# dl-methionine v. l-methionine



## vampares

Is there a veterinary or pet food industry directive to use only DL-methionine and not L-methionine?


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## Jace

DL Methionine is the only listed form in the AAFCO approved book. Are you asking because of this info?.. "Methionine is an indispensable amino acid for humans, but there is evidence that if given in excess, it can interfere with the utilization of nitrogen from dispensable amino acids."
There doesn't seem to be studies on pets in relation to this.


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## vampares

I don't have access to a copy of the AAFCO Pet Food and Specialty Pet Food Labeling Guide or any other publications.

Is DL-methionine listed in the context of other amino acids (which ordinarily would not be added to petfood) or is it mentioned along with the more common ingredients?

"Methionine is an indispensable amino acid for humans, but there is evidence that if given in excess, it can interfere with the utilization of nitrogen from dispensable amino acids."

DL-methionine is not regularly given to humans. I believe it may be added to food _and_ disguised as "artificial flavor" but I've have never once seen it on an ingredients label intended for human consumption. I have never seen it on vitamin store shelves. I did find the pure-bulk website. This is the only source I would have for the actual racemic methionine. Obviously the benefits (whatever they may be -- cost is one) are not enough to make DL-methionine desirable on the human market.

I only ever see DL-methionine listed on dry food stuffs. Protein and fat calories are typically expensive. It may be that dry foods are produced with less protein. And in order to keep costs down DL-methionine is added in minute quantities to prevent malnutrition. Outside of sawdust and a bouillon cube, this seems sort of suspect but entirely possible. Soy may not be the choice source of methionine but it is typically an ample supply.


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## DaViking

There is no directive as far as I know but methionine is an essential amino acid with multiple vital functions. Deficiency will lead to serious complications and synthetic sources are more predictable than natural sources. If a manufacturer are ready to guarantee consistency from their natural sources they will not add DL-methionine. This is one explanation. I have seen others too related to taste and acidity.


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## vampares

Well what is the virtue of DL-methionine vs. L-methionine? 

D-methionine is never found in nature. Why not use L-methionine?

Ordinarily the L-amino acid would be desirable. The D-amino acid would lead to unpredictability. It would be, in essence a foreign substance, a drug, if you will -- even combined with the L-amino acid.

This amino acid has no role in any metabolic process of nature. It is absurd to think that a omnivorous mammal would be able to do anything useful with it.

I do agree that petfood would be more appetizing with methionine.

And I will also concede that methionine (in any form) is an excellent cleating substance.

If animals have diets that are inappropriately balanced, ie "ash content", "alkalinity", etc.: the correction of imbalance should not be made with D-methionine. It would require far too much of this substance. In the meantime, non-problematic nutrients would be leached from the system.

I will also say that being a substance that is never found in nature that the biological system would not be able to correctly eliminate the problematic substance while retaining the non-problematic substances _as organisms naturally will do_. I would even go as far as to say that D-methionine may leach calcium from the bones, the time it is available for repossession would be in the (potentially) acidic excretion of the kidneys, at which point it may be freed from the methionine.


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## vampares

I bought a cat food -- green peas and salmon -- very expensive. The ingredient listed methionine.

Green peas are one of the highest sources of L-methionine known. While the cat may starve, the methionine would not be an issue.

Except rather than listing DL-methionine or L-methionine or D-methionine (for that matter), they just listed *methionine*.

Is this not a dubious label?


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## DaViking

vampares said:


> I bought a cat food -- green peas and salmon -- very expensive. The ingredient listed methionine.
> 
> Green peas are one of the highest sources of L-methionine known. While the cat may starve, the methionine would not be an issue.
> 
> Except rather than listing DL-methionine or L-methionine or D-methionine (for that matter), they just listed *methionine*.
> 
> Is this not a dubious label?


So is corn gluten meal.
I would at least question the labeling since it is listed as an independent ingredient. I don't know what AAFCO says about labeling added methionine. Dr Tim Hunt might be able to shed some light on this if he reads this thread.


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## DaViking

vampares said:


> I would even go as far as to say that D-methionine may leach calcium from the bones


You have me interested. Could you elaborate a little more? Any research, theories or concerns inked on this?


