Sunday, October 6, 2013

Other Paleolithic Diet Trials: Part 1

In diet trials it’s important to have a control group to control for placebo-like effects (for example, you often hear about how the control group eats better, does more exercise and loses weight).  Preferably this group, or another group, will be a second experimental group to be able to compare one diet/food to another.  This is because you should only eat a certain amount of food, so it’s important to know what foods (and exercise programs as well) are ‘better’. 

The two Paleo diet trials I blogged about previously did this, and so you were able to compare one diet to another.  There are other Paleo diet trials and unfortunately these ones didn’t have a control group.

The effect of transition from traditional to urban life-style on the insulin secretory response in Australian Aborigines (1980)

In each study a small group (13 and 10) of Australian Aborigines who had T2D went foraging in the outback with some modern aids like rifles and fishing tackles. 

Their previous diet was pretty poor and high in refined foods and alcohol.  The estimated macronutrient compositions for the traditional diets varied from (P:F:C) 50:30:20 in the first study to 80:20:<5 in a coastal area and 54:13:33 in an inland area in the second study, which came mostly from animal foods, yams and honey.  The first study described food as being “…plentiful and at no time was the group undernourished” while the second study had calorie intakes averaging only 1200 per day.  They also had high levels of physical activity.  Both studies observed weight loss and quite impressive improvements in glucose tolerance, insulin sensitivity and triglyceride levels (interestingly cholesterol didn’t change). 

I don’t think you should conclude from these studies that the ‘Paleoness’ of the diet (↑ meat, fruit, veg and ↓ grains, dairy, legumes) was responsible for the changes.  Their original diet was so poor that almost anything would have been better and there were a number of confounding variables in the intervention such as an extremely high protein intake (50%), a very low calorie intake which may have not been ad libitum, an increase in physical activity and weight loss.  Also, since the traditional diets were so high in protein they would really only be suitable for short-term, low calorie, weight loss diets. 

24 Piglets post weaning were randomly allocated to a ‘Paleo diet’ (mostly fruit and vegetables with some meat) or a cereal based swine feed with some added rapeseed oil.  Guess which group did better

The Paleolithic group ended up weighing less, had less subcutaneous fat, lower diastolic blood pressure, were more insulin sensitive and had much lower CRP (82%).  Although the cereal group ate more calories and weighed more, they didn’t have a higher body temperature. 

14 Healthy participants (5 male, 9 female), aged 20-40, ate a Paleolithic diet for 3 weeks. 

The Paleolithic diet was: ad libitum amounts of fruits and vegetables, unsalted fish, seafood, lean meats and nuts and flaxseed or rapeseed oil; limited amounts of dried fruit, salted seafood, fatty meats, potatoes, honey and cured meats; and no grains, dairy, legumes and processed foods. 

Energy (kcal)
Protein (%)*
Fat (%)
Carbohydrate (%)

Despite the fewer calories, the Paleolithic diet was higher in vitamin B6, C, E and potassium, but lower in calcium and sodium.  Although diet data only came from 6 participants 

Weight, waist circumference, systolic blood pressure, and PAI-1 (a pro-thrombotic protein) decreased 

9 Overweight, but not obese, sedentary and healthy participants (6 male, 3 female) aged 38±12 ate a Paleolithic diet for 10 days.  The diet seemed to be mainly lean meat, fruit, non-starchy vegetables and lots of carrot juice (see table 2). 

Energy (kcal)
Protein (g)*
Fat (g)
Carbohydrate (g)

The average intakes of potassium, phosphates and magnesium were higher and intake of sodium was lower.  The average calcium intake wasn’t significantly lower but calcium excretion was, suggesting a positive calcium balance. 

Total cholesterol, LDL-C, triglycerides, fasting insulin, insulin resistance and diastolic blood pressure decreased (see table 3 and 4). 

What I liked about this study was that they tried to control for potential effects of weight loss by increasing calories if the participants started to lose weight.  While weight is an important factor in IR, CVD, etc, this study (and I’m sure others) show that weight is not the only factor. 

Why the calories needed to be higher to prevent weight loss could be due to the calories in fruits and vegetables being far less easily extracted than refined foods, a change in the body fat setpoint/leptin sensitivity and/or for another reason.

The impact of the stone age diet on gingival conditions in the absence of oral hygiene (2009) 

For 4 weeks, 10 participants without periodontitis lived in semi-hunter-gatherer conditions (similar tools, shelter and food) with some aids (some food such as grains, salt, honey, herbs and milk.  A hunter would shoot an animal to provide meat.  But they also had to gather food themselves).  They had no access to dental equipment to clean their teeth although some of them used twigs to clean their teeth

The average number of sites with 'bleeding on probing' decreased from 34.8% to 12.6%.  However, the average gingival index increased but not significantly, due to the increase in plaque scores (0.68 vs. 1.47), which is not surprising given the lack of dental equipment.  Figures 2 and 3 are two pictures of a participant's mouth (before and after) and show that the experiment increased plaque and stuff on the teeth, but reduced inflammation in the gums.  Bacterial count was higher in all 74 species (again not surprising), but there was a reduction in some pathogenic bacteria in the tongue that is likely due to an absence of  simple sugars (except some fruit and honey).  The participants also lost between 1-5 kg and had a reduction in blood pressure (given the conditions and that they were in Switzerland and had to make their own fire, they probably had a forced calorie deficit).

The researchers suggest that a near absence of simple sugars and increase in phytonutrients may have been responsible for the decrease in inflammation.  Since their diet had whole grains, including wheat, you couldn't use this as evidence against grains.  This could be a good example where we have the potential to be healthier than hunter-gatherers, unless we're meant to have plaque and stuff on our teeth

See Part 2 for the uncontrolled trials after 2010

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