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Malden C. Nesheim
Malden Nesheim, PhD, is a professor and provost emeritus of Cornell University.
Wellness: Food & Nutrition
Stores are selling more and more dog foods labeled “natural,” “human grade” and “organic,” and the industry considers them to be the hot new trend. But what can these words mean?
Because the government has never bothered to define “natural” for human foods, this word essentially means anything the manufacturer says it does. For pet foods, however, the Association of American Feed Control Officials (AAFCO) has an official definition:
Natural: A feed or ingredient derived solely from plant, animal or mined sources, either in its unprocessed state or having been subject to physical processing, heat processing, rendering, purification, extraction, hydrolysis, enzymolysis or fermentation, but not having been produced by or subject to a chemically synthetic process and not containing any additives or processing aids that are chemically synthetic except in amounts as may occur unavoidably in good manufacturing processes.
Got that? You can render or extrude a pet food to mush, but it’s “natural” if you haven’t added anything synthetic—unless you had to. AAFCO also says that “natural” must not mislead; if it appears on the label, every ingredient in the product must meet the definition. But even AAFCO knows this is impossible. Pet food companies typically buy vitamins, minerals and other additives from factories overseas, where, as we learned in last year’s pet food recalls, quality controls are sometimes nonexistent.
We do not see too many claims about human-grade ingredients on package labels, mainly because AAFCO does not have an official definition of the term. Without an approved AAFCO definition, an ingredient or term is not supposed to be used on pet food labels. AAFCO says “human-grade” is false and misleading, and constitutes misbranding, unless every ingredient in the product—and every processing method—meets FDA and USDA requirements for producing, processing and transporting foods suitable for consumption by humans, and every producer of the ingredients is licensed to perform those tasks. Few pet food companies can meet these criteria.
But AAFCO’s unease does not stop pet food makers from using the term, particularly because larger legal concepts appear to be on their side. In 2007, a case against The Honest Kitchen led the Ohio courts to rule that the company had a constitutional right to truthful commercial free speech, and could use “human-grade” on its labels. The Honest Kitchen advertises on its website that it is “the only pet food manufacturer in the United States to have proven to the Federal FDA that every ingredient it uses in its products are suitable for human consumption.”
Only a few other companies make human-grade claims on their food labels, but many use the term freely in their in-store materials and website advertising. For example, Newman’s Own Organics presents this information in a question-and-answer format: “Q: Does Newman’s Own Organics use human grade materials? Why isn't that written on the bag? A: Newman’s Own Organics organic pet food uses human grade and fit for human consumption ingredients such as natural chicken and organic grains. The AAFCO Board … actually prohibits the printing of ‘Human Grade’ on pet food packaging.”
That brings us to organics. For human foods, “organic” has a precise meaning defined by the USDA’s National Organic Program (NOP). To be certified as organic, plant ingredients in pet foods must be grown without pesticides, artificial fertilizers, genetic modification, irradiation or sewage sludge. Animal ingredients must come from animals raised on organic feed, given access to the outdoors, and not treated with antibiotics or hormones. Producers must be inspected to make sure they adhere to these standards. (Note: They do, but whether the standards are good enough is a separate question.)
In 2002, the NOP did not include pet foods in the organic rules because it could not figure out how to do so. In 2005, it appointed a pet food task force to handle the figuring. A year later, this group quite sensibly recommended that organic standards for humans be applied to pet foods. But, the NOP cautioned, “these requirements will present challenges for pet food manufacturers, especially sourcing non-genetically engineered ingredients.” No kidding. More than 90 percent of soybeans and half the corn grown in United States now come from genetically modified varieties.
Because the NOP has not yet adopted the task force recommendations, organic pet foods are in regulatory limbo, leaving AAFCO with the unenviable task of explaining how to label “organic” pet foods. AAFCO says that (1) under NOP rules, pet foods may not display the USDA organic seal or claim that they were produced according to organic standards. But (2), NOP also says labeling terms such as “100% organic,” “organic” or “made with organic ingredients” on pet foods may be truthful and do not imply organic production or certification. Therefore (3), AAFCO recommends that labeling rules for human foods apply to pet foods.
