Biting veterinary dogma for a back-to-basics look at vitamins

As I teach, I learn. In October,  I was updating my lecture on holistic diets for cats and dogs for my course, “Critical Overview of Complementary and Alternative Medicine.” In this talk, I speak about the plusses and pitfalls of various veterinary diets, such as raw meat, home-cooked, Chinese veterinary food therapy and more. But the pros, cons, benefits, and risks of going natural versus mainstream used to be clearer.

That distinction disappeared for me this year. The seemingly endless recalls of commercially prepared pet foods both “natural” and “not so natural” (i.e., those touted “holistic” and others more traditional), made me realize that we still have serious problems with pet food, three years after the melamine tragedy. No matter what the label claims as to its health benefits, the food can still be tainted, or the vitamins in the package present in excess or deficient amounts.

This past October, Vitamin D toxicity in “all natural,” “healthy,” and “holistic” dog food led to canine health problems across the country. In June, 2010, Iams recalled ProActive Health Cat and Kitten Food due to insufficient levels of vitamin B1, or thiamine. Thiamine deficiency, as I discuss later, can lead to serious neurologic impairment and weight loss.

No wonder we’re scared.

Then, there’s the veterinary dogma about not feeding table scraps. I cringe when I hear colleagues insist that the foods their clinic sells constitute the only safe options. I have further unease with their insistence that providing freshly prepared “human” food is sinful and detrimental. I refuse to regard my clients as incapable of setting limits on the types and amount of food they feed their dog or cat from the dinner table. I resent the paternalistic stance and belief that, left any latitude, clients will cause their companion pancreatitis or obesity. Doctoring includes teaching, and with that comes dialogue and assessment of caregivers’ capacity to follow instructions and guidelines. Some of my most-well educated clients prefer to feed their dog from a bag or can. That’s OK; I do as well. But I’m not against adding medically appropriate human food in reasonable quantities. At least when consumers cook their own food for a canine companion, they can track its source and freshness to a greater degree than the unidentifiable mixture contained in a can or bag.

In fact, if human-grade food is so detrimental, and a diversity of foodstuffs so dangerous, why is a mainstream manufacturer now advertising their “natural” diet, replete with whole grains, fruits, and veggies? I’m accustomed to seeing this panoply on “holistic” labels, but not an industry giant’s.

Home cooking offers the benefits of selecting high-quality meats and vegetables while destroying organisms that might otherwise pollute our households. Home-prepared meals, however, usually require supplementation in order to compensate for potentially missing nutrients. On the other hand, hypervitaminosis (i.e., vitamins in excess) is not good, either. Both can cause serious metabolic, orthopedic and neurologic problems.

Nutrient needs vary with species and state of health. Not all vitamins essential for humans are needed by other species. For example, aside from primates, guinea pigs and some fish, vitamin C is not essential to add into the diet for most other species, as they can make their own. However, animals facing certain disease states may require additional vitamin C, rendering the nutrient “conditionally essential.” Physiologic changes during illness, pregnancy, or lactation alter requirements. Anyone considering home-prepared meals for their dog or cat should work in conjunction with their veterinarian and/or a board-certified veterinary nutritionist to ensure that the foods meet muster.

Becoming acquainted with the signs of vitamin deficiency and excess can help us identify contributors to chronic ailments in our companions. We can then “consider the source” of vitamins and then add foods rich in daily requirements that might otherwise be missing from the diet.

Vitamin A

What It Does: Vitamin A provides chemical components necessary for vision, reproduction, and normal development of skin, bone, and muscle. Pregnancy and lactation increase vitamin A needs.

Sources: Vitamin A levels vary in foods; processing and storage can destroy it. Liver, fish oil, egg, and dairy products contain high amounts of pre-formed vitamin A. While dogs can transform beta-carotene from vegetable sources into vitamin A, cats cannot. As such, they require it pre-formed, from animal sources.

Deficiency: Prolonged deficiency of vitamin A causes dry eye, night blindness, retinal degeneration, weight loss, poor skin and hair coat, kidney and reproductive problems, bone changes, and immune deficiency. A recent report linked vitamin A deficiency to epilepsy in calves.

Toxicity: Cats fed home-made diets of raw pork liver may develop hypervitaminosis A, or vitamin A toxicity. The bones in their neck and elsewhere deform or fracture, compressing nerves and the spinal cord. They experience neck pain and loose teeth. Hypervitaminosis A can also cause appetite depression, skin thickening, internal bleeding, conjunctivitis, and impaired liver and kidney function.

B vitamins

Syndromes associated with deficiency of the various vitamins B overlap. If a veterinarian suspects a B vitamin deficiency, they ordinarily treat with vitamin B-complex. B vitamins balance immune function. Vitamin B-complex given along with vaccinations may improve protection against canine distemper infection in dogs. Since B vitamins are water soluble, they rarely accumulate in toxic amounts.

