← All research storiesThe China–Cornell–Oxford Project

What 65 Counties Can — and Can't — Tell Us

One of the largest snapshots of diet and disease ever taken. A brilliant curiosity engine, and a perfect lesson in what observational research can and cannot say.

EcologicalObservational

Conceptual illustration of ~65 counties varying widely in diet and disease — not data, not a reproduction of any published figure.

What it was

In the 1980s, the China–Cornell–Oxford Project surveyed diet, lifestyle, and mortality across roughly 65 rural Chinese counties — a collaboration of Cornell University, the University of Oxford, and the Chinese Academy of Preventive Medicine. It took advantage of unusually wide regional variation, from largely plant-based eating to more animal-food-inclusive patterns, in fairly stable rural populations.

What showed up

Across regions, more plant-dominant dietary patterns were associated with lower rates of some chronic 'Western' diseases, while higher animal-food intake and higher blood cholesterol tracked with higher rates of some of those diseases. These are population-level associations — patterns across counties, not effects measured within individuals.

What it suggests

When diet patterns vary dramatically across regions, disease patterns vary too — a rich source of hypotheses worth testing more rigorously.

What it does not prove

Because it is ecological and correlational, it cannot prove diet causes the disease patterns. County-level correlations are vulnerable to confounders (such as hepatitis B or other regional infections) and to the ecological fallacy of reading individual cause from group data.
The popular 2005 book that drew on this work has been criticized by scientists for causal, diet-prescriptive conclusions that the underlying observational data do not support.

The takeaway

Treat the project as a map of interesting questions, not a verdict. Big associations are where good science starts, not where it ends.

Sources & citations (3)Tap to open

Diet, Lifestyle, and Mortality in China: A Study of the Characteristics of 65 Chinese Counties
Chen J, Campbell TC, Li J, Peto R (eds.) · Oxford University Press · 1990
Foundational monograph of the China–Cornell–Oxford Project. Linking to the publisher; bibliographic details corroborated via encyclopedic sources.
Diet, lifestyle, and the etiology of coronary artery disease: the Cornell China Study
Campbell TC, et al. · American Journal of Cardiology 82(10B):18T–21T · 1998
The China Study Revisited (critical analysis of causal claims)
Hall H · Science-Based Medicine · 2015
Included for balance: scientists have criticized the popular book's stronger causal claims.

We summarize these sources in our own words and link to the originals. Summaries can simplify nuanced findings — follow the links for the full picture.