In Search For The Highest Quality Protein (And The Issues It Causes For Diet Guidelines)


If you are passionate about your health you only want to put the best food into your body.

And if you have spent some time reading my articles, you would know that not all food is the same. A grassfed, grass finished, organically raised cow will produce much healthier milk than a feedlot raised, GMO grain fed, antibiotic injected cow.

We know that food quality is crucial when it comes to keeping the body healthy and disease free.

You are already well versed on finding quality fats and carbs, but what about protein quality? Would you know what the best protein is for your health?

And would you know what protein you want to avoid? 

Outside of bodybuilding and hard core vegan communities, protein quality is often neglected. But this should not be the case, especially by us in the health and wellness space.

We want the best for our body, and that means eating the best foods. So let's find out what the best protein is for us to reach out goals. 

Protein Basics

First things first - what is protein?

Protein is a macronutrient made up from multiple amino acids. Protein is vital for humans. It is a building block for the body which is used for muscle, skin, hair, nails, tendons, etc. 

Protein is either animal or plant based. Animal based protein sources include muscle meats, organ meats, diary products, and eggs. Plant based protein sources include nuts, seeds, tubers, legumes, lentils, and grains.

There is a big difference between animal and plant based proteins when it comes to our health. More on this soon.

Amino Acids – Building Blocks of Protein

As mentioned above, protein is vital for life. In particular, the body requires three types of protein molecules,  known as Amino Acids, in order to function properly.

Some amino acids are essential to the body – thereby called essential amino acids (EAA’s), which the body must receive through diet.

Non-essential amino acids are made by the body from essential amino acids or protein we eat.. Lastly, conditional amino acids are needed during times of illness, growth, etc.

In these situations, the body demands more of these amino acids than can be produced and therefore we must consume them in our diet.  Examples of conditional amino acids include arginine, cysteine, glycine & glutamine.

Researchers have found over 200 amino acids. Of these, 20 are ‘common’  amino acids (meaning the body can make protein from them), and 10 are EAA’s.

Amino acids act as precursors to neurotransmitters in the brain, and play a crucial role in the bodies metabolic processes and immune function.



Complete Protein

For a protein to be ‘complete’ it must include an adequate proportion of all the essential amino acids. Think back to your Tetris days as a kid – a row required a block in every spot for it to be ‘complete’, and you couldn’t carry blocks over to the empty slots in another row.

This is similar for protein. If you have an abundance of 6 EAA’s, but lack other amino acids, you’re stuck with an incomplete protein.

The missing amino acids lead to an imbalance, which can lead to all sorts of problems, such as poor skin quality, growth & developmental issues, fatigue & poor concentration.

So what’s the best way to stay in balance? Consume complete proteins. 

Complete protein sources are generally derived from animal foods such as meat, fish, poultry, and eggs. Plant sources of complete proteins include chickpeas, pumpkin seeds, quinoa, cauliflower, and soy.

However, plant based protein quantity is usually much lower than the animal based protein.

That said, don’t think that incomplete proteins are not worth eating. Your body can store the amino acids found in incomplete proteins. If you do eat some peanuts for example, the body will store the amino acids that are present in the food. Ask any well researched vegan, they understand the importance of balanced amino acids and avoid imbalances by eating a variety of protein sources.

Determining Protein Quality

When determining protein quality, we need to look at the following 3 factors:

  1. Amino Acid Profile – how much of each amino acid (EAA, non-essential, conditional) are in the particular food
  2. Absorption – how well are the amino acids absorbed by the body. If the body cannot digest, absorb, and utilize the amino acids in proteins, including complete proteins, the protein is effectively useless. As an example, eggs are a complete protein source but cooked eggs are better digested than raw eggs. In addition, many plant-based proteins are not absorbed well by the human gut, whether cooked or raw, because of substances such as phytic acid. These ‘anti-nutrients’ are commonly found in grains, beans, seeds and nuts, and have been shown to block nutrient absorption. Chris Kresser covers anti-nutrients in detail in his post “Another reason you shouldn’t go nuts on nuts.” And I touch on this topic in my article on the dangers of Soy
  3. Toxicity – how the body tolerates protein sources. Some protein sources are not tolerated well by the human body and may cause allergic or immune problems. 

Measuring Protein Quality - The Old Methods

There are numerous ways you can measure protein quality. Let us take a look at each method.

  • Biological Value

This primarily looks at the amino acid makeup of the source. It is often referred to in bodybuilding circles.  Biological Values (BV) are calculated as a percentage and measure the nitrogen uptake of the protein versus the nitrogen excreted. A figure of 100 means that all the protein provided has been retained by the body. Eggs have a value of 94, Cows milk 91, Beef 74, Soy 72 and Wheat is 64 (a higher number means the protein will be more easily used than a low BV value). BV values cannot be higher than 100.

There are a lot of criticisms with BV however BV is measured under very strict scientific settings not everyday conditions. Also BV does not look at factors that may influence the proteins absorption in the body. Finally, there is a lot of variability in the results of BV testing.

