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Why are proteins important in the diet?

Why are proteins important in the diet?

Protein is found throughout the body—in muscle, bone, skin, hair, and virtually every other body part or tissue. It makes up the enzymes that power many chemical reactions and the haemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.

Protein is made from twenty-plus basic building blocks called amino acids. Because we don’t store amino acids, our bodies make them in two different ways: either from scratch, or by modifying others. Nine amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—known as the essential amino acids, must come from food.

So, how much protein do I need in my diet?

Under normal circumstances, your body breaks down the same amount of protein that it uses to build and repair tissues. Other times, it breaks down more protein than it can create, thus increasing your body’s needs.

The Dietary Guidelines for Australians, recommend the following daily amounts of protein for different age groups:

  • Children under 4: 13 grams
  • Children ages 4 to 8: 19 grams
  • Children ages 9 to 13: 34 grams
  • Women and girls ages 14 and over: 46 grams
  • Boys ages 14 to 18: 52 grams
  • Men ages 19 and over: 56 grams

Simply put, most everyone should get 10% to 35% of their calories each day in the form of protein. You need more calories for activities like biking, lifting weights, or running, but the percentage of protein remains in the same range.

What are the dietary benefits of protein in the diet?

  1. Causes Biochemical Reactions

Enzymes are proteins that aid the thousands of biochemical reactions that take place within and outside of your cells. The structure of enzymes allows them to combine with other molecules inside the cell called substrates, which catalyse reactions that are essential to your metabolism. Enzymes may also function outside the cell, such as digestive enzymes like lactase and sucrase, which help digest sugar. Some enzymes require other molecules, such as vitamins or minerals, for a reaction to take place.

Bodily functions that depend on enzymes include

  • Digestion
  • Energy production
  • Blood clotting
  • Muscle contraction

Lack or improper function of these enzymes can result in disease

  1. Acts as a Messenger

Some proteins are hormones, which are chemical messengers that aid communication between your cells, tissues and organs. They’re made and secreted by endocrine tissues or glands and then transported in your blood to their target tissues or organs where they bind to protein receptors on the cell surface.

Hormones can be grouped into three main categories :

  • Protein and peptides : These are made from chains of amino acids, ranging from a few to several hundred.
  • Steroids: These are made from the fat cholesterol. The sex hormones, testosterone and estrogen, are steroid-based.
  • Amines : These are made from the individual amino acids tryptophan or tyrosine, which help make hormones related to sleep and metabolism.

Protein and polypeptides make up most of your body’s hormones. Some examples include :

  • Insulin: Signals the uptake of glucose or sugar into the cell.
  • Glucagon: Signals the breakdown of stored glucose in the liver.
  • hGH (human growth hormone): Stimulates the growth of various tissues, including bone.
  • ADH (antidiuretic hormone): Signals the kidneys to reabsorb water.
  • ACTH (adrenocorticotropic hormone): Stimulates the release of cortisol, a key factor in metabolism.
  1. Provides Structure

Some proteins are fibrous and provide cells and tissues with stiffness and rigidity. These proteins include keratin, collagen and elastin, which help form the connective framework of certain structures in your body. Keratin is a structural protein that is found in your skin, hair and nails.

Collagen is the most abundant protein in your body and is the structural protein of your bones, tendons, ligaments and skin

Elastin is several hundred times more flexible than collagen. Its high elasticity allows many tissues in your body to return to their original shape after stretching or contracting, such as your uterus, lungs and arteries.

  1. Balances Fluids

Proteins regulate body processes to maintain fluid balance.

Albumin and globulin are proteins in your blood that help maintain your body’s fluid balance by attracting and retaining water. If you don’t eat enough protein, your levels of albumin and globulin eventually decrease.

Consequently, these proteins can no longer keep blood in your blood vessels, and the fluid is forced into the spaces between your cells. As the fluid continues to build up in the spaces between your cells, swelling or oedema occurs, particularly in the stomach region. This is a form of severe protein malnutrition called kwashiorkor that develops when a person is consuming enough calories but does not consume enough protein.

  1. Provides Energy

Proteins can supply your body with energy. Protein contains four calories per gram, the same amount of energy that carbs provide. Fats supply the most energy, at nine calories per gram. However, the last thing your body wants to use for energy is protein since this valuable nutrient is widely used throughout your body.

Carbs and fats are much better suited for providing energy, as your body maintains reserves for use as fuel. Moreover, they’re metabolized more efficiently compared to protein. In fact, protein supplies your body with very little of its energy needs under normal circumstances.

Is it safe to say that protein has many roles in your body? It helps repair and build your body’s tissues, allows metabolic reactions to take place and coordinates bodily functions. In addition to providing your body with a structural framework, proteins also maintain proper pH and fluid balance. Finally, they keep your immune system strong, transport and store nutrients and can act as an energy source, if needed. Collectively, these functions make protein one of the most important nutrients for your health.

References:

National Academies of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients).

Song M, Fung TT, Hu FB, Willett WC, Longo VD, Chan AT, Giovannucci EL. Association of animal and plant protein intake with all-cause and cause-specific mortality. JAMA internal medicine. 2016 Oct 1;176(10):1453-63.

Fehrenbach KS, Righter AC, Santo RE. A critical examination of the available data sources for estimating meat and protein consumption in the USA. Public health nutrition. 2016 Jun;19(8):1358-67.

Bernstein AM, Sun Q, Hu FB, Stampfer MJ, Manson JE, Willett WC. Major dietary protein sources and risk of coronary heart disease in women. Circulation. 2010 Aug 31;122(9):876-83.

Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, Willett WC, Hu FB. Red meat consumption and mortality: results from 2 prospective cohort studies. Archives of internal medicine. 2012 Apr 9;172(7):555-63.

Bernstein AM, Pan A, Rexrode KM, Stampfer M, Hu FB, Mozaffarian D, Willett WC. Dietary protein sources and the risk of stroke in men and women. Stroke. 2011 Jan 1:STROKEAHA-111.

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