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## Jace

> Is DL-methionine listed in the context of other amino acids (which ordinarily would not be added to petfood) or is it mentioned along with the more common ingredients?


It is listed under ingredient definitions


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## DaViking

This is what I got in reply regarding this. The person who replied to me is a nutritionist and a formulator for a big manufacturer.

"You are correct that L-amino acids need to be provided in the diet as they are metabolically active (example: for protein synthesis, etc.) This is due to the fact that the body cannot convert L into D or D into L. However, Methionine is one of 2 exceptions to this rule and it can be converted from one to the other, reason why it is added as DL-methionine to pet foods (I use the DL form as well in [nnn brand] and all the other brands I formulate for).
If some companies prefer to only use the L-form it is likely due to personal preferences (or maybe marketing?), but in my view not due to a nutritional requirement.

I do not have knowledge of d-methionine leading to calcium losses, but I will get my assistant to run a search for journal articles in the morning to see what we can find.

Hope this helps!"


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## vampares

Sorry about the delay.

I do not have evidence that d-methionine can be converted into l-methionine outside of breaking the amino acid into it's constituent parts and completely reworking the sulfur into a biologically usable form.

The breakdown of methionine can be evidenced by excretion of the d-methionine and the breakdown products, hydrogen and methyl sulfides. Seeing that these *are* products of said efforts, it is highly unlikely *any* d-methionine is converted into l-methionine in the common domestic pet (known for very short digestive tracks).

Excessive l-methionine can lead to calcium deficiency in humans.


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## monster'sdad

Maybe you should write the NRC and ask this question. I don't see the need to scare people by posting something like this. What is your agenda? 

Is this the next Boogeyman ingredient?


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## bett

monster'sdad said:


> Maybe you should write the NRC and ask this question. I don't see the need to scare people by posting something like this. What is your agenda?
> 
> Is this the next Boogeyman ingredient?


really? why is this a scare instead of informative?
i doubt that anyone is running out to change anything they're doing yet.


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## monster'sdad

Topic: DL-methionine v. L-methionine: please clarify

It is pure nonsense with an ulterior motive. This reminds me of Vitamin K3.

Perhaps business is slow at the fear-mongering website run by Sabine Contreras and she needs another topic to scare people with.

The next thing will be a study where rats were injected with 6,000,000 times the amount of this nutrient and seemed depressed and withdrawn.


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## bett

no one seems to be in a panic, monster.


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## Jace

NRC for dogs and cats has some details regarding this, but most of the info from a research perspective is done on humans.. Because this AA is essential for cats, and added into many pet food where levels may not be met naturally (or in the case of heat sensitivity), IF there was an "issue" with in, I am sure it would have shown up by now...


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## FBarnes

monster'sdad said:


> Maybe you should write the NRC and ask this question. I don't see the need to scare people by posting something like this. What is your agenda?
> 
> Is this the next Boogeyman ingredient?


Gee, isn't it a good thing you don't decide what topics can be discussed here. Lord knows the slightest criticism of or question about a dog food ingredient can't be mentioned around you or you immediately go into full attack mode.


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## vampares

I would say that it is in no way intended to not "scare" people.

The first and foremost thing I want is for someone to come up with *one* petfood manufacturer who states it uses only L-methionine as an additive.

But if there is some directive involving the feed industry to only use DL-methionine -- well I guess that would definitively solve my problem as well.


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## vampares

What is sort of freaky concept is that D-methionine _could_ be bio-accumulated in some of the other ingredients such as eggs specifically. Egg protein has a high affinity for methionine and the forming egg does not have the same excretory capability the hen has. The metabolism of the hen would use the L-methionine and nothing would be left accept the D-methionine. The same may be true with other sources of "natural" methionine.

I think it is a broadly held belief that additives -- as well as nutritional value -- should be scrutinized when deciding whether or not to purchase food products. It is certainly not the concept to be debunked. Not only is it the right of the consumer but it is necessary for good health.

It would be especially deceptive if the supposed nutrition of the product was actually acting like an anti-vitamin.


