Well generally natural food is healthier, but food additives and preservatives can make food look and taste better and last longer, so that’s why the companies that produce food use them, that’s not to say that they are not without their side effects and in many cases they are totally unnecessary. Take artificial colours for example in most cases they are just not needed. I will happily eat food that is the natural colour it is meant to be and whether I will experience side effects or not, see no point in taking the risk.
Also an important point to mention, Artificial Preservatives will preserve the food product for a longer period than if it was left in its natural state. If natural food products are what you prefer you can always opt for fresh food products (usually found in the chill counter), these will always show whether they contain any Artificial Preservatives.