Monday, March 19, 2018

The “Myth” Of Complete And Balanced Nutrition

A common theme heard from those who believe in paleolithic feeding claim that the “complete and balanced diet” is unnecessary. Their reasoning goes like this –
  • ·         Humans don’t eat a complete and balanced food every day. We even raise children without a daily complete and balanced, all-in-one food like pets eat, and they do just fine, don’t they?
  • ·         Wolves and wild cats don’t eat complete and balanced foods every day.  Not only does their native diet supply all they need, but the foods that they can hunt or forage varies on a day to day or week to week basis – this variety in the diet leads to a complete/balanced nutrient profile over time.
  • ·         Complete and balanced nutrition has not resulted in pets living longer lives – my childhood dog lived to be 20 years old!
  • ·         ONE complete and balanced food is not, by itself, able to provide complete and balanced nutrition over months to years.
Let’s look at these claims one by one.

Humans don’t eat a complete and balanced food every day. We even raise children without bothering to balance every meal, and they do just fine, don’t they?

Actually, no.  Both young and aging humans experience different kinds of illnesses than dogs and cats, particularly atherosclerosis, hypertension and metabolic syndrome, which are rampant in developed countries.  And humans could be considered a sentinel population for the increasing problem of obesity, childhood diabetes, and preventable cancers.  No, humans are not doing just fine.

Wolves and wild cats don’t eat complete and balanced foods every day.  Not only does their native diet supply all they need, but the foods that they can hunt or forage varies on a day to day or week to week basis – this variety in the diet leads to a complete/balanced nutrient profile over time.

The natural diet of wolves and African wild cats are perfect for repeated reproduction, not longevity.  Wild animals eat diets that are high in protein and energy to support repeated production of offspring - as many and as much as possible. Repeated reproduction is associated with shorter life expectancy, and the body is worn out from optimal reproduction, there is no further use for that individual in the population, so they die from exhaustion and inability to fend for themselves. 

We have different plans for our pets - we want them around for 15 or more years, and we know that neutering them and keeping them thin adds many years to their lives in comparison to their wild ancestors We also know that preventing nutrient deficiencies through development of complete and balanced diets has been associated with an increase in life expectancy. Paleolithic diets are too high in fat for many of our pets whose most intense exercise is a few 30 minute walks or play sessions a day.  In order to achieve our goals for our pets, we may not always be able to feed a paleolithic diet, and balancing that diet appears to optimize an animal’s life expectancy..

Complete and balanced nutrition has not resulted in pets living longer lives – my childhood dog lived to be 20 years old!

If you don’t believe that pets are living longer, just look at the surge in old age diseases in the last 50 years. Veterinarians now treat more degenerative issues like osteoarthritis and kidney disease than ever before.  And cancer!  Yes, it’s possible cancer is on the rise due to environmental or other exposure issues, but pets are also living long enough to contract cancer.  We just did not see as much cancer to treat 50 years ago.

In addition, we now have evidence for certain interventions that increase life expectancy – a great example is that of keeping dogs and cats thin -the increase in lifespan is up to 2 years.

There is evidence that life expectancy is greater in pet or domesticated dogs and cats than in feral or ‘wild’ dog and cat populations. The average life expectancy in pet cats (12–14 years) is considerably higher than the reported median lifespan in feral cats (4·7 years). It is not known what factors contribute to this difference between feral and pet cat populations, however, accidents, diseases, parasites, food availability and stress due multiple and frequent pregnancies may contribute. 

A study from Banfield showed that, over the past decade, average lifespan has increased by 1 and 0·5 years in cats and dogs. 

Results from a yearly survey of UK households over a 34 year period, totaling 233,461 households, showed that the average age of dogs and cats increased by about 13% from 1960 - 1994. The percentage of both dogs and cats over the age of 8 years also increased. During this same time period, the feeding of "prepared pet food" increased from 49 - 69% for dogs, and from 64 - 90% for cats.  Veterinary databases from academic sources also show greater longevity in dogs

And those 20 year old beloved family pets?  These are the pets who made it past deadly infectious diseases (for which there were no vaccines) and traumas (such as fights, vehicular accidents, etc). Those pets that died early were not remembered later in the owners’ lives, but the few who did lived on as beloved memories.

