With all of the discussion on dog diets lately, I'm curious: has anyone seen research related to objective, measurable differences in dog health, coat, or activity after changing to a different diet?

When we changed from what the rescue group had Scout on to what Scout's currently on (Solid Gold), I was mentally prepared for her to have a shinier coat and for her poops to be more consistenyl solid. It took time before I decided that yup, her coat is more solid--but I don't have any true measures of that.

And I'm a completely biased source. I can't think about this objectively. I wanted the food to make a difference, and so I selectively interpret any "changes" I see due to her food. Of course this isn't conscious and I don't think I'm doing it that bad... but there's no way to know, as our minds just don't work that way.

So there have GOT to be studies out there that have compared dogs before and after different kinds of diets. Anyone know of any, or anything else that's objectively changed as a result of a diet change?

I haven't seen research, but I've seen more than enough proof with my own eyes (and bank account, lol).

I think the key word is "objective". And that is what is so hard to find. I'm not sure its even possible :(

Well, for humans, you can measure body fat composition, heart rate, various levels in the blood, etc, to see how diet and exercise are changing their bodies.

Do they do body fat composition tests on dogs? What about their heart rate--do dogs who are in "better shape" have different heart rates than those who are not? What about changes in the blood? I could even see there being some sort of measure for reflectance in the coat relating to shinyness--does that exist?

I don't know if there is a shine factor test. ;)
I have only ancedotal evidence. I have seen fosters go from dull dry coat to nice coat on my food. But, I have also seen one of my cats get more dandruff on the more expensive food (Innova regular kibble) than he had on the cheaper food (Science Diet). Even on the Innova EVO, he had more dandruff than he did on Science Diet or Iams before that. Now that he is getting canned Innova Lite with his Reduced Fat Innova kibble, he seems to have less dandruff than he did on the EVO or the regular Innova, which is odd because the fat in the regular Innova should've helped his coat and skin, in theory.

Calvin went from a greasy, smelly dog, with yeasty ears to a smooth, great smelling dog, with no yeast! Also went from very skinny to thin.

Well, for humans, you can measure body fat composition, heart rate, various levels in the blood, etc, to see how diet and exercise are changing their bodies.

Do they do body fat composition tests on dogs? What about their heart rate--do dogs who are in "better shape" have different heart rates than those who are not? What about changes in the blood? I could even see there being some sort of measure for reflectance in the coat relating to shinyness--does that exist?It's an interesting question! I'm afraid what most of us think of in terms of "change" may be be too subjective for study. In any case, I wouldn't suggest a "shiny coat" test, since a really good Labrador double coat actually isn't terribly shiny ;) and the growth-rest-loss cycle of a dog's hair follicles means the coat will have different qualities at different stages of the cycle. For instance, 2 of my dogs are heavily into their spring shed. If I changed their food today, I could almost guarantee their coats would show huge improvement in a couple of months. But the same improvement will occur if I change nothing.

There are a couple of useful studies referenced on this web page:
http://www.southbaydoggiedaycare.com/doggiehealthinfo.html

The first is an excellent 14 year longevity study which used paired littermates (Labradors, in fact) to assess the difference a restricted calorie diet might make. Body fat composition and many other variables were tracked during the years, and the results were quite dramatic in terms of age of onset of health problems and length of life. These dogs were fed identical diets (the particular diet was never identified) but the role of overnutrition was quite clear, and this should apply to any diet. This study could also provide a good model for others attempting to assess differences in diets.

There was also an intriguing Alzheimer's study (using beagles as the model) investigating the effects of diet, exercise, social interaction and mental stimulation on a population of aging Beagles. It's worth quoting here as a reminder that food by itself is NOT the sole key to our dogs' health. I worry sometimes that some folks spend so much time pondering (or preparing, in some cases) their dogs' diets that the other equally important, interrelated components of health are neglected. Balance is the key :)


In the study, researchers divided 48 older beagles, ages 7 to 11, into four groups. One group received regular dog food and standard care. The second group got a nutrient-rich special diet fortified with vitamins E and C from tomatoes, carrots, spinach, and citrus fruits, providing the equivalent of five or six servings of fruits and vegetables a day. The third group got standard dog food but an environment enriched by daily contact and play with other dogs, regular exercise, and special toys and games. The fourth group got both the enriched diet and environmental stimulation.