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## monster'sdad

vampares said:


> I would say that it is in no way intended to not "scare" people.
> 
> The first and foremost thing I want is for someone to come up with *one* petfood manufacturer who states it uses only L-methionine as an additive.
> 
> But if there is some directive involving the feed industry to only use DL-methionine -- well I guess that would definitively solve my problem as well.


What are you worried about? Why does anyone have to come up with a food? 

Sounds to me like your thread is a prelude to something else, but that's just me. 

I don't find any value in worrying about it.


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## FBarnes

Pet food manufacturers don't like us to look at individual ingredients. They tell us they develop their products "as a whole" and we shouldn't be concerned about what's in there, only the final result. I find that so incredibly laughable I can't even express it.


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## vampares

monster'sdad said:


> Is this the next Boogeyman ingredient?


D-methionine is technically a drug because it is not found in nature and is not preforming a function for the food itself, i.e., acting as a preservative or holding the food stuff together somehow. Furthermore DL-methionine is a prescribed veterinary medicine. So it is certainly a drug.

I don't really need to know why the drug is added. I would just like to know if there is a directive for it to be added as DL-methionine and not L-methionine.

Let's suppose the hypothesis that L-methionine *is* better than DL-methionine and dogs and cats everywhere who ate the L-methionine food were much healthier and happier. So these pet owners get what they payed for, right? Maybe even more. So now how does this affect the universe of petfood in anyway?


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## vampares

FBarnes said:


> Pet food manufacturers don't like us to look at individual ingredients. They tell us they develop their products "as a whole" and we shouldn't be concerned about what's in there, only the final result. I find that so incredibly laughable I can't even express it.


My impression of petfood was that the ingredients were quite "kosher" for lack of a better word (petfood tends to not conform to kosher requirements due to the yeast added, which is a whole nother topic). The vitamin nutrients, the protein sources -- right down to the balancing of the diet with some greener vegetables. I feel like the effort is there to make a better pet food.

Let's say I eat Cheerios. I like that Cheerios are a wholesome grain. I don't sprinkle Nitro-Tech on my Cheerios, however. So adding DL-methioinine, IMO, to petfood is somewhat extreme. I don't need the animal to be, like, insane at ultimate frisbee. Never-the-less I don't see dog or cat displaying benefits from the DL-methionine.


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## monster'sdad

vampares said:


> My impression of petfood was that the ingredients were quite "kosher" for lack of a better word (petfood tends to not conform to kosher requirements due to the yeast added, which is a whole nother topic). The vitamin nutrients, the protein sources -- right down to the balancing of the diet with some greener vegetables. I feel like the effort is there to make a better pet food.
> 
> Let's say I eat Cheerios. I like that Cheerios are a wholesome grain. I don't sprinkle Nitro-Tech on my Cheerios, however. So adding DL-methioinine, IMO, to petfood is somewhat extreme. I don't need the animal to be, like, insane at ultimate frisbee. Never-the-less I don't see dog or cat displaying benefits from the DL-methionine.



Why not call or write Purina. Pro Plan Performance (Sport) does not use it while Pro Plan Selects, the more expensive food, does.

There are dozens of Phd's there that do this stuff for a living.


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## vampares

monster'sdad said:


> What are you worried about? Why does anyone have to come up with a food?
> 
> Sounds to me like your thread is a prelude to something else, but that's just me.
> 
> I don't find any value in worrying about it.


Well, DL-methionine is in all petfood that contains methionine supplementation (for all intents and purposes). I would love to espouse the benefits of methionine:


L-methionine conforms biologically
there are far less toxic byproducts of L-methionine
only half as much would need to be added
that's half as much calcium that could be leached, most L-methionine is absorbed after all...​

But if there is a directive to use DL-methionine or not its in there and I can't "sell" the L-methioinine without finding out why.

Do you have an email address for someone at Purina? How about a corporate mailing address?


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## vampares

copied from some yahoo answer:


> Veterinarian Oath.
> As a member of the veterinary medical profession, I solemnly swear that I will use my scientific knowledge and skills for the benefit of society.I will strive to promote animal health and welfare, relieve animal suffering, protect the health of the public and environment, and advance comparative medical knowledge.I will practice my profession conscientiously, with dignity, and in keeping with the principles of veterinary medical ethics.I will strive continuously to improve my professional knowledge and competence and to maintain the highest professional and ethical standards for myself and the profession.”


