Innumerable diets have come and gone over the years, all of them singing the same tune. The Paleo diet on the other hand, has persisted and garnered a real following in diet and nutrition circles. Have we finally stumbled upon the panacea for modern civilization? An analysis reveals the good, bad and downright ugly.
False Premises And Erroneous Extrapolations
The Paleo paradigm is basically predicated on a simple observation with the help of a little deduction. When hunter-gatherer societies not yet influenced by modern, industrialized culture are studied, they are seen to have freedom from 'diseases of civilization'. So we're talking about the usual killers here - the metabolic syndrome, cancer of all varieties, cognitive and neurological disorders, bone disorders etc. the list goes on and on. Thus, in making this observation, it can be extrapolated that mimicking the natural diet of hunter-gatherers will also give modernized people freedom from these pathological consequences . This reasoning is corroborated by the fact that diseases of civilization have followed modernized populations since the major neolithic revolution some 7,000-10,000 years ago .
Sounds perfectly rational so far right? Steady there, tiger, not quite. One of the most fundamental and utterly elementary facts of experimental science is that observation alone cannot establish cause and effect relationships . With the corollary being, correlation does not imply causation. Studying these primitive cultures and simply observing a non-directional, unadjusted correlation between diet variables and disease variables is not at all sufficient for ascertaining causation.
So right out of the starting-gate we have a huge problem. In science, given that observations are primarily used for developing hypotheses, we can only hypothesize that eating a diet similar to that of hunter-gatherers (problematic statement in itself, I'll get to it soon) will grant us immunity from the litany of terrible diseases that ravage the modern world. By absolutely no scientific or objective standard may we assert that same statement as if the association was bound in causality.
Paleo also gets an award for making the blind assumption that we as a species cannot evolve and adapt to a more nutritionally superior diet than that of hunter-gatherers. For example, the development of cereal grains did not truly begin until the agricultural revolution, or more specifically, the 'Green revolution' . What might hunter-gather societies have to say about the nutritional quality of cereal grains? They tell us close to nothing. Therefore, evidence based medicine should be used to answer such questions.
Wait A Sec...What Really Is The Paleo Diet?
Perhaps the greatest falsehood of the Paleo diet as presented across the internet is that it is a rigidly defined diet being limited to a specific macronutrient ratio (almost always low-carbohydrate) and characterized only by certain foods. Hunter-gatherer societies hail from far and wide, from the polar plains of Greenland, to the deserts of Africa. On which society do we model our diet on? The Tokelau who obtain over 60% of their calories from coconut ? Or perhaps the Masai, whose young men eat virtually nothing but meat, blood and milk ? Or maybe the Samburu, who drink in excess of 3 gallons of whole milk a day ? How about the Kitavans, who get 70% of their calories from carbohydrate ? Or maybe the Nunamiut, who eat a diet 99% animal derived ? And so on.
I don't deny that these societies have certain nutritional similarities and I will talk about these later on, but as clearly demonstrated, Paleo is not just one thing. In a letter to the editor regarding the meat-based diet of many hunter-gatherer tribes, K. Milton offers a brilliant argument for their natural diets and health outcomes which I find particularly compelling. Milton writes, :
Hunter-gatherers were not free to determine their diets, rather, it was their predetermined biological requirements for particul"ar nutrients that constrained their evolution. At the same time, these dietary needs apparently allowed for selection to favor increased brain size in the human lineage and the concomitant development of technologic, social, and other abilities directed at securing these nutrients. In turn, cultural behaviors buffered hunter-gatherer biology from many selective pressures related to diet that other species must resolve largely through genetic adaptations.In essence, she argues that it was not these people who chose their diet, it was their diet that chose them.
Devil In the Dairy?
The conventional Paleo diet requires that dairy be eschewed because of it's "evolutionary discordance" . But as I detailed before, this unfortunately tells us nothing about whether dairy is inherently deleterious or not. Some proponents have caught wind of this and instead claimed that dairy promotes cancer due to its acute influence on IGF-1, a growth hormone and there does seem to be some evidence supporting this . So is it true, does dairy promote cancer?
