Count: 0 — No recognized vitamins start with the letter X. This page addresses the search term “Vitamins that start with X” and clarifies that, among the officially defined vitamins (A, the B-complex vitamins, C, D, E, and K), none bear names beginning with X. Note that vitamin names arose from discovery order, chemical classification, and established nutrition science, so the absence of an “X vitamin” reflects naming history rather than a gap in nutrition.

Understand why this criterion yields no results. Define vitamins as essential organic nutrients required to prevent specific deficiency diseases; historically these received single-letter or descriptive names (A, B, C, D, E, K) or systematic chemical names. No essential nutrient accepted by authorities like NIH, WHO, or EFSA carries a common name beginning with X. Consider related terms that might appear in searches: xanthophylls (yellow carotenoid pigments such as lutein and zeaxanthin) and compounds like xylitol are nutrient-related but are not classified as vitamins. Consult established vitamin lists (A, B1–B12, C, D2/D3, E, K1/K2) when you need authoritative guidance on benefits, food sources, and RDIs.