cis-beta-Carotene

Cis-beta-carotene is a geometric isomer of beta-carotene: the same molecule, bent into a different shape instead of beta-carotene's straight all-trans chain. That shape change matters — cis-beta-carotene converts to vitamin A at roughly half the efficiency of the all-trans form, and shows up only in trace amounts across the USDA dataset.

Most dietary carotenoids occur in the all-trans configuration; cis isomers like this one form in smaller amounts naturally, or when carotenoid-rich food is heated or processed. Per the NIH National Academies Press — Dietary Reference Intakes for Vitamin A, cis-beta-carotene's roughly half-strength conversion to retinol compared with all-trans beta-carotene is why food-composition data tracks it as a separate analyte rather than folding it into the all-trans figure.

In the USDA data behind this page, cis-beta-carotene is measured at trace levels only, every food on record carries under 50 micrograms per 100g, led by grape tomatoes, salted butter, and vitamin-D-fortified milk. That is a different profile from beta-carotene overall, which concentrates heavily in carrots, sweet potatoes, and leafy greens: cis-beta-carotene instead turns up as a minor trace component scattered across a wide range of foods rather than being concentrated in any single food group. With only 12 measured values on record, it is one of the more sparsely measured nutrients in this dataset.