When it comes to settling the issue about protein, its various sources and the amounts we need in order to build skeletal muscle there are four key questions that truly matter:

Which source of protein is better for muscle?
Which source of protein is better for health?
Which source of protein is better for longevity?
How much protein do you need to build muscle?

There is now a body of scientific evidence which can provide some pretty compelling answers to these questions, but before we get into it let’s first dispel a myth. The myth that animal protein is somehow better than plant-based protein is exactly that: a myth. The misunderstanding comes because of two reasons. Both are directly linked to whether our protein source is animal or vegetable.

First, animal protein is absorbed faster by the body. This speed of absorption is regarded as being ‘better’. Scientific evidence however shows that this is not the case and, in some cases the speed at which a protein is absorbed by the body exceeds the body’s capacity to build muscle which means that the excess protein is stored as fat, excess amino acids are oxidized and absorbed by the body, or excreted through urea. A study published in the Journal of Sports Science & Medicine that examined protein types agreed that plant-based protein can be as beneficial as animal protein provided a sufficient variety of plants is introduced in the diet.^[1]

Second, animal protein is usually classed as whole, or complete protein because it is usually high in the nine amino acids which the body can’t produce on its own that are essential for building muscle mass. This means that plant-based protein is incomplete in the sense that a single plant source, with some exceptions that we cover a little further down, is unlikely to provide all the amino acids necessary for building muscle.

Plant-based protein is not just as good as animal protein for building muscle but it also has significantly fewer side effects.

The following table lists the optimal profile of the nine essential amino acids in the human diet, which comprises complete protein, as recommended by the Institute of Medicine's Food and Nutrition Board.

Essential amino acid	mg/g of protein	% of total protein	Raw, Whole, Egg	Quinoa	Spinach
Tryptophan	7	0.7%	1.33%	1%	1.36%
Threonine	27	2.7%	4.42%	3.2%	4.27%
Isoleucine	25	2.5%	5.34%	4.2%	5.14%
Leucine	55	5.5%	8.65%	7.3%	7.8%
Lysine	51	5.1%	7.27%	6.1%	6.08%
Methionine+Cystine	25	2.5%	5.18%	2.7% + 1.3%	1.85% + 1.22%
Phenylalanine+Tyrosine	47	4.7%	9.39%	4.3% + 3.6%	4.51% + 3.78%
Valine	32	3.2%	6.83%	5%	5.63%
Histidine	18	1.8%	2.45%	3.1%	2.24%
Total	287	28.7%	50.86%	41.8%	43.88%

The term ‘incomplete’ is a scientific one instead of a purely nutritional one. All protein is ingested and fully processed by the body, regardless its source. Similarly the rate of absorption of protein is not a reliable guide as to what constitutes ‘good’ or ‘bad’ protein types. A very recent study that compared animal vs plant-based protein^[2] supplements concluded that provided a plant-based diet is sufficiently varied, it is just as effective at building muscle as a diet that uses animal products as a primary source of protein.

This means that protein obtained from plants is every bit as effective as protein obtained from animals at building good quality muscle. It is, however, different and it should be treated as such. In other words while you may get all the protein you require from a single steak, you will need to be more creative and have a varied diet from different complementary plant sources to get the same amount of protein over the course of a day’s eating. Also bear in mind that the regular ingestion of animal protein presents us with health risks we talk about below.

How Much Protein Do You Need To Build Muscle?

There is one additional factor to consider when deciding whether to get your protein from animal sources (fast absorption rate by the body) or plant-based ones (slower absorption rate by the body) and that is the limit at which the body can absorb protein for muscle building. The studies here are a little vague because protein absorption by the body for muscle building, specifically, is a little hard to study in action.

However, The Journal of the International Society of Sports Nutrition published a review^[3] of the large number of studies that have been carried out which indicates that when it comes to building muscle the optimum amount of protein ingested appears to be 0.4 g/kg/meal across a minimum of four meals in order to reach a minimum of 1.6 g/kg body weight/day. The review, which looked at a large number of studies in order to reach a “best” type of recommendation took into account the type of protein that is consumed, its packaging (i.e. fat and carbohydrates when it comes from animal sources and fiber when it comes from plant-based sources) and the percentage of daily calories represented by the protein intake.

A similar in-depth review presented at the Protein 2.0 summit and published in The American Journal of Clinical Nutrition suggests that even when exercising, reaching the upper daily intake of 2.2 g/kg body weight/day can result in lower levels of usage of the protein for building muscle as more of it is oxidized and used by the body elsewhere.^[4] So, paradoxically, taking more protein than needed or taking a lot of protein in a single meal that is absorbed by the body quickly (like Whey protein) can result in less protein being channeled to building muscle.

