In Part I of this series I introduced you to Professor Rod Jackson, who has quite a strong view of the dangers of saturated fat from animal sources in the human diet. This series of posts is intended to examine his claims and, yes, ultimately call them into serious question if not discredit.
In this installment it is my intention to establish a foundation from which we can build. I find it particularly odd that so many of the studies I look at appear to have been done in a vacuum, with no reference to guiding principles; like, human evolution. When epidemiological associations suggest that some variable may be at the root of causing some problem, we ought to be highly suspicious of such associations when they contradict what we would infer from our evolutionary past. While that past is certainly not fully known and we'll probably be gaining knowledge about it for many decades, even centuries or millennia to come, what has been established is sufficient to constitute solid, established knowledge about how we evolved and what we ate that drove our evolution forward.
Against All Odds
Before we proceed, let's keep something in mind, which is this: we are talking about a species of hominid -- Homo sapiens -- that is the last and sole survivor of a long line of bi-pedal hominids going back six million years. As early as 50,000 years ago, there were still three species of humans (erectus, neanderthalensis, sapiens), living concurrently on Earth. Yet, we alone survived, and we did so without a shred of our modern medicine and conveniences. It was the logic of natural selection, chance, environmental upheavals such as floods, droughts, fires, ice ages and perhaps even predation that drove us forward -- that from three angles of varying degrees of niche exploitation (and many before that; evolutionary dead ends) to more generalist, one species came out on top in spite of huge odds against it.
Genetic analysis has now established that at one point the entire world population of our species was only 600 individuals. That is to say, the entire human genome comes from no more than 600 individuals, and this was after the great migration out of Africa, so at one point there must have been many thousands of H. sapiens. And yet, against all those odds, here we are, numbering in the billions.
And given all that, saturated fat -- the fat that makes up a large percentage of our own body fat and that of the animals -- the sort of fat your body will manufacture from excess carbohydrate in your body -- is, in the words of Dr. Jackson, "pure, natural poison?" Does that make any sense? Would that not be about the most surprising thing ever if it were even questionably true?
Imagining The Ridiculous
Suppose some zoologist were to claim that the natural, wild diet of some species of animal is killing them off early. Imagine an omnivorous animal like a bear, for instance. What if some researcher claimed that the super high-fat diet of salmon bellies and fatty skin was detrimental to their health?
What would you think about that? If you have any sense, you'd have to think it absurd. Catching those salmon that run upstream annually in the fall is how bears survive & thrive, packing on the mass they need for winter hibernation. They evolved as the prime animal to exploit that food resource.
But let's stop and think about animals in zoos, where they may be fed some combination of natural food and specially designed chow or other concoction. If you Google for "zoo diets," "animal nutrition," or similar terms, you quickly come to the realization that it's highly varied; lots goes into it and, guess what?
Every Species is Different
And just how do they know this? Well, obviously they have some knowledge about what these animals eat in the wild -- what they evolved to eat -- from observing them. It's not hard. Moreover, they observe their animals in captivity for signs that they're not thriving. And when they don't thrive, what's the first thing you think they'd consider? Would the zookeeper wonder if that saturated fat in the rump steak he's feeding the lions is the culprit, or, would he more likely think something essential was missing from the diet or in the captive environment? As we know, predators typically go for the rich, nutritionally dense organs first, then the meat -- probably the fattiest meat.
Is this difficult? Do you read about zoo animal epidemiology? How about long-term intervention studies employing diets of differing lion chow macro-nutrient composition to compare differences in thriving, disease, mortality? Would you expect to find zoos seeking grants and attempting to study the implications of the meat and fat consumption of a bengal tiger's sustenance and to affirm that the tiger's dry chow is heart healthy over his natural diet in his natural environment? No?
