They Tested Kibble – Guess What They Found This Time?

Analysis by Dr. Karen Shaw Becker

ultra-trace minerals in kibble

Story at-a-glance -

  • A recently published study has confirmed the presence of relatively high levels of ultra-trace minerals in 49 different brands of dry dog food
  • These minerals include aluminum, chromium, molybdenum, nickel and silica, and their presence in pet food is unregulated
  • Now that we have these results, additional research is needed but unlikely, since it would require inducing toxicity to the point of ill effect in dogs and cats
  • If you’re feeding kibble, the presence of ultra-trace minerals is a minor issue compared to all the major problems inherent in this type of pet food
  • A better option is a nutritionally balanced, species-appropriate diet of fresh food

Recently, researchers at Cornell University College of Veterinary Medicine conducted a study to analyze the “ultra-trace” mineral content in dry dog foods sold in the U.S.1

Whereas “major” and “trace” minerals in pet foods are regulated by the National Research Council (NRC) and the Association of American Feed Control Officials (AAFCO), neither organization regulates ultra-trace minerals — substances that occur in minute amounts in both human and pet foods, and include aluminum, chromium, molybdenum, nickel and silica.2

Study Analyzed 49 Different Dry Dog Foods

For the study, the researchers used 49 samples of different kibbles formulated for dogs at all life stages. You can find the complete list of brands on my Facebook page. The foods came from the Cornell Veterinary Medical Center, local pet food stores, national pet food retailers and grocery stores, and were analyzed within one week of purchase.

The ultra-trace minerals were quantified, normalized to a specific standard, converted to consumption per megacalorie, and compared to values set by the World Health Organization (WHO) for average chronic (daily) human consumption and toxicity. To better compare the different dog food brands, the results were normalized against the manufacturer’s calculated food energy density and expressed as mg/1000 kcal of metabolizable energy (ME).

Results Showed High Levels of Some Ultra-Trace Minerals

The results showed levels of aluminum, chromium and molybdenum concentrations in the tested kibble to be higher than those an average human ingests eating a 2,900-kcal diet on a daily basis.

Chromium was found to be about 30 times higher; and molybdenum was 15 times higher in one case, and above the estimated required value in the remaining foods. Aluminum levels were above daily human intake in 46 of 49 foods, and 38 times higher in one case.

The remaining two ultra-trace minerals, nickel and silica, were at levels that weren’t significantly different when comparing human and dog daily intake.

According to the American Veterinarian, excessive levels of chromium can cause liver damage and gastroenteritis; high levels of nickel can result in gastrointestinal (GI) irritation; and excess silica may play a role in the development of silica “jack-stone” uroliths (bladder stones) in certain breeds.3

Aluminum accumulates in the body and is a known toxin, however, the levels of aluminum hydroxide present in the tested kibble were well below the published dose recommendations for patients with kidney disease (who are routinely given aluminum hydroxide as a phosphorus binding agent).

The American Veterinarian concluded that while the study shows that dogs eating kibble are exposed to higher concentrations of ultra-trace minerals compared to average human consumption, it’s not necessarily harmful (i.e. we simply don’t know), “but the levels … appear safe in dogs.”

Further Study Is Necessary, but Unlikely

The Cornell University researchers’ conclusion:

“Our findings of relatively high ultra-trace mineral concentrations in pet foods which were compared with ultra-trace mineral ranges of total dietary intakes of humans or other species suggest slightly higher exposure in dogs than in humans.

The exact reasons for this finding are unclear but may have to do with the slightly higher metabolic demands of dogs than humans who require fewer calories per kilogram body weight and/or the modest differences in common food ingredients used in the dog food industry compared to foods consumed by humans.

Further study investigating the bioavailability of each mineral and establishing dietary ultra-trace mineral allowance would be ideal for dogs consuming typical dry commercial dog foods.”4

According to Greg Aldrich, Ph.D., president of Pet Food & Ingredient Technology Inc., writing for, the suggested research probably won’t happen “because no one is going to fund it and no one would likely conduct it.” He explains:

“Most of this toxicity work requires that we feed the animals (dogs and cats) a diet in which high levels of these non-nutritional minerals are ingested and produce an ‘effect.’ It is essential that a no-effect level be determined — this implies that an [ill] effect [will] occur, something like organ failure, lesions, tumors, impaired growth, even death.

Today that would be considered unacceptable. So, while we have critics decrying the notion that we’re poisoning our pets with foods that contain these minerals there is real reluctance to determine what a true safe-upper-limit might be.”5

Aldrich also cautions that reports of non-nutritional minerals are often “sensationalized to create alarm in pet owners.” He argues these minerals come into both pet and human food as a natural part of the raw ingredients, and that “no company intentionally adds these to a pet food nor are they being negligent.”

In other words, zero quantities don’t exist, so it’s important for everyone concerned to ask questions about the true origin of the minerals, the methodology used to measure them, their bioavailability, and tolerance levels and/or how their physiological effects may be influenced by other dietary factors.

With regard to bioavailability, Aldrich makes the point that “Mineral present doesn’t equal mineral absorbed. Said another way, many of the earth elements in foods are simply passed through the body unaltered and unutilized.”

When It Comes to Kibble, Ultra-Trace Minerals May Be the Least of Its Problems

What Aldrich fails to acknowledge is there are plenty of other examples of possibly intentional and undoubtedly negligent issues with processed pet food that rightfully cause alarm for pet parents. These range from deceptive labeling and marketing practices, to contamination with euthanasia drugs and antibiotic residues, to dangerously high levels of vitamin D and dangerously low levels of thiamine.

The fact is, the presence of ultra-trace minerals is way down a long list of problems with kibble. As regular readers here know, I recommend ditching dry food altogether in favor of a nutritionally balanced, species-appropriate diet. This means food containing high-quality animal protein, moisture, healthy fats and fiber, with low to no starch content.

A nutritionally balanced raw or gently cooked homemade diet is my top choice for pets, but you should only attempt this if you're committed to doing it right. If you don't want to deal with balancing diets at home, a great alternative is to feed a pre-balanced, commercially available raw or gently cooked food. A freeze-dried/dehydrated diet is second best. Human-grade canned food is a mid-range choice but can be hard to find.

And be sure to incorporate a variety of fresh foods into your dog’s diet, too. Blueberries, chia and hemp seeds in coconut oil, raw pumpkin seeds, fermented vegetables and kefir can provide your furry family member with a variety of nutrition and flavors.