Controversy is swirling around recent tests on a sample of Nutro dry cat food, which detected what two leading veterinarians consider worrisome levels vitamin D3.

The veterinarians recommended additional testing to confirm the finding, but also told the blood work performed on the sick feline that ate the food is not consistent with vitamin D toxicity. The non-profit group that hired a private lab to test the food disagrees and calls the Nutro sample one of the most deadly pet foods we've tested to date.

Nutro disputes that assessment and the labs findings, saying tests it performed on the same lot of cat food revealed the product is safe.

An analysis performed earlier this month on a sample of Nutro Chicken Meal and Rice cat food -- identified as lot number 09 01 10 11:03 and purchased in February 2010 -- revealed the product contained 197 IU/g of vitamin D3, according to the Pet Food Products Safety Alliance (PFPSA).

I was shocked by these results, said Don Earl, founder of PFPSA. The vitamin D was so high in this sample that I called the lab to see if that was really what they meant. That level is off the chart.

Earl said he hired NPA Laboratories in California to analyze the sample for vitamin D when he learned a healthy, one-year-old, indoor male cat was on deaths door after eating the Nutro food for five days. He suspected high levels of vitamin D might be the culprit for the felines illness, which he said included vomiting, diarrhea, weakness to the point of being unable to stand and considerable pain.

I look at things that should be in the food to see if they are in the wrong amounts and if the ingredients and supplements are formulated correctly, Earl said, adding that previous tests on this sample of Nutro food detected what he called high levels of calcium. Vitamin D is an essential vitamin in the right amount, but its toxic in the wrong amount. And this is a huge amount.

More evidence needed

Two veterinarians contacted by about the test results agreed the levels of vitamin D3 in the sample are concerning and should be further investigated. But they cautioned Earl and worried pet owners not to jump to conclusions based on one test.

I appreciate what he (Earl) is doing, said Dr. Justine Lee, emergency critical care veterinary specialist and associate director of veterinary services for the Pet Poison Helpline (PPH). I commend him for advocating for healthy pet food. But it needs to be done in a way that is accurate and we have to make sure the information is medically and scientifically accurate.

Dr. Lee and her colleague, Dr. Lynn Hovda, director of Veterinary Services and toxicologist with PPH, said another sample of this Nutro cat food should be tested by a certified lab to verify NPA Laboratories results.

A single sample submitted at a single point in time is certainly cause for concern, but it needs to be scientifically verified, the veterinarians said, adding whatever lab tests the food should sign and notarize a statement that confirms its analyzing the sample for Vitamin D3.

On its Certificate of Analysis, NPA Laboratories stated it tested the Nutro cat food for Vitamin D. contacted the lab, which confirmed it tested the sample for vitamin D3. And the levels of vitamin D3 the lab reported in the Nutro sample are troublesome, Drs. Lee and Hovda said.

The fact that cholecalciferol (Vitamin D3) is the Vitamin D source in the sample is worrisome as D3 is generally associated with a higher incidence of toxicity than ergocalciferol (Vitamin D2), they told us. In the world of toxicology, Vitamin D3 toxicity is associated with a total amount ingested based on the animals body weight (IU ingested/kg body weight). learned the cat that ate the Nutro food tested weighs 12 pounds -- or 5.45 kilograms (kg).

Assuming the cat ate 2 ounces of food (56 grams which is a fairly normal amount) and that the cholecalciferol level is 197/gram of food, (the) total amount ingested would be 11032 IU /5.45 kg or 2024 IU cholecalciferol/kg BW, Drs. Hovda and Lee wrote in response to our questions. If you assume the cat ate 4 ounces of food and that the cholecalciferol level is 197 IU/gram of food, the total amount ingested would be 22064 IU/5.45 kg or 4048 IU cholecalciferol/kg BW.

High doses of vitamin D3 can cause various health problems in cats and dogs, the veterinarians said.

Ingested doses of 4000 to 5000 IU/kg body weight of D3 are associated with mild clinical signs such as anorexia, lethargy, and vomiting, they said. Blood work changes (serum chemistry) occur but become very striking when the ingested amount is 15,000 to 20,000 IU/kg body weight.

At this level, the calcium level becomes very elevated and severe and may be irreversible or non-responsive to treatment, they added. The likelihood of depositing calcium in various body organs (kidney, heart, etc.) increases, resulting in severe, acute kidney failure which often times can result in chronic kidney changes. This would be the same for both dogs and cats.

But the blood work performed on the cat that ate this sample of Nutro food does not indicate any type of vitamin D toxicity, Drs. Hovda and Lee told us.

This cat has a high white blood cell count, Dr. Lee said. This type of count is almost always seen with feline leukemia. Any veterinarian looking at this blood work would agree that its not consistent with vitamin D3 toxicity.