Vitamin B1 (Thiamine)

What It Does: Thiamine participates in a number of metabolic pathways. Without it, a brain problem called “progressive encephalopathy” takes hold.

Sources: Foods high in thiamine include whole grains, yeast, and liver, especially pig liver. While raw meat supplies significant amounts of thiamine, cooking, ionizing radiation, oxidation, and alkaline conditions all destroy it. Therefore, food manufacturers must replace thiamine after cooking kibble.

Deficiency: Thiamine deficiency arises from two possible causes – either inadequate intake or too high an ingestion of thiamine antagonists. One thiamine antagonist (a “thiaminase”) is an enzyme that restructures the vitamin, rendering it inactive. Another group of antagonists include chemicals such as tannins that likewise disturb thiamine function. Raw fish, shellfish, and microorganisms such as yeast, bacteria, and fungi contain high concentrations of thiaminase. Cooking fish destroys thiaminase.

Without thiamine, young animals fail to grow correctly. Their muscles weaken and their nervous system functions poorly. Dogs can develop cardiac hypertrophy (i.e., an enlarged heart) and incoordination.

Vitamin B2 (Riboflavin)

What It Does: Riboflavin metabolites produce energy for metabolism.

Sources: Since riboflavin does not accumulate in the body, animals must ingest it daily. Dairy products, organ and muscle meats, eggs, and green plant matter offer abundant supplies. Yeast also contains riboflavin.

Deficiency: Though uncommon, dogs and cats lacking sufficient riboflavin exhibit skin eruptions, weight loss, impaired reproduction, neurologic changes, cataracts, and poor appetite.

Vitamin B3 (Niacin)

What It Does: Niacin provides chemical factors critical for proper cell function, energy production, and metabolism.

Sources: Foods highest in niacin include yeast, meats and fish, cereals, legumes, and oily seeds. The body utilizes the amino acid tryptophan to form niacin.

Deficiency: Niacin deficiency manifests as the “4D”: dermatitis, diarrhea, dementia, and death. Cats are more likely to develop deficiency than dogs if insufficient amounts are present in the diet.

Vitamin B5 (Pantothenic acid)

What It Does: Pantothenic acid is crucial for metabolism and energy production from food components, including fat, glucose, and amino acids.

Sources: Most foods contain pantothenic acid, though the highest amounts appear in liver, heart, rice, wheat bran, yeast, and peanuts.

Deficiency: Dogs and cats lacking pantothenic acid develop fatty livers and poor appetites. Their immune system becomes depressed and they may fall into a coma in later stages of deficiency.

Vitamin B6 (Pyridoxine)

What It Does: Pyridoxine participates in the synthesis of a number of important neurotransmitters, including serotonin, norepinephrine, epinephrine, and gamma-aminobutyric acid (GABA). It assists in forming histamine and helps create niacin from tryptophan. Pyridoxine is involved in synthesizing taurine from the amino acid cysteine as well as in making carnitine from lysine.

Sources: Pyridoxine is found in most foods, but meats, whole-grains, nuts, and vegetables contain an abundant quantity. Cooking destroys as much as 70% of the vitamin B6 found in animal products.

Deficiency: Signs of pyridoxine deficiency include seizures, anemia, irreversible kidney disease, muscle weakness, growth impairment, and loss of appetite. Pyridoxine-deficient cats can form oxalate crystals in their urine.

Excess: Over-supplementation of pyridoxine can induce toxicity, in contrast to most other B vitamins. However, signs of excess pyridoxine resemble those of deficiency, including incoordination and muscle weakness, confusing the picture.

Vitamin B12 (Cobalamin)

What It Does: Cobalamin is critical for folic acid metabolism, and as such participates in the synthesis of many biochemicals vital for life, including neurotransmitters and nucleotides (i.e., the molecules that make up the structural components of DNA and RNA).

Sources: Organ meats, milk products, microbes, and yeast contain cobalamin. Plants do not make cobalamin; as such, carnivores placed on a vegan diet risk becoming deficient.

Deficiency: Low vitamin B12 levels lead to poor growth, nerve damage, and a specific type of anemia.

Vitamin C

What It Does: Vitamin C assists in the formation of collagen, a vital element of tissue repair. Vitamin C, an antioxidant, protects against free-radical damage. It may help prevent cancer as well as gum and periodontal disease.

