Wednesday, December 31, 2014

Paleolithic Diet Trials: Boers, et al (2014)

 
34 people with at least 2 aspects of the metabolic syndrome were randomised to follow a Paleolithic diet (PD) or a diet based on the Dutch Health Council guidelines (DHCG) for 2 weeks.
 
At baseline there were some significant differences between the groups: the PD group weighed more (98.0kg vs. 86.0kg), had more aspects of the metabolic syndrome on average and more people with low HDL-C and high fasting glucose.  HDL-C, triglycerides, the triglyceride:HDL-C ratio, the total:HDL-C ratio and hs-CRP were almost significantly higher in the Paleolithic group (p = 0.06-0.11) (table 2 and table 3)
 
The Paleolithic diet “was based on lean meat, fish, fruit, leafy and cruciferous vegetables, root vegetables, eggs and nuts. Dairy products, cereal grains, legumes, refined fats, extra salt and sugar were not part of it”.
 
The participants were given daily menus for the trial period, which were calorie controlled to 2078 calories (so the diets were isocaloric).  “Although coffee and tea were not part of a Palaeolithic-type diet, subjects were allowed to drink, in view of possible withdrawal symptoms, up to two cups of coffee or black tea per day. Any medication was continued at the same dosages”
 
Nutrient intake is presented in table 1 and I summarised the calorie and macronutrient ratios in the table below.  Micronutrient intake was also measured and the PD group had a high intake in 15/19 of micronutrients measured (including LCO3, excluding sodium and vitamin D), except phosphorus (equal), calcium, iodine and vitamin B3 (lower), see graphs below
 
Although we weren’t told what both groups actually ate, we can have a good guess.  Since the PD group had a higher intake of animal protein and most of their carbohydrates came from sugars they were probably consuming more meat and fruit, with starchy vegetables being a minor part of the diet
 
 
Energy (kcal)
Pro:Fat:Carb
PD
2079
24:41:32
DHCG
2076
17:29:50
 
Nutrient intake (% of RDA)
Average: PD 173%, DHCG 117%
Median: PD 143%, DHCG 118%

 One of the aims of the study was to keep body weight stable.  However, 9 participants (7 in PD group, 2 in DHCG group) had over 2kg of weight loss and so were given extra snacks even though they weren’t hungry.  This could indicate a change in the body fat setpoint (leptin resistance)
 
Both groups had a number of improvements, specifically in waist circumference, blood pressure, fasting glucose and blood lipids (table 3, table 4 and table 5).  Neither group had a significant change in AUC glucose, AUC insulin, hsCRP, TNFα and the lactulose:mannitol ratio (measure of intestinal permeability).  Also see the table below
 
 
Paleolithic
Diet
Dutch Health Council Guidelines
Mean
SD
Mean
SD
Abdominal circumference (cm)
-3.1
2.0
-3.3
2.4
Systolic BP (mmHg)
-8.5
12.0
-4.2
5.6
Diastolic BP (mmHg)
-8.0
8.3
-3.5
5.6
Glucose fasting (mmol/l)
-0.4
0.5
-0.4
0.4
Insulin fasting (mU/l)
-2.7
5.0
-1.4
3.2
HOMA IR
-0.9
1.5
-0.5
0.7
AUC insulin (mU/l x min)
-1918
4361
362
1515
TG:HDL-C (mol/mol)
-0.8
1.2
0.2
0.3
TC (mmol/l)
-0.7
0.7
-0.4
0.5
HDL-C (mmol/l)
-0.0
0.1
-0.2
0.1
LDL-C (mmol/l)
-0.3
0.5
-0.2
0.5
TG (mmol/l)
-0.9
1.1
0.1
0.4
TC:HDL-C (mol/mol)
-0.5
0.7
0.9
1.3
Homocysteine (μmol/l)*
1.2
1.3
0.3
1.9
Bold: p < 0.05, underline p < 0.10
 
After adjusting for weight loss, the improvements in systolic blood pressure, characteristics of the metabolic syndrome, TG:HDL-C, HDL-C, TG and TC:HDL-C were significantly greater in the PD group relative to the DHCG group (table 6)
 
Overall, this trial found a Paleolithic diet is more successful than convention dietary guidelines at improving features of the metabolic syndrome even though the diets were isocaloric.  The main limitations though are the small number of participants (n=34) and the higher starting weight and worse health of the PD group at baseline gives them more room for improvement.  The short duration of the trial mainly makes it difficult to access long term compliance.  It’s worth noting that: “after two weeks 89% of the Palaeolithic group and 64% of the reference group were still motivated to continue their dietary regimes”.  I don’t see the short duration of the trial being a limitation in so far as getting improvements in metabolic health as things like glucose tolerance and insulin resistance can be altered (even completely restored) in much shorter timeframes.
 
* It’s odd that homocysteine significantly increased in the PD group, but not the DHCG group even though folate and vitamin B12 intake were higher in the PD group

3 comments:

  1. These researchers were most interested in comparing the two diets' effects on metabolic syndrome. I wonder why they didn't just take metabolic syndrome patients and put them all on their paleo diet. That's what they were interested in anyway. Adding the second diet only complicated matters in my view. They said the paleo diet had never been tested in metabolic syndrome patients.

    I took a fresh look at this study as if it were simply a paleo diet trial involving 18 subjects who had metabolic syndrome. If I’m interpreting Table 5 correctly, and I think I am, these are the statistically significant changes after two weeks:

    abdominal circumference decreased by 3.1 cm
    systolic and diastolic blood pressures dropped by 8.5 and 8, respectively
    fasting glucose dropped by 0.4 mmol/l (7 mg/dl)
    fasting insulin fell
    HOMA-IR decreased (less insulin resistance)
    the fall in AUC (area under the curve) for insulin approached but didn’t reach statistical significance (p=0.08)
    total cholesterol, LDL-cholesterol, and triglycerides decreased
    Body weight fell from 98 kg (216 lb) to 95.3 kg (210 lb) but I found no p value. HDL-cholesterol was unchanged (the higher HDL I mentioned above is only in comparison to the reference diet, in which HDL fell)

    All of these changes (except the lack of change in HDL-chol) would tend to promote health in someone with metabolic syndrome, prediabetes, or overweight type 2 diabetes.

    -Steve

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    Replies
    1. In the abstract they say:

      "The main goal of this randomized controlled single-blinded pilot study was to study whether, independent of weight loss, a Palaeolithic-type diet alters characteristics of the metabolic syndrome"

      Then in the introduction they say:

      "The main goal of the current pilot study was to compare metabolic effects of a Palaeolithic-type diet with those of a healthy reference diet, independent of weight loss, in subjects with the MetS"

      So it's hard to know what their end goal was: was it just the effects of a Paleo diet, or was it also a comparison? Given that calories were matched, I would guess they were after a comparison without calorie intake and weight loss potentially mediating differences between the groups

      Having a group to compare to is extremely important to see if the Paleo diet is better, equal or worse than the conventional guidelines

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