Protein has long been considered the magic macronutrient that for a lot of dieters is either over-consumed or under-consumed based on misunderstanding or misguidance. In this article, we will discuss protein as a macronutrient, how often and why you should consume it, and how much per day based on your body and goals. We will consult reliable anecdotal studies together with scientific research and data in order to formulate general guidelines for protein size and frequency at meals.
What is protein?
Protein is primarily responsible for cell repair and growth, meaning muscle growth or preventing muscle loss. Making up 15-20% of your bodyweight protein is therefore second to water as the most abundant substance present in the body.
When we think of protein it’s easy to draw conclusions to mountains of chicken ultimately producing muscles upon muscles. But in actual fact, protein is the key ‘building’ nutrient for a variety of bodily tissues, not only muscle growth but enzymes, skin, hair, nails, bones, and connective tissue are all constructed from protein. Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains, some of which are essential (and cannot be created through our own metabolism and need to be obtained through food) and others which are nonessential (produced from other amino acids and substances in the diet and metabolism). There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function. Their conformation is vital, because the protein cannot function until it is a certain shape, as the shapes determine their function.
How do we get protein?
The answer to this question is two-fold. Essentially, our own metabolic function produces protein in which our body can recycle the essential amino acids, though it cannot produce them. Therefore, through our diet, a supply of them must be provided so that the body has enough raw materials in the form of essential amino acids to replace the normal, everyday losses.
Listed below are food sources that are high in protein. It is advised to select lean cut meats and also be aware that nuts are dominant in fat over protein and as a result, are quite calorie-dense as 1g of protein = 4 calories whereas 1g of fat = 9 calories.
High Protein Foods:
Dairy: Cheese, Milk, Yogurt (particularly Greek Yogurt)
Meat and Poultry: Chicken, Turkey, Beef, Ham, Fish, Pork, Seafood
Beans and Legumes: Beans, Lentils, Tofu, Tempeh, Soybeans, Split Peas, Chickpeas, Falafel
Nuts: Almonds, Pistachios, Walnuts, Cashews, Peanuts, Nut Butters
Other: Whey Protein Powder, Pea Protein Powder, Quest Bars and other Protein Bars
When Our Bodies Build Protein
So once the amino acids are either eaten in food or synthesised by the body cells, this next process is called protein synthesis. It is often used to refer to protein translation but encompasses a multi-step process.
….Put your science cap on, this is where we get to put our heads in the laboratory!
There are three basic stages of protein synthesis:
RNA is created so it can go and instruct the making of protein. So, protein synthesis begins with DNA. The reason for this is simple: DNA contains the genetic information for everything in our bodies. From skin cells to hormones, it all originates from DNA. Within our DNA, there are sequences of nucleotides (building blocks, of DNA and RNA) that form a code to make the proteins, a vital part of existence. During transcription, in the nucleus of a cell, enzymes make an RNA copy using a portion of DNA. The RNA is then transformed into a messenger RNA (mRNA) and leaves the nucleus through the pores and gets into the cytoplasm. Here, the mRNA mixes with the ribosome, which begins the process of protein synthesis.
Basically, at this stage an amino acid activating enzyme (adaptor) is connected to an amino acid so it can be energised and have enough strength to continue its journey. The tRNA molecule brings an amino acid that is coded for by codons on the mRNA. Amino acids are bonded together as the mRNA moves through the ribosome.
Remember: it takes many amino acids to make up one protein, so this is the point where one amino acid is attached to an adaptor. Therefore, there must be a way to link these amino acids into a single protein in order to complete protein synthesis. This is where the ribosome comes in which is often termed ‘a protein factory’ for its competency in producing proteins. It reads the code created by condons in the transferral stage and then links all the amino acids. Once done the mRNA signals STOP; the ribosome releases the mRNA and the amino acid, and a protein has been made.
How much is enough?
The general guidelines for the minimum amount of protein required have come from using nitrogen balance data as a parameter. Nitrogen balance studies measure the total amount of nitrogen in the form of dietary protein that is consumed and compares that with the total amount of nitrogen excreted in the urine, feces, integumental losses, sweat, hair as well as semen, menstrual fluid and even the breath. The idea is that if the amount of protein eaten is as much as that given off, the body is subsequently getting enough to maintain balance.
Nitrogen balance can be negative, positive or at equilibrium. A negative nitrogen balance means that your body is in a catabolic state (essentially depleted) and is more or less cannibalising muscle tissue to meet its nutritional needs. A positive nitrogen balance puts your body in an anabolic state which on the contrary refers to the metabolic process that is characterised by molecular growth, such as the increase of muscle mass. Thus, it means ‘muscle-building’ in most common bodybuilding contexts. This state also means that your body is sufficiently recovering from your workouts.
A nitrogen balance that is at equilibrium indicates that no progress is being made but the body isn't in a catabolic state either. Here, nitrogen intake and loss are the same. You won't get any bigger but at the same time, at least you're not losing muscle too, so even though it's not ideal it's superior to a negative nitrogen balance.
