Pet Foods Plus

Pets come in all sizes, shapes and types, as do the humans who care for them. According to the American Pet Products Manufacturers Association, Inc. (APPMA), Greenwich, CT, dogs resided in 39% and cats in 34% of U.S. homes in 2000. Most pet owners consider their animal companions family members, worthy of high-quality food, nutrition and health care. Thus, an increased demand for functional foods for all species of pets parallels that for similar products for humans. Do these products really offer extra benefits?

"Marketers are giving us what we perceive our pets need," says Glen Mayer, DVM, Chicago Veterinary Medical Association, Hinsdale, IL. Indeed, according to the 2002 report from Packaged Facts, a division of MarketResearch.com, New York, the U.S. dog- and cat-food market, currently at $10 billion in sales, will increase to more than $12 billion by 2006, with much of the growth attributed to increased sales of value-added products for an expanding pet population.

In the last century, processed foods for pets developed alongside those for humans. However, pet foods combine various ingredients to create a complete, nutritionally adequate diet in a single item in various physical forms -- dry, semi-moist and canned -- rather than a variety of individual foods. Typical ingredients in traditional pet foods include processed meat, fish and poultry, their byproducts, grains, added vitamins and minerals, and natural and chemical preservatives. In recent decades, as some researchers and pet owners questioned the nutritional value of these ingredients and the safety of chemical additions, two new approaches to feeding pets emerged: natural foods and the raw diet.

Today, major pet-food manufacturers offer a line of products made from natural ingredients, including real vegetables, without chemical preservatives and meat byproducts. The market for convenient natural and organic pet foods is projected to grow in tandem with the consumer trend for natural and organic foods. According to the USDA, organic pet foods must also meet the National Organic Standards.

Advocates of the raw diet believe that unprocessed and uncooked foods are more natural, easier-to-digest and healthier for dogs and cats because animals in the wild eat raw meats and plants. "Holistic vets feed their dogs a raw diet because the dogs' intestines are built to eat this way," says Jean Beau, DVM, Chicago Veterinary Medical Association. She adds that cats are obligate (strict) carnivores and need a higher percentage of animal protein.

However, many veterinarians, such as Mayer, do not agree with this practice. "The vast majority of pets do well with commercial products...the raw-meat diet is dangerous," he says.

Although serving raw meat, poultry, vegetables and fruits seems easier than a home-prepared natural diet, pet owners need to expend time and energy to stock fresh foods and at times, purée them. Consequently, some convenience products are now available in the form of frozen pellets and flash-frozen pouches. Technically, these products qualify as foods and are not subject to pre-marketing approval or certification.

However, in December 2002, FDA issued a draft guidance document on the manufacture and labeling of raw-meat foods that outlines safety concerns, such as bacterial contamination and potential problems from unground bones, and regulatory requirements for labeling and claims. It includes several recommendations on ingredient sourcing, manufacturing, storage and handling, plus suggested wording for consumer-handling instructions. It also raises questions on the nutritional adequacy of raw-meat products as a sole source of nutrition, citing potential calcium, phosphorus, essential-fatty-acid and trace-mineral deficiencies, as well as the potential for excess vitamin A, if liver is the main ingredient.

Except for a few species-specific conditions, health issues for dogs and cats parallel those of humans: Obesity, arthritis, allergies, omega-6 to omega-3 fatty-acid ratio, and enhanced immunity in senior years are common concerns. According to Brian Rooney, DVM, Chicago Veterinary Medical Association, many manufacturers have special formulas to treat medical conditions, such as restricted-protein diets for pets with kidney failure, as well as products to help prevent health problems. He cites Science Diet® t/d®, a tartar-control diet from Hill's Pet Nutrition, Inc., Topeka, KS, featuring a specially extruded food that contains fiber. For cats, the company offers a product designed to decrease the frequency of hairballs, as well as formulas with an adjusted mineral and pH content to help prevent urinary-tract problems. "Most products have years of extensive research behind them," he adds. "The same can't be said for many of the natural products."

Obesity ranks high on the list of problems for companion animals, who frequently mimic both the physique and health risks of their owners. According to Nestlé Purina PetCare's Pet Institute, St. Louis, obesity is on the rise among pets. The Washington, D.C.-based National Research Council, in a September 2003 update to its recommendations on the nutrient requirements of dogs and cats, states that one out of four dogs and cats in the Western world is obese. Suggestions for trimming down the overweight pet include smaller portions, low-calorie and/or high-fiber foods, limiting access to other pets' food and no table scraps. Mayer concurs, "Low-calorie foods are OK, but what's really needed is portion control." Sound familiar?

