Tag Archives: Australian Aborigines

Are Rats Related to Tooth Decay?

From Karl Gruber at Scientific American:

You could be forgiven for thinking that tooth decay is an inevitable fact of life; even ancient Egyptians practiced dentistry. But the study of human teeth suggests that before our ancestors started cultivating plants for food, cavities were uncommon. Tooth decay, it seems, spread once we changed to an agricultural lifestyle.

New evidence from Omar Eduardo Cornejo Ordaz, a postdoctoral research fellow at the Stanford School of Medicine, and his colleagues back up this hypothesis. They analyzed the genomes of several strains of the prevalent caries-causing bacterium,Streptococcus mutans, to determine when new genes evolved in this species and its close relatives. The team’s statistical analyses suggest the bacteria’s population started expanding exponentially about 10,000 years ago, which coincides quite nicely with the birth of agriculture.

Smiling LipsThe article mentions Peter Brown, an Australian paleoanthropologist, who favors sugar and other refined carbohydrates as a cause of dental decay.  No need to invoke rats.  Australian aborigines and Japanese samurai in the Edo period saw deterioration of dental health after introduction of sugars and other refined carbs.

Maybe it’s true: No carbs, no cavities.


h/t Amy Kubal

Classic Australian Aborigine Study on Return to Ancestral Diet and Lifestyle

Did you know kangaroo is edible?

The scientific article I review today is often cited by those who favor a Paleolithic diet for diabetics.  Cordain and Stefanson have written about it, for example.


Urbanized Australian Aboriginal communities have a high prevalence of type 2 diabetes.   Kerin O’Dea writes:

The change from an urban to a traditional lifestyle involves several factors that directly affect insulin sensitivity: increased physical activity, reduced energy intake and weight loss, and changes in the overall dietary composition.  All of these factors improve insulin sensitivity and should, therefore, be of benefit to the insulin-resistant diabetic.


Ten urban type 2 diabetic and four nondiabetic full-blood Aborigines agreed to revert to their traditional lifestyle as hunter-gatherers in an isolated region of Australia for seven weeks.  Average age was 53.  Half of them were moderate to heavy alcohol drinkers.  Average diabetic weight was 82 kg (180 lb); nondiabetics averaged 77 kg (169 lb).  There were equal numbers of men and omen.  None of the diabetics was on insulin, and only one was on an oral diabetic drug (a sulfonylurea). 

Ayers Rock, Uluru National Park, Australia

The study was carried out at Pantijan, the traditional land of these Aborigines.  It’s a day-and-a-half drive in a four-wheel vehicle from Derby.  At least it was in 1984.

For seven weeks, the participants ate only what they hunted or collected.  Diet composition was dependent on whether they were travelling to the homeland (1.5 weeks), at the coastal location (2 weeks), or inland on the river (3.5 weeks). Protein sources were mainly beef, kangaroo, fish, birds, crocodiles, and turtles.  Carboydrate content ranged from under 5% to 33%.  Protein content varied from 50 to 80%.  Fat was 13 to 40%.  So, very high protein and low-carb.  Carb sources were yams, honey, and figs.  Yams were the predominant carb source.  They also eat yabbies (shrimp or crayfish (“crawdads” in Oklahoma)).  Average energy intake was a very low 1,200 calories a day. 

The author implies this was the traditional Aboriginal diet.

What did they eat back home in the city? 

The main dietary components were flour, sugar, rice, carbonated drinks, alcoholic drinks (beer and port), powdered milk, cheap fatty meat, potatoes, onions, and variable contributions of other fresh fruit and vegetables. 

O’Dea estimates a macronutrient breakdown of 50% carb, 40% fat, and 10% protein (similar to the Standard American Diet, then).

What Did O’Dea Find Out?

Everyone lost weight, a group average of 8 kg (18 lb) over the seven weeks.

Fasting blood sugars fell in the diabetics from 11.6 mmol/l to 6.6 mmol/l (209 to 119 mg/dl).  After-meal blood sugars also fell dramatically.

Fasting insulin levels fell from 23 to 12 mU/l.

Fasting triglycerides fell drastically. 

HDL cholesterol fell significantly, whereas LDL cholesterol tended to rise.

So What?

How often do you see a scientific article with just one author?  Rarely, these days.

The investigator wrote that, “Under the conditions of the study it is difficult to separate out effects of dietary composition, low energy intake, and weight loss.”

O’Dea estimates that experimental activity levels were probably higher than in the urban setting, but not dramatically more so.  (He was with the participants throughout the experiment.)

The main carbohydrate sources in this ancestral diet were yams, honey, and figs.  Modern Australian honey is probably similar to the honey of 100,000 years ago.  But what about yams and figs? 

These folks had to have been eating twice as many calories, at least, back in their urban environment.  O’Dea didn’t comment on how well the participants tolerated calorie restriction.  Did they complain?  Did they eat to satiety?  They had no access to food other than what they could hunt and gather.  Was food in short supply?  It’s not documented.  You’d think O’Dea would mention these issues if they were a problem. 

This particular ancestral diet was extremely high in protein: 50–80% of calories.  (Eaton and Konner suggest that an average ancestral diet provides only 25–30% of total calories from protein.  A typical modern high-protein diet derives about 30% of calories from protein, compared with 15–18% in the standard American diet.)  Protein helps combat hunger.  But halving caloric intake for seven weeks is extreme.  Don’t believe me?  Just try it.  This degree of caloric restriction by itself would tend to lower blood sugar levels and body weight in most humans, regardless of macronutrient ratios and ethnicity.

I know nothing about Australian Aborigines as an ethnic and genetic group.  Is their diabetes similar to European diabetes?  Pima Indian diabetes?   

O’Dea never called the study diet Paleolithic, because it wasn’t. It was a modern hunter-gatherer diet eaten by rural, isolated Australian Aboriginal communities.

This calorie-restricted, very-high-protein, natural diet was very effective for weight loss and blood sugar control in this tiny, seven-week study on a specific ethnic population.  I bet the caloric restriction was the most effective component of the lifestyle change.  Restriction of refined sugars and starches also helped. 

This ancestral diet was beneficial for a few Australian Aborigines.  Are the lessons widely applicable?  Not yet.  As they say, “further studies are needed.”  You can’t just cite this study to say that paleo diets are healthy for diabetics.

It does jibe with plenty of other research that shows severe calorie restriction leads to weight loss and lower blood sugar levels.

Steve Parker, M.D.

Reference: O’Dea, Kerin.  Marked improvement in carbohydrate and lipid metabolism in diabetic Australian Aborigines after temporary reversion to traditional lifestyle.  Diabetes, 33 (1984): 596-603.