What to make of this? We think the statements imply that nobody is going to make a fuss about organic claims on pet foods, even when some, most or even all of their ingredients are not really organic.
Mind you, following the rules for organic labeling is complicated (see chart). Even so, you can go into a pet food store and easily find products that violate these standards. Our favorite: companies calling themselves organic when their foods do not contain a single organic ingredient. They get away with this because the USDA, unlike the FDA, doesn’t regulate company names.
At the moment, “organic” means something for human food; it does not mean much for pet food. We worry that the USDA doesn’t think pet foods are important enough to care what is said on their labels. This may be a good situation for unscrupulous marketers, but we do not think it is good for pet food companies, buyers of pet foods or the organic industry itself. If products are labeled organic, they should follow the rules for organic certification—all of them. If they do not, the organic standards won’t mean much.
Organic foods command higher prices because people believe in the integrity of the standards. If the standards are not met, why pay more? If the USDA allows weaker standards for pet foods, we wonder whether it will continue to defend strong organic standards for human foods. Without strong standards, organics are just about marketing, not production methods. We think everyone—pet food makers, the USDA, AAFCO and the readers of Bark—should demand nothing less than the highest possible standards for natural, human-grade and organic claims on dog foods.
Wellness: Food & Nutrition
Stores are selling more and more dog foods labeled “natural,” “human grade” and “organic,” and the industry considers them to be the hot new trend. But what can these words mean?
Because the government has never bothered to define “natural” for human foods, this word essentially means anything the manufacturer says it does. For pet foods, however, the Association of American Feed Control Officials (AAFCO) has an official definition:
Natural: A feed or ingredient derived solely from plant, animal or mined sources, either in its unprocessed state or having been subject to physical processing, heat processing, rendering, purification, extraction, hydrolysis, enzymolysis or fermentation, but not having been produced by or subject to a chemically synthetic process and not containing any additives or processing aids that are chemically synthetic except in amounts as may occur unavoidably in good manufacturing processes.
Got that? You can render or extrude a pet food to mush, but it’s “natural” if you haven’t added anything synthetic—unless you had to. AAFCO also says that “natural” must not mislead; if it appears on the label, every ingredient in the product must meet the definition. But even AAFCO knows this is impossible. Pet food companies typically buy vitamins, minerals and other additives from factories overseas, where, as we learned in last year’s pet food recalls, quality controls are sometimes nonexistent.
We do not see too many claims about human-grade ingredients on package labels, mainly because AAFCO does not have an official definition of the term. Without an approved AAFCO definition, an ingredient or term is not supposed to be used on pet food labels. AAFCO says “human-grade” is false and misleading, and constitutes misbranding, unless every ingredient in the product—and every processing method—meets FDA and USDA requirements for producing, processing and transporting foods suitable for consumption by humans, and every producer of the ingredients is licensed to perform those tasks. Few pet food companies can meet these criteria.
But AAFCO’s unease does not stop pet food makers from using the term, particularly because larger legal concepts appear to be on their side. In 2007, a case against The Honest Kitchen led the Ohio courts to rule that the company had a constitutional right to truthful commercial free speech, and could use “human-grade” on its labels. The Honest Kitchen advertises on its website that it is “the only pet food manufacturer in the United States to have proven to the Federal FDA that every ingredient it uses in its products are suitable for human consumption.”
Only a few other companies make human-grade claims on their food labels, but many use the term freely in their in-store materials and website advertising. For example, Newman’s Own Organics presents this information in a question-and-answer format: “Q: Does Newman’s Own Organics use human grade materials? Why isn't that written on the bag? A: Newman’s Own Organics organic pet food uses human grade and fit for human consumption ingredients such as natural chicken and organic grains. The AAFCO Board … actually prohibits the printing of ‘Human Grade’ on pet food packaging.”
