Nicotinic acid is used in high doses to treat hyperlipidemia. Which statement about this therapy is accurate?

• A. Nicotinic acid is given in high doses to treat hyperlipidemia.
• B. Increasing dietary niacin is sufficient to treat hyperlipidemia.
• C. Nicotinamide reduces plasma lipoproteins.
• D. Dietary tryptophan is converted to nicotinic acid in sufficient amounts.

Answer: (A)

High-dose pharmacologic niacin is used for hyperlipidemia because the lipid effects only appear at amounts far higher than what diet provides. At these therapeutic doses, nicotinic acid decreases hepatic production of VLDL, which lowers triglycerides and LDL, and it can raise HDL levels. This is not something achieved by normal dietary intake of niacin. The amide form, nicotinamide, does not produce the same lipid-lowering effects. Similarly, relying on body conversion of dietary tryptophan to nicotinic acid isn’t sufficient to reach therapeutic levels for lipid control.