One of the most controversial and confusing aspects of nutrition is how much protein people should consume each day. There are several factors to take into account to get a good answer to this question, and there are potential problems with eating too much protein. There are also definitely problems with not eating enough protein. It is also important to consider what type of protein is being consumed.
Height, weight, age, sex and activity level all factor into your protein needs. Obviously the larger you are the more protein you need to take in to support structural proteins throughout the tissues of the body including the muscles, bone, skin and organs. In the same way the more active you are the more protein you need to consume. In addition, protein is used to create enzymes, and enzymes are critically important for all cellular function.
Protein is made up of amino acids and there are essential and non-essential amino acids. Essential amino acids MUST be consumed because they cannot be made by the body. Complete proteins contain all the amino acids and come from meats, poultry, fish, eggs and dairy. While vegetarian proteins are not complete it is not hard to combine different plant protein sources to obtain all the protein the body needs to function.
Other factors which influence how much protein is required is overall caloric/energy status. If you are eating enough calories to maintain bodyweight or gain bodyweight you require less protein as a percentage of overall calorie intake while those people in caloric deficit require a higher percentage of their overall calorie intake to maintain lean tissue mass (losing lean mass like muscle is usually NOT a good idea so this is important).
How much is too much?
In large amounts and for certain populations (such as those with compromised Kidney Function) excess protein can cause problems. That being said, for the normal healthy individual, the body can easily and safely process and use a lot of protein. A portion of the protein you eat is frequently converted to glucose (blood sugar) and if your overall calorie intake is too high you will convert excess protein into fat like ALL unused excess calories.
Another potential problem with too much protein is that high protein intake stimulates the release of mTOR which stands for Mammalian Target of Rapamycin. mTOR is a key regulatory protein that signals for cell growth through the creation of new proteins. Consider protein building similar to a race car. The larger the engine, the greater potential for speed. Similarly, the more mTOR present in any given cell, the greater potential for more protein construction. And just like the gas pedal fuels the engine, mTOR is a signaling protein, and can be various levels of active (like a pedal’s ability to regulate speed). If a number of different processes all signal for ‘Go’, then the cell builds as much protein as it can, as quickly as it can. So just as a souped-up car takes off rapidly, a muscle cell can signal for tremendous muscle growth very quickly, given the right conditions. n
For this reason, mTOR is a good thing when you are looking for muscle-building! However, there is a potential dark-side to mTOR. Cancerous tumors are designed to grow as fast as possible, and they rely on mTOR signaling to build proteins just like healthy cells. So too much mTOR could theoretically put people at a higher risk of developing rapid and serious cancers. In fact, a lot of cancer research is based around slowing down and minimizing mTOR activity in tumor cells (the exact opposite goal of muscle research).
This doesn’t necessarily mean that eating more protein for muscle building is going to cause cancer. Numerous other proteins and factors come into play, and some may respond differently in muscle cells than in cancerous cells.
Safe and Adequate Protein Intake
The Institute of Medicine's protein RDAs are calculated using 0.8 grams of protein per kilogram of body weight. This means an adult who weighs 68 kilograms needs at least 54 grams of protein each day. The RDA for pregnant and nursing women is 71 grams of protein per day. Keep in mind the RDA is a MINIMUM and does not mean this is ideal! This also assumes you are sedentary! So, if you are exercising and trying to build muscle or older and trying to prevent muscle loss higher protein intake is better. To determine your minimum daily intake, divide your body weight by 2.2 to determine your weight in Kilograms and then multiply by .8 to get your minimum daily protein intake.
The Academy of Nutrition and Dietetics states that although athletes only need about 1 gram of protein per kilogram of bodyweight to maintain muscle mass, they require 1.4 to 1.8 grams of protein per kilogram to build muscle mass; this is equivalent to about 0.64 to 0.82 grams of protein per pound of body weight each day.