There’s no question that older dogs are more vulnerable to various medical conditions than younger ones. Therefore, it might seem reasonable to give your older pet supplements prophylactically. At the very least, you may want to feed your geriatric friend a dog food that has supplements added.
But there’s no reason for a healthy dog, including a healthy older dog, to take supplements. Dog food that has undergone AAFCO feeding trials truly contains everything your pet needs to maintain good health.

Truth be told, supplements can create problems where there hadn’t been any before. For instance, they can interact with a medicine in a way that causes adverse effects—everything from gastrointestinal problems like vomiting and nausea to more serious outcomes that can affect health over the long term. They can also cause side effects by themselves. And sometimes supplements contain contaminants that cause side effects.

At least as important to consider is that, unlike foods and drugs, supplements require no review prior to marketing to test for product efficacy or safety, meaning that a supplement may not do what its manufacturer says it does and, worse still, may be bad for your pet. In fact, while drug manufacturers have to prove their products are safe and effective before putting them on the market, the Food and

Drug Administration must prove a supplement unsafe in order to remove it from the marketplace. With ever-dwindling government funds earmarked for such testing, and thousands of supplements reaching the market today, such an event is unlikely to happen.

Okay, now you know why you don’t need to—and often shouldn’t—give your older dog supplements. But the marketing pressure, not to mention pressure from various websites and chat rooms on the Internet, can make it difficult not to at least consider them.

The three most popular supplements, or supplemental ingredients, for dogs that fall into the “senior” category are antioxidants, glucosamine, and omega-3 fatty acids.


With antioxidants, as health food stores for people go, so goes the pet food aisle. There are literally dozens of dog foods with boosted levels of antioxidants, not to mention antioxidants in the form of supplements. Some dog guardians even give their dogs antioxidants intended for humans, which means those dogs are getting awfully high doses, since dogs tend to weigh significantly less than people.

Even half the amount intended for humans is too much. Among the more popular antioxidants people buy for their pets are vitamins C and E, often with the assumption that extra doses of those nutrients will help stave off cancer and heart disease.

But in the vast majority of cases, there’s no inherent reason to make sure an older dog ingests antioxidants beyond the levels of vitamins C and E already in dog foods. Vitamin C is not even required by dogs (as compared to people, monkeys, and guinea pigs, all of whom do require it in their diet). Its value in dog food is primarily as a preservative.

In fact, at high levels it acts as an oxidant, wreaking metabolic havoc on cells and possibly causing chemical reactions that could potentially contribute to causing diseases such as cancer. It can also increase the risk for certain types of bladder stones.

And too much vitamin E can predispose a dog to excessive bleeding. In addition, antioxidants may be detrimental by interfering with other treatments. For example, they can interfere with the effectiveness of chemotherapy or radiation therapy during cancer treatment.

Keep in mind that even in people, clinical studies have not shown unequivocally that a specific antioxidant confers a particular health effect. That is, scant research has ever indicated that taking x amount of y for a certain period of time prevents disease z.

The large bulk of the evidence comes from epidemiologic studies in which eating patterns were simply observed in large populations. In those kinds of studies, it’s hard to tease out whether it’s a particular antioxidant or some other chemical in the overall diet—or some other aspect of people’s lifestyle—that appears to go hand in hand with good health.

All scientists can do in these cases is make associations rather than prove any cause and effect between a single substance and a particular health outcome. The evidence for any antioxidant’s benefit in dogs is even more tenuous (although there has been some provocative, albeit inconclusive, evidence regarding certain antioxidants to treat signs of the canine version of Alzheimer’s disease—


When it comes to glucosamine, a supplement used to quell arthritis pain, the evidence is a little more compelling, with the emphasis on a little. That is, the science showing any benefit is not nearly as strong as word on the street.

Note that as an ingredient in store-bought food, there will probably never be enough glucosamine to have a therapeutic effect. That’s true even for therapeutic foods you can get only at the doctor’s office. Yes, they are analyzed so that glucosamine levels indicated will be in the food. But most do not reach levels that may have potential therapeutic benefits. Glucosamine must be taken in the form of pills to reach a therapeutic level.

Specifics on choosing glucosamine for an arthritic dog will be addressed, but be aware that even if you do choose to give your arthritic dog glucosamine supplements, whatever it does for him won’t be a drop in the bucket compared to the benefit of helping him get into optimal body condition, meaning helping him to lose weight if he’s overweight. Lifestyle-wise, that’s the number one thing you can do to lessen an arthritic dog’s pain.