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## monster'sdad

vampares said:


> Well, DL-methionine is in all petfood that contains methionine supplementation (for all intents and purposes). I would love to espouse the benefits of methionine:
> 
> 
> L-methionine conforms biologically
> there are far less toxic byproducts of L-methionine
> only half as much would need to be added
> that's half as much calcium that could be leached, most L-methionine is absorbed after all...​
> 
> But if there is a directive to use DL-methionine or not its in there and I can't "sell" the L-methioinine without finding out why.
> 
> Do you have an email address for someone at Purina? How about a corporate mailing address?



This is how the K3 scare started. With lots of vague and creepy misinformation, but I am not suggesting that is your goal. Just that this is so arcane and meaningless that it makes me wonder.

There are many more things in pet foods, especially expensive foods, that are much worse or haven't been tested at all. This particular ingredient seems to have been vetted out by time and broad use.

I am much more concerned with things in supplements and herbal remedies.


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## vampares

Questions always arise when an ingredient seems, mmm, weird. Natural additives may avoid scrutiny at times but _the thing is these ingredients aren't added to all petfood._ I realize that some sterols interfere/interact with the endocrine system. This may be viewed as therapeutic. *By no means are these ingredients unavoidable on the pet product shelves of America.*

And as far as effectiveness goes, I would think you would see some effectiveness. What the motivation for directly inserting this into a product line is, you may have a valid argument.

Have I tested these ingredients as potentially entering the environment on a broad scale? No.
Have I tested what the effects would be? No.

There may be a weak androgen dominance in a blue fluted pelican somewhere who happens to be particularly susceptible to this "pollution" because of his natural attraction to it.


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## vampares

monster'sdad said:


> especially expensive foods


You bring me back to one of my number one considerations: 

There is a price difference between L-methionine and DL-methionine. But that price difference is so minuscule.

The selling point of using L-methionine is the conformance to the biology of earth. The environment should not contain foreign materials, your millage will vary. Animals would never have access to DL-methionine in the natural world in any concentration whatsoever. I can shell out the clams, and I would be more than happy to do so. Really.

But, OK, back to the world we actually live in today...*what is the motivation for not using L-methionine?*


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## vampares

The use of DL-methionine as a main dietary staple is only justifiable in Isaac Asimov novels.

(these novels would involve primitive cultures on the brink of starvation)


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## DaViking

There seem to be enough knowledge in this thread to figure out *what is the motivation for using DL-methionine*? But still it goes unanswered (except from one nutritionist, that was apparently rejected), that itself is questionable to me.


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## PDXdogmom

Commenting here purely from reading this thread and numerous other threads that Vampares has started and posted at length on multiple dog sites - obviously have no in-depth scientific background myself.

A posted response to Vampares on another dog food site suggests that the reason for using dl-methionine rather than l-methionine is that l-methionine oxidizes more easily; hence the use of dl-methionine to increase stabilization. I don't suppose the answer could be as simple as that could it? Or perhaps so.

If a person is going to this level of time, research and concern about methionine in kibble, it seems illogical for them to continue feeding kibble. Home-cooked or raw would be a better route for Vampares. Look at all the other aspects about kibble that potentially play a more important role than the methionine concern. Some people don't like that the entire vitamin pre-mix in kibble is synthetic; but that's what it is for all but one dog kibble that I'm aware of plus the majority of human vitamin pills. You have to really search for vitamin supplements made from whole foods. Then there is also the whole chicken meal or "meals" issue and what goes into rendering them. And so on and so on.

I do feed primarily kibble and try to make pretty informed decisions about them; but anyone concerned to such a degree about the difference between which type of methionine is used, should just not feed kibble. Every aspect of kibble would be too worrisome for such a person. If, on the other hand, it's more a theoretical discussion, then I suggest Vampares develop a few concise questions to pose to a full list of pet food manufacturers through e-mail (not phone); and then share the responses with us.


