When considering the nourishment of your dog and cat, the two main important key points are to:
Provide optimal amounts of nutrients.
Avoid unnatural chemicals, preservatives or food additives as far as possible. These are foreign to the body and can potentially cause health problems as the body is unable to eliminate or process them.
Unfortunately many commercial foods don't manage to achieve this. They are generally heavily processed destroying a significant amount of nutrients and, especially biscuit or crumble formulations are very deficient in vital omega 3 and 6 fatty acids. In addition to this, they frequently contain additives to improve the taste of the food, make it look more visually appealing and to preserve the shelf life.
The list of ingredients will list the food components in order of the highest amount to the least amount. It is concerning that one of the first ingredients listed for many foods are grains. Grains can be helpful in moderation to bulk up dogs' food but certainly for cats, which are carnivores and some dogs that have health conditions such as inflammatory bowel disease and allergies, they can be detrimental to health as they have a pro-inflammatory effect which contributes to dis-ease.
Many food additives have little or no safety testing and some such as propylene glycol, potassium sorbate, sodium nitrite and propyl gallate have been linked to health problems in animals. Ethoxyquin is a preservative of many commercial animal foods that was originally used in rubber production. It helps to prevent fat from becoming rancid and has been approved as safe by the overseers of food production, however, ethoxyquin is alleged to cause cancer - as well as kidney, liver and thyroid problems.
BHT (butylated hydroxytoluene) is another poorly tested preservative implicated by some scientists to cause liver damage, metabolic stress and foetal abnormalities while BHA (butylated hydroxysanisole) has been implicated in liver and kidney problems as well as birth defects, behavioural problems and is potentially considered a carcinogen (cancer causing substance).
High concentrations of sugar (also listed as corn syrup or sucrose) and some artificial flavouring have also been linked to behavioural abnormalities such as nervousness, hyperactivity, anxiety and aggressive behaviour in children and pets. Sugar in high amounts can also lead to health problems of the adrenal glands and pancreas such as diabetes.
A good quality food will only be preserved with natural substances such as naturally occurring tocopherols and vitamin C. In addition to this, high quality foods source their ingredients from farms where care has been taken to minimize exposure to herbicides, fungicides, anti-biotic residues and hormones which many food producing animals are treated with to improve their production.
Allergens are food components which are involved in initiating allergies and while there is the potential for many types of food to fall into this category for different individuals there are certain foods which are more likely to be allergens than others. These include beef, beef bye products, milk and grains.
All in all it can be challenging to find great quality food that takes all of this into consideration helping to enhance the health of your pet. But the bottom line, as usual, is that nature knows best and by respecting natural principles and feeding a natural raw food diet as nature intended you can be sure that you're making a substantial investment into your animal's health and well-being.