Most products for weight control create lower caloric density with sufficient bulk to achieve satiety by lowering fat and increasing fiber. Some add L-carnitine to help burn fat and preserve muscle mass. Besides incorporating L-carnitine in vet-prescribed and over-the-counter (OTC) formulations, Dan Carey, DVM, Iams Company, Dayton, OH, says, "On the vet side, we use a fiber blend to help with the insulin-glycemic response. On the OTC side, we use selective carbohydrates." He explains that rice elicits an increased glycemic response. In cats, however, corn and sorghum, and in dogs, corn, sorghum and barley, blunt it. Studies at Purina also demonstrated that a higher protein-to-calorie ratio in energy-restricted diets fed to obese dogs and cats resulted in less loss of lean body mass.

Overweight pets are at risk for diabetes. For diabetic dogs, a diet high in complex carbohydrates helps to reduce glycemic response and lower insulin requirements. But cats metabolize carbohydrates less efficiently. Thus, high-protein, low-carbohydrate formulas help moderate blood glucose, resulting in lower insulin needs in diabetic felines.

For joint health, pet owners can find products that contain dietary supplements that they themselves use to treat or prevent osteoarthritis -- glucosamine and chondroitin. However, "in the products with glucosamine and chondroitin, the amounts are below a therapeutic dose," Rooney says. "There are no studies on prevention effect, so we don't know if this helps, but it does not appear to do any harm, either." Dietary supplements, like glucosamine, and other novel ingredients technically need regulatory approval or definition before use in pet foods. The National Animal Supplement Council, Valley Center, CA, contends that glucosamine is an approved supplement under DSHEA, but has also submitted an application for its definition as an approved feed ingredient.

Omega-3 fatty acids benefit skin and coat of dogs and cats. "Omega-3 and omega-6 fatty acids are needed in a specific ratio to be most effective," Rooney says.

Carey adds that the ratio should be balanced, in the range of 5:1 to 10:1 omega-6 to omega-3; otherwise, adverse effects, such as suppression of cell-mediated immunity and prolonged bleeding, can occur.

Omega-3s also appear to play a role in vision, cardiac and cognitive function. The primary sources of these fatty acids in premium and super-premium products are fish and fish oil or meal. Flaxseed, used in some products, provides alpha-linolenic acid, a precursor to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

As with humans, daily brushing is recommended to prevent tartar and other dental problems -- something that is easier said than done with animals. Several food products address oral care and provide an easy, more reliable method for dealing with dental hygiene. Iams uses hexametaphosate on the outside of its kibble. "This product can reduce tartar buildup up to 45% in cats and 55% in dogs," Carey notes. Other products rely on the size and texture of the kibble to scrub plaque and tartar from teeth. Some snack foods add parsley as a natural breath freshener.

Allergies are another common problem that pets share with their owners. "Traditionally, novel proteins have been used to treat allergies, but an animal can develop an allergy to any protein," Rooney says. "The newest development for treating allergies is a nonmeat protein and low-molecular-weight diets from Purina and Science Diet."

However, according to Carey, the jury is still out on protein size and its effect on allergies. "There is no solid research to show that the allergic animal doesn't develop an allergy to small-sized protein," he says. Additionally, he notes that these hydrolyzed proteins are expensive and their palatability is questionable. "Vets reach for those products with limited protein first, rather than hydrolyzed protein," he adds.

Formulas for senior pets aim to enhance immunity through the addition of antioxidants, while also decreasing caloric density. Some products have lower protein concentration to minimize the potential for kidney problems, but recent research indicates that seniors may actually need a higher percentage of calories from protein to maintain protein reserves. Beau says, "Antioxidant packages with vitamins C and E, co-enzyme Q-10 and selenium are important for slowing aging."

The choice and the amount of antioxidants used varies from manufacturer to manufacturer. For example, Hill's Science Diet contains a blend of selenium, beta-carotene and vitamins E and C.

Iams' antioxidant blend includes beta-carotene, lutein and vitamin E increased three- to fourfold over minimum requirements. Carey explains that research shows beta carotene boosts dogs' antibody response, while an increased uptake in white blood cells is observed in cats. Lutein is synergistic with vitamin E to improve immune defense. The company has added vitamin C to its food for the past 20 years based on research with sled dogs that demonstrated an improved ability to handle stress when supplemented with vitamin C. He continues, "It may be of benefit in older dogs, but it is hard to tease out. It is also included in cat food, but we're not sure what its role is -- it's difficult to find ways to test stressed cats."