In his masterwork, Nutrition and Physical Degeneration, Weston Price details the many cultures that have thrived on dairy foods for millennia . The populations he observed to consume dairy included Arabs, Tibetans, Northern Indians, the Swiss, the Sudanese and several other African tribes. In most instances, dairy was in the form of butter with milk and cheese constituting the rest. People of these cultures had outstanding dental development and were generally in excellent health compared to modern comparisons of the same region. He makes no clear comment on the cancer in these populations, rest assured if it was prevalent he would have said something. In fact, based on my reading of the book, I believe Price mentions cancer only about twice and even this when describing health in modern civilization.
But it would be hypocritical of me to use this data exclusively as the basis for my argument against the avoidance of dairy. Which is exactly why I'll look into what contemporary evidence-based medicine has found.
Is there a positive association between dairy or milk consumption and bladder cancer? Possibly to the contrary , or at the very least, no . How about breast cancer? Total dairy foods might actually be protective . Gastric cancer? Again, dairy seems protective . Prostate cancer? Nope . Colorectal or colon cancer? And once more, dairy might be protective [18,19]. Perhaps ovarian cancer? Nope . How about total dairy with total cancer? I searched the literature and found 15 studies supplying information on butter and/or cheese and/or milk or total dairy consumption. I didn't find a single study where increased cancer risk or cancer mortality was associated with higher dairy intakes [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]. Surely cardiovascular disease then?! Nope .
I couldn't find very many controlled trials but the few that do exist have shown improvements in blood pressure and other minor health parameters [37,38]. You might charge me with failing to acknowledge industry funding in these studies, but if we were to exclude studies with conflicting interests, we wouldn't be left with much, anywhere. Nevertheless, there is a large body of evidence indicating that the association between total dairy and dairy products and cancer is probably hugely overrated. But what are the benefits of dairy?
Dairy products contain a vast constellation of unique micronutrients with independent and documented health benefits [39,40]. More specifically, dairy clearly promotes bone health contrary to false claims that animal protein causes bone loss [41,42,43,44]. Cheeses also contain the rather elusive fat-soluble vitamin, Vitamin K2 which is critical for brain, heart and tooth health amongst many other things . Furthermore, lets not forget the fairly well established role of milk in strength and resistance training .
I think it's pretty clear that the evidence does not seem to support the claim that dairy causes cancer. Avoiding dairy would probably be more of a disadvantage than an advantage to someone seeking optimal health status. Paleo also levels criticism at grains. How much of this warranted?
Going Against The Grain?
Virtually every single Paleo website across the net will have grain-avoidance down as once of its most fundamental principles. Their evidence? Once again, because "grains were not available during our 2 million years of evolution." There is some evidence to actually suggest this isn't true  but even I grant that, there is still our contemporary understanding of grains that require consideration.
There are claims about grains causing all sorts of problems. I find this most interesting given the large body of both observational and clinical research that has shown grains to improve a long-list of risk-factors for various degenerative diseases [48,49,50,51,52,53,54]. Particularly those who wrongly conflate Paleo with 'low-carbohydrate' claim that carbohydrates make you fat mediated by insulin. The idea that carbohydrates are exclusively fattening or that you can lose weight faster on a low-carbohydrate diet is not supported by any closely controlled evidence .
Other claims may center on the anti-nutrient content of grains. Well, it may be true but anti-nutrients are certainly not restricted to grains alone. They are also present in leafy green vegetables . Anti-nutrients have been thought to inhibit the absorption of iron, zinc, and calcium although controlled trials have generally found absorption and balance of these minerals to not deteriorate to a significant degree on higher grain diets [57,58,59]. Also compounding this is the fact that vegetarians in particular do not have adverse health effects from mineral deficiencies . Also, iron overload has been hypothesized to be implicated in a number of diseases, making reduction possibly healthful .
Claims about inflammation also overstated, there is some observational and strong clinical evidence showing grains improve or at the very least, not negatively affect markers of inflammation [62,63,64,65,66,67,68,69,70]. What about clinical trials? What do they tell us about grains and mortality?
