The problems with paleo
Neil Mann currently holds the position of Adjunct Professor in the School of Applied Science at RMIT University and has over 30 years' experience in nutrition research. He is author of over 70 refereed research papers and more than 100 national and international conference proceedings. He was also a Visiting Research Fellow at Oxford University, School of Anthropology for three years that included investigating the diet of early humans. We asked him about the current paleo diet trend.
What do we know about what early humans ate?
We know quite a lot through many fields including physics, anthropology, mathematics, biochemistry, archeology, genetics, anatomy, intestinal physiology and paleobiology. The consensus is early hominins left the African jungles for more dry grassland environments some 4 million years ago. Their diet had to change to suit this new environment and shifted from a frugivorous diet of wild fruits, nuts, flowers, non lignified leaves and stems, insects and opportunistic animal kills and eggs, to a diet involving more scavenged animal foods -mainly bone marrow and brain tissue- from large carnivore kills and any seeds, nuts, fruits and underground roots that could be found. With brain development and bipedalism these hominins began to hunt animals, gradually increasing the game size taken until by the paleolithic period just prior to agriculture we were heavily dependent on animal protein and fat for energy. Estimates vary with location but the median animal food content was approximately 60%. Plants still made up much of the diet but they were low in energy and their main role was provision of vitamins and minerals.
Is there one ‘paleo’ diet that we are evolved to eat?
The term paleo diet itself is unscientific and meaningless. It implies a diet we ate in one relatively short time period (the early stoneage) is the one we always ate and should eat because it’s "normal for us". This ignores the several million years of pre-paleo period food intake patterns during which most of our adaptations were taking place. There is no one paleo diet because the foods consumed during the paleolithic period varied depending on location. If it was edible, we ate it. We were omnivores but with high energy intake from animal sources in almost every area of the planet (and more so at higher latitudes).
Are humans adapted to grains that have arisen out of the development of agriculture?
Yes, but not as well as many other mammals and certainly not in the quantity and processed form we mainly consume today. We have learned to process grains to make their starch content higher and in a physical form that is rapidly digested causing a high glycemic response (high GI). Humans are not well equipped for constant high blood glucose peaks. In our pre-agricultural days there were virtually no high GI foods at all and they represent a new dietary insult to our metabolism.
Paleo diet followers typically eliminate dairy and suggest it is an unnecessary food. Is this accurate?
Many paleo proponents will tell you milk is not a normal adult food for us in an evolutionary sense. But it is normal in early childhood and with evolutionary exposure the ability to keep the lactase gene active in adulthood has developed, such that almost half the human race has this ability. Dairy foods have replaced pre-agricultural intake of some nutrients from other food sources, particularly calcium previously obtained from bulk intake of leafy greens that we longer consume in the same way. Whether there are aspects of milk that are harmful is still being debated, but the current weight of evidence is definitely on the ‘no’ side.
One of the most contentious parts of the paleo diet is avoidance of legumes, the reason being we only started eating them in agricultural times. Is this correct?
We probably did eat legumes where available, as we ate everything else. We probably don’t have a long evolutionary adaptation to legumes, but is it really relevant? They are nutritious foods and absolutely critical for survival in many parts of the world. Allergy and intolerance may be an issue to some populations that have a short history of exposure, but to say they are a serious universal health issue is alarmist.
Paleo diet proponents criticise the Dietary Guidelines for Australians because they include grains and dairy. Is this criticism valid?
In the Australian context both grains and dairy provide important sets of micronutrients critical to our well being. The message should be eat broadly from all five food groups to gain adequate nutrition and don't let any single food group dominate (or vanish) from your diet. Common sense and balance are the key messages. Absolute statements to avoid whole food groups are nonsense.
What are some of the biggest nutritional mistakes followers of the paleo diet make?
The more extreme versions that remove whole food groups can lead to micronutrient deficiencies, like any restrictive diet. Our ancestors ate anything that wasn’t toxic and we can too. It’s all a matter of balance, avoiding excess, and consuming more natural, minimally processed versions of foods from each group.
The biggest mistake of paleo dieters is at the planetary level. They want to eat a hunter-gatherer type diet on a planet of 7 billion people that at best could only accommodate around 500,000 million hunter gatherers. So the question to them is: If everyone followed the diet they promote as the healthiest for humans, will they volunteer to be one of the 6.5 billion people to starve?