The Real Reason Experts Fight on Nutrition EXPLAINED
Q: “Why don’t the experts agree, they keep telling us to do different things?”
Dr. Matt explains the truth:
A: I recommend timeless strategies for human nutrition over fad diets and pop culture. The strategy is simple. We all have a hunter-gatherer genome that requires the same nutrients and lifestyle interaction as our ancestors for thousands of years. Following an ancestral or ancient traditional diet will always be safer and more effective for our long term health because our human genome is programmed to understand and execute what it has recognized, evolved from and adapted to. Here is a small incomplete list why animal studies which are the dominant source of research for human nutrition just don’t make sense; and the reason experts fight and change their mind on topics in nutrition. This is also the reason, despite all the great content in nutrition and all the gurus teaching it, “nutrition science is still stuck in the year 1650 when surgery was just beginning. Very promising, but I think I will wait.” – Michael Pollan.
This is taken word for word out of The Journal of Nutrition, Animal Models in Nutrition Research by David Baker, 2008. I think this article serves as an excellent baseline for people to understand that when we study animals for humans, it just doesn’t make sense. The Species Wide concept I teach about from the new biology and the new science in Epigenetics teach us that every single species that has ever been studied as a specific blueprint, a specific genome with a specific set of instructions for that species. If you fed a cat a vegetarian diet, you would kill the cat. Animal studies will always give us an anamorphic lens of the reality. When we know about DNA, and how our ancestors lived for thousands of years, why do we continue the rat race for scientific discovery? Do what your great- great- great- great- great grandmother did, it really is that simple!
Animal research has contributed heavily to what we know today about nutrition and metabolism. In recent years, the young pig has come into particular prominence as an animal model, i.e., for studies of amino acid metabolism (9,44), total parenteral nutrition (45–48), rotavirus infection (49), and bacterial and viral pneumonia (50). Other than monkeys, pigs are thought to be the most nearly like humans of any animal model (51,52).
Among the animal species that have contributed useful nutrition information, many exhibit well-documented differences in how they use, metabolize, and excrete nutrients. Some species-specific features are listed below:
1. Doubling of starting body weight is generally considered a minimum requirement for growth bioassays with young animals. The time required to accomplish this doubling varies greatly among species: 3 d in chicks, 7 d in rats, 14 d in mice, 20 d in pigs and puppies, 50 d in kittens, and 5 y in 6-y-old children.
2. Protein accretion per se dominates the amino acid requirements of growing mammals and avians, but the slower growth rate of children results in maintenance dominating the amino acid requirements of children.
3. Humans generally give birth to a single offspring, whereas rodents, pigs, dogs, cats, and rabbits are multiparious.
4. Rodents and chicks are “nibblers,” whereas pigs, dogs, and humans are “meal eaters.”
5. Nutrient losses in sweat (Na) and menstruation (Fe) occur in humans, but these losses are of little consequence in rats, pigs, chicks, and dogs.
6. Consumption of gestation diets very low in protein concentration, or of poor protein quality, has little effect on pregnancy outcome in swine, but it results in either abortion or very poor pregnancy outcome in rats (53–56).
7. Animals have the advantage of allowing invasive tissue sampling to assess nutrient status, but humans have the advantage of reporting how they “feel” when nutrient deficiencies or toxicities are imposed. However, monitoring compliance with dietary protocols is easy with animals but difficult with humans.
8. Adipose tissue is the main site of fatty acid biosynthesis in pigs and ruminant animals, but adipose tissue and liver are equally important as sites in rats and rabbits. Lipogenesis in chicks occurs mainly in the liver; the site in humans is controversial, although the liver is known to be a significant site (57).
9. The rate of gluconeogenesis in nonruminant animals is lowest after feeding and highest during an energy deficit; in ruminant animals the rate of gluconeogenesis is highest after feeding (57).
10. Because of rumen fermentation, ruminant animals derive far more energy from fiber and volatile fatty acids than nonruminant animals; likewise, they obtain far more of their amino acid needs from nonprotein nitrogen and ammonia (microbial protein synthesis) than nonruminant animals.
11. Rodents and rabbits practice coprophagy, whereas pigs, chicks, and humans do not.
12. Pigs and humans obtain usable energy from fermentable fiber, but chicks do not.
13. Most mammals use sucrose (or fructose) poorly during the neonatal period, but young chicks and neonatal humans use sucrose efficiently (58).
14. Mammalian neonates use lactose efficiently, but avians use both lactose and galactose poorly (59).
15. Vast differences exist among species in their ability to absorb β-carotene and other carotenoids intact (19,20).
16. Chicks and rats convert β-carotene to vitamin A more efficiently than pigs (18,19).
17. Avian species excrete urine and feces together, whereas mammalian species excrete them separately; avians also excrete uric acid as an end product of nitrogen metabolism, whereas mammals excrete urea. Most fish species excrete ammonia via the gills as an end product of nitrogen metabolism.
