Tuesday, August 3, 2010

China Study - truth or goof?

Recently, there had been a lot of talk about this lady, Denise Minger who shoots down Dr T. Colin Campbell for his work on the China Study. At her blog - raw food SOS, she used the raw data gathered for the China study and create her own statistical analyses using those numbers. This new data contradicted much of what is claimed by the results of the China Study - generally, that a plant-based diet is good.

Dr Campbell has replied to these studies conducted by Denise in his reply here (pdf file).

One interesting thing that Colin mentioned about statistics is this:

"In a study like this survey in China (ecologic, cross-sectional), univariate correlations represent one-to-one associations of two variables, one perhaps causal, the other perhaps effect. Use of these correlations (about 100,000 in this database) should only be done with caution, that is, being careful not to infer one-to-one causal associations. Even though this project provided impressive and highly unique experimental features, using univariate correlations to identify specific food vs. specific disease associations is not one of these redeeming features, for several reasons. First, a variable may reflect the effects of other factors that change along with the variable under study. Therefore, this requires adjustment for confounding factors—mostly, this was not done by Denise. Second, for a variable to have information of value (as in making a correlation), it must exhibit a sufficient range. If, for example, a variable is measured in 65 counties (as in China), there must be a distribution of values over a sufficiently broad range for it to be useful. Third, the variables should represent exposures representative of prior years when the diseases in question are developing."

Just based on the 1st point alone, we could understand, for example, that we can't just take numbers on egg consumption and numbers for disease rates, do an analysis, and then say "eggs causes this disease" or "eggs don't cause this disease".

Say for example, if eating eggs does not always lead to high blood pressure, and high blood pressure does not always lead to heart disease; then a study that tries to find out the relationship between eggs and heart disease have to take into account the "high blood pressure" factor. We can't just take the numbers for egg consumption and heart disease, put them into analysis and claim the result of "association" or "not association" alone. Correlations results have to be adjusted for these factors, which wasn't performed for the analyses on raw food sos website.

Figures and numbers aside, frankly speaking, I really do not understand why there is a need to claim Colin Campbell as someone trying to tweak data for his own "plant-based is good" ideal, isn't using uncorrected analyses that pushes the "plant-based is bad" sentiment the same as tweaking statistics?

I don't see why there's a need to do all this fighting and disproving of the China Study, or the necessity of hateful remarks to vegetarians in the comments, what does it lead to? We can't get the world to agree on the optimal diet for everyone. Ultimately, we still end up eating what we want to eat. Most people are still going to believe in what they want to believe in. If someone think that meat is good, they are still going to eat it. If we want to eat plants, we will still eat plants. No point wasting effort refuting or arguing with others.

1 comment:

Fresh from the Source said...

I really must read this book, as I heard the author several years ago and was very impressed with the quality of the study itself, and very pleased with the message about a plant-based diet.

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