Sunday, April 6, 2014

Low-Fat Diet in Myocardial Infarction (Ball, et al)

Low-fat diet in myocardial infarction (1965) 

Participants and Diets 

264 men, under 65, who had recently had their first heart attack, were randomised to one of two diet groups: a low fat diet or the control diet.  The low fat diet group were advised to eat only 40g of fat per day.  “The daily allowance included 14 g. (1/2 oz.) butter, 84 g. (3 oz.) of meat, 1 egg, 56 g. (2 oz.) cottage cheese, and skimmed milk. The nature of the fat consumed was not altered, nor were any additional unsaturated fats given”
 
We have a limited amount of data on what they actually ate, but we’re told the low fat group had a large reduction in fat (~ 45g vs. 110-130g*) and ate fewer calories (~ 1900-2000 vs. 2300-2600) compared to the control group
 
 

Those who were overweight (21% of controls and 15% of LF group) were put on calorie restricted diets.  In the control group the calories that were restricted mostly came from carbohydrate instead
 
* Even though they didn’t meet the target of 40g, it’s a good effort considering “the diet was often unpleasant” and there was a large difference between the groups
 
Results
 
Both groups, particularly the low fat group, lost weight and lowered their cholesterol.  (The reduction of cholesterol in the control group may have been due to weight loss) 

 
 
Low Fat Diet
Control Diet
Total Cholesterol
(mg/dl)
Baseline
260
266
6 Months
223
251
4 years
216
241
Weight
(lb)
Baseline*
161
166
6 Months
148
159
4 years
151
158
* This difference was almost significant (01 > p > 005)
** Unfortunately we aren’t told whether the differences were significant, but they probably were
 
Ultimately though, despite the large difference in fat consumption and the reduction in cholesterol levels, there was no difference in either relapses or death, both in the general study population (table VII), and among those with severe CHD (table VIII).  (Fortunately the people who assessed the CHD events in this trial were blinded)
 

Also, “the mean follow-up time to first relapse or end of trial was 3-04 years for the low-fat group, and 3-05 years for the control group”.
 

One might argue that the lack of difference was because the low fat group almost doubled their intake of added sugar, but the researchers found that carbohydrate and added sugar consumption wasn’t associated with relapses.  Although if you ignore the 0-5 g/day group in table VI (which I find difficult to believe) there’s a trend, but it’s not that exciting
 

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