Question:medium
Fishy odour occurs due to deficiency of which vitamin from the diet?
Fishy odour occurs due to deficiency of which vitamin from the diet?
Show Hint
Think of the flavin-containing enzyme FMO3 and the vitamin that supplies its cofactor.
Updated On: Jun 23, 2026
- Biotin
- Thiamine
- Riboflavin
- Vitamin A
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Link the clinical clue to the chemistry. A fishy smell from the body points to excess trimethylamine, a volatile amine that is normally detoxified by oxidation.
Step 2: The detoxifying enzyme is hepatic flavin-containing monooxygenase 3 (FMO3). The word $flavin$ is the key: this enzyme uses flavin cofactors ($FAD$ and $FMN$) which the body builds only from dietary riboflavin.
Step 3: Therefore a shortage of riboflavin starves FMO3 of its cofactor, trimethylamine piles up, and it escapes in urine and sweat as a fishy odour. Clinically, riboflavin is even prescribed to boost leftover FMO3 activity.
Step 4: Rule out the rest. Biotin is a carboxylase cofactor, thiamine drives carbohydrate metabolism, and vitamin A is needed for vision - none of these feeds the FMO3 reaction, so none explains the smell.
\[\boxed{\text{Riboflavin}}\]
Step 2: The detoxifying enzyme is hepatic flavin-containing monooxygenase 3 (FMO3). The word $flavin$ is the key: this enzyme uses flavin cofactors ($FAD$ and $FMN$) which the body builds only from dietary riboflavin.
Step 3: Therefore a shortage of riboflavin starves FMO3 of its cofactor, trimethylamine piles up, and it escapes in urine and sweat as a fishy odour. Clinically, riboflavin is even prescribed to boost leftover FMO3 activity.
Step 4: Rule out the rest. Biotin is a carboxylase cofactor, thiamine drives carbohydrate metabolism, and vitamin A is needed for vision - none of these feeds the FMO3 reaction, so none explains the smell.
\[\boxed{\text{Riboflavin}}\]
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