According to European guidelines, 'natural' pet food ingredients are defined as...
"pet food components to which nothing has been added and which have been subjected only to such physical processing as to make them suitable for pet food production and maintaining the natural composition."
This excludes almost all artificial additives (preservatives, colourings and flavourings), ingredients that have undergone chemical treatment like bleaching or chemical oxidisation and all GMO products. It does, however, allow synthetic vitamins and digest (meat hydrolysate) to be called 'natural'.
If all of a food's ingredients fit the above criteria, the food can be labelled as 'natural'.
Although seeing the word 'natural' on a pet food can offer some peace of mind, there are a number of issues which you should be aware of:
Firstly, just because an ingredient is natural, it does not necessarily mean that it is suitable for your dog, after all, arsenic and cyanide are perfectly natural products. If you are unsure of any ingredients in your dog's diet, take a look at our Ingredients Glossary to make sure it is the best thing for your pet.
Synthetic vitamins and digest are extremely widespread in pet foods and although both can legally be labelled as 'natural', neither really is. Most synthetic vitamins are not found in nature and can only be produced artificially. Digest may be an animal product but the process of chemical/enzymatic hydrolysis used to make it is far from what most people would regard as 'natural'. It is also worth noting that pet food manufacturers are able to use both of these ingredients without disclosing them on the ingredients list.
Despite the proviso that "nothing should be added" to any of the ingredients in a natural pet food, many industry experts suggest that artificial preservatives still routinely find their way into pet foods in the form of pre-prepared meat meals and animal fats. These ingredients are produced and preserved in meat rendering plants before being sold to the pet food manufacturer. Manufacturers often don't know or don't care where their meat products come from and what sort of additives they contain and as long as they don't add any more artificial additives of their own, they can still legally label their food as 'natural'.
Of course, this doesn't apply to all meat meals. Some are preserved completely naturally and more and more manufacturers are actively stating that their meat and fat sources are chemical free. Nevertheless, many still do not so if you are unsure about your dog food, your best bet would be to ask the manufacturer directly and if their reply is at all fuzzy or if they merely state that they don't add any additives to their foods, it's probably a bad sign.