Sources: Exogenous sources of vitamin C include fruits, vegetables, and organ meats. While nonhuman species that manufacture their own vitamin C rely less on dietary sources, research indicates that their capacity to do so falls far short of previous assumptions. Aging liver cells lose some of their ability to synthesize and recycle vitamin C, making this a conditionally essential nutrient for geriatric dogs and cats. Health status may further influence vitamin C requirements. For example, dogs with lymphoma had significantly lower levels of vitamin C in their system after chemotherapy, suggesting a possible need for post-chemotherapy supplementation with this and other antioxidants.

Deficiency: Insufficient vitamin C causes delayed tissue healing and increased susceptibility to disease.

Excess: In too great quantities, vitamin C can lead to diarrhea and flatulence.

Vitamin D

What It Does: Metabolites of vitamin D regulate calcium and phosphorus absorption from the intestines and assist in the distribution and mobilization of these minerals throughout the body. As bones form and repair, their needs for calcium and phosphorus change. Vitamin D allows the body to adapt to these variations.

Sources: Fatty fishes provide the richest natural sources of vitamin D. Additional sources include fresh water fish, egg yolk, beef, liver, and dairy products. In the wild, carnivores obtain vitamin D by consuming the body fat, blood, and liver of their prey.

Deficiency: Depending on the contents of homemade diets, dogs and cats may not be receiving enough vitamin D. They cannot meet their needs simply through sun exposure, as dogs and cats lack the ability to cutaneously synthesize D3 in adequate amounts. Growing puppies and kittens receiving inadequate vitamin D or calcium exhibit soft bones that may bend and fracture Problems such as “rubber jaw syndrome”, or secondary hyperparathyroidism, have arisen in young dogs. Cats may become paralyzed due to injury of the spinal cord. Adults can experience weakening of the bone and osteoporosis. Humans with low vitamin D experience disturbed muscle function. Vitamin D deficiency has been linked to a host of chronic conditions, including inflammatory bowel disease (IBD), certain types of cancer, rheumatoid arthritis, and even multiple sclerosis in humans.

Excess: Overnutrition with supplemented vitamin D, calcium, and calories in puppy diets has been linked to predisposition for canine elbow dysplasia. Like its fat-soluble counterpart vitamin A, excessive administration of vitamin D may result in serious negative consequences. Hypervitaminosis D produces high circulating calcium levels, calcification of soft tissues, and even death. Be wary of those advocating megadoses of both vitamin A and D for pets with cancer.

Vitamin E

What It Does: Vitamin E functions as an antioxidant. In so doing, it is one of the first lines of defense against oxidative stress, protecting cells and their membranes from the damaging impact of free radicals. Dogs with chronic liver disease may benefit by vitamin E supplementation (along with other supplements) to prevent further oxidant damage to their liver.

Vitamin E actually comprises eight subtypes, including four tocopherols and four tocotrienols.  Attention is turning to this latter group, the formerly neglected half of the natural vitamin E family. Tocotrienols confer neuroprotective benefits and possibly more antioxidant properties than a-tocopherol. Tocotrienols distribute more widely throughout the fatty layers of cell membranes and tocotrienol, not tocopherol, suppressed growth of human breast cancer cells.

Sources: Tocopherols are found in highest concentrations in green, leafy vegetables. Tocotrienols come from the bran and germ portions of some plants. Since only plants synthesize vitamin E in nature, this argues in favor of including plant products and certain cereal grains and seeds in foods made for dogs and cats.

Deficiency: Lacking sufficient vitamin E, veterinary patients develop membrane dysfunction and cell breakdown. Clinically, this translates in dogs to muscle deterioration, sterility in males, and intestinal dysfunction. Cats can develop heart, muscle, and liver problems, as well as a condition known as pansteatitis (“yellow fat disease”), a problem identified in cats fed mainly fish (especially red tuna) or fish by-products. Cats suffering from pansteatitis develop lethargy and progressive abdominal enlargement, along with blood chemistry changes. Unbalanced home-made diets have been shown to cause this condition, which can mimic feline infectious peritonitis, perhaps spelling diagnostic confusion and inappropriate treatment.

Excess: Vitamin E toxicity rarely develops, as both human and non-human animals tolerate large quantities without negative effects.

To supplement or not? Clearly, questions remain about whether or not a given pet food regimen has adequate, balanced vitamins, even if it claims to do so on the label, given the recent recalls. If your animal companion is suffering from any of the medical conditions noted above, ask your veterinarian if a vitamin imbalance could be contributing to the problem. Ask about adding home-made veggies and meats that might boost the intake of specific nutrients. Before giving any vitamins or supplements, check with your vet. Then check the recall list, because multivitamins for pets have been recalled, too.

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Note from Gina: Blogs aren’t really made for footnotes, but the references on Dr. Robinson’s post are so valuable I have added a Word version complete with references. Click here to access. (Gina again: There’s a problem with this file at our end. Bear with me while I figure it out and then I’ll re-post the link.)

View the original article here