Food sources and Facts of Protein


The name protein is derived from the Greek term proteos, which means “primary” or “to take place first.” Protein was first identified in a laboratory about a century ago at which time scientists described it as a nitrogen-containing part of food that is essential to human life. While protein has long been the darling of the weight lifting and sport community, over the past few years there has been more attention focused on the importance of protein during weight loss and general health.

Consuming enough protein is vital for maintaining health. Proteins form important structures in the body, make up a key part of the blood, help regulate many body functions, and can fuel body cells. North Americans generally eat more protein than is needed to maintain health. Our daily protein intake comes mostly from animal sources, such as meat, poultry, fish, eggs, milk, and cheese. In contrast, in the developing world, diets can be deficient in protein.

Diets that are mostly vegetarian still predominate in much of Asia and areas of Africa, and some North Americans are currently adopting the practice. Plant sources of protein are worthy of more attention from North Americans. In the early 1900s, plant sources of proteins—nuts, seeds, and legumes—were consumed just as often as animal proteins. Over the years, though, plant proteins have been sidelined by meats. During this time, nuts were viewed as high-fat foods, and beans had the inferior reputation of “the poor man’s meat.” Contrary to these popular misconceptions, sources of plant proteins offer a wealth of nutritional benefits—from lowering blood cholesterol to preventing certain forms of cancer.

What Foods Contain Protein?

Because protein is vital to life, all life-forms will contain protein; however, the protein content will vary. In general, foods of animal origin will have greater protein content than plants and plant-derived foods. Among the foods that have the highest protein content (percent of calories) are water-packed tuna and egg whites. Being an animal, tuna (and other fish) contain skeletal muscle for locomotion. Hence consumption of finned or shellfish offers protein sources which is similar to human skeletal muscle proteins. At the same time, predominant protein found in egg whites is albumin and globulins, ovomucoid & lysozymes. Milk is another well-known protein source due to its protein density. Caseins and whey are the key proteins in milk.

Cereal grains produce a vast array of proteins (including albumins); however, the most interesting proteins may be gliadin and glutenin. When these proteins gets combined with water, such as when making dough, it forms gluten which provides structural basis for network which traps gases created by yeast when dough rises.

Food name Weight (g) Protein (g) DV%
Turkey 863 254 508%
Soybeans 172 66 132%
Lupins 180 65 130%
Spirulina 112 64 128%
Mungo beans 207 52 104%
Hyacinth beans 210 50 100%
Lentils 192 47 94%
Navy beans 208 46 92%
Chicken 140 46 92%
Kielbasa 370 45 90%
Mothbeans 196 44 88%
Kidney beans 184 44 88%
Tuna 146 42 84%
Black beans 194 41 82%
Lima beans 202 41 82%
Parmesan cheese 100 41 82%
Egg 85 40 80%
Yardlong beans 167 40 80%
Whelk 85 40 80%
Peanuts 144 40 80%

 How Much Protein Should We Eat Daily?

The RDA for protein for adults is set at 0.8 grams of protein per kilogram of body weight. This works out to about 54 to 60 grams for most men and about 44 to 50 grams for most women. You can estimate basic protein needs based on percent of total calories, where by 12–15 percent will give you approximately the same level. This protein level slightly compensates for normal regular body protein loss; yet it is not an adequate protein level in various situations such as exercise, weight loss, and illness. The protein level of 25 percent of calories is appropriate in these situations.

Are High-Protein Diets Dangerous?

At one time there was a belief that higher intakes of protein can be problematic to health. Today we know that for most people this isn’t the case. In fact, diets with a higher level of protein then the RDA are encouraged for athletes as well as people during weight loss. Two areas of health have been the target for concern regarding higher protein intakes. First comes kidney health. It was believed that high protein intakes results in formation of nitrogen-based compounds like urea, this become destructive to kidneys. Today we know this is not the case unless a person has a situation associated to kidneys and a guidance receiving from his/her physician.

The second area is in relation to bone. Some research efforts have determined that when diet protein levels increase, so too does the level of calcium in the urine. This lead to the conclusion that high-protein diets cause a loss of calcium from bones, rendering a person more prone to osteoporosis. However, follow up research has shown that the higher protein intake also increases calcium absorption, thus leading to a corresponding increase in calcium in the urine. So, like kidney dysfunction, the notion that a high protein intake, such as 25 percent of calories for weight loss or maintenance, leads to osteoporosis has not been shown to be true.

Health Benefits of Protein

Let us discuss on health benefits served by protein:

  1. Contributing to immune function

Proteins are a key component of the cells within the immune system. An example is the antibodies, proteins produced by one type of white blood cell. These antibodies can bind to foreign proteins in the bloodstream an important step in removing invaders from the body. Without sufficient dietary protein, the immune system lacks the materials needed to function properly. For example, a low-protein status can turn measles into a fatal disease for a malnourished child.

  1. Provides energy

Proteins supply little energy for a weight-stable person. Two situations in which a person does use protein to meet energy needs are during prolonged exercise and during calorie restriction, as with a weight-loss diet. In these cases, the amino group (2 NH 2) from the amino acid is removed, and the remaining carbon skeleton is metabolized for energy needs. When the carbon skeletons of amino acids are metabolized to produce glucose or fat, ammonia (NH3) is a resulting waste product. The ammonia is converted into urea and excreted in the urine. Under most conditions, cells primarily use fats and carbohydrates for energy needs. Although proteins contain the same amount of calories (on average, 4 kcal per gram) as carbohydrates, proteins are a costly source of calories, considering the amount of processing the liver and kidneys must perform to use this calorie source.

