Count: 0 — No officially recognized vitamins begin with the letter W. The established set of vitamins used by health authorities and nutrition science is limited to vitamins A, the B‑complex (individual B vitamins), C, D (D2/D3), E, and K; none of these names or their accepted abbreviations start with W. Note that the phrase “water‑soluble vitamins” does start with W, but it describes a group (B vitamins and vitamin C) rather than a single vitamin name.

Understand why this specific search returns nothing. Vitamin names arose historically from discovery order, chemical identity, or physiological function, and major authorities (NIH Office of Dietary Supplements, WHO, EFSA) maintain that list; no new, officially recognized vitamin has been designated with the letter W. Scientific naming conventions and consensus, not an exhaustive alphabet, determine vitamin labels, so some letters simply remain unused.

If you searched for “Vitamins that start with W,” look instead for related topics. Check “water‑soluble vitamins” (B vitamins and C), “vitamin list A–K” for authoritative RDIs and food sources, or nutrient categories that begin with W such as whey protein or water (essential but not a vitamin). Consult trusted sources — NIH, EFSA, WHO, and USDA FoodData Central — for accurate RDIs, food sources, and nutrient guidance.