Cysteine

Cysteine carries a safety score of 5/5 and appears in 15 indexed US food products. CSPI rates it “Safe.”

Safety score 100.0%

5/5 from FDA SAFFA + CSPI Chemical Cuisine

How common is vs other flagged additives?

Number of indexed products containing each of the most common flagged additives — Cysteine highlighted.

Indexed products containing each flagged additive. Source: Open Food Facts ingredient lists × FDA SAFFA × CSPI Chemical Cuisine.

Caramel Coloring22612Red 4021595Yellow 518987Carrageenan17853Blue 116643Yellow 613560Sucralose10490Cysteine15
Indexed products containing each flagged additive. Source: Open Food Facts ingredient lists × FDA SAFFA × CSPI Chemical Cuisine.
CSPI Rating
Safe
Safety Score
5/5

Function

Preservative

Safety Assessment

Cysteine is generally considered safe for consumption based on available regulatory and scientific data. It has a safety score of 5/5, indicating broad acceptance by food safety authorities.

What the Data Says About

Cysteine currently appears in 15 products across the OpenFoodFacts catalog we index, which gives a concrete measure of its footprint on US grocery shelves. Our internal safety score of 5/5 synthesizes FDA Substances Added to Food (SAFFA) regulatory status with the Center for Science in the Public Interest (CSPI) Chemical Cuisine classification of "Safe." These two frameworks capture different questions: regulators ask whether exposure at typical intake is acceptable, while consumer-advocacy groups examine cumulative dietary load and vulnerable-population risk.

In food manufacturing, Cysteine functions as a preservative. That technical role explains why it recurs across many product categories — formulators select specific additives for stability, shelf life, color, or texture performance, and substitution is rarely a one-for-one swap when regulations or consumer preferences shift. Inspection and outbreak data often trace back to breakdown in the control of exactly these kinds of functional ingredients, either through contaminated batches, undisclosed substitutions, or labeling errors that trigger FDA-initiated recalls.

No specific concern flags are attached to Cysteine in our current data snapshot beyond the regulatory and CSPI classifications above. That does not rule out individual sensitivity reactions, and anyone managing allergies, elimination diets, or chronic conditions should verify with a qualified healthcare professional before relying on population-level ratings.

Safety Profile at a Glance

Regulatory and safety classifications for Cysteine
Source Classification Year
FDA SAFFA Not listed 2024
CSPI Chemical Cuisine Safe 2024
PlainFoodSafe Score 5/5 2026
Product footprint 15 products OpenFoodFacts

FDA SAFFA database, CSPI Chemical Cuisine ratings, OpenFoodFacts product index. See methodology.

Frequently Asked Questions

Is Cysteine safe to eat?

Cysteine has a safety score of 5/5. The Center for Science in the Public Interest (CSPI) rates it as "Safe." Always check with a healthcare provider if you have specific dietary concerns.

What products contain Cysteine?

Cysteine is found in 15 products in our database, spanning various food categories and brands.

What does Cysteine do in food?

Cysteine is used as a preservative in food products.

Where does this ingredient safety data come from?

Safety data comes from the FDA's SAFFA (Substances Added to Food) database, CSPI (Center for Science in the Public Interest) ratings, and the OpenFoodFacts product database. Product counts reflect items cataloged in OpenFoodFacts.