Ultra-processing markers
L-cysteine
Definition
What it is
L-cysteine: amino acid dough conditioner used in commercial bread; commonly sourced from human hair, duck feathers, or hog bristle (source not required to be disclosed). Major transparency flag for vegan consumers.
On the label
Label names covered by this flag
- l-cysteine
- l cysteine
- e920
Regulation
Regulatory status
No bans or restrictions are recorded for this ingredient in the jurisdictions clearlabel tracks (US, EU, UK, Canada, Japan, Australia/NZ, Brazil).
Explainer
In plain language
L-cysteine is an amino acid used as a dough conditioner in commercial baking, where it relaxes gluten so dough stretches and shapes more easily. You will meet it most often in soft, mass-produced breads, buns, and bagels. It can be made by bacterial fermentation, but a significant share is still extracted from keratin-rich materials like human hair, duck feathers, or hog bristle.
Assessment
Why it is flagged
L-cysteine (E920) is permitted as a processing aid by the FDA and in the EU, and at the amounts used in bread it raises no established safety concern. Clear Label flags it mainly for transparency, because the source is not required to be disclosed on the label, which matters to vegan, vegetarian, and some religious-diet shoppers who want to avoid animal- or human-derived inputs. The keratin sources, hair and feathers and bristle, are widely documented in trade and food-industry literature, though fermentation-derived L-cysteine is increasingly common. There is no reliable way to tell from the label which source a given product used. This is a values and disclosure question more than a health one.
In the aisle
Where it commonly shows up
- Soft commercial sandwich bread and rolls
- Bagels and pretzels
- Pizza dough and flatbreads
- Croissants and pastries
- Some tortillas and wraps
- Bakery mixes and frozen dough
Practical
Reading the label
It appears as L-cysteine, L-cysteine hydrochloride, or E920 in the ingredient list, usually near the flour and conditioners. The label rarely states the source, so a plant-only claim or a certified vegan mark is the most reliable signal for people who care where it came from.
Alternatives
If you want to avoid it
Some people choose breads from bakers who list simple ingredients, or products carrying a certified vegan label, which effectively rules out the animal- and human-derived sources. Sourdough and many artisan breads skip added dough conditioners entirely.
FAQ
Common questions
Is L-cysteine really made from human hair?
Some of it is. Industrial L-cysteine has long been extracted from keratin sources including human hair, duck feathers, and hog bristle, though fermentation-based production is now also common. Labels do not have to say which source was used.
Is L-cysteine safe to eat?
Regulators including the FDA permit it as a dough conditioner, and no safety concern is established at the small amounts used in baking. The flag here is about disclosure and dietary values, not toxicity.
How can vegans avoid it?
Because the source is not printed on the label, a certified vegan mark or a call to the manufacturer is the practical way to confirm. Breads without added dough conditioners avoid the question entirely.
Citations
Sources
Citation
Primary reference
About this page: the definition, label names, severity, and regulatory chips come from the clearlabel ingredient taxonomy, the same data the scanner uses to score products. Research summaries describe associations reported in published studies, not diagnoses; individual responses vary. Scan any product with clearlabel to see which of its ingredients carry flags.