Over the next two years, the dogs were regularly tested with increasingly difficult mental acuity tasks, such as learning how to uncover treats under black or white- blocks. Those dogs who got the enriched diets, exercise, and social stimulation performed much better on these tests than those given standard care. Having any one of the enrichments, such as a nutrient-dense diet, exercise, or environmental stimulation, also improved results, but not as much as having all three.

The only changes I have noticed when I change food is in the stools....

The first is an excellent 14 year longevity study which used paired littermates (Labradors, in fact) to assess the difference a restricted calorie diet might make. Body fat composition and many other variables were tracked during the years, and the results were quite dramatic in terms of age of onset of health problems and length of life. These dogs were fed identical diets (the particular diet was never identified) but the role of overnutrition was quite clear, and this should apply to any diet. This study could also provide a good model for others attempting to assess differences in diets.

Very interesting! I've heard some talk of this before but haven't tracked down studies about it. Maybe this information will help us find the real study and see what food they used:
The ambitious dog study was led by researchers at Nestlé Purina, and included scientists at Cornell, the University of Illinois, Michigan State University and the University of Pennsylvania. Results of the study were published in the Journal of the American Veterinary Medical Association in May. The study also was the focus of a September symposium in St. Louis, sponsored by Nestlé Purina, called "Advancing Life Through Diet Restriction."

There was also an intriguing Alzheimer's study (using beagles as the model) investigating the effects of diet, exercise, social interaction and mental stimulation on a population of aging Beagles. It's worth quoting here as a reminder that food by itself is NOT the sole key to our dogs' health. I worry sometimes that some folks spend so much time pondering (or preparing, in some cases) their dogs' diets that the other equally important, interrelated components of health are neglected. Balance is the key :)

That's so interesting! This one was published in the Neurobiology of Aging in January 2005. I tracked it down. Here's what it said about food:
The control and antioxidant foods were formulated to meet the nutrient profile for the American Association of Feed Control Officials recommendations for adult dogs (AAFCO 1999) [4]. The two foods were identical, except for the inclusion of a broad-based antioxidant and mitochondrial cofactor supplementation to the test food. The control and enriched foods had the following differences in formulation on an as fed basis, respectively: -alpha-tocopherol acetate (120 ppm versus approximately1000 ppm), -carnitine (<20 ppm versus approximately 275 ppm), -alpha-lipoic acid (<20 ppm versus approximately 125 ppm), ascorbic acid as Stay-C (<30 ppm versus approximately 80 ppm), and 1% inclusions of each of the following (1:1 exchange for corn): spinach flakes, tomato pomace, grape pomace, carrot granules and citrus pulp. The rationale for these inclusions is as follows: Vitamin E is lipid soluble and acts to protect cell membranes from oxidative damage; Vitamin C is essential in maintaining oxidative protection for the soluble phase of cells as well as preventing Vitamin E from propagating free radical production; alpha-lipoic acid is a cofactor for the mitochondrial respiratory chain enzymes, pyruvate and alpha-ketoglutarate dehydrogenases, as well as an antioxidant capable of redox recycling other antioxidants and raising intracellular glutathione levels; -carnitine is a precursor to acetyl--carnitine and is involved in mitochondrial lipid metabolism and maintaining efficient function; fruits and vegetables are rich in flavonoids and carotenoids and other antioxidants. The diet was produced by an extrusion process and was fed for no more than six months before a new lot was manufactured.

Anyone know what that means? LOL!