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## dr tim

Quick facts on methionine ;

Methionine is one of the 10+ essential and (or) indispensable amino acids that are required by both the cat and dog. At the whole-animal level, methionine is part of body proteins and is important for skin and coat condition, eye health, heart health, etc. It is a non-polar, glucogenic amino acid and according to the 2006 NRC it is typically the first limiting amino acid in cat diets and the first or second limiting amino acid in dog diets.

Common petfood ingredients rich in methionine include animal proteins such as meat 
and poultry and their associated protein meals, egg products, marine proteins such as 
fish and fish meals, corn co-products such as corn gluten meal, and brewers dried yeast. 
Many diets which contain these ingredients are adequate in methionine and do not 
require any supplementation. For diets that contain minimal amounts of meat proteins, 
are heavily weighted to vegetable proteins like soy, or are low calorie foods diluted with 
inert ingredients such as cereals and cellulose, there may be a need for supplemental 
methionine.

Unlike many of the other amino acids, a fermentation method to produce methionine 
has not been developed – though many have tried. Instead, supplemental methionine is produced in a complex chemical synthetic process. There are numerous companies 
and locations around the world that produce DL-methionine commercially; and there 
are hundreds of patents that describe the subtle nuances regarding DL-methionine 
synthesis and purification. Regardless of company, geography, or patent, the general 
process is fairly similar and yields a racemic (50:50) mix of D and L isomers. Animal 
tissues require the L form for active protein synthesis. The D form can be inverted and 
effectively utilized by both the dog and cat. Conversion of the D form to the L form has 
been reported to be approximately 80-90% in cats.

Crystalline DL-methionine has become the standard of the petfood industry. This is a dry form of methionine, but there is also a liquid form that can be used. The liquid form is a bit harder to handle but is considered biologically similar to the dry form despite it needing to be converted over in the liver of the animal via transanimation to the DL form. My thought is this is where the D versus L debate has arisen here.

So, the final decision regarding the DL-methionine source to use falls not to nutrition or food concerns, but rather to cost, handling, and labeling considerations.

info taken from a paper by Dr. Aldrich


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## vampares

PDXdogmom said:


> A posted response to Vampares on another dog food site suggests that the reason for using dl-methionine rather than l-methionine is that l-methionine oxidizes more easily; hence the use of dl-methionine to increase stabilization. I don't suppose the answer could be as simple as that could it? Or perhaps so.


D and L methionine would oxidize in at exactly the same rate in a non-biological environment. L-methionine would not ordinarily be "oxidized" in a biological environment. Food stuffs subjected to an adverse biological environment are not sanitary.

I haven't seen any evidence that there are positive preservative like qualities to DL-methionine. Salmonella is a frequent contaminant of recalled petfood. I think these potential benefits actually lean towards promoting deadly pathogenic bacteria.


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## vampares

PDXdogmom said:


> and numerous other threads that vampares has started and posted at length on multiple dog sites


I started a few. I tried to engage other sites. Initially I looked toward veterinary oriented sites but they wanted money for an answer ((what mine is yours...)) or would not allow me to register.

I am really looking for an answer to the OP question. *Is there a directive to use DL-methionine and not L-metionine?*

I am an industrial systems technologist. I have nutritional, chemical and biological background. The question is not trite or tried or tired.

_Is L-methionine better for animals?_ Anyone can test this for themselves. I welcome any comments regarding the results of L-methionine supplementation.



PDXdogmom said:


> it seems illogical for them to continue feeding kibble


Well, now then, how do they get the methionine in to the cans in such a way that practically no kibble has yet to accomplish?


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## vampares

DaViking said:


> There seem to be enough knowledge in this thread to figure out *what is the motivation for using DL-methionine*? But still it goes unanswered (except from one nutritionist, that was apparently rejected), that itself is questionable to me.


Like I don't need to know that DL-methionine is DL-methionine, man (sorry I had to say it).

Cost is a factor but they put some "higher" quality ingredients into premium pet foods? No? Heck, L-carnitine and every other amino under the sun in some cases.
.
.
Anecdote
I used to stock groceries at the Giant in York. I left on a world of confusion. Nevermind my rational.
The petfood isle is one place you'll need to stock everyday. Petfood is not a small market by any means. And, so, while I shop premium petfood shops I expect top quality ingredients. Not that I'm "too good" for yall. I would just like to use something that is, say, quasi-*non*-experimental. Eh?​


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## vampares

Anecdote 2
I've got this lady who came to my home once and boy'o'boy could you smell this thing. It's not uncommon to own dogs but god damn.​


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## DaViking

There's a lot of thinking in this thread. Until it moves beyond that, thinking is all it is.