That brings us to organics. For human foods, “organic” has a precise meaning defined by the USDA’s National Organic Program (NOP). To be certified as organic, plant ingredients in pet foods must be grown without pesticides, artificial fertilizers, genetic modification, irradiation or sewage sludge. Animal ingredients must come from animals raised on organic feed, given access to the outdoors, and not treated with antibiotics or hormones. Producers must be inspected to make sure they adhere to these standards. (Note: They do, but whether the standards are good enough is a separate question.)
In 2002, the NOP did not include pet foods in the organic rules because it could not figure out how to do so. In 2005, it appointed a pet food task force to handle the figuring. A year later, this group quite sensibly recommended that organic standards for humans be applied to pet foods. But, the NOP cautioned, “these requirements will present challenges for pet food manufacturers, especially sourcing non-genetically engineered ingredients.” No kidding. More than 90 percent of soybeans and half the corn grown in United States now come from genetically modified varieties.
Because the NOP has not yet adopted the task force recommendations, organic pet foods are in regulatory limbo, leaving AAFCO with the unenviable task of explaining how to label “organic” pet foods. AAFCO says that (1) under NOP rules, pet foods may not display the USDA organic seal or claim that they were produced according to organic standards. But (2), NOP also says labeling terms such as “100% organic,” “organic” or “made with organic ingredients” on pet foods may be truthful and do not imply organic production or certification. Therefore (3), AAFCO recommends that labeling rules for human foods apply to pet foods.
What to make of this? We think the statements imply that nobody is going to make a fuss about organic claims on pet foods, even when some, most or even all of their ingredients are not really organic.
Mind you, following the rules for organic labeling is complicated (see chart). Even so, you can go into a pet food store and easily find products that violate these standards. Our favorite: companies calling themselves organic when their foods do not contain a single organic ingredient. They get away with this because the USDA, unlike the FDA, doesn’t regulate company names.
At the moment, “organic” means something for human food; it does not mean much for pet food. We worry that the USDA doesn’t think pet foods are important enough to care what is said on their labels. This may be a good situation for unscrupulous marketers, but we do not think it is good for pet food companies, buyers of pet foods or the organic industry itself. If products are labeled organic, they should follow the rules for organic certification—all of them. If they do not, the organic standards won’t mean much.
Organic foods command higher prices because people believe in the integrity of the standards. If the standards are not met, why pay more? If the USDA allows weaker standards for pet foods, we wonder whether it will continue to defend strong organic standards for human foods. Without strong standards, organics are just about marketing, not production methods. We think everyone—pet food makers, the USDA, AAFCO and the readers of Bark—should demand nothing less than the highest possible standards for natural, human-grade and organic claims on dog foods.
Wellness: Food & Nutrition
Update on calorie labeling standards
In the wake of the 2007 recalls, Congress ordered the FDA to work with state regulators and the industry to develop national standards for pet food processing and labeling. We’d like to go on record right away as seconding the need for better regulation of pet foods.
We were pleased when the FDA announced a hearing on pet food labeling standards for May 13, 2008. We asked to attend the hearings, but when we didn’t get a reply from the FDA, we decided not to bother. We were surprised that we didn’t hear anything much about the hearings afterwards, but Christie Keith of PetConnection.com explained why. Hardly anyone came, she said, and the FDA shut down the hearings after 90 minutes.
We did see a handful of short press accounts, but these covered only one item of testimony: the American Veterinary Medical Association called for calorie counts to be listed on pet food labels. This proposal hardly seems groundbreaking, but the Pet Food Institute, the trade association for pet food manufacturers, vigorously opposes it. So calorie labeling for pet foods, just as it does for human foods, makes news.
Because obesity is now as much of a health issue for pets as it is for humans, we can hardly believe that calories are not required to be listed on pet food labels. The Association of American Feed Control Officials (AAFCO), the group that oversees what is printed on the labels, says that listing calories is voluntary unless the product claims to be “lite.” If companies do list calories, these “shall be separate and distinct from the Guaranteed Analysis and shall appear under the heading Calorie Content.” In our experience, some pet food companies reveal calorie counts on their labels or websites, but most do not.
