They have been scientifically tested and found to be both safe and effective.
Clinical trials use the scientific process to determine whether a treatment is safe and effective.
A treatment may be a drug or another method of treating disease in human beings. Before it can even be tested in humans, though, a treatment is tested in the laboratory, then on animals, then, if it is determined to be safe, it is tested on humans. If it is verified to be safe, the FDA approves its use in medical care. Alternative therapy is treatment that is promoted as a cure, yet has not been scientifically tested, or if tested, was found to be ineffective. Alternative therapies are usually promoted by those not in the medical profession.