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## vampares

DaViking said:


> There's a lot of thinking in this thread. Until it moves beyond that, thinking is all it is.


So far not a single reason dl-methionine is given to dogs but never to humans.

Does it taste like shit and dogs and cats eat it anyways? Has anyone eaten dl-methionine? Is it good? Perhaps this person could provide insight.


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## vampares

dr tim said:


> Quick facts on methionine ;
> 
> Methionine is one of the 10+ essential and (or) indispensable amino acids that are required by both the cat and dog.


L-methionine



dr tim said:


> At the whole-animal level, methionine is part of body proteins and is important for skin and coat condition, eye health, heart health, etc. It is a non-polar, glucogenic amino acid and according to the 2006 NRC it is typically the first limiting amino acid in cat diets and the first or second limiting amino acid in dog diets.


OK facetiously speaking: _L-methionine is not available in a mass quantity greater than the can, label and product._

"Limiting" Limiting what? What function of cats or dogs is limited by lack of DL-methionine? Which protein?



dr tim said:


> Common petfood ingredients rich in methionine include animal proteins such as meat
> and poultry and their associated protein meals, egg products, marine proteins such as
> fish and fish meals, corn co-products such as corn gluten meal, and brewers dried yeast.
> Many diets which contain these ingredients are adequate in methionine and do not
> require any supplementation. For diets that contain minimal amounts of meat proteins,
> are heavily weighted to vegetable proteins like soy, or are low calorie foods diluted with
> inert ingredients such as cereals and cellulose, there may be a need for supplemental
> methionine.


I don't argue the need for supplementation. *But I would like to point out that soy protein is rich in methionine, if I am correct.*

green peas 1.5% l-methionine of protein content
soybean 1.4% l-methionine of protein content -- but protein content is higher overall
chicken 0.9%
Eggs rank around 3% to 3.6%
Beef is anywhere from 1% to 4%
Wheat gluten is about 1.5%

These are all sources of proteins found in petfoods, they are all sources of dietary methionine.

Eggs are highest in methionine but also contain the least amount of protein. "76% moisture content" I question. This seems to be suspect data. I've fried a lot of eggs and while there is "moisture" in them, 76% is a piece of data.

But eggs we cannot include because *these animals are also fed DL-methionine*. There is no evidence that these eggs do not contain DL-methionine.



dr tim said:


> Unlike many of the other amino acids, a fermentation method to produce methionine
> has not been developed – though many have tried. Instead, supplemental methionine is produced in a complex chemical synthetic process. There are numerous companies
> and locations around the world that produce DL-methionine commercially; and there
> are hundreds of patents that describe the subtle nuances regarding DL-methionine
> synthesis and purification. Regardless of company, geography, or patent, the general
> process is fairly similar and yields a racemic (50:50) mix of D and L isomers. Animal
> tissues require the L form for active protein synthesis.


Production of L-methionine is possible and affordable. It has been so for several decades.



dr tim said:


> The D form can be inverted and
> effectively utilized by both the dog and cat. Conversion of the D form to the L form has
> been reported to be approximately 80-90% in cats.


There is no evidence of "new" methionine arising in dogs or cats. There breakdown products excreted in urine. There is D-methionine in the urine. Homocysteine (simply a demethylated methionine) is in the urine. There is no enzyme which is concurs to transamination theory in mammals. *I've checked DNA databases*. There is no evidence D-methionine has *not* been *malignantly* assimilated _as if it were_ L-methionine.

