What is it?
A nearly colorless ingredient made by hydrogenating curcuminoids, the yellow pigments extracted from the rhizome (root) of turmeric, Curcuma longa. The result is a creamy white to pale yellow powder that is mostly tetrahydrocurcumin, a compound the body also makes when it breaks down curcumin. It is used as an antioxidant in face serums and creams, where it does not add curcumin’s strong yellow color.
Key information
- Tetrahydrocurcuminoids are made by hydrogenating turmeric curcuminoids; one food-grade material was more than 95 percent tetrahydrocurcuminoids, about 87 percent of it tetrahydrocurcumin.
- EFSA concluded in 2021 that this material is safe as a food supplement for adults at 140 mg a day and raised no concern about genotoxicity.
- A 2003 case report described contact allergy to tetrahydrocurcumin.
- We found no safety review of tetrahydrocurcuminoids as a cosmetic ingredient by the Cosmetic Ingredient Review or the EU's Scientific Committee on Consumer Safety.
More information
Turmeric’s curcuminoids are mainly curcumin, with smaller amounts of demethoxycurcumin and bisdemethoxycurcumin. Hydrogenating them over a palladium catalyst turns each into a colorless “tetrahydro” form. A material assessed by the European Food Safety Authority (EFSA) in 2021 was more than 95 percent tetrahydrocurcuminoids, on average about 87 percent tetrahydrocurcumin. Tetrahydrocurcumin is also one of the compounds the liver makes from curcumin. It is not the same ingredient as Curcumin, the yellow pigment itself.
EFSA assessed that material as a novel food for supplements. Bacterial and human-cell tests raised no concern about genotoxicity, and rats given up to 400 mg/kg a day for 90 days showed no adverse effects. In a reproduction screening study, EFSA set the no-effect level at 200 mg/kg a day because of possible effects on pup survival at the highest dose. It concluded the material is safe for adults (excluding pregnant and breastfeeding women) at 140 mg a day, less than the 300 mg the applicant proposed.
Data on skin are limited. In a Thai study of 36 women, tetrahydrocurcuminoids under a single occlusive patch caused significantly less irritation than the strong irritant used for comparison, and the authors judged the materials tested unlikely to irritate skin under normal use. A 2003 case report in Contact Dermatitis described a woman with contact allergy to tetrahydrocurcumin, confirmed by patch testing. We found no review of it as a cosmetic ingredient by the Cosmetic Ingredient Review (CIR) or the EU’s Scientific Committee on Consumer Safety. On labels it appears as tetrahydrodiferuloylmethane, tetrahydrocurcumin or tetrahydrocurcuminoids.
Sources: EFSA Journal (2021): Safety of tetrahydrocurcuminoids from turmeric (Curcuma longa L.) as a novel food; Journal of the Medical Association of Thailand (2007): Human skin irritation of a herbal skin care product and ingredients by single closed patch testing; Contact Dermatitis (2003): Contact allergy to tetrahydrocurcumin; European Commission CosIng: Tetrahydrodiferuloylmethane
