66 THE CHINA STUDYcer, and how did they interact with different carcinogens and different
organs? Might the effects of other nutrients, carcinogens or organs
cancel each other, or might there be consistency of effect for nutrients
within certain types of food? Would promotion continue to be revers-
ible? If so, cancer might be readily controlled, even reversed, simply by
decreasing the intakes of the promoting nutrients and/or increasing the
intakes of the anti-promoting nutrients.
We initiated more studies using several different nutrients, including
fish protein, dietary fats and the antioxidants known as carotenoids.
A couple of excellent graduate students of mine, Tom O'Connor and
You ping He, measured the ability of these nutrients to affect liver and
pancreatic cancer. The results of these, and many other studies, showed
nutrition to be far more important in controlling cancer promotion than the
dose of the initiating carcinogen. The idea that nutrients primarily affect
tumor development during promotion was beginning to appear to be a
general property of nutrition and cancer relationships. The Journal of
the National Cancer Institute, which is the official publication of the U.s.
National Cancer Institute, took note of these studies and featured some
of our findings on its cover.^52
Furthermore, a pattern was beginning to emerge: nutrients from ani-
mal-based foods increased tumor development while nutrients from plant-
based foods decreased tumor development. In our large lifetime study of
rats with aflatoxin-induced tumors, the pattern was consistent. In mice
with hepatitis B virus-altered genes, the pattern was consistent. In stud-
ies done by another research group, with breast cancer and different car-
cinogens, the pattern was consistent. In studies of pancreatic cancer and
other nutrients, the pattern was consistent.^52 ,53 In studies on carotenoid
antioxidants and cancer initiation, the pattern was consistent. 54,55 From
the first stage of cancer initiation to the second stage of cancer promo-
tion, the pattern was consistent. From one mechanism to another, the
pattern was consistent.
So much consistency was stunningly impressive, but one aspect of
this research demanded that we remain cautious: all this evidence was
gathered in experimental animal studies. Although there are strong argu-
ments that these provocative findings are qualitatively relevant to human
health, we cannot know the quantitative relevance, In other words, are
these principles regarding animal protein and cancer critically important
for all humans in all situations, or are they merely marginally important
for a minority of people in fairly unique situations? Are these prin-