HUNTERGATHERERS: A shift in conventional thinking – less hunting and more fishing!

THE STORY SO FAR…

About ten years ago several world leading authorities published a raft of medical papers evaluating the diets of hunter-gatherers. Th e basis for their studies were many and included observational information, an analysis of an ‘ethnographic atlas’ (a data source of 1167 primitive societies), and the study of fossil records as well as current day hunter-gatherer tribes. Now the interesting thing about these series of articles, which appeared in the prestigious American Journal of Clinical Nutrition, is that several authors had different views as to what our ancestors ate. One group said high meat, low amounts of plant food, one said more plants and lower meat, and another said more fish and less meat.

When I read through these, I developed a really strong affinity to the last paper. In particular I was drawn to the relationship between fish, the nutrients it contained and the rapid accelerated growth of the human brain. The article, written by expert Stephan Cunnane came under a bit of fire by the other authors. It seems the preference was for HG’s to tuck into some steak as opposed to a fillet of salmon.

Ten years later, in the prestigious British Journal of Nutrition (2010), the meat theorists and the fish theorists have put their differences aside and come up with a rather robust theory – with some reasonably strong supporting evidence. It may seem that aft er all that, HG’s were not the successful hunters that have been portrayed in the scientific literature, but rather fish eaters!

WHY DO WE KEEP HARPING ON ABOUT HG DIETS?

Our genetics are a product of millions of years of evolution, and we have been able to adapt and thrive as a species given a host of ever changing environmental conditions. Our current environment has again changed (although this time it’s not an ice age), nor is it severe global drought. In fact it’s a sedentary society that over consumes food, a recipe that has unleashed a myriad of diseases. These diseases are killing off the human species. Obesity, type II diabetes, cancers and heart disease… were all absent from HG times. Yes we are living longer, but our increased life expectancy comes from technology, public health sanitation, prevention of childhood infections and famines in the western world.

However, in Remko Kuipers paper (titled: Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet, British Journal of Nutrition (2010), page 1 of 22), other changes are taking place in the human body due to our changing environment. It’s not just the eating and sitting, but the type of food we are consuming is diametrically opposed to what HG’s ate. For example we eat very little omega-3’s but plenty of omega-6’s. We now eat too much saturated fat, cholesterol, and trans fats, lower intakes of vitamin D and K, an imbalanced intake of antioxidants, high intakes of sugars, and little dietary fibre. We also have little exposure to sunlight. They hypothesise that the optimal diet is the one that our Paleolithic ancestors consumed living 2.5 million to 10,000 years ago.

Drilling a bit deeper than we previously have, is it that the environment from which our genetics evolved was not just a matter of eating meat or fish or plants? In fact it was much more and when scientists analyse the nutrients that our ancestors consumed, we gain a greater appreciation for Paleolithic nutrition. In order to obtain this full array of vitamins and minerals in their diet, scientists are now even more convinced that the savannah was not the preferred Paleolithic supermarket. The nutrients included fatty fish oils, namely EPA and DHA (the healthy long chain omega-3 fats), vitamin D and vitamin A as well as oils from plant foods, iron, iodine, zinc, copper, selenium, as considered ‘brain selective nutrients’.

From 1.9 million to 200,000 years ago our ancestors tripled the mass of their brains relative to their body weight. It has been hypothesised that brain growth was preceded by the body being able to store a substantial fat supply to feed it energy. Larger brains require more energy and that has been approximated at 20-25 per cent of resting metabolic rate. Th is is called the survival of the fattest theory. Hence during this time our ancestors moved out of the forest (where they’d been eating energypoor plant foods) and out to the shoreline. It was not just a matter of eating DHA though; it was about consistently eating it over many millennia.

A decrease in DHA and or the brain selective nutrients in the young of a species, results in sub optimal development. Hence newborn humans (and some primates) depend upon the mothers DHA status during the brain growth spurt, which occurs from the last trimester of pregnancy up to 2-years aft er birth. Mice fed low amounts of DHA from three days prior to conception, showed that the growing fetal brain is extremely sensitive to low maternal DHA. Hence during the explosion of the human brain and for many millennia aft er, it seems highly unlikely that DHA was not available in large amounts.

There is evidence our ancestors were consuming food from the sea as far back as 2.3-2 million years ago, and this is still a practiced today in east Africa. According to Remko Kuipers and his collegues, picking up, clubbing, spearing or killing aquatic animals from a distance seems to be much easier that hunting game on the Serengeti plains. It’s relatively easy (apparently) to hunt and gather spawning catfish, shellfish, crustaceans, and cephalopods (lobster, crab, shrimp, squid, octopus etc), sea urchins, amphibians, birds, reptiles and their eggs.

While it is possible that the brains of animals in the savannah were consumed (as they are high in DHA), this new research suggests that this was not done regularly enough. Their reason: iodine, which is absent from non aquatic animal brains. Iodine is found in abundance in marine based animals. The wide occurrence of iodine deficiency in people living inland suggests that our ancestor’s brain growth occurred from primarily a fish based diet.

TAKE HOME MESSAGE

Nutrition research never stands still. In just 10 years scientists have gone from being convinced that HG’s were primarily meat eaters, to being fi sh eaters. As I have pointed out many times, in western society we consume very little fish and very little DHA. The median intake of DHA in Australia is just 29 mg, while the average is less than 200mg. This is extremely low. The Japanese eat on average 1600mg per day and Greenland Eskimos eat 9000mg per day. The National Health and Medical Research Council recommend women eat about 430mg and men 610mg per day.

The point of this article is that it’s not just the fi sh we should be concerned about, but the brain selective nutrients we get with it: zinc, iodine, copper, selenium, iron, and EPA and DHA. About 10% of the human brain is comprised of the DHA found in fi sh. A lack of DHA has been linked to increasing the risk of Alzheimer’s disease, a decrease in IQ, increased anxiety, depression and ADHD. Consuming more DHA and its nutrients has been shown to increase higher order brain function in humans. It simply means people can ‘become’ smarter.

A more interesting point however, is how a diet rich in fish, fruit, vegetables, nuts and seeds translates when it comes to health. It would certainly require some imaginative meal preparation, but personally I think it would be amazing. Fish/aquatic sources such as canned tuna, salmon, sardines, perhaps tinned muscles and oysters (in spring water), as well as some whole salmon fillets, whole snapper, trout, barramundi, prawns, and crabs. With vegetables, the less cooking the better and provided they are not drenched in butter or oil and remain somewhat crispy, then they will remain healthy.

When it comes to fruit, dietary variety is important and eating many diff erent colours is a good guide. Breakfast might be tricky, but perhaps some untoasted muesli with honey and banana and low fat high calcium milk. While honey was treated as a delicacy in Paleolithic times, unless you want to get your calcium from some crunchy insects, low fat dairy calcium might be the way to go!

My take on such a diet – well if it led to the growth and sustained maintenance of the human brain, and worked in parity with the environment to mitigate almost all chronic diseases… it could only be amazing. If you try it let me know!