In the United States, roughly 60 percent of the human population is overweight, and obesity is a worldwide problem. In developing as well as industrialized countries, as many people are overweight as suffer from extreme malnutrition. Pets have joined this trend. Perhaps up to 60 percent of dogs in America also weigh more than is healthy for them. Just as with people, being overweight raises the chance that pets will develop diabetes, heart disease, joint problems, urinary tract disorders and cancers. Most important, thinner dogs live longer. But owners may not even be aware that their dogs are overweight. Surveys have found that veterinarians consider 44 percent of the dogs they see in their practices to be overweight, but only 17 percent of owners view their pets as anything but normal.
The basic explanation for obesity trends in humans and dogs is the same: eating more calories than are expended in physical activity. For dogs, the fattening trend is explained not only by reduced activity, but also by the increasing use of high-calorie dry pet foods as well as treats. Premium dog foods, for example, are deliberately made to be highly concentrated in calories so the animals won’t have to eat as much to satisfy their appetites and will produce less poop. Treats may not look calorific, but they have calories, and sometimes lots of calories. If owners don’t take treats into account in feeding regimens, dogs can quickly pack on the pounds.
Calorie labels would seem to be an obvious way to address this problem. Other veterinary groups also have called on AAFCO to require calorie labeling. In January of this year, the AAFCO pet food committee agreed to look into the matter. Like most such committees, this one will be doing a thorough study that is likely to take years. In the meantime, the Pet Food Institute opposes calorie labels on the grounds that they are unnecessary and will not prevent obesity in pets.
We are baffled by this stance, since it seems so consumer unfriendly. Owners are totally responsible for the food intake of their pets, but figuring out how much food a dog needs is a real challenge. Dogs vary in their calorie needs. Some dogs regulate their body weight well and will not become overweight even when given continuous access to food; others are gluttons and will overeat in such situations. The feeding directions on pet foods offer general guidelines but cannot account for a particular animal’s activity pattern or disposition. And then there are the mysteries of calories in treats; you have no way of knowing how many each has.
The only way to know for sure that your dog is gaining weight is to weigh him regularly. If he is, you need to feed him less and exercise him more. Feeding less is also not so easy to do, because the number of calories your dog needs is tricky to figure out. Veterinarians determine calorie needs using a formula based on weight and expected activity, but these needs are not in direct proportion to body weight (the formula involves a fractional exponent). Smaller dogs need more calories to maintain the right weight for their size than do larger dogs. Without a clear idea of calorie requirements, you have to adjust food intake by trial and error. Our conclusion: More information about calories could help.
Will calorie labeling eliminate obesity in pets? Of course not, but it could be useful, especially if accompanied by information about the calorie needs of dogs based on size, age, condition and activity levels. We think that the time has come for calorie labeling of pet foods and treats. And we cannot think of a single good reason not to do it.
This exactly parallels the situation in New York City, where the Health Department wants fast food outlets to post calorie information on menu boards. Surprise! The New York Restaurant Association (NYRA) strongly opposes this measure for now-familiar reasons: unnecessary and useless. Although the NYRA still is fighting the measure, restaurant chains must post calorie information. For many customers, including us, the information is a revelation. Our favorite example so far: a blueberry-pomegranate smoothie that sounded wonderfully healthy until we saw its 1,100 calorie count. No wonder the NYRA doesn’t want customers to know such things.
So let’s get those calories onto the labels of commercial pet foods as well as onto treat packaging. Let your veterinarian, AAFCO and the FDA know that you want calories revealed. Use those customer call numbers and website addresses on package labels to ask pet food and treat companies to give you the calorie counts. We think calorie labeling will be required eventually, but we’d like to see it come sooner rather than later.