She added: Weve been contacted by veterinarians reading various pet food forums about this (test result) and weve told them that the blood work is not consistent with vitamin D toxicity.

Earl disagrees

Earl, who is not a veterinarian but has done considerable research on this issue, respectfully disagrees.

The information that I found in the Hazardous Substances Data Bank had clinical information on vitamin D toxicity that was an across-the-board match for what was found in the vets lab work, he told us.

On his organizations Web site, Earl cites various studies and reports that support his contention. And he doesnt mince any words about a link between Nutros cat food, the felines illness, and vitamin D toxicity.

The pet owner's cat nearly died after eating the food for 5 days and the symptoms appeared to be consistent with toxic levels of Vitamin D, he states, adding the cats condition gradually improved after it stopped eating the Nutro food. Based on the above, unbiased, peer reviewed, independent research, this food is one of the most deadly has tested to date. No reasonable person, of average intelligence, could view the research, data, circumstances and symptoms, without reaching the inevitable conclusion this food was the sole cause of this pet's near death experience.

Asked what action Nutro should take in response to these latest test results, Earl said: They need to recall this food. Its deadly.

Drs. Hovda and Lee arent convinced that Nutro needs to take such drastic measures. But they encouraged the pet food giant to address this issue.

We are neither opposed to nor in favor of Nutro pet foods, but hope that the company responds in a professional and courteous manner, they said. Mistakes can be made, as we have learned before, and this may be due to calculation errors or mixing errors; if this occurs, obviously we feel that the company should thoroughly investigate this and take responsibility to evaluate this.

Nutro: It's safe

In a written statement, Nutro told us it investigated this matter and determined the cat food is safe.

As a result of a consumer inquiry regarding possible elevated levels of Vitamin D in one lot of NUTRO NATURAL CHOICE Chicken Meal and Rice cat food, we sent a retained sample -- taken at our factory from this specific lot -- for independent testing, the company wrote. The test results confirm our previous analysis that the Vitamin D levels are well within AAFCO (Association of American Feed Control Officials) requirements and achieve the target Vitamin D level designed for this food.

NUTRO NATURAL CHOICE cat food does not contain elevated levels of Vitamin D, the statement added.

Nutro told us today that it sent its retained sample of cat food to a company called Covance, which it claims has expertise in Vitamin D analysis.

They performed testing for Vitamin D3 and found the level to be 566 IU/kg, which is 628 IU/kg for dry matter, said the companys Corporate Communications Manager, Julie Lawless. The AAFCO minimum for cat adult maintenance is 500 IU/kg and the maximum is 10,000 IU/kg for dry matter.

Lawless also told us the company ran routine tests on the food the cats owner submitted to Nutro. That sample, however, was not analyzed for vitamin D because the cats blood work -- and conversations with the owners veterinarian -- did not indicate the feline had a vitamin D toxicity problem, Lawless said.

Asked if the company would post its test results, Lawless said: We have provided the lab results directly to the consumer.

In its written statement, Nutro disputed Earls findings and the conclusions he reached about the companys food.

Claims of elevated levels of Vitamin D are being reported on the website of the Pet Food Product Safety Alliance (PFPSA), the company said. Our test results clearly indicate that PFPSAs information is incorrect. In addition to the test results, a number of facts question the validity of the PFPSA claims. Conversations with the consumers own veterinarian did not indicate that food was the cause of the cats illness.

Nutro also said the cats blood work did not show the feline had vitamin D toxicity.

Blood test results presented on the website are not consistent with a diagnosis of a cat that has been consuming elevated levels of Vitamin D, the company said.

Nutro also claims its food is safe and did not play a role in the cats illness.

At Nutro, quality and safety are our most important priorities. We stand by the safety of our food. The consumers cat is now in good health and we are gratified that our food did not contribute to its recent illness. attempted to interview the cats owner for this story, but she declined.

We also contacted the U.S. Food and Drug Administration about these latest test results on Nutros cat food. Earl told us he reported the findings to the agency, but said the FDA didnt seem interested because he didnt have the bag the food came in.

A spokeswoman for the FDAs Center for Veterinary Medicine said she couldnt discuss an individual's FDA consumer complaint with us. Thats private, confidential information, said spokeswoman Laura Alvey.

Meanwhile, Earl said he still has some of the Nutro cat food his organization tested and is willing to share it with anyone who wants to run another independent analysis.

What I'd rather see, though, is if someone could find unopened bags close to that lot date and test those instead, he said. Unfortunately, opened bags always seem to generate unclean hands arguments.

If had suites of chrome and glass offices, and a 7-figure budget, we could do things I only wish we could do now, he added. As things are, about the best we can do is put the puzzle pieces together and hope someone with better resources will take it to the next level. I'm always glad to work with fellow travelers.