Report from the ‘Paleo vs Plant Based? Tackling Current Controversies in Nutrition’ seminar – Part 2
On Wednesday 11 February 2015 I attended the ‘Paleo vs Plant Based? Tackling Current Controversies in Nutrition’ seminar at Sydney Adventist Hospital, featuring the renowned Canadian dietitian and author Brenda Davis; the grande dame of the Australian nutrition scene, Rosemary Stanton; and diabetes and PCOS expert, Kate Marsh.
In last week’s post I summarised Kate Marsh’s lecture, titled ‘Plant-based Diets and Chronic Disease’. This week it’s time to review Brenda Davis’ lecture, ‘The Paleo Phenomenon: Facing Facts’.
Brenda Davis has authored or co-authored no less than 11 books aimed at both health professionals and the public, many of them best-sellers. She regularly presents on nutrition to doctors, medical students and dietitians, and was the lead dietitian on the Diabetes Wellness Program in the Marshall Islands, an island republic with one of the highest rate of type 2 diabetes in the world. So it’s fair to say she knows her stuff when it comes to nutrition, and her critique of the so-called Paleo diet – what she has dubbed ‘New Paleo’ – is well worth listening to.
The underpinning philosophy of the Paleo diet is that we humans are best adapted genetically, anatomically, physiologically and even psychologically, for the diet eaten by our ancestors during the Paleolithic period (the Old Stone Age, spanning from about 2.5 million years ago to 10 000 years ago), and that the litany of diseases that are now at epidemic levels in the modern world – obesity, diabetes, heart disease, cancer, autoimmune diseases, mental health issues such as depression and anxiety and so on – is due to the adoption of a diet based on the products of agriculture, particularly carbohydrate-rich foods such as grains and legumes.
It’s important to point out at the outset that
A) There’s no such thing as ‘the Paleolithic diet’ since stone-age humans ate whatever they could obtain in their environment, which varied depending on latitude, climate and season. The bulk of calories eaten by hunter-gatherer societies studied by 20th century ethnographers were found to come from gathered plant foods, with hunting only providing a substantial proportion of the diet in societies who lived furthest from the equator. It’s likely that Paleolithic-era humans followed similar patterns.
B) There’s no scientifically sound reason for singling out the paleolithic period as being pivotal in the development of human beings and their nutritional needs. After all, as Katharine Milton has pointed out here and here, our earliest ancestor – a plant-eater – branched off from the common great ape tree over 25 million years ago, and our nutrient requirements and digestive physiology were shaped by the evolutionary path that our primarily plant-eating anthropoid primate ancestors followed, long before they were humans or even protohumans. The relatively brief hunter-gatherer phase of human existence, which came at the tail end of our evolutionary process, is unlikely to have had much impact.
However, even if you accept that the diet of our paleolithic ancestors may have shaped our nutritional requirements, determining what those ancestors ate is not a simple matter. Unlike animal bones, most plant materials don’t leave physical remains that can be discovered by archaeologists thousands of years after their consumption! The fact that butchered animal bones have been found in early human campsites has given rise to the cartoon notion of ‘man the hunter’ – early humans who munched on mastodon meat on a daily basis, and turned their noses up at plant foods.
Fortunately, modern techniques of bone and tooth analysis allow paleoanthropologists to calculate the approximate amount of animal and plant foods eaten by early humans, and from this research, Brenda Davis has calculated average nutrient intakes of paleolithic-era humans (‘True Paleolithic diet’), followers of the current Paleo fad (‘New Paleo diet’) and vegans (Plant-Based diet). Her analysis is summarised in the table below:
As you can see, nutrient intake on a diet of minimally processed plant foods is actually closer to the estimated nutrient intake of Paleolithic humans, than is the modern take on the Paleo diet!