Wellness: Food & Nutrition
Update on calorie labeling standards
In the wake of the 2007 recalls, Congress ordered the FDA to work with state regulators and the industry to develop national standards for pet food processing and labeling. We’d like to go on record right away as seconding the need for better regulation of pet foods.
We were pleased when the FDA announced a hearing on pet food labeling standards for May 13, 2008. We asked to attend the hearings, but when we didn’t get a reply from the FDA, we decided not to bother. We were surprised that we didn’t hear anything much about the hearings afterwards, but Christie Keith of PetConnection.com explained why. Hardly anyone came, she said, and the FDA shut down the hearings after 90 minutes.
We did see a handful of short press accounts, but these covered only one item of testimony: the American Veterinary Medical Association called for calorie counts to be listed on pet food labels. This proposal hardly seems groundbreaking, but the Pet Food Institute, the trade association for pet food manufacturers, vigorously opposes it. So calorie labeling for pet foods, just as it does for human foods, makes news.
Because obesity is now as much of a health issue for pets as it is for humans, we can hardly believe that calories are not required to be listed on pet food labels. The Association of American Feed Control Officials (AAFCO), the group that oversees what is printed on the labels, says that listing calories is voluntary unless the product claims to be “lite.” If companies do list calories, these “shall be separate and distinct from the Guaranteed Analysis and shall appear under the heading Calorie Content.” In our experience, some pet food companies reveal calorie counts on their labels or websites, but most do not.
In the United States, roughly 60 percent of the human population is overweight, and obesity is a worldwide problem. In developing as well as industrialized countries, as many people are overweight as suffer from extreme malnutrition. Pets have joined this trend. Perhaps up to 60 percent of dogs in America also weigh more than is healthy for them. Just as with people, being overweight raises the chance that pets will develop diabetes, heart disease, joint problems, urinary tract disorders and cancers. Most important, thinner dogs live longer. But owners may not even be aware that their dogs are overweight. Surveys have found that veterinarians consider 44 percent of the dogs they see in their practices to be overweight, but only 17 percent of owners view their pets as anything but normal.
The basic explanation for obesity trends in humans and dogs is the same: eating more calories than are expended in physical activity. For dogs, the fattening trend is explained not only by reduced activity, but also by the increasing use of high-calorie dry pet foods as well as treats. Premium dog foods, for example, are deliberately made to be highly concentrated in calories so the animals won’t have to eat as much to satisfy their appetites and will produce less poop. Treats may not look calorific, but they have calories, and sometimes lots of calories. If owners don’t take treats into account in feeding regimens, dogs can quickly pack on the pounds.
Calorie labels would seem to be an obvious way to address this problem. Other veterinary groups also have called on AAFCO to require calorie labeling. In January of this year, the AAFCO pet food committee agreed to look into the matter. Like most such committees, this one will be doing a thorough study that is likely to take years. In the meantime, the Pet Food Institute opposes calorie labels on the grounds that they are unnecessary and will not prevent obesity in pets.
We are baffled by this stance, since it seems so consumer unfriendly. Owners are totally responsible for the food intake of their pets, but figuring out how much food a dog needs is a real challenge. Dogs vary in their calorie needs. Some dogs regulate their body weight well and will not become overweight even when given continuous access to food; others are gluttons and will overeat in such situations. The feeding directions on pet foods offer general guidelines but cannot account for a particular animal’s activity pattern or disposition. And then there are the mysteries of calories in treats; you have no way of knowing how many each has.
The only way to know for sure that your dog is gaining weight is to weigh him regularly. If he is, you need to feed him less and exercise him more. Feeding less is also not so easy to do, because the number of calories your dog needs is tricky to figure out. Veterinarians determine calorie needs using a formula based on weight and expected activity, but these needs are not in direct proportion to body weight (the formula involves a fractional exponent). Smaller dogs need more calories to maintain the right weight for their size than do larger dogs. Without a clear idea of calorie requirements, you have to adjust food intake by trial and error. Our conclusion: More information about calories could help.
