Sunday, November 24, 2013

The Rose Corn Oil Trial


Participants and Diets

80 patients with either a history of MI or angina, but < 70 years old and without heart failure and other non-cardiac disease were randomised to one of three groups: (1) a control group; (2) an olive oil group; and (3) a corn oil group 

“Patients in both oil groups were instructed to avoid fried foods, fatty meat, sausages, pastry, ice-cream, cheese, cakes (except plain sponge), etc. Milk, eggs, and butter were restricted. An oil supplement of 80 g./day was prescribed, to be taken in three equal doses at meal-times” 

While, “No advice on dietary fat was give to control patients.” 

Period
Olive Oil
Corn Oil
No. of Patients
g/day (Average)
No. of Patients
g/day (Average)
0-6 Months
24
73
28
74
6-12 Months
19
52
22
64
12-18 Months
16
47
19
62
18-24 Months
13
51
13
51
Mean
58
64

They were prescribed 80g of oil, but ended up consuming less (table 2).   Still, ~60 grams is a lot and I think they did pretty well.  Even though these oils supplied an additional several hundred calories, they adjusted their calorie intake and ended up eating a fairly similar amount when measured at 24 months (table 3). 

Group
No. of Patients
Carbs
Protein
Fat
Calories
Calories from Oil
Total Calories
Control
16
249
64
70
1,933
1,933
Olive Oil
12
216
49
45
1,505
540
2,045
Corn Oil
15
189
57
50
1,475
595
2,070

Results 

Total cholesterol levels significantly decreased in the corn oil group except during the 18-24 month period, which might be due to lower compliance (table 4).



Control
Olive Oil
Corn Oil
Mean
P
Mean
P
Mean
P
0-6m
4.4
> 0.5
3.5
> 0.7
-25.0
< 0.01
6-12m
0.3
> 0.8
12.0
> 0.4
-30.8
< 0.01
12-18m
-7.9
> 0.4
4.0
> 0.6
-30.3
< 0.01
18-24m
-2.8
> 0.8
-0.9
> 0.8
-19.9
< 0.20

When participants suffered a major cardiac event they were withdrawn from the study.  Therefore the total major cardiac events = the number of men with major cardiac events.  Participants who had other significant cardiac pain remained in the study

The following data is compiled from table 6.  The corn oil group had a higher incidence of major cardiac events (12 vs. 6), total CHD events (15 vs. 11) and CHD mortality/total mortality (5 vs. 1) compared to the control group.

Control
Olive
Corn
Sudden death
1
2
3
Fatal infarction
0
1
2
Definite infarction, non-fatal
3
4
3
Probable infarction, non-fatal
2
2
4
Total major cardiac events
6
9
12
Other significant cardiac pain
5
2
3
Removed from trial for other complications*
0
2
2
Lost to follow-up
2
3
1
Proportion in trial and free of major cardiac events, as percentage of those not removed from trial for other complications nor lost to follow-up**
75
57
52

Olive oil is generally considered healthy, so the results from that group are surprising.  The instruction to avoid certain junk food in the oil groups would be expected to improve diet quality.  However, both oil groups had a higher incidence of major CHD events than the control group suggesting this was offset by the oil supplements.  This may suggest an adverse effect of high refined oil consumption, perhaps compounded by the poor diet quality of the participants (indicated by low protein intake), making them more sensitive to nutrient dilution and any potential adverse effects of high oil consumption

* One patient in olive oil for gangrene, one in corn oil for pulmonary embolism and one each for type 2 diabetes.  The incidence of type 2 diabetes in the oil groups is only N of 2, but the temporal relationship deserves attention: "One of them already had mild diabetes, but glycosuria increased considerably soon after he started oil.  Oil was stopped and glycosuria disappeared.  Oil was restarted, but was stopped a month later because heavy glycosuria recurred.  The other patient, not a previously recognized diabetic, developed glycosuria with a diabetic glucose-tolerance test a few weeks after starting oil."  

** “The likelihood that the difference between the control and corn-oil groups was due to chance is 0.05-0.1”

6 comments:

  1. So why is olive oil generally considered to be healthy? Are there, for example, some randomized controlled trials in which the group that got the olive oil was healthier in some way?

    ReplyDelete
    Replies
    1. Depending on who you listen to you'll probably hear at least one of these: 'it's part of the Mediterranean diet, MUFA, vitamin E or polyphenols'

      As for any RCTs, not to my knowledge, but then I haven't been looking. It's the right question to ask though

      Delete
  2. Steven, about the weight loss. The authors stated:

    "Patients in all three groups tended on average to lose a little weight as time went on. Unexpectedly, the average loss was greatest in the corn-oil group."

    I assume as they mentioned only within group changes that the weight between all groups was similar i.e. if they were differences between the groups I imagine they would have commented on it. However, I don't know why it was "unexpected" that the average loss was greatest in the corn-oil group. I wonder what the caloric intake was at baseline for all groups.

    Any thoughts?

    ReplyDelete
    Replies
    1. It's hard to know as they haven't given any figures regarding weight loss except baseline weight, which was slightly higher in the corn oil group (not significant)

      Perhaps it was unexpected as both the oil groups were consuming 25-30% of their calories from the oils, which is certainly not as nutrient dense as whole food. The oils may also not be as good as whole foods at promoting satiety per calorie consumed, which is supported by both oil groups having a slightly higher reported calorie intake

      Delete
    2. Thanks for your thoughts Steven.

      Delete
  3. The cranberry fundamental oil is likewise rich in Oleic corrosive, another irreplaceable component for the body. It is additionally extremely rich in Vitamin E and different components that prepare for harm to skin cells and trims down greasy substances in the body. click it

    ReplyDelete