Commercial dog foods today contain anywhere from two to dozens of main ingredients, as well as vitamins, minerals, preservatives, and other additives. People have become sensitized to the presence of certain ingredients that have a bad reputation – some deservedly, some not.
Let’s take a closer look at some of the “controversial” ingredients in dog foods. We have included several ingredients that we’ve seen pet food manufacturers either hype (in the case of ingredients they use) or denigrate (in the case of their rivals’ ingredients). We’re not going to address the hype, pro or con, but just tell you the facts.
Alfalfa
This leguminous plant is a source of fat soluble vitamins A, D, E, and K, and several important minerals. It contains some protein, but not enough to be a major source at the levels used in dog food. Its use in dog food is probably mostly for market appeal. Alfalfa is considered a tonic herb, and has mild laxative and diuretic properties. In dogs with kidney disease, it may be best to avoid alfalfa, since it may contribute to dehydration.
Antioxidants
This seems to be the “additive of the month,” and many dog foods are now specifically listing their content of various antioxidants such as vitamin C, vitamin E, beta-carotene, and so on. While the benefits of antioxidants to humans has not been conclusively demonstrated by studies, what all experts do agree on is that people should eat more fresh fruits and vegetables – the dietary source of many natural antioxidants. Since most of us are feeding primarily heat-processed commercial dog food to our canine friends, and little if any spinach salad, it may indeed be a good idea to supplement those doggy diets with healthy, helpful antioxidants.
Are the amounts now being added to those bags and cans enough to do any good? Well, they won’t hurt anything, but if you’re really serious about a healthy diet, a vitamin C supplement and a nice alpha-tocopherol supplement is probably the way to go. (Alpha-tocopherol is the only one of the eight tocopherols that the body can use as an antioxidant; the others are used by some manufacturers to preserve the food in the bag, that is, outside the body.) Some dogs also love carrots, and if your dog is one of them, that’s a bonus – carrots provide a nice crunchy tooth-cleaning action along with a bunch of beta-carotene.
Canola oil
Poor canola oil has gotten a very bad rap, mainly from a single article that has been widely propagated on the Internet, featuring extensive fear-mongering allegations. The plant from which it comes, rape (Brassica napus), is a member of the mustard family, along with other Brassica siblings such as the eminently edible cabbage, broccoli, turnip, horseradish, and watercress. The correct name for the product is thus rapeseed oil; the word canola derives from “Canadian Oil,” and was substituted many years ago to avoid the unpleasant connotations of “rape.”
Ordinary rapeseed oil contains a high percentage (30-60 percent) of toxic erucic acid, but in the 1970s, rapeseed varieties with a low erucic content were introduced. Canola oil now contains only trace amounts of this compound, if any at all. Canola oil is lower in saturated fat than other plant oils, and higher in monounsaturated fat than any except olive oil. It contains more Omega-3 fatty acids (10-15 percent) than any other plant oil except flaxseed. The major downside is that most canola being grown today is a genetically modified (GM) product.
Corn/ground yellow corn/corn meal
The main corn product used in dog food may be listed as any of these terms. There is nothing wrong with corn per se as an ingredient, as long as it’s free from mold contamination (major manufacturers routinely test incoming batches for the most common fungal toxins). Corn tastes good, and provides bulk, calories, nutrients, and texture to dry dog food. However, there are at least three potential problems with corn and corn products in dog food.
1. Because corn does contain protein (mainly in the gluten), dogs can develop allergies to it; however, this is relatively rare.
2. The presence of corn products (particularly if they’re high on the list of ingredients) may indicate that corn has been used instead of a more expensive alternative. For example, corn gluten meal is a concentrated source of protein that can be substituted for costlier animal protein. It is low in some essential amino acids such as cystine and methionine, but these are then added in a purified form to make up the difference.
3. About one-quarter of the corn produced in the United States today is GM.
Corn gluten meal
This is an extract of the high-protein gluten fraction of the corn kernel. It is usually listed separately from “corn.” In many bargain dry dog foods, corn gluten meal provides a large proportion of the total protein in the food. It can cause allergies in some dogs. Our main objection is when its use displaces higher quality, more digestible forms of protein such as meat.