Brenda also discussed one of the central tenets of the modern Paleo diet: the ban on eating grains and legumes. While there are some differences of opinion among the various camps of the Paleo movement in relation to whether certain types of dairy products – primarily butter – are acceptable Paleo foods, and whether saturated fat should be eaten with gay abandon or strictly limited, on the subject of grains and legumes the Paleo preachers are all singing from the same hymn sheet: they all agree that grains and legumes are products of the agricultural era, have harmful effects on human health, and should be completely excluded from the diet.
What are the facts?
Firstly, there is incontrovertible evidence that paleolithic-era humans – as well as our now-extinct ‘cousins’, the Neandertals – ate grains and legumes. For example, as I pointed out in the Hot Topics seminar in June 2014 (which you can purchase the webinar version of here),
- The grain sorghum has been a staple food along Africa’s east coast for at least 105 000 years;
- Cooked starch grains (from legumes and grass seeds) have been found between the teeth of Neandertal skeletons in Europe and the Middle East;
- Starch grains from wild plants have been found on grinding tools from archaeological sites in Italy, Russia and Czech Republic, that date from the Paleolithic period (around 30 000 years ago), indicatsting that paleolithic people;
- Charred seeds from the Kebara Cave in Israel (which was inhabited by humans during the Middle Paleolithic era i.e. from 200 000-45 000 years ago) indicate that humans subsisted on a wide variety of legumes along with some grains and nuts.
So if Paleo advocates think we should be eating what our stone-age ancestors ate, then clearly we should be eating grains and legumes!
Secondly, the reason usually given for the ban on grains and legumes is that they are high in ‘antinutrients’ such as phytates, which when eaten in large amounts can interfere with absorption of important minerals such as iron, zinc and calcium. But as Brenda Davis pointed out, the true paleolithic diet was incredibly high in fibre, which is found in the same parts of plants as phytates. Therefore, the true paleolithic diet must have been high in phytates too. It’s also logically inconsistent for Paleo advocates to ban legumes and grains because of their high phytate content, but give their blessing to plant foods such as nuts, seeds and green leafy vegetables, many varieties of which are even higher in phytates than certain grains and legumes.
As for lectins, Brenda shared that the entire argument that lectin-rich grains and legumes are harmful to the human gut rests on a single case report of hospital workers who became acutely ill with food poisoning-type symptoms, after eating improperly-cooked kidney beans. From this single report, Paleo enthusiasts have concluded that all high-lectin foods can cause serious damage to the gut wall, regardless of their preparation method.
But as with phytates, the Paleo position in completely inconsistent and illogical, because a wide range of foods including many fruits and vegetables that are on the ‘Paleo approved’ list contain lectins, including carrots, zucchini, melon, grapes, cherries, raspberries, blackberries, garlic and mushrooms.
Food preparation methods such as soaking, cooking, fermenting, germinating, blending, juicing, roasting and exposure to acid dramatically neutralise phytates, while lectins are largely deactivated by even brief cooking. Consuming the amounts that remain after these time-honoured preparation processes may offer dramatic health benefits: lectins induce apoptosis (‘suicide’) in cancer cells, while phytates are powerful antioxidants, help to repair damaged DNA that might otherwise lead to cancer, protect against the formation of amyloid plaques that causes Alzheimer’s disease, reduce serum cholesterol and triglyceride levels, and decrease tumour growth.
In a nutshell (pun intended),
“Low levels of antinutrients consumed as part of a varied diet have anti-inflammatory, antioxidant and antimicrobial effects.“
The bottom line, as hinted at in the title of Brenda Davis’ presentation, is that the facts just don’t support the ‘new Paleo diet’. This meat-centric eating plan, devoid of the plant starches that have been staple items in the human diet (and remain staples for the last remaining hunter-gatherer societies such as the Hadza and !Kung) does not remotely resemble what our ancestors ate, and is not a healthy way of eating for us now.
Only one way of eating has ever been shown, in controlled clinical trials, to reverse coronary artery disease, and control or reverse early-stage prostate cancer, and that is a wholefood plant-based diet. if you want to enjoy optimal health now and into the future, you need to break free of ‘Paleofantasy’ and familiarise yourself with the facts about nutrition.
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