Grapefruit and Diet

I have been told that eating grapefruit blocks the benefits of my herbal daily diet. Is this true? What does it do? Like to eat pink grapefruit here in Florida. Herbs have been good for me-are expensive. Do I need to quit grapefruit?

Grapefruit inhibits a liver enzyme that breaks down some drugs and herbs in the body, so that these drugs and herbs remain in the body longer, magnifying their effect. Information sheets accompanying prescription drugs will alert you to this effect.
Grapefruit helps to lower cholesterol, may help to prevent cancer and contains antioxidants to help fight disease.