White willow bark does convert to salicin (the active ingredient in aspirin) in the body. However, white willow (as well as meadowsweet, another herb that converts to salicin in the body) does not behave exactly the same way in the body as aspirin. Also, the conversion process of pain relief in the body is not immediate, but takes a few hours.

On the plus side, white willow bark does not cause the side effects such as gastrointestinal bleeding or other dangerous circulatory sequelae that aspirin does. That has been researched and confirmed.

So, while white willow bark can be used as a natural analgesic for also for headaches and pain caused by inflammation, mild fever, arthritis, rheumatic disorders, sore muscles, colds, flu and chills, aspirin is certainly the best choice for any trips to the ER with chest pains.