The use of herbs & nutrition (diet, vitamins and minerals) offers many advantages over conventional medicine. Although taking a little longer to act, it is far gentler on the body and the overall result is more holistic because the whole body is treated instead of just the symptoms. If disease represents an imbalance in the body, then natural medicine is about correcting that imbalance in a sustainable way.
Specifically herbal medicine (or medicine from plants) has a long history of traditional use as it is common to all cultures the world over. Allowing for individuals to take more responsibility for their own health, the knowledge of plants and their positive effects on the body has been passed down through families just as it has been passed down in texts.
These days scientists are endeavoring to validate the effects of herbal medicine via rigorous scientific studies which seek not only to prove the effectiveness of herbs for certain conditions but to understand the main chemical involved and the exact mechanism on the body. These studies have led to the use of plant chemicals in modern pharmaceuticals (e.g. pseudoephedrine in cold and flu medication). However most herbs have a complex chemistry and medical herbalists still acknowledge the benefit in using the whole herb because of the presence of other chemicals which may both reduce side effects of the most active chemical and/or enhance its effects.
You may decide to try natural medicine for a number of reasons:
There are some serious conditions (eg. cancer, HIV) where natural medicine plays an important adjunctive role in treatment but should not replace pharmaceuticals. Natural medicine can also help manage the symptoms of the condition and the side effects of the drugs.