  • Protein Efficiency Ratio

This looks at weight gain of a rat when fed various types of protein. Obviously there are many limitations here and this regarded as an older measurement tool.

  • Net Protein Utilization

Net Protein Utilization looks at the ratio of amino acids converted to proteins from the amino acids consumed. It works by looking at how much nitrogen is absorbed.  The range runs from 0 to 1.0. Eggs and Milk are 1.0 on this scale.  It has limitations in effectiveness as per the Biological Value method.

  • Protein Digestibility Corrected Amino Acid Score (PDCAAS)

PDCAAS has been the standard for evaluating protein quality. Not only does it look at the amino acid content of the food, but also the amino acid requirement by humans AND their ability to digest these aminos.

Finally, PDCAAS factors in how much of the protein is excreted as waste in poop. This extra step is why this test is commonly used today.

Using this test we see the following scores for common foods (higher is better):

  • Milk protein (casein & whey) – 1.0
  • Egg White – 1.0
  • Soy – 1.0
  • Beef – 0.92
  • Chickpeas – 0.78
  • Kidney Beans – 0.68
  • Peanuts – 0.52
  • Wheat – 0.40
  • Wheat gluten – 0.25

However, there are still problems with this test. Firstly, any scores above 1.0 are ’rounded down’ to 1.0, as ” as scores above 1.0 are considered to indicate the protein contains essential amino acids in excess of the human requirements” (1). Which I think is a bit silly, its almost like saying ‘thats enough, you don’t need to worry about anything beyond that level’.

Also, the amino acid and nutrient makeup between milk & soy is going to be very different, so to have them with identical ratings seems a bit absurd (read why in my article 13 Reasons Why Soy Is The Worst Food In The World)

PDCAAS also doesn’t identify where the protein has been digested. The body may not use the broken down protein but bacteria in the intestines may consume the amino acids. PDCAAS will see this as being utilized by the body no matter how it was ‘consumed’.

Finally, PDCAAS doesn’t look at anti-nutrients and any amino acids that are blocked due to these anti-nutrient content from food. This may lead to higher endogenous amino acid losses, meaning PDCAAS may lead to inaccurately higher scores (3). For those who want to avoid anti nutrients in their diet (and we all should) this is the key issue with PDCAAS.


The Revolutionary New Method To Test Protein Quality– Digestible Indispensable Amino Acid Score (DIAAS)

Digestible Indispensable Amino Acid Score (or DIAAS here-forth) is a new way of testing protein quality. DIAAS looks at the amino acid digestibility at the end of the small intestine (vs the fecal matter as per the PDCAAS test). Meaning the data is a lot more accurate at seeing what amino acids are absorbed and utilised by the body.

Along with this DIAAS values are not limited to a top figure (the PDCAAS caps at at 1.0). Meaning all those people out there that aren’t satisfied with ‘good’ can now see what the best of the best is.

Also, DIAAS uses pigs and humans to perform the test unlike the PDCAAS test which generally uses rats.

The DIAAS method is starting to gain traction as being a lot more reliable than PDCAAS. The United Nations is pushing it's use, and an expert from the Food & Agriculture Organization recommended that “the Digestible Indispensable Amino Acid Score (DIAAS) replace the Protein Digestibility Corrected Amino Acid Score (PDCAAS) as the preferred method of measuring protein quality. (5)

And there are peer reviewed papers that are showing the benefits of DIAAS over the older PDCAAS. A paper in the British Journal of Nutrition concluded : Thus, to better meet protein requirements of humans, values for DIAAS should be used to estimate protein quality of ingredients and diets.

If you are interested in the science behind the test I recommend looking at this presentation ‘Assessing Protein Quality’.

As more and more scientists discover the improved technology that is DIAAS, it's starting to send shockwaves through the scientific and health communities. 

I'll explain more about this soon, but first, now that we have found the best way to measure protein quality, let us look at what the best sources of food are.

Protein Quality of Foods Using The New DIAAS Method:

Now that we have found the best way to measure protein quality via the DIAAS method, lets look at some food sources and their protein quality score. Again, higher equals better quality protein)

  • Whole Milk – 132
  • Whey Protein Isolate – 125
  • Whey Protein Concentrate – 110
  • Beef – 110
  • Chicken Breast - 108
  • Skim Milk - 105
  • Soy Isolate – 90-100 (brand dependant) 
  • Pea Isolate – 82-95 (brand dependant)
  • Chickpeas - 83
  • Oat Protein Concentrate - 67
  • Chickpeas – 66
  • Peas – 64
  • Barley – 58
  • Tofu - 52
  • Kidney Beans – 51
  • Peanut Butter - 46
  • Roasted Peanuts - 43
  • Wheat – 40
  • Almonds - 40
  • Rice Isolate - 37
  • Sorghum - 29
  • Corn Based Breakfast Cereal - 1.7 

References – 2, 4, 6, 7, 8, 9, 10, 11

The obvious take away from this data is that animal based proteins are far superior than plant based proteins. 

