A nurse is providing teaching about dietary supplements to a client who has erectile dysfunction and has been prescribed nitroglycerin. Which of the following statements is the most important for the nurse to include in the teaching?

"There is not enough evidence that dietary supplements are effective for erectile dysfunction."

"Dietary supplements can cause a drug-drug interaction with nitrates."

"Dietary supplements have not been tested and approved by the government."

"Dietary supplements may be expensive and are not typically covered by insurance."