Will calorie labeling eliminate obesity in pets? Of course not, but it could be useful, especially if accompanied by information about the calorie needs of dogs based on size, age, condition and activity levels. We think that the time has come for calorie labeling of pet foods and treats. And we cannot think of a single good reason not to do it.
This exactly parallels the situation in New York City, where the Health Department wants fast food outlets to post calorie information on menu boards. Surprise! The New York Restaurant Association (NYRA) strongly opposes this measure for now-familiar reasons: unnecessary and useless. Although the NYRA still is fighting the measure, restaurant chains must post calorie information. For many customers, including us, the information is a revelation. Our favorite example so far: a blueberry-pomegranate smoothie that sounded wonderfully healthy until we saw its 1,100 calorie count. No wonder the NYRA doesn’t want customers to know such things.
So let’s get those calories onto the labels of commercial pet foods as well as onto treat packaging. Let your veterinarian, AAFCO and the FDA know that you want calories revealed. Use those customer call numbers and website addresses on package labels to ask pet food and treat companies to give you the calorie counts. We think calorie labeling will be required eventually, but we’d like to see it come sooner rather than later.
Wellness: Health Care
Recall Follow-up
For the last year or so, we have been working on a book about pet food, What Pets Eat, to be published by Harcourt late in 2009. One of the pleasures of a long-term project like this is the time to follow digressions wherever they lead. Last year’s (2007) massive pet food recall was so much of a diversion that it resulted in a spin-off publication—Pet Food Politics:Chihuahua in the Coal Mine —scheduled for release this September by University of California Press.
The recall made us especially curious about the role of melamine, the substance responsible for kidney failure in pets eating food that supposedly contained wheat gluten. Just a glance at the chemical structure of melamine shows that it is high in nitrogen, a nutrient usually obtained from protein. This made us suspect that melamine must have been added deliberately to boost the apparent amount of protein in wheat gluten, because methods that measure the amount of protein in animal feed count nitrogen, not protein itself. Our suspicions were confirmed. The toxic “wheat gluten” turned out to be wheat flour laced with melamine.
But why would melamine harm cats and dogs? A quick search for studies of melamine toxicity turned up several performed on rats and mice, but just one on dogs (which dated from 1945).These studies gave the impression that melamine was not very toxic except at extremely high doses. Furthermore, the kidneys of animals who had eaten the contaminated food contained odd crystals that did not look like crystals of melamine.These turned out to be formed from complexes of melamine and one of its by-products, cyanuric acid. Even so, researchers and federal officials were puzzled. They had not heard of associations of melamine or cyanuric acid with kidney failure.
Really? Our Internet search turned up a brief and not particularly informative abstract of a 1960s study on melamine toxicity in sheep.We thought we needed to look at the entire paper, and found it and others in old bound journals in the Cornell library. These decades-old studies demonstrated that melamine is quite toxic, and causes kidney-related symptoms in animals at doses nearly identical to those reported in contaminated pet food. The studies were designed to test the idea that, because melamine nitrogen is far less expensive than protein nitrogen, melamine might have two useful purposes: (1) as an honest feed additive for ruminant animals, whose microorganisms can convert nonprotein nitrogen to amino acids, and (2) as a dishonest adulterant that makes feed test as though it contains more protein than it really does.
By following other leads,we also found references to relevant studies from the early 1980s in Italian journals that we had to request through interlibrary loan. These showed that melamine was so frequently used for fraudulent purposes in the 1980s that Italian scientists developed a test for it. They used the test to show that melaminna had been used to adulterate more than half the samples of fish meal they examined.
Most of the early information about melamine toxicity came from attempts to use it as a drug or nutrient. In the 1940s, investigators explored its potential as a canine diuretic. To follow what comes next, pay attention to the size of the melamine dose in milligrams per kilogram (mg/kg) of body weight, and recall that a kilogram is 2.2 pounds. The 1945 study showed that at a dose of about 120 mg/kg, dogs excreted crystals in their urine but otherwise did fine. In the 1960s, investigators used cyanuric acid (which is 32 percent nitrogen) to feed ruminant animals, and observed no problems even at high doses.Wouldn’t melamine (66.6 percent nitrogen) work even better?
