Biologists in a stew over Paleo diet

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This was published 9 years ago

Biologists in a stew over Paleo diet

By Nicky Phillips

If you consider how we live in the Western world today very little resembles the way our hunter-gatherer ancestors lived 10,000 years ago.

We live in houses, sleep in beds, travel by cars and planes. We build bridges and skyscrapers. We can read and write.

'Kangaroo Fillet Salad' at the Paleo Cafe in Bondi Junction.

'Kangaroo Fillet Salad' at the Paleo Cafe in Bondi Junction.Credit: Tamara Dean

While most people are happy to exist in the present, when it comes to food, growing numbers of people are abandoning modern diets and returning to the food habits of our primitive forebears in the Paleolithic period, between 2.5 million and 10,000 years ago.

Broadly speaking, proponents of the Paleolithic, or paleo diet, believe longevity and good health comes from eating mostly fish, meat and vegetables - foods we presume ancient hunter-gatherers ate before the advent of agriculture and industry.

Paleo followers eschew grains, dairy and processed foods.

But the logic of the diet fails for a couple of reasons; it oversimplifies what early hunter-gatherers ate, and it assumes humans haven't evolved since the stone age.

So what do we know about the feeding habits of our Paleolithic ancestors, and how relevant are those habits to our own wellbeing?

While scientists cannot return to watch our ancestors prepare their meals, studies of archaeological remains, such as pottery and shells, combined with research on skeletal remains, particularly fossilised teeth, reveal many clues about their diets.

Significant insights have also come from observing contemporary hunter-gatherers, such as the Kalahari bushmen in southern Africa.

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Professor Vanessa Hayes, a geneticist who works with African populations, says, unsurprisingly, the diet of contemporary hunter-gatherers is based on what they can gather.

But apart from this commonality, their diets vary significantly, depending on climate and geography, says Professor Hayes, from the Garvan Institute of Medical Research.

"The basic diet of the hunter-gatherers in the Kalahari is the bush potato, bush cucumber and the manketti nut," she says.

But travel to a community 500 kilometres further south and a type of raisin berry is the centrepiece of their diet.

Where traditional hunter-gatherer diets diverge significantly from the paleo craze is meat consumption.

Professor Hayes says meat was not a daily staple of ancient ethnic groups in Africa.

"Meat was a celebration [because] you had to expend a lot of energy on the hunt," she says.

After a successful catch, the entire beast was consumed, more or less, at once.

"The hunter-gatherer diet was one based on stuffing yourself until everything was eaten, then you may live three or four days without eating at all," she says.

"I don't think anyone [today] would advocate that."

Professor David Raubenheimer, a nutritional biologist at the Charles Perkins Centre at the University of Sydney, says studies that examine what types of food were available also tells scientists about the food habits of these groups.

Sugars, starches and fats were scarce, he says.

And wild meat would have been significantly lower in fat, about 2 per cent of an animal's total body weight, he says.

Grain-fed farm animals have up to 20 per cent body fat.

Despite evidence that hunter-gatherers consumed a large ratio of protein to carbs, Professor Raubenheimer says that is not justification for people to eat excessive amounts of meat and cut out grains, as the paleo diet recommends.

Professor Hayes says some of the most compelling evidence against the paleo craze is genetic studies that show many ethnic groups, especially Caucasians and Asians, have adapted to eating grains.

"We've had 10,000 years of agriculture and during that time different populations have adapted in certain ways," she says.

Over a similar time period humans developed a tolerance to lactose, the main sugar in dairy products.

Before early Europeans started drinking milk, only infants produced the enzyme lactase, which break down lactose.

Professor Hayes says she understands some of the reasoning of proponents, who assume that because we lived as hunter-gatherers for 190,000 years, humans have evolved with the diet of those times, not the Western diet based on agriculture.

"But the thing they're forgetting is we've had 10,000 years to adapt," she says.

Professor Raubenheimer says recommendations on the best balance of protein, to fat and carbohydrates to reduce the risk of chronic diseases are based on how people live today.

In Australian and New Zealand that means eating a diet that is 15-25 per cent protein, 20-35 per cent fat and between 40 and 65 per cent carbohydrates.

"When we are speaking of paleo diets, they're proposing diets that are unbalanced," says Professor Raubenheimer

"That can only be a problem."

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