But wait: zoo animals typically live far longer than their wild counterparts. A male lion in the wild only lives to about 10, but can exceed 20 years of age in a zoo. Perhaps wild ones aren't living long enough to die from all that meat & fat? Does that sound familiar? Well, it should, because that's one of the chief counter-arguments I see against an evolutionary or paleo human diet, even where there is agreement on dietary composition. What they're claiming is that paleolithic hunter-gatherers didn't live long enough to encounter those collection of diseases we tend to call "diseases of civilization."
It's a difficult argument to deal with because there is at least some surface logic to it; and, because it's true that H-Gs and animals in the wild live average shorter lives than those in the zoo of civilization or the zoos we erect for non-human animals. But in the end, we understand that when you remove most of the risks of living in the wild -- like newborn mortality, injury accidents, pathogens, predation, and so on -- that you increase greatly the chances of survival to ripe old ages. Zoos -- for both human and non-human animals -- have been very successful in that. They have been successful in increasing average lifespans. This is not the same as increasing absolute lifespans, and there exists plenty of documentation that hunter-gatherers lucky enough to escape all that brutal nature throws at them, when able to obtain adequate nutrition from a natural diet, are able to rival the advanced ages we find in the human and animal zoos.
Meat & Fat in the Diet
When you run the numbers, there's no other way we could have evolved our huge brains and small guts without a significant quantity of meat & fat in the evolutionary diet. Kleiber's Law dictates that virtually all animals possess a metabolic rate that scales to the ¾ power of the animal's mass. What this means is that animals of different species that weigh the same have the same overall metabolic rate.
You have the same metabolic rate as a chimpanzee that weighs the same as you. Moreover, your heart, lungs, liver, kidneys and so on (major energy expensive tissue) will have comparable metabolic rates. But, your brain will have 4-5 times the metabolic rate of the chimp, and his gut will have 4-5 times the metabolic rate as yours. There's the difference. Why?
There are really only two necessary.
- We evolved from primates.
- Accomplishing (1) required at first the scavenging of animal-derived protein and fat, which in-turn allowed the shrinking of guts and expanding of brains over six million years.
And, so, the battlefield lines have been drawn. Dr. Jackson asserts that saturated fat is a poison and the chief culprit that underlies heart disease, "the single biggest killer in the western world."
I'm saying that a food so critical and essential to our very unlikely evolution -- against all odds and against all other hominids -- is logically most likely to be extremely healthful. And even if it were not particularly healthful in relation to other nutrition -- no more and no less -- it would be quite illogically odd if it were actually bad for us a priori, which is to say on its face, in any context, even a natural diet of real whole foods.
In Part III I want to attempt to look at what Dr. Jackson and people like him might regard as the best evidence and science out there implicating saturated fat in the diet. If anyone can steer me to some studies they believe are thusly touted by the authorities, I would greatly appreciate it.
11/20/09 Addendum: Prior to publishing this post I was able to have a draft copy reviewed by Dr. Monica Hughes and Dr. Stephan Guyenet, both PhD biologists. Monica helped correct a few errors in my descriptions of our ancestors and Stephan signaled a quibble with the shrinking gut hypothesis, described as follows.
It doesn't specifically imply that we ate more animal foods, but simply that we ate more easily digestible, calorie-dense foods. That could also include cooked starchy tubers. In my opinion, increased animal foods, cooking and starchy tubers probably all contributed to the gut shrinkage. The degree to which each contributed is debatable.
Yes, I'd agree with that, though we would have had to be cooking first, as meat, marrow, brain and other fat can be consumed raw while starchy tubers cannot. And, as it turns out there is some controversy just now over when the advent of cooking actually happened. At any rate, even if you use the advent of H. erectus 1.8 million years ago, you'd still have to conclude that we got near that point through raw animal food for several million years, and which was sufficient to get us large enough brains to invent cooking.
- Saturated Fat and Coronary Heart Disease, Part III: Cognitive Dissonance
- Saturated Fat and Coronary Heart Disease, Part IV: The Smell Test
- Saturated Fat and Coronary Heart Disease, Part V: The “Science”