Nutrition: pellagra and jowar: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Nutrition: pellagra and jowar

Sample item

In a rural area where jowar (sorghum) is the staple cereal, adults present with photosensitive dermatitis, diarrhoea and dementia. Which dietary factor in jowar is implicated in this niacin-deficiency syndrome?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Excess leucine

Pellagra develops from niacin deficiency, and diets based on jowar can cause it even when niacin intake seems adequate because the high leucine content inhibits the conversion of tryptophan to niacin. Diets based on maize carry niacin in a bound, unavailable form and little tryptophan. Correcting the diet with pulses, milk and eggs helps.

Option by option

  • A. Excess lysine

    Lysine is the limiting amino acid of cereals and is low, not high, in jowar.

  • B. Excess leucine (correct)

    Leucine excess impairs endogenous niacin synthesis from tryptophan.

  • C. Excess tryptophan

    Tryptophan is the precursor of niacin, so excess would not cause deficiency.

  • D. Excess methionine

    Methionine is the limiting amino acid in pulses and does not cause pellagra.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is B, Excess leucine. Pellagra develops from niacin deficiency, and diets based on jowar can cause it even when niacin intake seems adequate because the high leucine content inhibits the conversion of tryptophan to niacin.

Why is "Excess lysine" not the answer?

Lysine is the limiting amino acid of cereals and is low, not high, in jowar.

Why is "Excess tryptophan" not the answer?

Tryptophan is the precursor of niacin, so excess would not cause deficiency.

Why is "Excess methionine" not the answer?

Methionine is the limiting amino acid in pulses and does not cause pellagra.

What concept does this question test?

It tests Nutrition: pellagra and jowar in PSM. Diets based on maize carry niacin in a bound, unavailable form and little tryptophan. Correcting the diet with pulses, milk and eggs helps.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Nutrition: pellagra and jowar?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.