Sunday, July 12, 2015

Sondergaard et al (Mediterranean Diet for Endothelial Function)

The meta-analysis by Hooper et al 2012 included 4 other trials, one of which was a trial by Sondergaard et al.


Methods

131 people with ischemic heart disease and total cholesterol ≥5 mmol/L (193 mg/dL) were randomized to receive Mediterranean dietary advice (n = 68) or no specific dietary advice (n = 63).  In addition, both groups were treated with Fluvastatin (40 mg once daily)

The Mediterranean group was advised to “eat at least 600 grams of fruits and vegetables daily, to modify the intake of fat, especially saturated fat from meat and dairy produce, to eat fatty fish at least once a week and preferably several times a week, to eat plenty of bread and cereals, and to replace refined, hard, animal margarine products with vegetable oils, preferably canola oil”

While the control group “was offered booklets about heart-healthy diets that are usually delivered to patients in the coronary care unit (CCU). They were also offered a single visit to a dietitian who was not participating in the study”

Food and macronutrient intake is presented in table 4 and the differences between the groups is summarised below.  Calorie intake wasn’t reported, but I calculated* it to be approximately 1518 and 1545 respectively

Higher in Experimental Group
Higher in Control Group
Fatty fish
Beef, veal and pork
Carbohydrate
Fat
PUFA
SFA (P = 0.06)

MUFA

There were a few differences between the groups at baseline (table 3).  The experimental group had fewer men (62% vs. 79%), more people with hypertension (35% vs. 16%) and less people on ‘long-acting nitrates’ (6% vs. 19%).  The experimental group may have had more people taking multivitamins (35% vs. 24%) as I suspect the p value of 0.3 may be a typo

* SFA, MUFA and PUFA are measured in grams and total fat is measured in % of energy.  Therefore: total calories ≈ (SFA + MUFA + PUFA) x 9 / (percentage of calories as fat / 100)

Results

As expected from the use of statins, total-C and LDL-C significantly decreased in both groups.  Triglycerides also significantly decreased to a lesser extent, and both groups experienced a minor, non-significant increase in HDL-C (table 2)

Flow mediated dilation (a measure of endothelial function) was similar at baseline and improved in the Mediterranean group to a much greater extent such that the difference at 12 months was significant (P < 0.01) (table 2)


Mediterranean
Control
Baseline
4.32
4.30
12 Months
8.62
5.72

The paper didn’t publish any data on endpoints.  What we have comes from Hooper et al (who would have contacted the authors), which is presented below.  There weren’t many hard endpoints, such as myocardial infarctions (heart attack), strokes and deaths, most likely due to the small size (N = 131) and short duration (12 months).

What’s surprising is the relatively large number of total CVD events, most of which are likely to be very soft, which was unaffected by the Mediterranean diet used in this study despite a substantial difference in flow mediated dilation


Experimental Group
(N = 68)
Control Group
(N = 63)
Myocardial Infarction
2
3
Stroke
1
2
Combined CVD Events
40
42
CVD Mortality
3
4
Total Mortality*
4
4
* The extra death in the experimental group came from cancer (which was the only cancer diagnosis)

Hooper et al classified this trial as a reduced and modified fat trial, but there were other differences as well and Hooper et al flagged the trials as not being free of differences besides fat:

·         The higher fish intake in experimental group (67 vs. 46, P = 0.03)
·         The slightly higher intake of fruits and vegetables (572 vs. 504, P = 0.13)
·         The advice to reduce “refined, hard, animal margarine products”, which may include major sources of trans fat
·         The likelihood that the experimental group replaced refined grains with whole grains, given the kind of dietary advice the Mediterranean group was given, although the study didn’t differentiate whole grains and refined grains in the sections on dietary advice and food intake

In addition, this wasn’t much of a modified or reduced fat diet.  The difference in total fat was significant, but fat intake only differed by 2.7% (26.2% vs. 28.9%).  Likewise, while SFA intake was almost significantly lower (P = 0.06) and PUFA intake was significantly higher in the Mediterranean group, SFA intake only differed by 3g (17.4g vs. 20.4g) and PUFA intake by 2.4g (13.0g vs. 10.6) (MUFA intake was 13.8g vs. 18.6g).

3 comments:

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  2. Hi Steven,

    Such studies frustrate me, mainly because the dietary differences are never really different enough to draw meaningful conclusions. The 'statistically significant results' that do appear (also due to the many non-end point measures) nearly guarantee everyone to see what they what in them...somewhat akin to reading tea leaves!

    Cheers

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    1. Yes, it would be a lot simpler and more meaningful to compare foods rather than '+10% this, -10% that' eating patterns

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