Which statement about niacin in nutrition is correct?

Which statement about niacin in nutrition is correct?

• A. It is susceptible to destruction in foods exposed to light
• B. It participates primarily in reactions involving amino acids
• C. It is soluble in both water and lipids depending upon its chemical form
• D. It can be synthesized in the body from the essential amino acid tryptophan

Answer: (D)

Niacin can be made in the body from the essential amino acid tryptophan through the kynurenine pathway, with the help of vitamin B6 and riboflavin as cofactors. Because this conversion exists, not all niacin in the body must come directly from dietary niacin. In humans, roughly 60 mg of tryptophan can yield about 1 mg of niacin equivalents, and this efficiency depends on having adequate cofactors and overall protein intake. So the statement about synthesis from tryptophan is true and reflects why dietary niacin is not the sole source. Niacin itself functions as part of the coenzymes NAD and NADP, central to redox reactions in energy metabolism, not just in amino acid-related reactions. It is water-soluble rather than lipid-soluble, and it is relatively stable to light exposure.

Niacin can be made in the body from the essential amino acid tryptophan through the kynurenine pathway, with the help of vitamin B6 and riboflavin as cofactors. Because this conversion exists, not all niacin in the body must come directly from dietary niacin. In humans, roughly 60 mg of tryptophan can yield about 1 mg of niacin equivalents, and this efficiency depends on having adequate cofactors and overall protein intake. So the statement about synthesis from tryptophan is true and reflects why dietary niacin is not the sole source.

Niacin itself functions as part of the coenzymes NAD and NADP, central to redox reactions in energy metabolism, not just in amino acid-related reactions. It is water-soluble rather than lipid-soluble, and it is relatively stable to light exposure.