Vague/Ambiguous

For a long while, my mother would always tell me to eat healthy foods. She, being someone who is very careful with her diet and food habits, would always tell me the same things over and over again: "Don't consume foods with too many chemicals, they are bad for you. Try to eat foods that are natural, they are the most healthy." Every time she told me this, I would automatically assume that any type of food with chemicals, or containing artificial ingredients are bad. In addition, every time I came across any label that claims it is "100% natural" or something of that sort would be perceived as something my mother would support me eating. However, it never once crossed my mind that that very statement my mom always reminds me of is very vague, even though it may not seem like it at first. Until a few days ago (during my nutrition class lecture), I never gave it much thought as to what exaclty "natural" is in some of our foods today, and what types of chemicals there are out there.
From my nutrition class, my professor pointed out that not all chemicals are bad. In contrast, not all natural things are good. An example of this would be tobacco. Tobacco is "natural," yet it is the very opposite of being healthy for your body. My professor also noted that everything is made of chemicals. Even us, as human beings, are made of chemicals; therefore proving her point that not all chemicals are necessarily bad. After thinking about it, I guess it's just our ideal stereotype of what chemicals and natural things are, that brings us to thinking every item consisting of chemicals would fall under the "bad" category, and vice versa for "natural" things. Therefore, going back to the very quote that started this whole subject, telling someone to not consume foods with too many chemicals can be interpreted in many different ways. Although from this case, we can all assume that my my mother meant that it was bad chemicals in foods that we should avoid, she should include this in her statement next time so that it wouldn't be too ambiguous. For the second half of that quotation, she should maybe replace the word foods with fruits, and possibly replace natural with organic or healthy to specify what she means. That would make her whole statement entirely different: more specific and detailed.