The intervention is sort of sad to me...
The behavioral enrichment condition commenced after completion of the baseline cognitive testing. The animals in the enriched group were housed with kennel mates, exercised twice a week for 15 min intervals, and given sets of toys that were alternated weekly. None of these were provided to the control animals. The enrichment condition also included a cognitive enrichment protocol. The first year of cognitive enrichment started immediately after baseline with testing on a series of landmark discrimination problems, as previously described [31]. After completing the landmark task, the subjects were tested on to a series of oddity discrimination leaning problems [32]. After completing the oddity problems, the dogs were then tested for retention of the landmark task. The cognitive enrichment provided during the second year consisted of a series of nine discrimination learning tasks that were intended to study size concept learning [46] and a series of repeated reversal learning tasks that were intended to study learning set formation.

Not much enrichment. :(

Interestingly, the same author has an article that is in press right now in that journal finding that enrichment changes the brain in dogs:
Neuron loss within the hippocampus and entorhinal cortex occurs as a function of age in humans. We first tested the hypothesis that neuron loss occurs in the aged dog. The total unilateral number of neurons in the canine entorhinal cortex and subdivisions of the hippocampus from the left hemisphere were estimated using the optical fractionator. The brains from 5 old (13.0–15.0 years old) and 5 young (3.4–4.5 years old) beagle dogs were analyzed. The hilus of the hippocampus showed a significant loss of neurons (30%) in the aged dog brain compared to young. Differences were not detected in the remaining hippocampal subfields and entorhinal cortex. We further tested the hypothesis that an antioxidant fortified food or behavioral enrichment would reduce the age-related loss of hilar neurons. Behaviorally enriched aged dogs had more neurons in the hilus (18%) compared to aged controls. These results suggest that the aged canine hippocampus in the left hemisphere shows selective neuron loss and that behavioral enrichment may reduce this loss.

Looks like the enrichment in those studies is about the same as in the other one. So imagine what living a REAL life with a REAL family does for the brain!

Guess that's a little off topic... but I like the direction of trying to look at concrete evidence. Thanks!

Here's the abstract from the lifespan study. I do have the entire study in pdf but it is not meant to be reprinted without permission ;)
Abstract
Journal of the American Veterinary Medical Association
May 1, 2002, Vol. 220, No. 9, Pages 1315-1320
doi: 10.2460/javma.2002.220.1315



Effects of diet restriction on life span and age-related changes in dogs

Richard D. Kealy, PhD Dennis F. Lawler, DVMJoan M. Ballam, MSSandra L. Mantz, Darryl N. Biery, DVM, DACVRElizabeth H. Greeley, PhDGeorge Lust, PhDMariangela Segre, DScGail K. Smith, DVM, PhD, DACVSHoward D. Stowe, DVM, PhD
Pet Nutrition Research Department, Nestle Purina Pet Care Co, Checkerboard Square, St Louis, MO 63164. (Kealy, Lawler, Mantz); Statistical Services Department, Nestle Purina Pet Care Co, Checkerboard Square, St Louis, MO 63164. (Ballam); Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104. (Biery, Smith); Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801. (Greeley, Segre); James A. Baker Institute for Animal Health, New York State College of Veterinary Medicine, Cornell University, Ithaca, NY 14853. (Lust); Department of Large Animal Clinical Medicine, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48823. (Stowe)
Objective—To evaluate the effects of 25% diet restriction on life span of dogs and on markers of aging.

Design—Paired feeding study.

Animals—48 Labrador Retrievers.

Procedures—Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair-mate from 8 weeks of age until death. Serum biochemical analyses were performed, body condition was scored, and body composition was measured annually until 12 years of age. Age at onset of chronic disease and median (age when 50% of the dogs were deceased) and maximum (age when 90% of the dogs were deceased) life spans were evaluated.

Results—Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triiodothyronine, insulin, and glucose concentrations. Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.

Conclusions and Clinical Relevance—Results suggest that 25% restriction in food intake increased median life span and delayed the onset of signs of chronic disease in these dogs. (J Am Vet Med Assoc 2002;220:1315–1320)

McBain had an ear infection a month for the first year of his life - since I switched foods he hasn't had a single one and he's over 4 now. That's an objective measurable change to me!