Here's where it gets interesting. To my knowledge, there is only one controlled trial that has looked at wheat and mortality. In the group advised to increase fiber intake, there was an increase in mortality compared to those who were not given this advice. The difference however, did not reach statistical significance indicating this outcome was probably due to chance . In another often-cited study , those in the wheat bran group displayed slightly higher levels of oxidized LDL, a big deal to anyone who knows anything about heart disease. But it seems this outcome may have been the result of a high attrition rate skewing the data .
Much of the claims about grains are not supported by a great deal of evidence, or at least have substantial amounts of conflicting evidence. Controlled trials have not necessarily shown a survival advantage from fiber consumption, but evidence is exceptionally scant and there is a huge amount of other trials showing improved bio-markers and risk-factors with grain consumption.
The Great About Paleo
While much of Paleo is based on speculation, assumption and extrapolation, there are indeed many truths we can take home.
While it's not overtly supported by the leading Paleo proponent , the Paleo blogosphere much accepts that saturated fat is not the evil artery-clogging monster it's so often portrayed as. And rightly so, saturated fat has never been linked to heart disease . This is a huge leap in public health knowledge whichever way you look at it. The emphasis on whole foods is of paramount importance. The benefits of fruit and vegetables have been established extensively in the literature [76,77,78,79,80]. As with nuts [81,82] and fish [83,84,85]. Whole eggs,  and muscle meats are highly nutritious , especially with the fat left on [88,89] but Paleo takes it a step further and advocates the consumption of organ meats which are in many respects the most nutrient dense foods on the planet [90,91].
Avoiding processed and industrialized 'junk', like fast-food, sweetened beverages and refined sugar are just common sense. Another critically important recommendation is to avoid polyunsaturated fatty acid [PUFA]-dominant vegetable oils which are total garbage and offer no health benefit that can be justified. They contain way too much omega-6 , easily throwing out the crucial omega-3/omega-6 balance predisposing to a massive list of diseases . Vegetable oils and high omega-6 PUFA have also been shown to cause cancer in a well controlled trial  and is present in high quantities in cancer cells . Moreover, high PUFA has been shown to exert a harmful effect on the immune system  and directly kill white blood cells . When heated, they have been shown to increase the activity of free-radicals in humans [98,99,100]. PUFAs also more susceptible to oxidation due their double-bonds which make them chemically unstable [101,102] and have been shown to positively correlate with atherosclerosis development . It has also been found that PUFAs are toxic to the mitochondria , inhibit cellular respiration [105,106], and are immunosuppressive .
So yes, the Paleo diet does advocate quite a number of truly healthy things. And for this it needs to be recognized.
Take Home Messages
It needs to be understood that the Paleo diet advocates a number of things, some supported by science and some not. I would suggest that avoiding dairy is not likely to be of benefit, and can otherwise seriously augment your health by supplying a wide range of nutrients. Similarly, while keeping in mind that clinical results may not be as promising for overall mortality, there is good evidence that grains can lower several markers of disease. Advice to avoid fast-food, sweetened beverages and refined or processed carbohydrates are as I've said, just common sense. Props do need to be given for the vindication of saturated fat which is a very long time coming. Specifically, avoiding PUFA-dominant vegetable oils is another crucial recommendation which is reflective of several lines of evidence suggesting that the intake of such oils are damaging to health.
I don't doubt that if the average American was to adopt the conventional Paleo diet they would experience much better health outcomes. But this can be said for other every other diet as well, even low-fat ones. But for those of us who are already nutritionally inclined, Paleo does not present a compelling case to restrict the intake of certain foods just because of their "evolutionary discordance". The emphasis on other dietary factors is already common knowledge.
With all of this distilled, it does not change anything about what we already know to be a healthy diet. As it has been described before , we should change our food choices to better reflect a Paleo template. That is, a diet characterized first and foremost by whole, unprocessed natural foods, being nutrient dense, satisfying and all-encompassing.Pictures courtesy of Wikimedia, "sbshine", Mark Hillary, Wikimedia and Arnold Gatilao.