What are paleo diets?

Although paleo diets come in several guises they are all based on a similar theme. Throughout most of our time on planet Earth humans were hunter-gatherers eating game meats and wild plant foods and this shaped our genetic make-up. The development of agriculture during the last 10,000 years radically changed the human diet yet, as human evolution is slow, we have essentially retained our ancient genes. The mismatch between new diet and old genes is the root cause of high rates of obesity and other chronic diseases in the modern era.

The proposed solution is to eat like a caveman. Modern day paleo diets rely on meat, fish and seafood as staple foods. Fresh fruits and vegetables, nuts and seeds, eggs and healthful oils are all recommended. Sugar and many processed foods are restricted, though paleo diets also restrict grains, legumes, potatoes and dairy foods, which are fixtures in many healthy eating guides. The argument goes that these foods were all recently introduced into the human diet and are deleterious to health.

That’s the theory but critics of paleo diets are now coming out in force.

Critic No. 1: the evolutionary biologist

Professor Marlene Zuk, an evolutionary biologist from the University of Minnesota, argues that modern paleo diets are based on pseudoscience and speculation rather than actual research. In her book titled ‘Paleofantasy’ she argues that the paleo diet concept is based on misconceptions about how evolution works. She challenges the notion that human beings were ever perfectly adapted to their environment. The idea of past harmony and current discordance is little more than nostalgia, a yearning for the good old days.

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Professor Zuk dismisses the idea that modern humans have basically stopped evolving. Rather than modern humans being stuck with Stone Age genes she argues that we evolve more quickly than might be expected. Zuk highlights the increasing prevalence of lactase persistence as an example.

All mammals suckle their young and the newborns all have the enzyme lactase to break down lactose, the sugar in milk. The enzyme is lost after weaning in all species of mammals, except some humans. Persistence of lactase emerged in humans in Africa and Europe at about the same time as humans began to herd cattle, about 7000 years ago. Presumably the ability to easily digest milk conferred a survival advantage as lactase persistence has been spreading ever since. Now, 35% of the world’s population can tolerate milk products. A food that was unsuitable for Stone Age humans is now acceptable to billions – evolution at work.

If you have a spare 60 minutes take in Marlene Zuk’s lecture on the topic.

Critic no.2: the archaeological scientist

Dr Christina Warriner from the University of Oklahoma takes aim at present day paleo diets saying they have ‘no basis in archaeological reality’. She should know as she is an archaeological scientist who studies the health and dietary histories of ancient peoples using bone chemistry and ancient DNA.

Warriner dismisses the very idea that there was one diet that adequately describes the way ancient peoples ate. Firstly, primitive diets varied greatly according to latitude. There is no doubt that people living close to the Arctic ate a diet based on meat, fish and seafood – there was little plant food available. But plant foods were abundant in the tropics and undoubtedly formed a larger part of the diets of humans living in these areas.

Primitive diets also varied greatly with the seasons. Plants produce seeds and fruits at different times of the year, and animals migrate and fish spawn on a seasonal cycle. This ensured that primitive diets varied from month to month. It also demanded that people move from area to area to make the most of available food resources.

What about the idea that Palaeolithic peoples did not eat grains and legumes? It’s another myth, according to Warriner. She cites evidence that 30,000 years ago primitive humans were using stone tools similar to a mortar and pestle to grind seeds and grains. More tellingly, studies of fossilised human dental plaque have found remains of grains, legumes and tubers – all on the banned list of modern paleo diets.

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Warriner also makes the point that the foods recommended in modern paleo diets bear little resemblance to the foods our ancestors ate. In fact, virtually all of the recommended foods are products of modern agriculture. Modern day carrots, fat and sweet, are nothing like the small, fibrous, bitter wild carrots from which they were bred. Broccoli is ‘a human invention’. Bananas are the ultimate product of modern agriculture, totally dependent on humans for their reproduction. To Palaeolithic peoples meat typically meant lean meat from small game animals, together with the organs and bone marrow – quite different to the meats consumed in quantity by 21st Century cavemen.

Christina Warriner’s presentation on this topic is a must (22 minutes).

Reality check

So the assumptions underpinning paleo diets are highly questionable, but do they have a place nevertheless? Paleo diets may well be a useful approach to weight management – follow any restrictive diet and body weight will fall. Men, in particular, may respond better to a paleo diet than other approaches to weight reduction.

However, paleo diets are hardly a prescription for modern public health nutrition. For a start, paleo diets are expensive and out of reach of those most in need of healthier diets. As well as being sources of essential nutrients and fibre, grains, legumes and potatoes are all relatively cheap. And why would you recommend that people avoid nutrient-rich dairy foods, especially as calcium is a limiting nutrient in some diets?

As the world’s population increases towards a peak of 9 billion people there is no way that they could all be fed according to paleo principles. Like it or not, modern agriculture will be the only way to feed all those hungry mouths.