Why is plasma carotenoid not used as marker of vitamin A status?

• A. A plasma carotenoid level is not used because carotenoids are metabolized to retinol.
• B. A plasma carotenoid level is not used because carotenoids degrade quickly.
• C. A plasma carotenoid level is not used because carotenoids are not related to vitamin A status.
• D. A plasma carotenoid level is not used because retinol is more stable in plasma.

Answer: (C)

Plasma carotenoids do not mirror vitamin A status because they mainly reflect dietary intake of colorful plant foods rather than the body's actual vitamin A reserves. Vitamin A status is governed by circulating retinol and liver stores, which are tightly regulated and can stay normal until stores are depleted. Carotenoids can be converted to retinol, but this conversion is inefficient and varies widely among individuals, so plasma carotenoid levels do not reliably indicate how much vitamin A is available or stored. Additionally, carotenoid levels are influenced by recent meals and lipid status, adding more disconnect from true vitamin A adequacy. For these reasons, plasma carotenoids aren’t used as markers of vitamin A status; measuring retinol (or other indicators of vitamin A stores) provides a more accurate assessment.