A line is only as good as the place it is drawn. When defining natural products, this is a difficult place to locate. On an atomic scale, everything is natural. We are just combining naturally occurring elements in different ways.
If we think through the atomic issue, we quickly see the problematic nature of the natural product debate on this scale. The same elements that make up the hood of your car are found in an apple. They are just arranged differently.
Any discussion of natural products at the atomic scale clearly is not going to work of us. We mentally can divide an orange from a car door, but where do we make the distinction when defining a natural product?
There is an ongoing argument on this very issue, but most now look to the biological. Many try to define a natural product as anything produced by an animal or plant without over interference by mankind.
Clearly, this is a definition that is at least workable from a practical point of view. Watermelons are clearly a substance produced by a biological organism while no Twinkie plant exists on this planet.
The definition gets a bit murkier as we deal with less obvious substances. Aspirin is an amazing substance that is derived from the bark of a Willow. Of course, we do not take bits of bark for headaches. We take a processed product.
So much for our clean definition of natural products. On one hand, the aspirin we take is clearly natural because it comes from Willow bark. On the other hand, it is clearly processed and mixed with other chemicals to make the pills we actually consume.
This conundrum can be found with many products. As a result, the natural products definition has been refined. Many now argue a natural product is a substance produced by an organism that is not fundamentally altered by humans.
For instance, an ear of corn is clearly a natural product. Submerging it in water to remove dirt, bugs, leaves and the like clearly is not an issue when it comes to defining it. Altering the genetics of the plant to produce more corn, however, is.
The end all of this debate is the term natural product should be viewed skeptically when used for a product. In fact, skip over it and head to the label. The list of ingredients does not lie. Read it closely to make your choice.