A South African scientist fed daily doses of about 250 mg/kg to sheep, but most animals refused food and lost weight, and some of them died. Another South African investigator gave melamine doses to a single sheep, starting with 2,600 mg/kg. At such high doses, the sheep died within a few days from kidney damage, and the investigators could see crystals of melamine hanging from the animal’s prepuce. Lower doses of melamine caused sheep to stop eating, especially if their water intake was restricted. These studies suggested that a dose of about 250 mg/kg kills some— but not all—sheep over time.So, by 1968, melamine was known to induce kidney damage when fed to sheep over prolonged periods. Ten years later, American investigators tested melamine in cattle and found that a dose of about 100 mg/kg caused four out of six steers to refuse feed.
We think these studies are highly relevant to the pet food situation. The FDA reported that melamine could have accounted for 10 percent of the weight of the false wheat gluten, and the false wheat gluten could have accounted for as much as 10 percent of the weight of the pet food. If so, 100 grams—about 3 ounces—of pet food could have contained as much as a gram (1,000 milligrams) of melamine, and an average cat or small dog could have eaten an amount close to the 250 mg/kg level that proved toxic to sheep in the 1960s.
Recently, investigators from Georgia and the University of California, Davis, have shown that much smaller amounts of melamine can form crystals if cyanuric acid is also present. In cats, doses as low as 32 mg/kg each of melamine and cyanuric acid caused crystallization and kidney blockage.
We were surprised that neither the university or FDA veterinarians involved in the melamine investigations knew about this earlier work, but we think we can guess why. Papers in international journals are not readily accessible on the Internet, and the old animal feed literature is not likely to be studied these days.We had to discover the papers the old-fashioned way, by going to the library in person, sifting through reference lists, following up leads that sometimes required interlibrary loans and pursuing the reference trail back to its origins.We had the interest and time to pursue these questions. For the veterinarians and FDA officials caught up in the heat of the recall, a trip to the library might have seemed like a luxury they could ill afford.
We can’t say whether earlier suspicion of melamine would have hastened the recall or improved veterinary care of the sick dogs and cats.But we can say that the old experiments on animal feeding are well worth reading, that it’s best to read entire papers and not just their abstracts, and that libraries still have much to offer that the Internet cannot.
This article is based on Nestle M., Nesheim M.C. Additional information on melamine in pet food [letter]. JAMVA 231(2007):1647.
Wellness: Health Care
Recall Follow-up
For the last year or so, we have been working on a book about pet food, What Pets Eat, to be published by Harcourt late in 2009. One of the pleasures of a long-term project like this is the time to follow digressions wherever they lead. Last year’s (2007) massive pet food recall was so much of a diversion that it resulted in a spin-off publication—Pet Food Politics:Chihuahua in the Coal Mine —scheduled for release this September by University of California Press.
The recall made us especially curious about the role of melamine, the substance responsible for kidney failure in pets eating food that supposedly contained wheat gluten. Just a glance at the chemical structure of melamine shows that it is high in nitrogen, a nutrient usually obtained from protein. This made us suspect that melamine must have been added deliberately to boost the apparent amount of protein in wheat gluten, because methods that measure the amount of protein in animal feed count nitrogen, not protein itself. Our suspicions were confirmed. The toxic “wheat gluten” turned out to be wheat flour laced with melamine.
But why would melamine harm cats and dogs? A quick search for studies of melamine toxicity turned up several performed on rats and mice, but just one on dogs (which dated from 1945).These studies gave the impression that melamine was not very toxic except at extremely high doses. Furthermore, the kidneys of animals who had eaten the contaminated food contained odd crystals that did not look like crystals of melamine.These turned out to be formed from complexes of melamine and one of its by-products, cyanuric acid. Even so, researchers and federal officials were puzzled. They had not heard of associations of melamine or cyanuric acid with kidney failure.