A new study published in Nutrition and Metabolism^[5] showed that after exercise both adults and adolescents showed that ingestion of excess protein led to a plateau in muscle building. This corroborates the findings mentioned above where more is not necessarily better. A subsequent study published in the Journal of the International Science of Sports Nutrition^[6] reviewed the evidence to verify that excess protein taken in a single meal did not lead to better or faster muscle building and that the 1.6g/kg body weight/day guideline is valid.

Men and women have different protein needs but they also tend to have different weights so the easy-to-use 1.6g/kg body weight/day/number of meals formula provides a good guide here.

There are two additional questions that arise from all this:

Are there adverse effects from too much protein?
Is there a way to optimize protein intake?

The Recommended Daily Allowance (RDA) for protein intake for healthy adults is 0.8g/kg body weight/day. A healthy adult weighing 70kg would then need 56g of protein to maintain healthy function. As already mentioned above those who exercise can increase that amount.

A scientific review of 32 studies (21 experimental human studies and 11 reviews)^[7] however, showed that adverse effects “associated with long-term high protein/high meat intake in humans were (a) disorders of bone and calcium homeostasis, (b) disorders of renal function, (c) increased cancer risk, (d) disorders of liver function, and (e) precipitated progression of coronary artery disease.”

Too much protein for too long and protein that is taken primarily from animal sources, it would appear, is the cause of health issues that will affect both lifespan and quality of life. We build muscle to stay fit and healthy so knowing how to do this in as safe a way as possible is key to maintaining a long and healthy life.

To optimize the amount of protein we take through our diet and even through supplements it is essential to introduce two more terms: High-quality protein and the Acceptable Macronutrient Distribution Range (AMDR). The quality of protein we ingest is determined by two technical factors: the digestible indispensable amino acid scores (DIAAS) and the protein digestibility-corrected amino acid score (PDCAAS). This means that processed meat, sausages, hams and even some cheeses are definitely classed as low-quality protein and should be avoided. High quality protein from animal sources delivers fewer unnecessary calories and has lower fat content and additives that may be harmful to our health.

Here’s what all this means in plain English: Cheap protein of the kind found in highly processed meat products is also responsible for causing cardiovascular disease and excess weight gain. It should be avoided. High quality protein (determined by the digestibility of the amino acids it contains) helps build muscle and repair tissue. Plant-based protein has significantly fewer health side-effects than animal products. It is better to spread the total protein intake throughout the day than to try and eat all the protein your body needs in a single meal. The minimum recommended daily allowance (RDA) of protein is lower than that suggested by the Acceptable Macronutrient Distribution Range (AMDR)^[8]. If you’re not sure what your muscle building protein needs are and want to avoid putting weight on, the 1.6g/kg body weight/day guideline is a very good guideline to follow.

How Fast Can We Build Muscle?

The speed at which muscle can be built depends on four distinct factors: training, diet, lifestyle and genetics. For each individual the contribution of each will be different. This makes it hard to supply an answer that will be definitive for everyone. By understanding the factors involved however we understand what we can control and what we can’t.

The training we choose to do depends on personal preference, personal situation and circumstances. Some of this is within our control. Some other things may not be and we will have to adapt.

Diet plays a role. Muscle building requires protein in order to activate the muscle protein synthetic (MPS) response which leads to increased lean muscle mass in the body. In a perfect world where every possible muscle-building element aligns, the individual is young, fit and stress-free, the maximum amount of muscle that can be built in a year is 25lbs (approximately 11.3kg). Most individuals can only hope for half that or less.

The study of 2986 men and women, aged 19–72 y, from the Framingham Third Generation Study^[9] found that protein intake within the limits recommended above showed improved muscle mass gains, regardless of age.

Lifestyle is important. The stress levels experienced by a person however are also important. A study of individuals engaged in lifting weights showed that the body’s response to exercise (and its ability to build muscle) depended on how well they handled stressful situations.^[10]

Finally, genetics. This is an immutable variable. Even when training, diet and lifestyle are near-perfect, the ability to build muscle depends on such DNA-defined variables as the number of capillaries delivering nutrients and anabolic hormones to your muscle fibers and the thickness and malleability of the connective tissue that surrounds those fibers. These frequently determine the response to exercise so that, with the same training, one person grows bigger muscles while another one doesn’t.^[11]

Other genetic factors is the number and nature of satellite cells^[12]. These are cells that are in place around muscle fibers that are recruited when those muscle fibers need help to repair and grow.^[13]

In plain English: All this shows the complexity involved in something as seemingly simple as growing muscle. It also brings to light that just increasing protein intake is not sufficient to build muscle when other factors are involved.

How To Determine How Much Protein Is Best For Us

If you’re new to exercise or exercise three-four times a week the 1.6g/kg body weight/day of protein mentioned above will be fine for all your muscle-building and tissue repair needs. To work out exactly what that is for you multiply your weight in kilograms times 1.6.

How much protein
do I currently need
to build muscle?