In fact, the highest scoring unprocessed plant score is Chickpeas coming at 83 on the DIAAS scale. Compare this with the lowest scoring animal based protein (based on the data available at the time of writing) which is chicken breast at 108 points.

Milk, and milk derivatives are the superior sources of protein for human health. With whole milk taking out the top score with 132, and whey protein powders slightly behind it. (So my 1.5L of raw milk I drink a day is a good thing!) 

Even skim milk beats out all the plant based proteins. 



What This Means For You And Your Diet

So as you can see from the above table, animal protein remains the clear winner when it comes to protein quality.

It is another reason why vegan diets are far from optimal for the human body.

By using the DIAAS scoring system we can now see the ‘best of the best’. There is limited data available at the time this blog post was produced - hence why many common foods are missing -  but hopefully as the DIAAS method gains traction we start seeing more studies on various food sources to complete the picture. Not only will a more accurate measurement tool benefit us ‘health nuts’ but food manufacturers and health officials will be able to make more informed and reliable decisions.

My takeaway – make animal food a priority in your diet. Eat plenty of muscle meats, organs, diary, bone broth, eggs, fish etc. Ensure that your protein is coming from these sources and not from less superior plant based foods such as rice protein or that horrible soy

I should mention - it is OK to consume plant protein foods - I had peas with my dinner last night and some activated almonds today. The point I am trying to make is that these plant based food sources should not be your main protein source. Animal products such as muscle meats, milk, organ meats and eggs should be your main protein source.

If you are a vegan or vegetarian, spend some time researching the amino acid makeup of the foods you are eating, and also look into anti-nutrients and how you can minimise those (soaking, fermenting, sprouting etc). A great article was put together by Ben Greenfield titled ‘How To Be Extremely Active And Eat A Plant-Based Diet Without Destroying Your Body‘ I recommend all vegans and vegetarians check that out, especially if you’re an athlete.

Though I would still suggest you stop with the complete plant based diet and have a read of my article 8 Proven Reasons Why Vegan and Vegetarian Diets Easily Ruin Your Body.

For the bodybuilders and athletes out there, I’m sure this post just reinforces what you were already doing.


What Does All This Mean For Food Labelling/Regulations and Government Guidelines?

For me and my members - not a lot. As we no that a plant based diet is sub optimal for our health.

We know that many ‘meat substitutes’ are toxic and contain anti-nutrients.

And we know that animal based protein not only tastes the best, but is the best for growing a heathy, lean body.

The problem is with the big corporations and governments that are tied to the older, flawed PDCAAS system.

The new DIAAS system will mean that some foods that were claimed to be 'high quality proteins' will no longer be, and the same is true in reverse.

One researcher had this to say about the new DIAAS values on oat protein:

Regardless of the scoring pattern used, the DIAAS values for the oat protein concentrate used in this experiment did not satisfy the cut-off value (75 points) for DIAAS that has been suggested as the minimum value for making claims for the protein quality of foods. It is suggested that foods with a DIAAS value less than 75 should not make any claims related to protein quality.(12)

And another researched stated this:

Determination of the protein quality of food can have broad implications for jurisdictional regulatory frame- works as well as public health. From the perspective of the food industry, in some regions such as Canada and the United States, the ability to communicate that a food is a source of protein is dependent on estimates of both protein quantity and quality.

Wheat bran and rolled oats, protein scores were, respectively, 11.4% and 12.8% lower when the DIASS was used instead of the PDCAAS.

Conversely, animal sources of protein, such as milk protein concentrate (MPC) and whey protein isolate (WPI), stood to benefit the most if the PDCAAS were to be replaced by the DIAAS.

Further, for foods that already qualify for a protein source claim based on  the PDCAAS in the United States or the PER in Canada, would the application of the DIAAS make them ineligible for the claim? (13)

Despite WHO supporting the new DIAAS method for testing protein quality, it appears that there is a lot of resistance in making the switch. Why? Obviously there would be great expense involved, new testing procedures, new health policies & recommendations, marketing campaigns informing the consumers of the change etc.

However, the biggest hurdle for change is due to money. The grain and cereal industry is huge, there are a lot of powerful and influential people that would not be too keen on seeing this new method becoming the standard.

Dairy companies on the other hand are pushing for change. In researching this article I spoke to a research scientist at New Zealand’s largest Dairy company Fonterra. When questioned about the future of DIAAS, he responded saying that it will be a slow process. There are still a lot of issues in terms of testing techniques that need to be ironed out and that the main limiting factor is government and private regulation authorities.

My thoughts? I'll continue eating eggs, meat, bone broth, liver and washing it all done with my raw cows milk.

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This blog post was written by Alex Fergus. Alex is a ISSN Sports Nutrition Specialist, Fitness Professional and certified Superhuman Coach who continues to expand his knowledge base and help people across the world with their health and wellness. Alex is recognized as the National Record Holder in Powerlifting and Indoor Rowing and has earned the title of the Australian National Natural Bodybuilding Champion. Having worked as a health coach and personal trainer for over a decade, Alex now researches all things health and wellness and shares his findings on this blog. Learn more about Alex's Credentials HERE.

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