“Proteins are the building blocks of life.” This is one of the most commonly touted nutritional aphorisms, though I venture that most people are oblivious to basic facts regarding protein such as why they are a necessary part of our diet and what they are exactly. I will attempt to keep this as short and simple as possible.
What is Protein?
In a large sense, dietary proteins are one of the three essential macronutrients (beside fat and carbohydrates) that are required for living. On a micro level, they are organic molecules consisting of amino acids linked in a chain (called a polypeptide) located within cells.
While most plants can biosynthesize amino acids, animals, including humans, must rely on food to provide the nine out of 21 that our body requires and cannot form on it’s own. These nine are known as the essential amino acids. The remaining twelve can be synthesized internally using the essential amino acids.
After consuming food, during digestion, dietary protein is broken down by enzymes (which are also considered proteins) to shorter chains of amino acids, and ultimately into free amino acids, which are then absorbed into the blood stream and accumulated into a reserve to be combined with other amino acids and formed into a new protein complex and distributed throughout the body.
This process of our cells assembling new body proteins is called protein biosynthesis. Excess amino acids are not stored for later use, but are used as metabolic fuel.
Functions of Protein
Proteins are a part of virtually every process within our cells. As noted above, some proteins are enzymes, which are necessary to activate certain biochemical reactions such as digestion. Proteins also have a structural function, e.g. collagen and keratin.
Collagens make up connective tissues such as skin and cartilage. Keratin is the key protein that makes up hair and nails. Hormonal proteins are important for cell signaling to distant organs to promote bodily functions e.g. the pancreas releasing insulin in order to metabolize glucose.
Antibodies are another type of protein. These are involved in immune defense against pathogens such as harmful bacteria and viruses.
Transport proteins move molecules around the body e.g. hemoglobin which transports oxygen through the blood. And there are myriad functions as the body synthesizes over 100,000 different proteins.
How Much Protein Do We Need?
The Dietary Reference Intakes (DRIs) are nutrient reference values developed by the Institute of Medicine of The National Academies (and serves as the basis of US nutritional requirements), recommends 0.8 grams per kilogram of body weight per day, while the British Nutrition Foundation recommends .75 grams of protein per kilo. Therefore, a 57 kg-female (125 pounds) should consume between 43 to 46 grams of protein.
Power and endurance athletes require only slightly higher levels.
Best Sources of Protein
Good qualities of protein are measured by digestibility, amino acid composition and ability to provide sufficient nitrogen levels, and it is best to eat a varied diet to achieve protein complementation throughout the day which would ensure all essential amino acids are taken in.
Though meat affords all nine essential amino acids, I believe the best sources of protein provide adequate levels of protein, do not promote plaque buildup in the arteries, have no saturated fat and no dietary cholesterol, and simultaneously provide other macronutrients such as fiber, which many high-protein diets greatly lack. Diets too high in animal protein are linked to digestive malfunction and kidney damage.
Consuming plant-based protein-rich foods such as legumes, nuts, hemp seeds, and whole grains would provide enough protein and all other compulsory nutrients for healthy body functioning as well as preventing disease by lowering cholesterol, promoting healthy bowel movements (due to the high fiber content in plant-based foods), and regulating blood-sugar levels.
I usually advise to my clients that the best way to eat is the most efficient way to eat and that is by consuming foods that meet multiple macronutrient categories (carbs, fat, protein). Here is what I mean:
To fulfill the protein requirement, eat legumes such as lentils, beans, chickpeas, split peas. These provide both protein and fiber (a carbohydrate) as well as several invaluable micronutrients (vitamins and minerals).
To fulfill the fat requirement, instead of consuming simple oils, consume nuts which provide you with protein, fat and fiber. Avocados are another good choice since they provide high amounts of both fiber and fat. Seeds (such as hemp seeds, flax, sesame seeds, etc) provide all three macronutrients.
To fulfill the carbohydrate requirement, eat whole grains and legumes which will give you both protein and fiber.
Now we are informed enough to say with confidence that Proteins are the Building Blocks of Life!