The Three Most Common Supplements for Older Dogs

Should you buy in?


There’s no reason for a healthy dog, even for a healthy older dog, to take supplements. Dog food with a label that says it has undergone feeding trials by AAFCO (Association of American Feed Control Officials) or has been formulated according to AAFCO standards truly contains everything your pet needs to maintain good health. That said, dog supplements comprise a big industry, in all probability accounting for at least $1 or $2 billion of the $60 billion Americans spend each year on their pets. The three most popular for our geriatric canine companions are antioxidants, glucosamine, and omega-3 fatty acids. Is there ever a reason to administer any of these to your aging pal?

Antioxidants. When it comes to antioxidants, as health food stores for people go, so goes the pet food aisle. Not only are there many antioxidant supplements for dogs, there are literally dozens of dog foods with boosted levels of antioxidants, quite often, vitamins C and E. The thinking is that they will help stave off, or treat, cancer and heart disease. Some dog owners are so convinced that they give their dogs antioxidants intended for people, which means their pets are getting quite high doses since dogs tend to weigh significantly less than their human guardians. Even half the amount intended for people is too much.

More to the point, in the vast majority of cases, there’s no inherent reason to see that a dog swallows vitamins C and E beyond the levels already in dog foods. Vitamin C is not even required by dogs (as it is by such species as humans, monkeys, and guinea pigs). Its value in dog food is primarily as a preservative, not as a nutrient. Truth be told, at high levels it acts not as an antioxidant but an oxidant, having the opposite of its intended effect and wreaking metabolic havoc on cells. It could even contribute to chemical reactions that potentially have something to do with the development of diseases like cancer. It can also increase the risk for certain types of bladder stones.

Too much vitamin E can potentially predispose a dog to excessive bleeding. In addition, antioxidants can prove detrimental by interfering with other treatments. For instance, if you give your dog antioxidants while he’s receiving chemotherapy or radiation for cancer in an effort to “boost” his ability to fight the disease, the supplements can actually get in the way of the chemo or radiation doing its job.

Even in people, clinical studies have not shown that a specific antioxidant confers a definite health effect. Scant research has indicated that taking x amount of y for a certain period of time will prevent disease z. The large bulk of evidence comes from epidemiologic studies in which eating patterns were simply observed in large populations and scientists took a stab at trying to tease out whether a particular antioxidant or some other chemical in the overall diet had an impact on health. The evidence for any antioxidant’s benefit in dogs is even more tenuous.

Glucosamine. The evidence for glucosamine — often administered for arthritis pain — is a little more compelling than the evidence for antioxidants, with the emphasis on a little. That is, clinical testing has not shown a benefit that’s nearly as strong as word on the street. But the current thinking among veterinary orthopedists is that in combination with chondroitin sulfate, glucosamine may help protect joint cartilage that is damaged but not yet destroyed and in that way stave off the bone-on-bone contact that causes pain.

Veterinarians often recommend Cosequin or Dasuquin because they are manufactured with good quality control. They are actually combination pills containing both glucosamine and chondroitin. One thing you should know if you plan to give one of them to your dog: it doesn’t work overnight, so don’t administer it for a week or so and then give up because you don’t see any improvement. You need to commit to giving it to your dog for a month and a half to two months — or even longer — and then evaluate whether it’s helping. It doesn’t help every dog, so if it isn’t relieving your dog’s pain or letting him move around more easily after a couple of months, discontinue it and save your money. (For a dog about the size of a Lab, we’re talking a cost that can easily average $40 a month.)

Note that your arthritic dog may not have to take glucosamine forever. Often, a dog will require it for just a finite period of time to give him back the mobility he needs in order to move about with less pain. Some dogs are able to go on and off the supplement every so often.

Note, too, that taking a pill isn’t even a drop in the bucket compared with making sure your dog gets to ideal body weight. Lifestyle-wise, that’s far and away the most important thing you can do to lessen your pet’s arthritis pain.

Omega-3 fatty acids. You’ve no doubt heard of omega-3s — the fatty oils found in oily fish like salmon. Is there any reason to give them to your dog? Perhaps, if he has heart disease. In people, omega-3s help to thin the blood, so to speak. Specifically, they make blood platelets less likely to aggregate, or clump together, and thereby less likely to contribute to blockages in the blood vessels. Dogs, on the other hand, rarely develop such blockages. They more commonly have heart valve malformations that lead to congestive heart failure — the heart ceases to do its job well enough and fluid accumulates in the lungs or abdomen. In addition, dogs with congestive heart failure produce high levels of substances called cytokines, which lead to decreased appetite and also muscle loss (including heart muscle itself).

That’s where omega-3s come in. They can combat muscle loss associated with heart disease. As we said in a recent article on nutrition for dogs with heart disease, Tufts Cummings School’s HeartSmart website ( advises that for every 10 pounds of body weight, a dog should get one gram of fish oil that contains 180 milligrams of EPA (eicosapentaenoic acid) and 120 milligrams of DHA (docosahexaenoic acid). The site also advises choosing a brand from, which does testing for quality. Don’t give your dog fish oil in the form of cod liver oil. It can be toxic in vitamins A and D.


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