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Everything You Ever Wanted to Know About L-Cysteine But Were Afraid to Ask

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Veggielover99 Veggielover99 SA Posts: 4
1 22 Sep 2010
Did you know that L-CYSTEINE — A common dough conditioner, flavor enhancer in human and pet foods, and precursor in some dietary supplementsis most often derived from human hair or duck feathers and to a lesser extent from pigs’ bristles and hooves?

Ten years ago, the most common source was human hair found on the floors of Chinese barbershops. Today, it is derived from Chinese duck feathers approximately 80 percent of the time (estimation based on values given by several companies that manufacture and sell L-cysteine).

At least two forms of synthetic L-cysteine that were not readily available in 1997, though L-cysteine, is manufactured today. They are produced by Ajinomoto and Wacker Biochem. Ajinomoto stated that it uses industrial chemicals that undergo a biochemical transformation brought about by non-animal enzymes. Previously selling both the ‘natural’ (i.e., animal- or human-derived L-cysteine) and synthetic forms, Ajinomoto completely switched in 2000 to selling only the synthetic form of L-cysteine. Wacker Biochem informed us that they produce L-cysteine through a microbial fermentation process developed in 2001 using corn sugar as the growth medium. Since both forms are expensive, they are not commonly used. According to both companies, the synthetic forms of L-cysteine are certified kosher and halal. L-cysteine derived from human hair or duck feathers may or may not be certified kosher and/or halal.

The use of synthetic L-cysteine could increase over time. Doug Hackett of Premium Ingredients, a major supplier of L-cysteine derived from human hair or duck feathers, told us that he’s recently had to turn away several potential customers looking for synthetic L-cysteine because Premium sells only the non-synthetic variety. Requests from customers concerned about human- or animal-derived ingredients in their foods could also accelerate the use of synthetic L-cysteine in foods over feather- or human hair-derived L-cysteine.

L-cysteine is considered a substance that is generally recognized as safe by the Food and Drug Administration (FDA). It must be labeled by its “common and usual name” (i.e., “L-cysteine”) on food packages, even if present in very small amounts, as long as it has a functional effect in foods. In other cases, such as when it is used to make flavors that are in foods, it does not have to be labeled. When L-cysteine does have to be labeled, its source does not have to be specified, according to the FDA.

While researching L-cysteine,  several fast food chains and a major vegetarian food company was asked about the sources of L-cysteine in their products. McDonald’s told stated that L-cysteine derived from duck feathers is in their Honey Wheat Roll, the Deluxe Warm Cinnamon Roll, and the Baked Apple Pie. The L-cysteine in several items offered at Dunkin’ Donuts is also derived from duck feathers. Burger King/Hungry Jack’s  stated that it “could not guarantee” the source of L-cysteine in its products.

On the other hand, Subway announced that in 2007  it has removed the L-cysteine from its otherwise animal product-free Carb Conscious Wrap. When asked about the source of L-cysteine in several of Domino’s Pizza products, the company told me that L-cysteine is “microbially derived” in its Hand- Tossed Crust and informed us that the L-cysteine in Domino’s Breadsticks, Cheesy Bread, and Cinna Stix® is “vegetable-derived.” The public relations firm for Morningstar Farms told us that the L-cysteine in their Veggie Bites Country Scramble, Veggie Bites Spinach Artichoke, and Veggie Bites Eggs Florentine was a “microbial fermentation product.”

I've  never been a fast food person. Prefer to know what is going into my body but thought that it was interesting so decided to share it.  chick

ckimana ckimana NSW Posts: 2545
2 22 Sep 2010
That is interesting, never knew that! Thx for posting happy

...2 ...2 WA Posts: 2307
3 23 Sep 2010
Oh wow. This is really quite freaky. =) Thanks for the info.

Enlightened_vegan Enlightened_vegan TAS Posts: 3
4 26 Dec 2015
Very helpful. Thank you.
Do you know any brand of supplement that is vegan of NAC ? For example deliver to most countries and have a few brands of NAC to choose from. Just not sure if anyone here knows which one or ones might be vegan? Or have tried/ had experiences with taking this supplement?!?
With thanks

robert99 robert99 Sweden Posts: 1360
5 28 Dec 2015
Original article at



L-cysteine is manufactured by the electrolytic reduction method using l-cystine as the starting materials. L-cysteine is manufactured under cGMP conditions. No materials of animal origin are used in the manufacturing process. A Drug Master File for L-cysteine is on record at the FDA. L-cysteine meets DAB pharmacopeias standards.
Wacker-Chemie Producing L-Cysteine by Fermentation
September 17, 2001
ADRIAN, Mich.--Wacker-Chemie ( has begun commercial production of the amino acid L-cysteine through bacterial fermentation. The process is based on a bacterial strain that was engineered to synthesize L-cysteine from dextrose. Wacker formed an alliance with Kyowa Hakko USA to market and sell cysteine products in the United States.