So this ‘balance’ has long been used as the cornerstone for health guidelines on dietary protein recommendations in order to maintain short term nitrogen balance. The RDA provides the minimum amount of protein to maintain short-term nitrogen balance is 0.8g/ per kg of body weight. This is based largely on data from young adults of an ideal health and energy balance.
Our recommendation for protein intake in a moderate bodyfat and training load would be roughly 2.2-2.8g per kg TOTAL weight (about 1-1.25g per pound).
For a very low body fat or very low calorie or high training load = 2.4 - 3g per kg TOTAL weight (1.1-1.35g per pound).
For a high body fat, high calorie, or low training load = 1.6 to 2.2g per kg TOTAL weight (.8-1.1g per pound).
Studies have found a HIGHER protein intake better for satiety, partitioning, blood sugar control, and hypertrophy, unless guided for medical or other reasons to have a lower protein intake. So here’s why your training load and goals matter to your protein intake;
The Normal Person vs. The Athlete
Reports suggest that those performing resistance and (or) endurance exercise require more protein than their sedentary counterparts. Athletes are more active and have very different goals regarding nutrition compared to the average person. Not only are aesthetics important but so too are performance levels. Athletes looking to maximise muscle mass and strength may benefit from protein levels well above the RDA and more so in-line with our previous recommendations above. While the RDA recommendation of 0.8/kg of bodyweight focuses on the minimum needs to achieve nitrogen balance, athletes should focus on consuming sufficient protein to maximise beneficial metabolic outcomes of greater protein intakes.
Stimulating protein synthesis through a higher protein intake is more relevant to the athlete looking to maximise muscle mass, and performance. For these individuals the concern is not only the minimum protein intake to meet requirements, but rather the optimal intake of protein to maximise the anabolic effects of amino acids for maximal muscle mass and function in high force requiring activities.
A positive nitrogen balance is optimal for athletes and those seeking to gain muscle (or avoid catabolism) and means that the body is retaining more protein than it is using as fuel or just otherwise excreting. If you're in a negative nitrogen state where nitrogen loss is greater than intake, then this is the worst state for a bodybuilder and means nitrogen is then taken from muscles or organs and put to where it's needed for growth (and repair). If you think that combating this through protein alone is sufficient then you’re only partially correct.
A negative state can actually be caused by insufficient carbohydrate and fat consumption too. Without carbs not only is protein synthesis hindered, but there's a huge deficiency in energy. If you consume primarily protein, without considering the importance of carbs, the body may metabolise protein for energy purposes, and therefore lower the nitrogen balance - valuable amino acids will be moved to support vital organs and deprive the muscles of exactly what they need for growth.
The branched-chain amino acid leucine has been proposed as the key amino acid for stimulation of muscle-protein synthesis. Dr Layne Norton recommends for athletes - as suggested by current research, that as the amino acid leucine is responsible for much of the anabolic properties of a meal and maximisation of muscle protein synthesis that it is optimal to consume sufficient leucine (3g or ~0.05g/kg body weight) to ignite growth factors. The amount of protein required at a meal to achieve this outcome will differ based on the leucine content of the protein source and Layne suggests that there are protein sources that are more superior and leucine-rich like dairy, egg, meats and poultry which are preferable to leucine poor sources of protein such as wheat.
For the normal person not engaging in strenuous exercise or on an athlete level training regime and perhaps looking to lose fat, change overall body composition or even maintain; protein intake should go beyond RDA minimums. The Food and Nutrition Board admitted that relying solely on results from nitrogen balance studies to determine the RDA did have limitations, because this method does not measure any relevant physiological endpoint.
Not only this, but the existing data was gathered almost exclusively in early 20s-30s men whereas a greater nitrogen intake is likely required to maintain nitrogen balance in e.g. elderly persons. Regardless of whether .36 grams/pound/day is an appropriate value for the RDA for elderly persons as well as for individuals 18- to 50-years-old, the point is the RDA is functionally defined as the amount of protein needed to avoid a deficiency that would lead to a progressive loss of lean body mass (as reflected by negative nitrogen balance).
The Acceptable Macronutrient Distribution Range (AMDR) of protein was noted to be between 10% and 35% of the daily energy intake (DRI) and in light of this, the RDA is therefore below the lowest intake recommended by the AMDR when considered in the context of the overall dietary intake of macronutrients. To avoid symptoms of protein deficiency such as loss of muscle tissue, anaemia, physiological implications and for optimum aesthetic weight loss results our recommendation is that about 30% of your total caloric intake account for protein (for non-athletes).
It should be noted that current evidence is relatively unsatisfactory to draw on precise conclusions because there is no method available for the independent validation of an optimal state of protein nutrition. However, the information above has been concluded based on assessment of a number of sources and studies and therefore supported recommendations, though studies and generation of conclusive evidence is ongoing.
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