The catch here is that methionine is not typically endlessly assimilated anyways. *L-Cysteine is that lovely little amino which grows fur long and luxurious.* L-Methionine is evolved with creatine and L-carnitine.



dr tim said:


> Crystalline DL-methionine has become the standard of the petfood industry. This is a dry form of methionine, but there is also a liquid form that can be used. The liquid form is a bit harder to handle but is considered biologically similar to the dry form despite it needing to be converted over in the liver of the animal via transanimation to the DL form. My thought is this is where the D versus L debate has arisen here.
> 
> So, the final decision regarding the DL-methionine source to use falls not to nutrition or food concerns, but rather to cost, handling, and labeling considerations.
> 
> info taken from a paper by Dr. Aldrich


"converted over in the liver of the animal via transanimation to the DL form."

Yeah basically. It like the same thing man. :bored:


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## vampares

"Transamination" would mean that a simple carboxylic acid could, in theory, be converted into an amino acid.

This completely defies the logic of "essential amino acid". Non-essential amino acids are non-essential because they can be generated from other amino acids. Typically this involves a metabolic process that is not obscure or esoteric.

Creation of amino acids from otherwise non-amino acid sources is just not done in mammals; mammals do not biologically produce amino acids, in the strict sense. To think that a bizarre -- and highly unneeded function (d-amino's are not natural) -- would be present in an animal who is basically a consumer of enriched bio-mass is ludicrous.


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## vampares

dr tim said:


> So, the final decision regarding the DL-methionine source to use falls not to nutrition or food concerns, but rather to cost, handling, and labeling considerations.


Do you know that it is "cheaper" to produce _any_ amino acid in racemic form? With the chemical technology we have today why not feed them a highly engineered blend of DL-amino acids?

Transaminase will fix everything for us, no? Why not exercise this enzymatic muscle and start eating just D-amino acids for that matter? Wouldn't that really be the wholistic roughage that society needs?

It's not difficult proposition. If you've got a commercial location, we can have D-amino acids by the barrelfull. What's your pleasure?


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## vampares

Here is another question that may be easier to answer (_answers to any of these certainly would help me out_):

*How much DL-methionine is added to petfood?*
.
.

If DL-methionine supplementation varies:

Is methionine supplemented based upon the amount of methionine in the primary ingredients? What is the methionine content objective?

Is the objective content based on daily intake? Or does amino acid percentage methionine content dictate the amount of DL-methionine that is added?​.
.

What is the maximum amount of DL-methionine supplementation that can be added to petfood?


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## vampares

I've found information that may provide some answers my question.


Selecting Nutritious Pet Foods
animalveterinary/resourcesforyou/ucm047120.htm
The following consumer information is provided by David A. Dzanis, D.V.M., Ph.D., DACVN Division of Animal Feeds, Center for Veterinary Medicine.

Dzanis, David A., D.V.M., Ph.D. Division of Animal Feeds, Center for Veterinary Medicine. "Selecting Nutritious Pet Foods" _Animal & Veterinary_. November 1997, updated 02/03/2010, FDA. [url=http://www.fda.gov/animalveterinary/resourcesforyou/ucm047120.htm]Selecting Nutritious Pet Foods.
[/URL]









_Photo of David A. Dzanis and three tortoises_​.
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The percentages of "methionine-cystine" are much higher for cats (1.10%) than for dogs (0.53%). Methionine and cystine ( /cysteine ?) are grouped as one category. Levoratory isomers are not distinguished from dextrotory isomers.
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OK. I am a nutritional expert. I learned a lot 16 years ago. I don't doubt this information.

Unfortunately, it does not answer any of the questions.


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## vampares

I have just emailed Dr. Dzanis. He is a contact of Regulatory Discretion, Inc which was formed in 1998 a year after the sited information was published. Dr. Dzanis previously worked for the FDA for 8 years.
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Dr. Dzanis-

I am in the business of wild yeast production. These yeast are the primal genetic link earth has to life as we know it.

I do not make yeast for pet food.


I would like to get to the point and ask my question:
Is there a directive or industry standard to use DL-methionine in petfood as opposed to L-methionine?


I pose the question because I believe that there are environmental issues with DL-methionine pollution. I also believe that there are probable health consequences involved with racemic methionine.

I do not want to make "trouble" with veterinary standards. My industry and the petfood industry will not collide on this issue.​


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## vampares

The reply message:

No, I am not aware of a directive or standard that would preclude use of either form.​


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## Roger Biduk

Good article What is DL-Methionine by Susan Thixton. Roger Biduk


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