When speaking about food products and medicine, it seems to be a relatively modern phenomenon, at least in the western societies, that everything that is perceived to be "natural" and "organic" is good, or at the very least the lesser of two evils, while anything that is perceived to be "man-made" and "artificial" is considered to be bad and harmful, and should be avoided. The common notion is that if a product has only "natural" and "organic" ingredients, it's much healthier than a product which has "artificial" components.
Advertisers know this, and may in fact do their part in actually spreading this notion. Catch-phrases like "100% natural ingredients", "fully organic" and "no artificial preservatives" are an extremely common way of making a product sound more desirable and healthy (regardless of how healthy it really is, or whether it really is healthier than an alternative, or whether "artificial" alternatives even exist in the first place).
Naturally this ignores the fact that many naturally-occurring substances can be quite unhealthy, harmful and even lethal, while many man-made substances which do not occur in nature can be beneficial to health.
Anyways, whether artificial preservatives can be unhealthy and harmful in the long run is a subject of heated study and discussion, and basically an open question, but actually not the subject of this article. It served simply as an introduction.
The real problem with this natural vs. artificial conundrum is when people take it farther, even to the point where it becomes outright stupid and dangerous.
For example some advocates of homeopathy fully endorse this notion, in other words, that homeopathic substances are "natural", induce some natural processes in the body (by some unexplained mechanism), and that regular medicine is artificial and thus harmful. In some extreme cases some such people go so far as to outright refuse to get regular medical treatment (either for themselves or people in their care) because of this twisted notion they have that "artificial medicine is harmful", while homeopathic substances are natural and healthy.
For example, last year an Australian man was convicted because he refused to take his baby daughter to a doctor or administer the medicine that would have saved her life, and instead stubborningly kept giving her homeopathic remedies until she died from the illness. (Source.) Her illness would have been trivially treatable with modern medicine, and hardly fatal, except if untreated like in this case.
Likewise people who oppose vaccinations, besides spreading all kinds of lies about them (such as vaccines containing mercury or causing autism, even though numerous studies have shown no relationship between the two, and exactly one old study suggested a possible relationship, without actually claiming its existence), usually have at its core the same notion of "natural = good", "artificial = bad".
In this case many such people think that children should get immunity to diseases by actually contracting the disease and getting the immunity in such a "natural" way, rather than getting the immunity "artificially" with a vaccine. An underlying notion is that the immunity one gets by the actual "natural" disease is somehow "better" than the immunity one gets from the "artificial" vaccine.
Some of these people even go to such extremes as deliberately exposing their children to the diseases. For example, if a friend's kid is suffering from some common children's disease, they will take their own children there in order for them to contract it as well. (There was an episode of South Park that satirized this practice. It was not an invention of the TV show. It really does happen in real life, as incredible as that might sound.)
This kind of mentality is not only completely stupid, it's in fact dangerous.
Firstly, there's no difference between the immunity one gets from suffering the actual disease and the immunity one gets from a vaccine. The former is not somehow magically "better" than the latter. To the immune system it's all the same: It doesn' really make a distinction between the vaccine and the real thing; it "learns" the infecting agent all the same.
Secondly, there's no such a thing as a "safe" or "harmless" disease. It's never a good thing if a child contracts a disease because he did not get a vaccine to prevent it. Diseases always have risks involved. Infectious diseases can behave unpredictably, and their severity can depend a lot on the individual: Some people have slightly stronger immune systems to begin with, while others may have weaker immune systems. There's no telling how much harm the disease may do to a person, especially a child.
Moreover, such a disease may open the doors to other diseases (so called opportunistic infections) which may thrive on a weakened immune system because the child's body is fighting the first infection. The risks grow larger the longer the disease lasts.
A vaccine offers a considerably safer method for getting the immunity to the disease. Since there are no actual viruses or bacteria, they do not multiply, spread (prolonging the "illness") or cause any damage. The process is usually either completely asymptomatic or with only minor symptoms (such as temporary pain where the vaccine was administered). Thus it's not only safer from a health point of view, the child also doesn't need to suffer nor detract from normal activities.
The notion that suffering from the actual disease is "more natural" and somehow better is based on nothing but old wives' tales and superstition. Basically "nature" is given some magical safety properties which "man-made" and "artificial" substances do not have. The notion seems to be that nature somehow "protects" the human body from ill effects better than man-made substances, which often do the opposite, ie. harm the human body with its "unnatural artificiality".
When talking about medicine the opposite is often true: "Natural" medicine, even if it really is beneficial, can often be less effective and healthy than artificially-produced medicine, which can often be more effective, safer and with less side-effects (because it contains less contaminants than the "natural" medicine). There's nothing special about the medicine being "natural" or "man-made": The body does not care where or how it was produced. It only cares what it does, and there is nothing in nature which would somehow "protect" the body more effectively than man-made substances.
The whole fuss about genetic engineering of plants also presents signs of a superstitious "natural vs. artificial" mindset. Many people and countries are worried about genetic engineering because they fear the consequences this might have. Ok, that's fine. What is jarring is that these exact same people are in no way whatsoever worried about the "soft genetic engineering" that people have been doing for several millenia to plants via selective breeding, which is, for the lack of a better term, artificial selection (as opposed to natural selection) where mutations seen beneficial are artificially selected and retained.
Nobody is concerned about the artificial genetic selection done by selective breeding of plants because it's deemed as "natural", and hence by definition "safe". Once again, there's an underlying mentality that if something is done in a "natural" way, it's somehow safe to humans, that humans are somehow "protected" by these natural processes, but once we go to artificial genetic engineering via direct manipulation of genes, alarms immediately go off. It's artificial, hence it must be bad and dangerous.
Nature and natural processes do not somehow protect humans. That's superstition. There's no benevolent "mother nature" who watches over us and protects us from harm as long as we don't start messing with her ways. That kind of mentality (even if only at an implied level) is pure bollocks.