Really? Our Internet search turned up a brief and not particularly informative abstract of a 1960s study on melamine toxicity in sheep.We thought we needed to look at the entire paper, and found it and others in old bound journals in the Cornell library. These decades-old studies demonstrated that melamine is quite toxic, and causes kidney-related symptoms in animals at doses nearly identical to those reported in contaminated pet food. The studies were designed to test the idea that, because melamine nitrogen is far less expensive than protein nitrogen, melamine might have two useful purposes: (1) as an honest feed additive for ruminant animals, whose microorganisms can convert nonprotein nitrogen to amino acids, and (2) as a dishonest adulterant that makes feed test as though it contains more protein than it really does.
By following other leads,we also found references to relevant studies from the early 1980s in Italian journals that we had to request through interlibrary loan. These showed that melamine was so frequently used for fraudulent purposes in the 1980s that Italian scientists developed a test for it. They used the test to show that melaminna had been used to adulterate more than half the samples of fish meal they examined.
Most of the early information about melamine toxicity came from attempts to use it as a drug or nutrient. In the 1940s, investigators explored its potential as a canine diuretic. To follow what comes next, pay attention to the size of the melamine dose in milligrams per kilogram (mg/kg) of body weight, and recall that a kilogram is 2.2 pounds. The 1945 study showed that at a dose of about 120 mg/kg, dogs excreted crystals in their urine but otherwise did fine. In the 1960s, investigators used cyanuric acid (which is 32 percent nitrogen) to feed ruminant animals, and observed no problems even at high doses.Wouldn’t melamine (66.6 percent nitrogen) work even better?
A South African scientist fed daily doses of about 250 mg/kg to sheep, but most animals refused food and lost weight, and some of them died. Another South African investigator gave melamine doses to a single sheep, starting with 2,600 mg/kg. At such high doses, the sheep died within a few days from kidney damage, and the investigators could see crystals of melamine hanging from the animal’s prepuce. Lower doses of melamine caused sheep to stop eating, especially if their water intake was restricted. These studies suggested that a dose of about 250 mg/kg kills some— but not all—sheep over time.So, by 1968, melamine was known to induce kidney damage when fed to sheep over prolonged periods. Ten years later, American investigators tested melamine in cattle and found that a dose of about 100 mg/kg caused four out of six steers to refuse feed.
We think these studies are highly relevant to the pet food situation. The FDA reported that melamine could have accounted for 10 percent of the weight of the false wheat gluten, and the false wheat gluten could have accounted for as much as 10 percent of the weight of the pet food. If so, 100 grams—about 3 ounces—of pet food could have contained as much as a gram (1,000 milligrams) of melamine, and an average cat or small dog could have eaten an amount close to the 250 mg/kg level that proved toxic to sheep in the 1960s.
Recently, investigators from Georgia and the University of California, Davis, have shown that much smaller amounts of melamine can form crystals if cyanuric acid is also present. In cats, doses as low as 32 mg/kg each of melamine and cyanuric acid caused crystallization and kidney blockage.
We were surprised that neither the university or FDA veterinarians involved in the melamine investigations knew about this earlier work, but we think we can guess why. Papers in international journals are not readily accessible on the Internet, and the old animal feed literature is not likely to be studied these days.We had to discover the papers the old-fashioned way, by going to the library in person, sifting through reference lists, following up leads that sometimes required interlibrary loans and pursuing the reference trail back to its origins.We had the interest and time to pursue these questions. For the veterinarians and FDA officials caught up in the heat of the recall, a trip to the library might have seemed like a luxury they could ill afford.
We can’t say whether earlier suspicion of melamine would have hastened the recall or improved veterinary care of the sick dogs and cats.But we can say that the old experiments on animal feeding are well worth reading, that it’s best to read entire papers and not just their abstracts, and that libraries still have much to offer that the Internet cannot.
This article is based on Nestle M., Nesheim M.C. Additional information on melamine in pet food [letter]. JAMVA 231(2007):1647.
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