the formation of harmful compounds during high-temperature cooking. These findings emphasize the need for informed dietary choices to lower the risk of cancer potentially.

Protein and Our Planet

Protein production and consumption have significant impacts on the planet, affecting various aspects of the environment. Here are some key ways in which protein impacts the planet:

Land Use: Protein production, particularly from livestock, requires vast land for grazing animals and growing feed crops. Large-scale livestock farming often leads to deforestation and habitat destruction, which can result in the loss of biodiversity and disrupt ecosystems.

Greenhouse Gas Emissions: Livestock farming, especially beef and dairy production, is a major source of greenhouse gas emissions, primarily methane and nitrous oxide. These gases contribute to global warming and climate change. The livestock sector is estimated to be responsible for a significant portion of total global greenhouse gas emissions.

Water Usage: Protein production, especially animal agriculture, is water-intensive. Livestock farming requires substantial water for drinking, cleaning, and growing feed crops. The inefficient conversion of plant-based protein into animal-based protein results in a higher overall water footprint for animal-derived protein sources.

Deforestation: The expansion of livestock farming, particularly in regions like the Amazon rainforest, has been a driving force behind deforestation. As forests are cleared for grazing land or to cultivate animal feed crops like soybeans, it contributes to habitat loss and reduces the Earth’s capacity to absorb carbon dioxide, exacerbating climate change.

Pollution: Livestock operations produce significant amounts of manure, which can lead to water pollution when not managed properly. The runoff from animal agriculture can contaminate waterways with excess nutrients and pathogens, posing risks to aquatic ecosystems and human health.

Overfishing: The consumption of seafood as a protein source has led to overfishing in many parts of the world. Overfishing disrupts marine ecosystems, depletes fish populations, and can lead to the collapse of fish stocks.

Energy Consumption: Protein production and processing require substantial energy inputs, from powering farm equipment to running processing plants. The energy demand associated with protein production contributes to overall energy consumption and associated environmental impacts.

Food Security: The global demand for protein, particularly animal-based, can strain food resources. Feeding livestock requires large quantities of grains and crops that could otherwise be used to feed humans directly. This resource competition can impact food security in regions with limited access to adequate nutrition.

Waste and Antibiotics: The livestock industry generates significant waste, including manure and byproducts. Mismanagement of this waste can lead to environmental contamination. Additionally, the use of antibiotics in animal agriculture can contribute to the development of antibiotic-resistant bacteria, posing a threat to human and animal health.

In response to these environmental concerns, there is growing interest in sustainable protein production methods, such as plant-based proteins, insect farming, and lab-grown (cultured) meat. These alternative protein sources aim to reduce the ecological footprint associated with traditional livestock farming and contribute to more environmentally friendly and sustainable food systems.