Protein is an essential nutrient for your body. Proteins are the building blocks of body tissue and can also serve as an alternate source of fuel when needed. Your body uses protein for growth and maintenance. Proteins also function as enzymes in membranes and as transport carriers and hormones; their components serve as precursors for nucleic acids, hormones, vitamins, and other integral molecules.
One gram of protein contains four calories, and you can stock up on proteins from both animal sources—meats, dairy products, fish, and eggs—and vegan sources—whole grains, pulses, legumes, and nuts.
Proteins are made up of amino acids, which are like building blocks. There are 20 different amino acids that join together in various combinations to make all types of proteins. Some of these amino acids can’t be made by our bodies, hence they are known as essential amino acids, because it is essential that our diet provide them. In terms of diet, protein sources are categorized according to how many of the essential amino acids they provide.
A complete protein source is one that provides all of the essential amino acids. Complete proteins are also referred to as high quality proteins. Animal-based food sources such as meat, poultry, fish, milk, eggs, and cheese are complete protein sources.
An incomplete protein is one that is low in one or more of the essential amino acids. Plant-based food sources such as grains, lentils, and rice are incomplete proteins.
Complementary proteins are two or more incomplete protein sources that together provide adequate amounts of all essential amino acids. For example, rice contains low amounts of the amino acid lysine and high amounts of the amino acid methionine; however, dry beans contain greater amounts of lysine and lesser amounts of methionine. Together, these two food sources can provide adequate amounts of all the essential amino acids required by the human body.
Protein Requirements for Sedentary Versus Active Individuals
The main factors that determine how much protein an individual needs are training regime and habitual nutrient intake. At the same time, current literature suggests that it may be too simplistic to rely on current recommendations for daily protein intake. There are various factors that need to be considered, such as the quality of proteins according to the biological value of the source, caloric intake, exercise intensity, duration and type of exercise, training history, gender, age, etc.
Currently, the RDA for protein intake is 0.8 grams per kilogram of bodyweight, which is based on the needs of sedentary individuals; this represents an intake level necessary to replace losses and avert deficiency. However, this recommended intake is not likely to offset the oxidation of protein/amino acids during exercise, nor it is sufficient to provide an increase in lean tissue and repair of exercise-induced muscle damage because RDA guidelines do not reflect the requirements of hard training individuals seeking to increase muscle mass.
Here’s an example to illustrate this clearly.
If an individual weighs about 70 kilograms (154 pounds) and his energy intake averages around 2,000 calories per day, his protein requirement depends upon his choice of activity (intensity, duration, and type) and is one of the following:
The International Society of Sports Nutrition suggests that individuals who exercise ingest protein ranging from 1.4 – 2.0 grams/kg/day.
Individuals engaging in endurance exercise should ingest levels at the lower end of this range, or 1.4 grams/kg/day. In this case, the person should consume about 70 (bodyweight in kilos) x 1.4 (grams of protein) = 98 grams of protein per day.
Individuals engaging in intermittent activities, such as football, rugby, etc., should ingest levels in the middle of this range, or 1.7 grams/kg/day. In this case, the person should consume about 70 (bodyweight in kilos) x 1.7 (grams of protein) = 119 grams of protein per day.
People engaging in strength/power exercises, such heavy weight training, should ingest levels at the upper end of this range, or 2 grams/kg/day. In this case, the person should consume about 70 (bodyweight in kilos) x 2 (grams of protein) = 140 grams of protein per day.
A protein intake above 2 grams/kg/day is only advised in special cases, such as very high energy intake. In the above example, if an individual is an athlete and has a caloric requirement of 4,000 calories, then calculating his protein requirement at a modest level of only 12 – 15 percent of the total calories gives us about 150 grams (15 percent of 4,000 calories = 600/4 = 150 grams), which is 2.14 grams/kg/day. However, these cases are very rare, and the lower amounts described above should be sufficient for most recreational athletes.
Protein and the Kidneys
You might be wondering if consuming 1.4 – 2 grams of protein per kilogram of bodyweight will harm your kidneys. The long-term effects of high protein intake on chronic kidney disease are still poorly understood, and there isn’t significant evidence which can link a high protein diet with kidney issues.
A study compared normal healthy adults following a normal, unrestricted protein diet with a group of vegetarians who maintained a long-term low-protein diet. The results suggest that a high protein non-vegetarian diet does not significantly affect how the kidney functions with regards to “normal aging” in healthy subjects. However, if you have renal issues, consult your physician before you embark on a high protein diet.
RDA guidelines for protein intake are less than the amount actually required for active individuals and should thus be adjusted according to one’s type of activity as explained above. Aim to consume at least 1.4 grams/kg/day of protein from various foods to get all the essential amino acids. If you are planning to add a protein supplement to your diet, read my article on choosing the right whey protein supplement. If you are vegetarian and worry about how you can consume 100g of protein in a day, read this.
What do you think about protein requirements? Have something you like to add. Let me know in the comments below!