104 THE CHINA STUDYCIRCLING BACK
In the beginning of my career, I concentrated on the biochemical pro-
cesses of liver cancer. Chapter three delineates the decades-long labo-
ratory work we did with experimental animals, work that passed the
requirements to be called "good science." The finding: casein, and very
likely all animal proteins, may be the most relevant cancer-causing sub-
stances that we consume. Adjusting the amount of dietary casein has
the power to turn on and turn off cancer growth, and to override the
cancer-producing effects of aflatoxin, a very potent Class IA carcinogen,
but even though these findings were substantially confirmed, they still
applied to experimental animals.
It was therefore with great anticipation that I looked to the China
Study for evidence on the causes of liver cancer in humans.^62
Liver cancer rates are very high in rural China, exceptionally high in
some areas. Why was this? The primary culprit seemed to be chronic
infection with hepatitis B virus (HBV). On average, about 12-13% of our
study subjects were chronically infected with the virus. In some areas,
one-half of the people were chronically infected! To put this into perspec-
tive, only 0.2-0.3% of Americans are chronically infected with this virus.
But there's more. In addition to the virus being a cause of liver cancer
in China, it seems that diet also plays a key role. How do we know? The
blood cholesterol levels provided the main clue. Liver cancer is strongly
associated with increasing blood cholesterol,III and we already know
that animal-based foods are responsible for increases in cholesterol.
So, where does HBV fit in? The experimental mice studies gave a
good signal. In mice, HBV initiated the liver cancer but the cancer grew
in response to the feeding of higher levels of casein. In addition, blood
cholesterol also increased. These observations fit perfectly with our hu-
man findings. Individuals who are chronically infected with HBV and
who consume animal-based foods have high blood cholesterol and a
high rate of liver cancer. The virus provides the gun, and bad nutrition
pulls the trigger.
A very exciting story was taking shape, at least to my way of think-
ing. It was a story full of meaning and suggestive of important principles
that might apply to other diet and cancer associations. It also was a
story that had not been told to the public, and yet it was capable of sav-
ing lives. Eventually, it was a story that was leading to the idea that our
most powerful weapon against cancer is the food we eat every day.