Appeal to Nature, similar to the naturalistic fallacy, when used as a fallacy, is the belief or suggestion that “natural” is always better than “unnatural”. It assumes that “nature” is good, and “unnatural” is not. Unfortunately, in many discussions about science and medicine, individuals take this as their default belief.
Of course, this fallacy ignores what might be considered the line between “natural” and “unnatural.” Sucrose, table sugar, can be manufactured by plants or by chemistry. Both sugars are exactly the same, containing “natural” carbon, hydrogen and oxygen.
High fructose corn syrup is not natural so it must be bad for you.