Sunday, September 15, 2013

Paleolithic Diet Trials: Part 1


29 male patients with ischaemic heart disease and either glucose intolerance or type 2 diabetes and a waist circumference >94cm were randomised to 2 groups (a Paleolithic group and a Mediterranean/Consensus group).  Patient characteristics at baseline were not significantly different, except the Paleolithic group was significantly older 65 vs. 57. 

Diets: 

Paleolithic diet
“They were advised to increase their intake of lean meat, fish, fruit and vegetables and to avoid all kinds of dairy products, cereals (including rice), beans, sugar, bakery products, soft drinks and beer. The following items were accepted in limited amounts for the Paleolithic group: eggs (one or fewer per day), nuts (preferentially walnuts), potatoes (two or fewer medium-sized per day), rapeseed or olive oil (one or fewer tablespoons per day). The intake of other foods was not restricted and no advice was given with regard to proportions of food categories (e.g. animal vs. plant foods).” 

Mediterranean diet
“Based on whole-grain cereals, low-fat dairy products, potatoes, legumes, vegetables, fruits, fatty fish and refined fats rich in monounsaturated fatty acids and alpha-linolenic acid” 

“Advice about regular physical activity was given equally to the two groups. Both groups were advised not to consume more than one glass of wine per day” 

Significant differences in food
Foods higher in the Paleolithic diet
Foods higher in the Mediterranean diet
Fruits
Cereals without rice
Nuts*
Rice*
Meat
Milk/milk products
* Significant, yet small differences 

Macronutrients
Paleolithic diet
Mediterranean diet
Energy (kcal)*
1388
1823
Weight (g)
1493
1649
Energy Density (kcal/g)
1.07
1.29
Protein (%)*
27
20
Fat (%)
(SFA*/MUFA/PUFA (g))
28
(13 / 18 / 10)
28
(19 / 22 / 12)
Carbohydrate (%)*
39
47
Alcohol (%)
3
2
Fibre (%)
3
3
* Significant differences 

You may realise that the average energy density doesn’t equal the average energy/weight.  That’s because they would have calculated each individual’s energy density and averaged that instead 

There were only a few significant differences in micronutrients.  The Mediterranean diet provided significantly more calcium and sodium.  However, the Paleolithic diet contained 24% fewer calories 

See table 2 

Results: 

Glucose Tolerance Related 

The table below has the results where the Paleolithic group had a significant difference within group compared to baseline and a significant difference at 12 weeks between groups and a significant difference in the change 0-12 weeks between groups.  Italics indicate a non-significant difference within group compared to baseline 

Paleolithic
(n=14)
Mediterranean
(n=15)
Waist circumference (cm)
Baseline
105.8
106.6
12 Weeks
100.2
103.6
Change 0–12 weeks
-5.6
-2.9
AUCb Glucose0–120 (mmol/l×min)
Baseline
1104
1145
12 Weeks
807
1065
Change 0–12 weeks
-290
-80
30 min plasma glucose (mmol/l)
Baseline
10.0
10.7
12 Weeks
8.0
10.3
Change 0–12 weeks
-2.0
-0.4
120 min plasma glucose (mmol/l)
Baseline
8.9
8.8
12 Weeks
5.6
7.9
Change 0–12 weeks
-3.3
-0.9
Normal Glucose Levels
Baseline
2
2
6 Weeks
10
10
12 Weeks
14
7
Diabetic Glucose Levels
Baseline
10
9
6 Weeks
1
3
12 Weeks
0
5

Insulin levels didn’t change that much.  Italics indicate a non-significant difference within group compared to baseline 

Paleolithic
(n=14)
Mediterranean
(n=15)
Fasting plasma insulin (pmol/l)
Baseline
102
123
12 Weeks
86
101
Change 0–12 weeks
-16
-22
30 min plasma insulin (pmol/l)
Baseline
575
625
12 Weeks*
453
507
Change 0–12 weeks
-121
-118
120 min plasma insulin (pmol/l)
Baseline
988
674
12 Weeks
615
631
Change 0–12 weeks*
-374
-42
AUCb Insulin0–120 (nmol/l×min)
Baseline
80.5
69.7
12 Weeks
56.1
60.4
Change 0–12 weeks*
-24.3
-9.3
* Significant differences between groups 

Both groups also lost weight, but the differences between groups was not significant 

Paleolithic
(n=14)
Mediterranean
(n=15)
Weight (Kg)
Baseline
91.7
96.1
12 Weeks
86.7
92.2
Change 0–12 weeks
-5.0
-3.8

See table 2, table 3 and table 4 of the first study 

Satiety 

There was no significant difference between the groups in the time between meals (~3.5 hours), the meals per day (~4.5) and reported satiety before and 30 minutes after the meal.  The difference was in the number of calories it took to reach a given level of satiety. 