Chicory, inulin, FOS
These little items are included in dog food to promote “colon health” and its population of “friendly bacteria.” The colon, or large intestine, is the site of water absorption, protein breakdown and absorption, and other important functions. It is definitely important to keep the cells lining the colon happy. These ingredients do provide certain beneficial nutrients as they’re broken down by colonic bacteria. They won’t hurt anything and may actually do at least a little bit of good.
Glucosamine and chondroitin
These anti-arthritis ingredients enjoyed a brief popularity spurt in late 2000, but on the shelves today, few foods include them on their labels. Glucosamine sulfate (or hydrochloride) and chondroitin sulfate are both components of cartilage. The point of taking them orally is to increase their concentrations in the joint (synovial) fluid, thus nourishing the cartilage, which has no direct blood supply and must get its groceries from that fluid.
There has been considerable debate about whether or not these compounds are absorbed into the bloodstream from the gut, and even if they are, if they ever make it into the joint fluid. The upshot seems to be that glucosamine is very well absorbed, chondroitin less so.
While human studies have shown that taking high amounts of glucosamine and chondroitin can be beneficial in arthritic patients – reducing pain and enhancing mobility – here are no studies showing a preventive effect. That is, feeding glucosamine and chondroitin to a normal dog has not been shown to prevent the development of arthritis. Given that the stated purpose for using them in dog food is to “support” or “promote” healthy joints, this claim seems specious. In fact, when I asked a major premium food maker for citations of research supporting their use of these compounds, all the studies they sent were done in people who already had arthritis. Moreover, at the minute levels of these compounds in dog food, it is unlikely that they have much of an effect at all, except to enhance the market appeal of the food.
There is one other sticky fact about glucosamine and chondroitin – they are not approved ingredients, and so far, no manufacturer has petitioned AAFCO to obtain approval. For this reason, when these ingredients first made their appearance in dog food, at least three states promptly slapped “stop sale” orders on the food. This is rather a big deal to the manufacturer, who is temporarily prohibited from selling that food in those states. However, promises and politicking by the manufacturer got the orders lifted. The state officials are waiting for FDA to take a position on the use of these ingredients; meanwhile, most manufacturers appear to have stopped using them.
Soy
The soybean is a very nutritious, high-protein legume that is grown primarily for livestock feed, but is also used in some dog foods. Dogs reportedly lack an enzyme needed to break down part of the carbohydrate content of the bean, and therefore large amounts of soy in the diet may cause gas and flatulence. However, there is not, and never has been, any scientific evidence linking soy to bloat in dogs. Vegetarian dog foods are commonly soy-based, and many dogs do very well on them. Soybeans are relatively high in fat, but “soybean meal” has had the oil and most of the moisture removed. Soy is another agricultural product that has spent a lot of time in a lab – more than half of all soy grown in the United States in 2000 was GM.
Wheat
Like corn, wheat contains gluten, a protein-rich fraction that can cause allergies. Bear in mind, however, that very few dogs ever develop a true food allergy. The vast majority of allergic reactions in dogs is to airborne allergens that the dog inhales, like pollen or dust mites. Most food reactions are due to a food “intolerance,” rather than a real allergy. In that case, wheat is no more likely than any other food ingredient to be at fault.
Yeast
A single-celled fungus, yeast is a tiny powerhouse of protein and B vitamins. If added to the food after the cooking process, it also provides live enzymes that can aid in digestion. Most dogs love the taste of yeast, making it a desirable dog food ingredient. As usual, however, the protein can serve as an allergen in sensitive dogs.
Yucca schidigera
The natural saponins (soap-like compounds) in the yucca, a desert plant with long spiky leaves and waxy white flowers, are thought to have steroid-like anti-inflammatory properties. Yucca has been used for generations by Native Americans and folk healers for both rheumatoid and osteo-arthritis. Again, whether or not a food maker can (or should) include therapeutic doses of yucca in their products is highly debatable. However, yucca is also used in pet food to reduce fecal odor which – much to my pleasant surprise – it does quite well (although it is technically not “approved” for that use).
-by Jean Hofve, DVM
Dr. Jean Hofve is a holistic veterinarian with a private practice in Colorado. Dr. Hofve is also a contributor to Whole Cat Journal.
