Is it true that a person who takes medicine for high cholesterol should not eat grapefruit due to the acid?

Grapefruit juice inhibits certain enzymes that metabolize some drugs. Due to the enzyme inhibtion these drugs remain in high concentrations in the blood and can cause unwanted side effects.

Statins (e.g. atorvastatin, simvastatin), a class of cholesterol lowering drugs, are affected in this way and it is advisable to avoid grapefruit and it's juice altogether if you are taking these medicines.

there are a number of cardiac meds which require avoidance of grapefruit, and several mental health drugs which require the avoidance of grapefruit, this because of enzymes that interact with the medications. But, there is NO documeted reason to avoid any kind of citrus, grapefruit included with regards to cholesterol lowering drugs.