  1. Contributing to satiety

Compared to the other macronutrients, proteins provide the highest feeling of satiety after a meal. Thus, including some protein with each meal helps control overall food intake. Many experts warn against skimping on protein when trying to reduce energy intake to lose weight. Meeting protein needs is still important, and exceeding needs somewhat may provide an additional benefit when dieting to lose weight. Several effective weight-loss diets include a percentage of calories from protein at the upper end of the Acceptable Macronutrient Distribution Range of 10% to 35% for protein. So in general, these diets are appropriate if otherwise nutritionally sound, especially with regard to being moderate in fat and having enough fiber.

  1. Increase muscle mass

Intake of adequate protein is essential to build or maintain healthy muscle mass by supporting tendon, body tissues and ligaments. So protein is essential for bodybuilding but is essential to develop leaner muscles. The diet lacks amino acids; muscle wasting could take place when muscle fibers are broken down for supporting body’s energy needs. Protein is crucial after exercise since physical activity such as strength training damages muscle tissues so it could repair and grow back stronger. For process to conduct effectively, it requires some extra protein for repairing damage. Protein won’t promote athletic performance; research shows that consumption of protein before and after exercise increases recovery of muscles, enhances muscle synthesis and acts as effective muscle ache treatment.

  1. Manage weight

Research shows that diet rich in protein makes one feel full and prevents overeating. For weight loss to be effective, dietary or lifestyle change is must. Studies have shown that controlled intake of calorie with moderately high protein intake is effective and practical weight loss strategy. Foods rich in protein increases satiety to higher extent than fats or carbohydrates which prevents snacking and overeating. Intake of protein forms process in the body called thermogenesis which requires body to spend more energy for digesting food. Protein helps to forbid muscle loss which results from low calorie diet which makes some proteins superfoods for weight loss.

  1. Maintain blood sugar levels

Insulin is a hormone which is essential for fat, carbohydrates and protein to be metabolized. Major determinate of blood sugar levels is glycemic index response from foods we consume, so consumption of high carb or high sugar foods result in fluctuation in level of blood sugar levels consumption protein does opposite. Protein rich foods have minimal effect on blood glucose levels and slow down sugar absorption during meal. Diet rich in protein prevent spikes in blood glucose which is essential to prevent type 2 diabetes, balance energy levels and keeps appetite or mood in check.

  1. Enhance mood

Some amino acids from protein foods are essential to balance hormones naturally, control mood and acts as remedy for anxiety. It assists neurotransmitter function or synthesizes hormones such as serotonin and dopamine which calms and keeps outlook positive.

  1. Bone health

Studies show that positive association exists between consuming foods with protein and better bone health. Diet with high protein from whole and nutrient rich foods heal broken bones and prevent weakness, fractures and even osteoporosis by promoting absorption of calcium and assisting bone metabolism. Protein effect on bones relate to particular protein foods being consumed and intake of vital bone building nutrients such as magnesium and calcium.

  1. Healthy heart

Studies show an inverse relationship between intake of protein and chances of heart diseases. Diets with higher protein are a natural remedy for high blood pressure. Substitute carbohydrate foods with protein to lower bad cholesterol and triglyceride levels. Diets rich in protein balances blood sugar and prevent other heart ailments, diabetes and obesity.

  1. Promote longevity

Protein helps the body to synthesize glutathione known as master antioxidant. Glutathione is saved within our own cells and assist to detox and lower carcinogens which age us. Studies conducted on human and animal shows that adequate intake of protein is essential to maintain glutathione and assist body to remain in state of balanced homeostasis. Deficiency of glutathione contributes oxidative stress with key role in age associated diseases such as Parkinson’s disease, Alzheimer’s disease, cystic fibrosis, liver disease, cancer, sickle cell anemia and viral infections.

Diet with high balanced amino acids from protein foods helps to treat muscle loss due to aging. Diet with adequate protein levels slows down aging process by maintaining muscle mass intact, maintaining high cognitive or immune function and support strong bones. In elderly, deficiencies of amino acid results eye problems such as heart problems, cataracts, weakness, muscle loss and mood changes.

Body helps to synthesize amino acids due to which muscle tends to decline over years by accumulating fat. It makes it crucial to consume plenty of protein rich foods for supporting healthy body weight with energy, sharp memory and strength and balance in place.

What Happens If We Do Not Eat Enough Protein?

Our diet needs to at least replace a quantity of protein equivalent to what is lost to energy pathways and processes that produce amino acid-derived molecules such as neurotransmitters, nucleic acids, some hormones, niacin, etc. If more amino acids are inadequate in our cells, then protein synthesis is restricted to that level. If it continues over time then there will be decline in total body protein. It is visually apparent as skeletal muscle mass is declined. The deficiency still continues then protein levels in blood would become lower and immune system has to be compromised making us prone to infections.

Allergies to Food Protein

Allergies occur when the immune system reacts to what it thinks is a foreign protein. In the case of food allergies, the immune system mistakes a food protein for a harmful invader. For some of us, food allergies to soy, peanuts and tree nuts (e.g., almonds and walnuts), and wheat are a concern. Overall, food allergies occur in up to 8% of children 4 years of age or younger and in up to 2% of adults. Eight foods account for 90% of food related allergies; soy, peanuts, tree nuts, and wheat are four of these foods. (The other foods are milk, eggs, fish, and shellfish). The allergic reactions can range from a mild intolerance to fatal allergic reactions.


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