What is Protein?
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 hemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.
The Institute of Medicine recommends that adults get a minimum of 0.8 grams of protein for every kilogram of body weight per day (or 8 grams of protein for every 20 pounds of body weight). The Institute of Medicine also sets a wide range for acceptable protein intake—anywhere from 10 to 35 percent of calories each day. Beyond that, there’s relatively little solid information on the ideal amount of protein in the diet or the healthiest target for calories contributed by protein.
In the United States, the recommended daily allowance of protein is 46 grams per day for women over 19 years of age, and 56 grams per day for men over 19 years of age.
Around the world, millions of people don’t get enough protein. Protein malnutrition leads to the condition known as kwashiorkor. Lack of protein can cause growth failure, loss of muscle mass, decreased immunity, weakening of the heart and respiratory system, and death.
How Much Protein Do You Need?
The amount of protein you need in your diet will depend on your overall calorie needs. The daily recommended intake of protein for healthy adults is 10% to 35% of your total calorie needs. For example, a person on a 2000 calorie diet could eat 100 grams of protein, which would supply 20% of their total daily calories.
Proteins play a key role in our bodies. They make up about 15% of the average person’s body weight. You probably know proteins as the major component of muscle. Muscles flex arms and legs, contract our hearts and create waves in the walls of our intestines to move food along. All this muscle activity accounts for most of the energy our bodies burn. The more muscle you have, the more calories you burn and the more food you need to maintain your weight.
Proteins also perform crucial activities within all the cells of your body. They move molecules from one place to another, build structures, break down toxins and do countless other maintenance jobs. Proteins play an important structural role in cells as well, making up a sort of miniature skeleton.
Proteins are actually chains of small molecules called amino acids. Some of these chains are constantly being broken down, and new ones are strung together to take their place. Your body can make some of these amino acid building blocks, but not all of them. The ones you can’t make are called essential amino acids.
Benefits of Protein Supplements
Proteins have an overall benefit on physical activity and on overall health. In a study with healthy male US Marines, “the protein supplemented group had an average of 33% fewer total medical visits, 28% fewer visits due to bacterial/viral infections, 37% fewer visits due to muscle/joint problems, and 83% fewer visits due to heat exhaustion” than the control, unsupplemented group.
Furthermore, protein may help reduce blood pressure. A protein mixture, consisting of 20% pea, 20% soy, 30% egg, and 30% milk-protein isolate, reduced systolic and diastolic blood pressure in overweight individuals (BMI = 25-35). This research suggests that protein intake might help manage blood pressure and prevent complications associated with elevated blood pressure.
Animal and human studies have shown that soy protein consumption is beneficial to cardiovascular health. The consumption of soy protein can lower triglyceride levels as well as total and LDL cholesterol levels, and increases HDL levels and HDL/LDL ratios.4 While an optimal soy protein intake is in the range of 15 to 20 g/day, an intake of 25 g/day of soy protein can be specifically used to reduce cholesterol levels.5 Furthermore, supplementation with soy protein can help reduce the markers of prostate cancer development, such as the prostate-specific antigen (PSA), “in patients with prostate cancer or in men at high risk for developing advanced prostate cancer.”
Whey proteins have the capacity to modulate adiposity, enhance immune function and anti-oxidant activity, and improve cardiovascular health. Furthermore, whey protein appears to have a blood glucose and/or insulin lowering effect. Some clinical studies have also shown that taking whey protein in combination with strength training can increase lean body mass, strength, and muscle size.
Does Protein Always Help?
A greater protein requirement has been reported in bodybuilders and endurance trained athletes compared to sedentary young men. In a retrospective re-assessment of data from more than 100 resistance-trained men and women in the age of 50–80 year, a positive relationship was established between the dietary protein intake and the change in lean body mass (LBM) and a daily protein intake of 1.0 g/kg body weight (BW) was established as sufficient. Whereas, in sedentary young and elderly men and women, a daily protein intake of 0.85 g/kg BW was found to be adequate, indicating that persons participating in resistance training may need a higher protein intake than sedentary persons.
During periods of inactivity, increasing the level of protein intake may be particular relevant to diminish the loss of muscle mass. During 7 days of bed rest an enhanced daily protein intake (from 0.6 to 1.0 g/kg BW) resulted in a maintained whole-body protein synthesis and nitrogen loss in young men. Whereas, an unchanged daily protein intake of 1.0 g/kg BW during 14 days of bed rest could not prevent a decline in the postabsorptive whole-body protein turnover rate in young men. Collectively, it was hypothesized that an elevated protein intake is required to maintain whole-body postabsorptive protein turnover during inactivity. Thus, when measured with the techniques usually applied on whole-body measurements, the increase in protein intake per se seems to be more important than the actual level of protein intake. The change in protein intake is crucial because the efficiency of protein utilization adapts to changes in physical activity level, energy balance, and amount of protein intake and it takes time before these adaptation processes are complete. This means that a constantly high protein intake does not necessarily lead to accumulation of body protein mass.
The recommended daily intake of protein for healthy adults is 0.75 g of protein/kg body weight, which translates into approximately 45 to 56 g of protein a day. The daily intake for adult athletes is about 1.5 g/kg body weight, with a range of 1-2 g/kg body weight. But excessive protein intakes can cause a buildup of ketones bodies. When there is an excessive accumulation of ketone bodies, an abnormal but not necessarily harmful state called ketosis results. With progressively higher levels of ketone bodies, the body’s pH is lowered to dangerously acidic levels, leading to a state called ketoacidosis. As your kidneys rid your body of these toxic ketones, you can lose a significant amount of water, which puts you at risk of dehydration, particularly if you exercise heavily. And dehydration from a ketogenic diet can make you feel weak and dizzy, give you bad breath, and lead to other health problems. While there is no evidence that high protein intake per se would be detrimental for bone mass, it appears reasonable to avoid high protein diets (i.e., more than 2 g/kg body weight/day) when associated with low calcium intake (i.e., less than 600 mg/day).
“Proteins (/ˈproʊˌtiːnz/ or /ˈproʊti.ᵻnz/) are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.”