ONE complete and balanced food is not, by itself, able to provide complete and balanced nutrition  over months to years.

I don’t completely disagree with point 4 – feeding a single brand of complete and balanced food may indeed reveal some shortcomings of that diet over months to years.  Or more precisely, reveal that the pet eating the diet has requirements that the diet cannot fulfill.  These diets are formulated to supply complete nutrition for 99% of normal animals.  However, even normal animals have individual nutrient requirements that may vary widely from “average”.  Pet owners and veterinarians frequently note how a pet’s haircoat declines on one diet over time, and immediately improves after a switch to another over the counter diet.  That pet just received missing nutrients of some sort, or conversely, got relief from an overdose of a nutrient that he or she couldn’t tolerate well.  There might well be a perfect diet out there for every individual pet, but with thousands of brands available, finding that one diet is challenging if it exists at all!

There is another aspect to this observation that pets may respond very decisively to diet changes.  Depending on how the food is formulated, there may be ingredients and nutrients present which are not considered essential but that do confer some benefit. Phytonutrients from fruits and vegetables are one example.  Nutritionists formulate complete and balanced foods to supply optimal (not minimal) amounts of all the essential nutrients, but a food containing more biochemical complexity may benefit an animal’s metabolism in ways that are not obvious or easy to study.

One of the most common areas for a nutrient deficiency or imbalance to show up is in the skin.  I see sparse hair growth and flaky or greasy skin pretty commonly in animals that are eating deficient diets. However, we generally do not see classical nutrient deficiencies if a pet is eating a diet that is deficient in 1 or 2 micronutrients but contains plenty of protein, fat, calcium, etc.  What we see instead is that if the pet becomes ill with another problem, that illness may be worse, or require more treatment or hospitalization than if the pet had been eating a complete and balanced diet. Those subclinical nutrient deficiencies leaves the patient wanting and without metabolic reserves when the system is stressed. The other relatively common situation is the sudden “appearance” of a nutrient deficiency that was developing for months to years while the animal seemed perfectly healthy.  A particularly dangerous example is taurine deficiency in dogs* – a dog can motor along seeming perfectly healthy, but behind the scenes, the heart is proceeding into heart failure, and the owner doesn’t notice anything wrong until failure has occurred.

Can you measure blood levels to determine whether a vitamin or mineral deficiency is present? In many cases, the test is either not very accurate or difficult to run so we don't typically do those tests unless special circumstances exist.  On the other hand, if a pet is chronically malnourished or has been starved, we do see indirect indicators such as w protein and other laboratory values.  But the physical condition often tells us what we need to know. 

To summarize, there are many good reasons to feed a complete and balanced diet, and no good reasons to avoid doing so.  It’s easy to find foods of all types – complete/balanced homemade recipes, raw foods, grain-free foods, paleo foods, kibbles, cans, prescription diets -why take chances when it just isn’t necessary?

*Taurine is not considered an essential nutrient in dogs, and yet some dogs develop heart failure due to taurine deficiency from certain diet formulations, including diets very high in fiber (we believe), or those composed of meats that are low in taurine. 

References
Watson D.  Longevity and diet (letter). Vet Rec 1996 (138) 3: 71
Butterwick RF. Impact of nutrition on ageing the process. Bridging the gap: the animal perspective. The British journal of nutrition. , 2015, Vol.113 Suppl, p.S23-S
 EJ Taylor , C Adams & R Neville (1995) Some nutritional aspects of ageing in dogs and cats. Proc Nutr Soc 54, 645–656.
 Banfield Pet Hospital (2013) State of pet health 2013 report. http://www.stateofpethealth.com/Content/pdf/Banfield-State-of-Pet-Health-Report_2013.pdf.
J Levy , D Gale & L Gale (2003) Evaluation of a long-term trap-neuter-return and adoption program on a free-roaming cat population. J Am Vet Med Assoc 222, 42–46.


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