Arthritis supplements bought by millions of pet owners for their dogs, cats and horses sometimes skimp on the ingredients the makers claim can help aching paws and aging joints, and some contain high amounts of lead, an independent laboratory found.
Four of the six joint supplements for animals tested by ConsumerLab.com lacked the amounts of glucosamine or chondroitin promised on their labels or had other flaws, such as lead. Wider testing by a trade group of 87 brands found that one-quarter fell short.
Over-the-counter dietary supplements for humans do not have to be proven safe or effective before they are sold, and pills for pets get even less scrutiny.
"There is and there always has been" a quality problem, although many companies do a good job, said Mark Blumenthal of the American Botanical Council, which tracks research on herbal products.
Even when these supplements contain what they claim, there is little evidence that they work, veterinary experts say. A large government study of people with arthritis found that glucosamine and chondroitin did no better than dummy pills in easing mild pain. Testing these supplements on pets is more difficult.
"You can't ask a dog or a cat to give you a subjective impression of how they're feeling after taking the product for several days. They can't say, 'On a scale of 1 to 5, I feel better or worse,'" Blumenthal said.
Giving supplements to an ailing pet can make its owner feel better, though. "The owner shelled out money for the pills and wants to believe they are helping," Blumenthal said.
Up to one-third of dogs and cats in the U.S. are given supplements, a government report estimates. Sales of pet supplements have roughly doubled since 2003, to nearly $1 billion a year in the United States, according to the Nutrition Business Journal. These supplements are sold over the Internet and at pet supply stores and some groceries.
Many pet owners believe they make a difference.
Nicole Albino, who lives in New York City, said her dog Chakka was constantly chewing and licking his knees until her veterinarian recommended glucosamine and chondroitin.
After taking the pills for a year, "he's definitely been licking his knees a lot less," she said. The dog resumed when she ran out of the stuff for a few weeks. "It just seems to help," Albino said.
Few high-quality studies have tested the effectiveness of animal supplements. The Food and Drug Administration says these products are not bound by quality rules for human ones.
In 2007, the FDA asked an expert panel to look into three popular pet supplements — lutein, evening primrose oil and garlic — but the group could not agree on a safe upper limit.
"Many people presume that supplements are safer than drugs, but the reality is that there is very limited safety data on dietary supplements for horses, dogs, and cats," the panel concluded.
That same year, 2007, pet food tainted with melamine sickened and killed thousands of cats and dogs. Melamine can mimic protein in some lab tests, and protein costs much more than melamine.
Similarly, certain substances can fool tests for chondroitin, an expensive joint-supplement ingredient, said Dr. Tod Cooperman, president of ConsumerLab.com. The company tests supplements for manufacturers that want its seal of approval, and publishes ratings for subscribers.
Chondroitin usually comes from pig and cow cartilage, though shark and chicken cartilage also can be used, as well as algae. Glucosamine usually comes from the shells of crabs. It is also sold in chemical forms — something that might surprise people who think of these as "natural" products.
ConsumerLab.com's most recent tests of human joint supplements, released this week along with the pet pill results, found that five out of 21 brands failed to meet quality standards, usually because of too little chondroitin. Four of the six pet supplements tested also failed. One contained only 17 percent of the promised chondroitin.
The National Animal Supplement Council, a trade group in suburban San Diego, found that 28 percent of the 87 brands it tested in April did not contain what was claimed, said council president, William Bookout. The group doesn't name names, but uses the results to help members improve quality control.
"Sometimes a company doesn't even realize they have a problem, or a company can make an honest mistake," Bookout said.
He warns consumers not to expect too much from a pill: "There isn't any magic bullet out there. It is not hip replacement in a bottle."
Dr. Babette Gladstein, a vet who makes house calls for dogs and cats in New York City, said she uses alternative methods but not supplements, because there is not enough proof they work. For overweight pets with bad knees, she advises healthy diets and weight loss.
"I teach the clients how to massage their animal, how to stretch their animal, how to get better range of motion" Gladstein said.
For people who do give pets joint supplements, experts suggest:
— Check with a vet beforehand to see if it is safe.
— Look for a seal of approval by an independent lab or organization.
— Keep a log of your pet's behavior, such as its ability to go up and down stairs, before and after supplement use so you can tell if it helps.
— Don't exceed recommended doses. Too much can cause loose stools and gas pains.
— Watch for shellfish allergies if using glucosamine derived from seafood.
— Avoid versions in salt form (NaCl, or sodium chloride on the label) if the animal has high blood pressure.
— Do not use glucosamine or chondroitin with blood thinners, such as heparin or aspirin, unless a vet advises it. Some breeds, such as Doberman pinschers, are predisposed to bleeding problems.
On the Net:
National Academy of Sciences report on supplements for animals: http://tinyurl.com/clmfff
American Botanical Council: http://tinyurl.com/lddnqq
National Animal Supplement Council: http://www.nasc.cc