While cats won't pull a sled, they do frequently become stressed by a unique feline health concern, hairballs. Premium and super-premium brands address this problem with special formulas designed to reduce hairball formation and help eliminate them. Typically, they incorporate a nonfermentable fiber, such as cellulose, to increase gastrointestinal motility and the eventual elimination of ingested hair. However, Carey cautions, a too-high cellulose level results in a drier stool and constipation. He says Iams uses a mix of beet pulp and cellulose in its hairball-control diet to achieve a balance between fermentable and nonfermentable fiber. Last February, Purina introduced a product with a patent-pending technology containing a soy-lecithin emulsifier that prevents dietary fat from combining with undigested, swallowed hair.

The Association of American Feed Control Officials (AAFCO), Oxford, IN, develops model regulations, ingredient definitions as well as   labeling requirements for state and federal officials. To substantiate its nutritional adequacy, a product must undergo animal feeding tests using AAFCO procedures; be deemed comparable to a product that has proven nutritional adequacy; or be deemed to chemically meet minimal nutritional requirements. New feed ingredients must demonstrate safety and efficacy before use, and go through an evaluation process similar to that used for human food additives. As with food for humans, the intended use determines its classification as a food or a drug, thus creating a gray area for products that aim to provide more than basic nutrition.

Most premium and super-premium brands use natural preservatives, such as tocopherol and rosemary extract, and antioxidant blends in all their formulas. Protein and carbohydrate sources vary considerably: Some products blend animal proteins and vegetable proteins, such as textured soy or wheat proteins, which are used in canned pet foods. The natural-foods proponents dispute the nutritive value of some grains and meat/fish byproducts and meals. According to Carey, the perception of byproducts and meal ingredients as low-quality is a misunderstanding of terms. "In reality, we use components that are not economical or acceptable for use in human foods, such as viscera," he explains. High-end processors ensure the protein quality of their ingredients and eliminate the indigestible parts. Definitions of protein ingredient names in the United States add to the misperception. For example, labels list dried chicken meat as "chicken meal."

Mayer says that egg protein is the best. Carey concurs, "Egg is the gold standard and dried egg is in all our formulas except the veterinary formula for food allergies."

However, protein needs of dogs and cats are different. "Cats need meat protein," Rooney says. "They are carnivores and have a higher protein requirement than dogs.... No one meat protein is better than others. Beef is as good as chicken and lamb."

While dogs, as omnivores, can derive nutrition from vegetable protein sources, studies show body-composition changes in dogs on vegetarian diets, according to Carey. Iams uses animal protein in all of its formulas except for its renal diet, which incorporates soy protein and supplemental amino acids because of the need to control phosphorus.

In the realm of carbohydrates, studies support the use of specific grains for different glycemic responses and a variety of fibers for gastrointestinal health and glycemic control. Iams' performance formulas use rice for a quick response. Its weight-loss and diabetic diets, however, which typically have higher fiber content, do not. As in humans, fermentable fiber, such oligosaccharides, acts as a prebiotic, and nonfermentable fiber adds bulk and stimulates motility. An excessive intake of either type results in negative consequences, so a balanced blend is desirable. Many manufacturers use beet pulp, a source of moderately fermentable fiber that contains both insoluble and soluble components. Carey says that Iams relies on beet pulp the most, especially for cats, who are colonic fermenters. The company also uses rice bran for dogs, and for seniors, added fructooligosaccharides provide prebiotic qualities.

In the end, quality does matter. Most veterinarians prefer premium and super-premium brands backed by research from the larger companies. Rooney recommends well-known brands matched to the age, breed, bite and activity level of their pet. He also advises to stay away from semi-moist foods, but that the nutritional quality of dry and canned foods is equivalent. Luckily, with a wide array of formulas available from reputable companies, owners can feed their companion animals customized diets designed to maximize nutrition and enhance their quality of life.

Angela M. Miraglio, M.S., R.D., (ammiraglio @aol.com) is a registered dietitian and Fellow of the American Dietetic Association from Des Plaines, IL. She has extensive experience in trade communications, public and consumer affairs and technical communications, as well as product development and nutritional assessment. Her firm, AMM Food & Nutrition Consulting, provides food and nutrition communications and technical-support services to food and beverage companies and trade and professional associations.

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