Low fat diet and ovarian cancer
You may have read a lot lately about a new piece of published research "showing" that a low-fat diet reduces the risk of ovarian cancer.
Here's what happened.
Researchers studied two groups of women. The first group- about 19,500 women- were assigned to a "low-fat" regimen complete with 18 group sessions of behavioral modification in the first year, and 4 sessions a year after that. They carefully recorded their food intake.
The second group- about 29,000 women- ate their "regular" diet. Which turned out to be, by the way, about 10 percent higher in fat. There was one other difference between the two groups, but I'll save that for later.
In all other areas- age, race, BMI, exercise- the two groups were statistically matched.
For the first 4 years of the study there were no differences in cancer rates.
For the second 4 or so years, women on the first diet- which researchers called the "low-fat" diet- had a 40 percent reduction in risk for ovarian cancer. Now understand what that means. It does not mean 40% of the women did not get cancer. In the second ("regular diet") group, the percentage of women who actually got ovarian cancer was .003 (that's 3/1000). The percent in the so-called "low-fat" group was .002 (that's 2/1000). From a percentage point of view that's a 40% reduction but it's pretty damn thin when you look at what it really means. (Remember, an increase from 1 in a million to 2 in a million is a 100 percent increase!)
So in fact, 103 women in the "regular diet" group got cancer, and 57 in the so-called "low-fat" group did. Percentage wise that's nothing (3/1000 vs 2/1000 of a point) but if you're one of the extra 46 women, it's pretty darn significant.
But remember I told you there was one other difference between the two diets?
Here's what it was: The "regular diet" people ate on average one less serving of fruits and vegetables per day.
So what I want to know is this: Why in the world would you attribute that small difference in ovarian cancer to a tiny difference in total fat intake and NOT attribute it to the power of even a single serving of fruits and vegetables?
From this data, it is just as possible to conclude that even one serving of fruits and vegetables a day has a powerful enough effect to prevent 40 out of 29,000 women from getting ovarian cancer.
That makes way more sense to me than attributing it to a tiny reduction in fat. Vegetables and fruits have anti-cancer properties. Fat does not have "pro-cancer" properties, at least not when it's in the diet. (When it's on your body, maybe, but that's a completely different issue, though many people confuse them.)
This study shows nothing more than the fact that if you start out believing something (low-fat diets are great) you can find something in the data to support it.
And that the headline "one extra serving of fruits and vegetables a day can reduce cancer risk" isn't quite as sexy as the "low-fat" diet stuff.
Here's what happened.
Researchers studied two groups of women. The first group- about 19,500 women- were assigned to a "low-fat" regimen complete with 18 group sessions of behavioral modification in the first year, and 4 sessions a year after that. They carefully recorded their food intake.
The second group- about 29,000 women- ate their "regular" diet. Which turned out to be, by the way, about 10 percent higher in fat. There was one other difference between the two groups, but I'll save that for later.
In all other areas- age, race, BMI, exercise- the two groups were statistically matched.
For the first 4 years of the study there were no differences in cancer rates.
For the second 4 or so years, women on the first diet- which researchers called the "low-fat" diet- had a 40 percent reduction in risk for ovarian cancer. Now understand what that means. It does not mean 40% of the women did not get cancer. In the second ("regular diet") group, the percentage of women who actually got ovarian cancer was .003 (that's 3/1000). The percent in the so-called "low-fat" group was .002 (that's 2/1000). From a percentage point of view that's a 40% reduction but it's pretty damn thin when you look at what it really means. (Remember, an increase from 1 in a million to 2 in a million is a 100 percent increase!)
So in fact, 103 women in the "regular diet" group got cancer, and 57 in the so-called "low-fat" group did. Percentage wise that's nothing (3/1000 vs 2/1000 of a point) but if you're one of the extra 46 women, it's pretty darn significant.
But remember I told you there was one other difference between the two diets?
Here's what it was: The "regular diet" people ate on average one less serving of fruits and vegetables per day.
So what I want to know is this: Why in the world would you attribute that small difference in ovarian cancer to a tiny difference in total fat intake and NOT attribute it to the power of even a single serving of fruits and vegetables?
From this data, it is just as possible to conclude that even one serving of fruits and vegetables a day has a powerful enough effect to prevent 40 out of 29,000 women from getting ovarian cancer.
That makes way more sense to me than attributing it to a tiny reduction in fat. Vegetables and fruits have anti-cancer properties. Fat does not have "pro-cancer" properties, at least not when it's in the diet. (When it's on your body, maybe, but that's a completely different issue, though many people confuse them.)
This study shows nothing more than the fact that if you start out believing something (low-fat diets are great) you can find something in the data to support it.
And that the headline "one extra serving of fruits and vegetables a day can reduce cancer risk" isn't quite as sexy as the "low-fat" diet stuff.
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