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February 25, 2012

Whey Protein Q&A - Whey Protein Isolate Versus Whey Protein Concentrate Part 2 - Denatured Proteins

BlogProQAC Q. What are denatured proteins and what are their health effects?

A. In simple terms, a protein is said to be denatured when its chemical shape changes in response to heat or extremes of pH (acid or alkaline). Some proteins (many enzymes, for example) lose their biological function when denatured; and particularly fragile proteins from whey protein must remain undenatured in order to exert their full biological activity.

Studies have found, for example, that heat and pH used in processing may denature up to 53% of the whey proteins found in whey protein concentrate:

Study Link - Influence of pH and heat treatment of whey on the functional properties of whey protein concentrates in yoghurt.

Quote from the above study:

Cheddar whey was heated at pH 6.4 or pH 5.8 at 72 °C for 15 s, eventually heated further at 82 or 88 °C for 78 s, ultrafiltered, and spray dried. Resulting WPC contained 38% protein; the denaturation level of the whey protein was 10–53%. 

Whey protein is somewhat unique among proteins in that its full biological function is largely dependent upon it being undenatured.  By contrast, many common food–based proteins are known to be somewhat denatured under normal cooking conditions; and, of course, these proteins still offer nutritional benefit. For example, an egg white which stiffens and turns white when cooked, is an example of a protein denaturing right before our very eyes.  Our body is still able to break the egg white down into its constituent amino acids, and is able to absorb and utilize these amino acids for use as the building blocks of our muscles, organs, tissues, and metabolic enzymes.  Cooking egg whites also denatures and inactivates certain substances which inhibit vitamin absorption – this is one instance, therefore, where denaturing protein is actually beneficial.

Similarly, many protein-based antinutrients (e.g., trypsin inhibitors) are denatured and inactivated by cooking.  So, clearly, it’s inaccurate to say that all denatured proteins are harmful, or that all undenatured proteins are beneficial.  The protein structures that are altered by cooking and processing really need to be assessed on a case-by-case basis.

But, as profitable methods of processing and preserving foods exploded in the early part of the twentieth century, there was often a tendency among food producers to simply ignore the health effects of the novel protein structures which formed as a result of processing.

This oversight continues to have serious effects upon public health.

Some modern industrial processes are likely to create unique protein structures which are not formed when foods are cooked normally. The extrusion cooking process, for example, allows for the creation of foods such as “puffed” breakfast cereals and snack foods (as well as protein “crisps” from soy and whey which are now commonly used to add texture to protein bars). Not only do the chemical changes resulting from the extrusion process reduce the amount of biologically active protein in the food, but the altered protein structures formed may impart some degree of toxicity.

Study Link - Nutritional effects of extrusion-cooking.

Though the scientific research gives clear reason for concern, we rarely hear about the health risks which arise when some foods are powdered, extruded, alkali-treated, or high-heat processed.  Perhaps this is partly because even the “health food” industry employs such methods in the processing of protein powders, drinks, breakfast cereals, meat replacements, and many non-dairy milks like soy milk.  These processes give the resulting products remarkably long shelf lives, which makes them far more profitable than fresh, perishable foods.

As scientists continue to study the effects of protein processing on nutritional quality, however, some interesting studies have emerged showing that many of the unnatural proteins formed in the production of modern foods and protein supplements are likely to be at least mildly toxic.

Q. What harmful denatured proteins can be formed in the production of protein powders and protein-containing beverages?

A. Scientists have long studied various toxic substances which are known to be formed during the production of protein–containing powders and beverages.  Though it’s likely that many protein–based toxins still have yet to be discovered, there is enough evidence in the scientific literature to make any educated person wary of certain protein powders and protein-containing beverages.

Alkali–treatment of proteins (including common nutritional supplement ingredients such as soy protein isolate, and calcium caseinate/casein), can lead to the production of unnatural cross–linked amino acids like lysinoalanine (LAL).  In animal studies at least, lysinoalanine has been shown to have many negative effects on digestion and overall metabolism:

Study Link – Influence of feeding alkaline/heat processed proteins on growth and protein and mineral status of rats.

Quote from the above study:

The data suggested that LAL, an unnatural amino acid derivative formed during processing of foods, may produce adverse effects on growth, protein digestibility, protein quality and mineral bioavailability and utilization. The antinutritional effects of LAL may be more pronounced in sole–source foods such as infant formulas and formulated liquid diets which have been reported to contain significant amounts (up to 2400 ppm of LAL in the protein) of LAL.

Study Link – Interaction of lysinoalanine with the protein synthesizing apparatus.

Quote from the above study:

These results indicate that LAL is an inhibitor of both prokaryote and eukaryote lysyl–tRNA–synthetase. Furthermore, it is incorporated into protein. Both of these actions can be factors in the nephrotoxicity [i.e., kidney toxicity] of this common food contaminant.