Your weight

You currently need

grams per day

Example: A 70kg person who exercises regularly and is relatively healthy and stress free would need 70kg X 1.6g/Kg Body weight/Day = 112g of protein per day. Be careful here to make sure that if you’re upping your protein intake to this level you do so by replacing elements of your diet with additional protein, instead of just adding extra protein to your diet which would mean more calories and the likelihood of gaining weight.

Another way to work this out would be by working out your total protein intake as a percentage of your total calorie intake per day. To do that work out your base metabolic rate (BMR) via this calculator. Then from this chart work out how many calories you burn through the daily activity and exercise you engage in each day.

Add that number to your BMR number.

Next, taking into account your fitness level, personal circumstances, age, body type and fitness goals, decide what percentage of that total will come from protein. The Dietary Guidelines for Americans 2015-2020 recommends that protein account for somewhere between 10 percent and 35 percent for adults.^[14]

Finally divide that number by 4. Each protein molecule is worth 4 calories.

Example: A 25-year-old person who weighs 70kg and exercises a lot will have a basic energy expenditure (B.E.E.) level of 1735 calories. That person, in the course of a day’s daily activities plus one hour of high impact aerobics (as an example) will need an additional 1046 calories, bringing the total to 2,781 calories.

2,781 X 20% = 556.2

556.2/4 = 139.05g of protein per day.

Complete Proteins That Aren’t Meat

If you need to increase your protein intake it doesn’t mean you need to eat more meat.

The table below provides ten plant-based complete protein sources and the amount of protein they provide per 100g serving:

Plant-based Source	Protein content in g per 100g
Barley	12
Quinoa	14.1
Buckwheat	13.25
Soybeans	36
Amaranth	14
Seitan	75
Spirulina	57
Hemp Seeds	36.66
Chia Seeds	17
Quorn	16

Also ten non-meat protein sources:

Non-meat Source	Protein content in g per 100g
Eggs	13
Greek Yoghurt	10
Cottage Cheese	11
Mozzarella Cheese	28
Kefir	3.3
Feta Cheese	14
Halibut	14.37
Whey Isolate	95
Cow's Milk	3.4
Prawns	25

To give you an idea of your "one-sitting protein meal" consider that:

The average steak is between 8 - 9oz which makes it 255g which means that a single steak gives you 63g protein.
The average medium egg weighs 43g which means three such eggs give you almost 17g of protein.
The average single serving cup of Greek yoghurt is between 150g - 170g which means that one of them contains up to 17g of protein
The average scoop of whey isolate is 29g; one such scoop provides 27.6g of protein.

Is There a ‘Best’ Time To Take Protein When Exercising?

The question that always pops up when training and trying to eat right is when a meal should be taken to help increase muscle and repair tissue. A meta-analysis of over 1,200 people and 40 studies published in the Journal of the International Society of Sports Nutrition^[15] found that there is no measurable benefit in taking protein pre- or post-workout. Instead what plays a pivotal role in muscle building, muscle repair and strength, is the total amount of protein in the diet.

Do Protein Supplements Provide A good Source of Protein?

As a rule supplements are easier to absorb because the protein they supply has been processed so there is very little 'packaging'. There are some studies that mention that Whey protein is absorbed by the body at the rate of 8g-10g per hour whereas protein from eggs is absorbed at the rate of 3g per hour. The body pretty much uses everything we give it so in terms of whether there is wasted protein the answer is no, never. But when it comes to building muscle and repairing tissue which is what building muscle and recovery are all about, there is an issue. Muscles can only handle a maximum of 25g-35g of protein at a time. So, if let's say you took 40g protein in Whey powder form (in a shake, let's say) nearly half of it wouldn't go to muscle building. If, however, you took the same amount of protein in an omelette, nearly all of it would go to building muscle and repairing tissue. This is why, while we can handle as much as 2.2g of protein per kg of body weight, per day we get way better results if we, instead try for 1.6g protein per body weight per day.

From a building muscle and repairing tissue point of view the body always takes into account the total amount of protein ingested which is why a slower absorption rate appears to deliver better results.

Summary

Protein is key to the healthy functioning of the body, cellular repair and muscle building. Taking too much protein does not accelerate muscle growth and in some cases may actually slowdown the repair and growth of muscle. Meat and dairy products deliver whole proteins that contain all nine of the essential amino acids necessary for the building of muscle tissue but they also have side effects that can affect a person’s health. Plant-based proteins are best but a varied diet is necessary to ensure that all the dietary requirements for health and muscle building are met. In an ideal world we'd all be on a plant-based diet because of the many health and longevity benefits it offers. If that is not possible however it makes perfect sense to reduce meat consumption wherever possible and replace the protein we ingest with protein that comes from plant-based sources. Finally one additional, and final, piece of nutritional information. B12 is the only vitamin that comes from meat and that is only because animals get it from the soil when they graze. We get it from them when we eat their flesh. Any diet that excludes meat will need B12 in the form of supplements to help the body maintain healthy cellular functions.