18. Avian species do not have a mitochondrial source of carbamoyl phosphate synthetase and therefore, unlike mammals, have no net arginine biosynthesis. Several fish species are similar to avians in this regard (9).
19. Pigs and rats use d-tryptophan as effectively as l-tryptophan; chicks, dogs, mice, and humans use d-tryptophan poorly (7).
20. Virtually all animal species use d-methionine almost as effectively as l-methionine, but apes and humans cannot invert d-methionine to l-methionine efficiently (7).
21. Excess dietary methionine can eliminate the need for dietary preformed choline in mammals but not in avians (15,60).
22. Regular cornstarch causes diarrhea when included in diets for puppies (it must be pregelatinized or extruded), but this does not occur when cornstarch is fed to rats, chicks, pigs, or kittens.
23. Chicks, rats, and mice respond more rapidly to vitamin and mineral deficiencies than pigs or humans.
24. Placental transfer of Fe from dam to fetus during late pregnancy in humans is much more efficient than that occurring in late pregnancy of swine (61).
25. Both glycine (or serine) and proline are considered dietary essential amino acids for avians but not for mammals (62,63).
26. Modest excesses of dietary l-cysteine (but not l-cystine) are lethal when included in diets for chicks but not for rats or pigs (43).
27. Hydroxy and keto analogs of amino acids are utilized more efficiently by chicks than by rats; the efficiency with which these amino acid precursors are utilized by humans is not known (7).
28. Excess dietary lysine antagonizes arginine in chicks, rats, and dogs but not in pigs or cats (8–13).
29. Chicks receive (some) endogenous nutrition (from the yolk sac) during the first week of life; mammals receive early nutrition from suckling the dam.
30. Chicks do not have a swallowing reflex, and they have a much shorter intestinal tract than rats, pigs, or humans; chicks also do not have a pyloric sphincter. Thus, rate of food passage through the gut is much faster in chicks than in rats, pigs, or humans.
31. Sea water consumption results in negative water balance in virtually all mammalian and avian species but not in feline species (64).
32. Feline species, including the domestic cat, evolved as strict carnivores. As such, their nutritional idiosyncrasies are legend: inability to effectively convert tryptophan to niacin, β-carotene to vitamin A, linoleic acid to arachidonic acid, cysteine to taurine, and glutamate in the gut to either ornithine or citrulline (65–67).
33. Cats develop severe hyperammonemia and often die within 24 h of consuming 1 or more meals of an arginine-free diet; no other nutrient void in any species causes death this quickly (9,65–67).
34. “Chemical” diabetes occurs in mammals, but not birds, treated with either alloxan or streptozotocin (68).
35. Recent estimates of the human adult requirements for methionine plus cyst(e)ine and threonine based on oxidation methodology are roughly 50% of the estimated lysine requirement (30), whereas adult pig requirements for methionine plus cyst(e)ine and threonine exceed the requirement for lysine (69). Some have questioned whether either the human or pig requirements may be wrong (9,69).
36. Phytate phosphorus utilization is improved markedly by addition of 1α-hydroxylated cholecalciferol compounds to chick diets containing surfeit vitamin cholecalciferol (70,71), but neither pigs nor laying hens respond in a similar fashion (72,73).
37. In terms of amino acid limitations, a casein diet for rats, mice, and pigs is first limiting and singly deficient in cyst(e)ine; a casein diet for chicks is first limiting in arginine and second limiting in cyst(e)ine (74).
38. The Ca requirement is 5 times higher for egg-laying hens than for growing avians and mammals.
It is obvious from this (incomplete) list of species differences that it is important to choose the right animal model for predictions of what might happen in humans. Other considerations include availability of facilities and cost of the experiments to be performed. Clearly, research with animal models has been valuable in advancing our knowledge of nutrition. The first 50 y of the 20th century might be thought of as the qualitative era of nutrition wherein most of the essential nutrients and their functions were discovered. The last 50 y could be thought of as the quantitative era, a time when nutrient requirements, nutrient-nutrient interactions, and pharmacologic aspects of nutrients were the focus. A 2006 Experimental Biology (History of Nutrition) symposium provided excellent reviews of how research with food animals has contributed to our knowledge of nutrition concepts and principles in energetics (75), carbohydrates and lipids (57), proteins (76), and body composition and growth (77). ”
We are thankful for the progress we have received from our scientific strategies, but it is time to move forward into the human era. Just sayin! – Dr. Matt