So, according to the above studies, processed proteins containing lysinoalanine may:

Inhibit growth

Inhibit protein synthesis

Inhibit digestion

Inhibit mineral absorption

• Harm the kidneys

• And impart numerous anti–nutritional effects

It’s more than a bit ironic then, that lysinoalanine (and many similar toxic “anti–nutrients”) can so commonly be found in the ingredients used by the nutritional supplement industry in an ever–increasing number of protein powders, bars, and drinks.

Decades ago, research into the toxic effects of protein processing centered on ways to create the least toxic infant formulas, or the least toxic enteral feeding formulas for hospital settings. Industrially processed proteins were never thought of as healthy, and the products in which they were used were produced for situations in which even poor nutrition was clearly better than dying of starvation. But, in recent years many of the same (or very similar) protein ingredients have been promoted as dietary staples for health–conscious consumers (e.g., soy and casein protein powders). Since so many people are currently being misled by flashy advertising and fancy product packaging, it’s important to point out the potentially harmful effects of some of the proteins found in nutritional powders, drinks, and bars.

In addition to alkali–treatment, toxins like lysinoalanine can also be formed as a result of the high heat processes now commonly used to pasteurize protein-containing beverages. Ultra heat treatment, or ultra high temperature (UHT) pasteurization and sterilization processes are now able to produce milk and milk–based products (like protein drinks), and non-dairy milks (e.g., soy milk, almond milk, rice milk) which require no refrigeration – but the formation of lysinoalanine in some of these products has been found to be shockingly high:

Study Link – Determination of lysinoalanine in foods containing milk protein by high–performance chromatography after derivatisation with dansyl chloride.

Quote from the above study:

The LAL contents analysed in raw and pasteurised milk ranged from 4 to 24 and 17 to 69 mg kg−1 crude protein, respectively. Compared to that, UHT–treated milk and sterilised milk showed higher LAL levels up to 186 and 653 mg kg−1 crude protein, respectively.

Note: As the above study indicates, normal pasteurization processes don’t necessarily lead to the production of high levels of lysinoalanine in milk.  Despite the common assumption among some health enthusiasts, pasteurization doesn’t always alter the nutritional value of milk to a great degree.  Milk (including organic milk) which has been “ultra-pasteurized,” however, is probably best avoided.

Protein drinks and many non-dairy milks (e.g., soy milk) are produced using protein powders.  Unlike fresh milk, the powders used in the production of these beverages may already contain significant lysinoalanine, even before further heat treatment:

Study Link - Lysinoalanine Content of Formulas for Enteral Nutrition

Quote from the above study:

. . .the preparation of caseinates and the thermal stabilization of the end products are the two steps more favorable for the formation of LAL.

And it’s important to note that lysinoalanine is far from the only toxic product formed by heat and pH treatment of proteins – it’s just one of the most extensively studied:

From: Lysinoalanine in Foods and Antimicrobial Proteins

Heat and alkali treatment of food proteins widely used in food processing results in the formation of crosslinked amino acids such as lysinoalanine, ornithinoalanine, lanthionine, and methyl lanthionine, and concurrent racemization of L–amino acid isomers to D–analogs.

Although many of the byproducts produced by protein processing have yet to be studied individually, there is clear evidence in the scientific literature that heat–treated protein drinks (the kind very commonly available, from soymilks, to protein–containing sports drinks) are likely to impart a cumulatively toxic effect.

As a practical example, the following study showed that both soy and casein protein, when subjected to ultra heat treatment (UHT) caused a significant elevation in LDL cholesterol levels:

Study Link – Ultra heat treatment destroys cholesterol–lowering effect of soy protein.

Quote from the above study:

Unexpectedly, at the end of the study, low–density lipoprotein cholesterol concentrations were significantly increased compared with baseline in all study groups. The magnitude of this increase (17–19%) was similar in all active and placebo study groups. Soy protein supplements previously shown to be effective in reducing serum cholesterol had in this study no such lipid–lowering effect after ultra heat treatment.

Without undergoing UHT treatment, soy protein or casein either have no effect, or may even lower LDL cholesterol. With UHT treatment, however, these proteins led to a 17% to 19% increase in LDL cholesterol. The study authors concluded that the altered protein structures resulting from heat treatment were responsible, and noted that the “heart health” claim currently allowed by the FDA for soy proteins should likely be revised to exclude UHT-treated soy protein.  This study is clear evidence that changes in protein structure can markedly increase the toxicity of food proteins in humans.

Note: the above study has nothing to do with the cholesterol content of the drinks, as soy and casein (unlike whey protein concentrate) don’t contain cholesterol.  The cholesterol elevation caused by heat-treated soy and casein is evidence of the generally toxic nature of these altered proteins.

Q. It is often assumed that since stomach acid breaks down or “denatures” proteins that the denaturation of protein is no big deal.  Why are the denatured proteins from protein powders and high-heat-treated beverages uniquely harmful?

