β-Carotene serum levels in patients with erythropoietic protoporphyria on treatment with the synthetic all-trans isomer or a natural isomeric mixture of β-carotene

The all-trans-β-carotene serum level of patients suffering from erythropoietic protoporphyria increases substantially during continuous treatment with β-carotene (either with the synthetic all-trans compound or with β-carotene from a natural source consisting of a cis-trans isomeric mixture). On continuous daily ingestion, the β-carotene serum level rose from day 0 to day 30, and no further increase was observed between day 30 and day 150. Slightly lower β-carotene steady state serum levels were observed with the natural isomeric mixture than with synthetic β-carotene. Higher levels of 13-cis-β-carotene, in some cases up to 10% of the total β-carotene, were detected after ingestion of the synthetic compound. The level of 9-cis-β-carotene was below or close to the limit of quantification in all samples, even when the isomeric mixture containing high amounts of 9-cis-β-carotene was applied.