Episode 3: A Better Understanding of a “Complete” Diet – Part 2

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Episode 3: A Better Understanding of a “Complete” Diet – Part 2

• In Episode #2, we talked about the “complete and balanced diet” myth.
• Now in Episode 3 we will look more at the issue of whether veterinarians and nutritional scientists really understand nutrition thoroughly enough to make a claim of “complete”
  • Are there examples of our continually improving understanding of nutrition that proves that the claim of “complete” at any point in time is always subject to revision  – to be ‘more’ “complete”?
  • Are there complexities in food which make the Nutritional Essentiality paradigm dangerous to our pets?
  • Are there concrete examples of these “complete” diets causing problems in pets that were eating them?

 “It is nothing short of a tragedy for a patient to be permitted to suffer from simple starvation while being given the so-called benefit of modern science in a modern hospital, and still gradually fade away by reason of some unrecognized form of malnutrition.”

{Lee R. October 23-24,1943. Malnutrition As A Primary Cause Of Disease, Lectures of Dr. Royal Lee p.32.}

• Look at the relatively recent example of Taurine
  • Currently considered “non-essential” in dogs
    • Able to synthesize taurine from sulfur amino acids cysteine and methionine
• Recent published reports of dilated cardiomyopathy in dogs eating “complete and balanced” diets associated with low blood taurine levels
  • Improved cardiac function with taurine supplementation
  • Prolonged survival time and withdrawal of medications other than taurine supplementation
  • DCM is typically progressive and fatal

{Backus, et. al. JAVMA Vol. 223, No 8, October 15,2003: Fascetti, et. al. JAVMA Vol. 223, No 8, October 15,2003}

• Reported cases of DCM in dogs
  • Diets “met recommended nutrient profiles or passed minimum feeding protocol tests recommended by the Association of American Feed Control Officials.”
  • Bioavailability of methionine and cysteine appeared to be adequate for the synthesis of taurine
  • Diet change improved taurine status
  • “…Other dietary factors precluded adequate synthesis of taurine”
  • 2 dogs fed home-prepared low protein tofu-based diet that met National Research Council requirements for adult maintenance

{Backus, et. al. JAVMA Vol. 223, No 8, October 15,2003: Fascetti, et. al. JAVMA Vol. 223, No 8, October 15,2003}

• Mechanism of heart failure in taurine deficiency is poorly understood
  • Heritable susceptibility – genetic component
  • Individual biochemical variations in taurine absorption, metabolism, excretion
  • Lacking a necessary contributing factor?
    • “The variation in clinical manifestation of taurine deficiency is suggested to be a result of the variable presence of contributing factors.”

{Backus, et. al. JAVMA Vol. 223, No 8, October 15,2003}

• Taurine in cats
  • Thought to be unimportant other than for bile conjugation until the 1960’s
  • Research showed that retinal degeneration in cats improved with addition of meat to casein-based diet
    • No change with added Vitamin A
• In 1987, a connection between taurine deficiency and feline dilated cardiomyopathy was discovered
• As in dogs, DCM was considered to be progressive, irreversible, fatal condition
• After more research, it was found that cats require dietary taurine
  • What other the other signs that might be visible with taurine deficiency?
    • Non-specific as with some nutrients (i.e. Scurvy with C)
      • Poor reproductive performance – abortions, stillbirths, low birth weights
      • Poor growth rates
      • Skeletal deformities
      • Neurological abnormalities – degenerative changes in retina, cerebellum, and visual cortex
      • Compromised immune function
      • Hearing loss
      • (We will mention this same list again when we talk about Pottnger’s Cats and the benefits of raw food in Episode 4!)

• BUT…Not all taurine depleted cats develop DCM
  • “It is, therefore, apparent that taurine deficiency alone is not sufficient to cause myocardial failure or central retinal degeneration in all cats. Still unknown is why taurine-depleted cats may manifest myocardial failure and/or feline central retinal degeneration, or neither.”

{Pion PD, Kittleson MD, et. al. July 15, 1992. Response of cats with dilated cardiomyopathy to taurine supplementation. JAVMA vol. 201, No. 2 pp. 275-284}

• Why is that?
  • “most likely in our opinion, these conditions may be caused by taurine deficiency and other, currently unidentified, cofactor or cofactors.”

{Pion PD, Kittleson MD, et. al. July 15, 1992. Response of cats with dilated cardiomyopathy to taurine supplementation JAVMA  vol.201, No. 2 pp.275-284}

• Acknowledgement of our limitations in understanding the complexities of nutrition

• Food companies attempted to correct the previously unknown deficiency
  • But, DCM still occurred in cats fed canned food even though taurine content had been increased significantly in both canned and dry foods
    • Proposed mechanism for taurine deficiency
      • Increased soluble fiber
      • Bacterial overgrowth
      • Increased deconjugation of bile acids
      • Loss of greater amounts of taurine in the stool
      • However…“We have found that these same canned diets when fed in an uncooked form, do not cause clinically significant taurine deficiency.”

{ Pion PD. 1992. JAVMA 201(2):275-284}

• “When you look at the classic example of taurine, many [diets] were deficient. The cats that didn’t become ill were those that were going outside and catching mice.”

{Smith CA. November 15, 1993. Dr. Donna Dimski quoted in Changes and Challenges in Feline Nutrition, J Am Vet Med Assoc.  Vol. 203, No. 10 pp.1395-1400}

• Taurine
  • Just one example of our continually improving understanding of nutrition that proves that the claim of “complete” at any point in time is always subject to revision
  • Provides insight into the complexities in food which make the Nutritional Essentiality paradigm dangerous to our pets – food is much more than protein, fat, carbohydrates, vitamins, and minerals
  • Is a concrete example of the way that “complete” diets can cause health problems in pets
  • Provides insight into the effect of heating on nutrient bioavailability.
    • In episode 4, we will talk more about heating effects on nutrient availability and raw food feeding