The Feb 8,2006 issue of JAMA published the results of a trial that will make headline news and reinforce the beliefs of some folks that the medical profession and research scientists still do not know what to tell people to eat or not eat.
The Women's Health Initiative Randomized Controlled Dietary Modification Trial consisted on over 48 thousand women aged 50-79 who were randomly assigned to a control or intervention group, the later of which was to reduced total fat intake to 20% of calories and increase the veggie-fruit servings to six/day.
The results: The intervention had had no effect on the risk of coronary disease,stroke or total cardiovascular disease.
Let the spinning begin. As the accompanying JAMA editorial asks "Why were there a null finding ?"
Here are some possible reasons:
1)The study did not follow the participants long enough (the follow up was 8.1 years, 2) both groups were fairly healthy and therefore it would be harder to show a difference. 3) there was not really that much difference in the fat intake between the two groups 4) the degree of fat reduction in the treatment arm was not sufficient to expect much of a difference. 5) The intervention was reduction in total fat not necessary in saturated and trans fats.
I believe number 5 is key. The WHI study was basically testing a hypothesis that by the time of publication was clearly outdated. The current party line is reduce saturated fat and trans fat to reduce heart disease risk and monounsaturated fat may actually be good for you.
This is major factor of life in these mega multiyear trials,the hypothesis of several years ago is often not even an issue by the time such a trial is underway less alone completed. Medical knowledge (or theory) grows much faster than we will even keep pace with randomized trials.
I have been advising patients for years that the issue is not to decrease total fat in an effort to decrease heart attack risk. I can now use this giant trial to illustrate how that ( the total fat reduction approach which no one really believe now anyway) does not seem to work.