Green Dye 3 vs Locust Bean Gum: which is worse?

What is Green Dye 3?

Green Dye 3 (Fast Green FCF) is a synthetic blue-green triarylmethane dye similar to Blue Dye 1. It produces a sea-green color and is among the least used certified US food dyes. Its chemical formula is C37H34N2Na2O10S3.

What is Locust Bean Gum?

Locust bean gum (LBG) is a galactomannan polysaccharide extracted from the seeds of the carob tree (Ceratonia siliqua), native to the Mediterranean. It is a fine white to yellow powder that forms a thick gel when dissolved in hot water. It synergizes strongly with xanthan gum and carrageenan to enhance gel strength.

Documented risks

Green Dye 3: Green Dye 3 has a limited safety database compared to other certified food dyes, partly due to its infrequent use. A 1981 NTP bioassay (Technical Report 27) found statistically significant increases in urinary bladder tumors in male mice at high doses. The FDA reviewed these findings and, as with Blue 2, concluded the doses far exceeded typical human dietary exposure. Green 3 is not approved in the EU — under the EU's positive list system, only specifically approved additives may be used. Since Green 3 is not on the positive list, it is effectively banned. EFSA has not conducted a formal re-evaluation because it is not authorized for EU use. Hypersensitivity reactions have been reported. Like other synthetic triarylmethane dyes, Green 3 may cause contact dermatitis. The FDA's April 2025 phase-out announcement includes Green 3 among the eight petroleum-based synthetic dyes to be removed from the US food supply. Its already limited use means this phase-out has minimal market impact compared to Red 40 or Yellow 5.

Locust Bean Gum: Generally recognized as safe. EFSA's Panel on Food Additives confirmed the safety of LBG in 2017, noting no concerns at current dietary exposures. It functions as a soluble dietary fiber and can have mild prebiotic effects. No significant adverse effects have been documented in human or animal studies at food-relevant doses.