Paleolithic
(n=13)
Mediterranean
 (n=14)
Energy from good and drink per day (MJ)
5.8
7.6
Quotient of mean change in satiety during meal and mean energy from food and drink per meal (RS/MJ)*
2.5
1.6

* The change in satiety before and after the meal divided by the energy content of the meal 

See table 1 

There weren’t many significant differences related to leptin and the only notable significant difference between groups was the relative change in fasting plasma leptin over 0-12 weeks when an outlier in the Paleolithic was removed (too many cereal grains). 

Paleolithic
(n=14)
Mediterranean
(n=15)
Fasting plasma leptin (ng/ml)
Baseline
10.7
13.5
12 Weeks
7.1
11.0
Change 0–12 weeks
-35%
-18%

See table 3 

“In post hoc analysis, the strongest correlation between relative change in leptin after 12 weeks and dietary variables was with intake of cereals excluding rice”.  See figure 3.  This correlation was dependent on changes with waist circumference. 

“In post hoc analysis, quotients of mean change in satiety during meal and mean consumed energy from food and drink did not correlate with any of the group dietary differences (intake of energy, protein, carbohydrates, GL, saturated fatty acid, fatty acid C14:0, vitamin A, calcium, sodium, fruits, nuts, meat, cereals without rice, rice, milk/milk products) except for fatty acid C4:0-10.0 and fatty acid C12, and also did not correlate with fiber, energy density, water or beverages.” 

Among the group dietary differences there was a correlation between Satiety Quotient for energy and intake of energy, absolute intake of carbohydrates, GL, saturated fatty acids and sodium.” 

The Discussion and Some Thoughts 

Insulin Resistance Related 

“The more pronounced improvement of glucose tolerance in the Palaeolithic group was unrelated to weight loss or decrease in waist circumference. In contrast, the insulin response changed more as a result of change in waist circumference than of dietary assignment or food choice.” 

To make my life easier, and this blog post easier to read, I didn’t include the data for 6 weeks, the change between 0-6 weeks and the change between 6-12 weeks.  In the results section you see that the Mediterranean group was more competitive in weeks 0-6 than in weeks 6-12.  At 6 weeks there was no significant difference between groups except for waist circumference in favour of the Paleolithic group, although a fair bit of this is probably due to the low number of subjects.  In several measurements the Mediterranean group had non-significant increases, which is reflected in the number of ‘diabetic glucose levels’ increasing 

So you would expect there to be more dropouts in the Mediterranean group, but that actually wasn’t the case.  3 people dropped out of the Paleolithic group, whereas none dropped out of the Mediterranean group.  Perhaps a decrease in compliance outside of dropping out was responsible, but if anything I would expect the Paleolithic diet to be harder to stick to (more expensive, more restrictive and more difficult to eat out).  Perhaps the Mediterranean diet had yielded the majority of its benefits by the 6 week stage, I don’t know? 

By the way, this is the study that people are referring to if they say the Paleo diet reversed type 2 diabetes 

Satiety Related 

“Our previously reported marked improvement of glucose tolerance from this study was not correlated to new data reported here on satiety, leptin, leptin receptor or free leptin index.” 

The leptin results are consistent with both groups achieving a significant reduction in weight and the satiety results are consistent with both groups being on an ad libitum diet.  See figure 4 

I wouldn’t put much weight on the correlations they found.  When you compare two fairly different diets there are many quantitative differences.  It’s difficult to control for the confounding variables and use correlations to find the actual cause.  You can see this especially in the two last paragraphs I quoted.  The researchers put forward the following mechanisms for sodium and carbohydrate:  ↓ sodium >> ↓ palatability >> ↑ satiety*; and replacing carbohydrate with protein >> ↑ satiety.  Beside those, why would intake of fatty acids 4:0-10:0 and fatty acid 12:0 (in such small quantities), other SFAs and total energy* consumed be associated with reduced satiety per calorie for any other reason than because those nutrients were significantly lower in the Paleolithic diet and the Paleolithic diet had greater satiety per calorie? 

* ‘↓ Sodium >> ↓ palatability >> ↑ satiety’ may be true at high sodium intakes but I suspect within the context of comparing two low sodium diets this would apply: ‘↓ sodium >> ↑ nutrient hunger >> ↓ satiety’ 

** This correlation is simply a consequence of measuring satiety per calorie on ad libitum diets 

I’ll save any general thoughts about both the Paleo RCTs for a later blog post 

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