A. While stomach acid does break down, or denature proteins to facilitate their absorption, some industrial and cooking processes (e.g., spray-drying of protein powder, extrusion of breakfast cereals, high-heat cooking and pastuerization) create unique protein-based structures (not just proteins broken down into their constituent amino acids).  In addition, these processes also create unique protein structures which are likely not to be broken down by stomach acid. Glycation products formed when proteins chemically combine with sugars and fats, for example, are increasingly being seen as a significant factor in aging and disease – the reason is likely to be precisely because the most toxic of them are unable to be broken down by stomach acids.

Unlike native, undenatured proteins (protein which the body recognizes as nutritive), these foreign protein–containing substances are apt to be poorly utilized and absorbed.  And if proteins aren’t absorbed properly, they don’t simply pass through the body unscathed. Rather, in their journey through our digestive tract, altered proteins are likely to be fermented into various other toxic compounds such as phenols, cresols, indoles, amines and ammonia by the bacteria which inhabit the colon (the vast majority of digestible protein is absorbed in the small intestine, and never makes it to the colon).

This is one reason why so many protein supplements (including many of the lower–quality whey protein supplements) often cause gas, bloating, cramping, or an upset stomach – this phenomenon is likely due to the fermentation of glycated proteins by colonic bacteria, and is not simply due to lactose intolerance as some people believe.

Because they support the growth of pathogenic colonic bacteria, denatured and glycated proteins can represent a unique toxic burden:

Study Link – p–cresol: a toxin revealing many neglected but relevant aspects of uraemic toxicity.

Quote from the above study:

P–Cresol is an end–product of protein breakdown, and an increase of the nutritional protein load in healthy individuals results in enhanced generation and urinary excretion. The serum p–cresol concentration in uraemic patients can be decreased by changing to a low–protein diet. p–Cresol is one of the metabolites of the amino acid tyrosine, and to a certain extent also of phenylalanine, which are converted to 4–hydroxyphenylacetic acid by intestinal bacteria, before being decarboxylated to p–cresol (putrefaction).

The action of intestinal bacteria on proteins (especially overly–processed, altered, and poorly absorbed proteins) may explain why the consumption of certain protein–rich foods (processed meat, for example) has often been implicated in the development of colon cancer:

Study Link – Meat Consumption and Risk of Colorectal Cancer.

Quote from the above study:

Our results demonstrate the potential value of examining long–term meat consumption in assessing cancer risk and strengthen the evidence that prolonged high consumption of red and processed meat may increase the risk of cancer in the distal portion of the large intestine.

But despite the implication of some vegetarians that meats are the sole source of such protein–derived toxins, it seems that many overly processed, extensively heated, or denatured proteins are apt to produce significant amounts of toxic byproducts in the intestines. The following study found that extensively heat–treated (thermolyzed) casein, egg white, and soy proteins (the kinds of protein sources commonly found in dietary supplements) all caused a marked increase in the production of protein–derived intestinal toxins:

Study Link – Colonic Protein Fermentation and Promotion of Colon Carcinogenesis by Thermolyzed Casein.

Quote from the above study:

We found that the thermolysis of casein reduces its digestibility and increases colonic protein fermentation, as assessed by fecal ammonium and urinary phenol, cresol, and indol–3–ol. Thermolysis of two other proteins, soy and egg white protein, also increases colonic protein fermentation with increased fecal ammonia and urinary phenols.

Although the heat–treated proteins didn’t lead to the development of colon cancer in the above study (which actually surprised the researchers), the formation of toxic byproducts was significantly increased in animals who consumed the heat–treated protein supplements.

Studies by other researchers have shown that heat–treated casein does, indeed, lead to the production of aberrant crypt foci (ACF) – well–known precursors to colon cancer development:

Study Link – Promotion of aberrant crypt foci and cancer in rat colon by thermolyzed protein.

Quote from the above study:

Thermolyzed casein promotes early colonic precursor lesions in a dose–dependent and thermolysis time–dependent manner; thermolyzed casein also promotes colon cancer.

Researchers have also found that feeding mice and rats cooked combinations of casein, sugar, and fat led to the formation of microadenomas in the colon (microadenomas are small tumors, a step closer to colon cancer development than aberrant crypt foci):

Study Link – Promotion of Colonic Microadenoma Growth in Mice and Rats Fed Cooked Sugar or Cooked Casein and Fat.

Quote from the above study:

. . .a diet containing 20% of cooked sucrose, or 40% of casein and beef tallow cooked together, promotes the growth of colonic microadenomas in initiated mice and rats, and would appear to contain promoters for colon cancer.

Given the above study, it’s truly frightening to note that one of the most popular ready–to–drink protein shakes currently is a “muscle milkshake” which contains particularly high amounts of casein, sugar, and fat.  These drinks are shelf-stable (i.e, they don’t require refrigeration) which indicates that they are high-heat/UHT processed - yet it’s doubtful that the millions of people consuming this drink have the faintest idea that they may be dramatically increasing their risk of colon cancer in the process.

With regard to protein-containing foods, the existing research lends support to the idea of choosing those which are “minimally processed.”  Along these same lines, ideal protein supplements (which are significantly processed, by definition) would be those produced specifically to maintain nutritional value, and the integrity of the protein structure. 

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