Mt. Goodman et al., ASSOCIATION OF SOY AND FIBER CONSUMPTION WITH THE RISK OF ENDOMETRIALCANCER, American journal of epidemiology, 146(4), 1997, pp. 294-306
The authors conducted a case-control study among the multi-ethnic popu
lation of Hawaii to examine the role of dietary soy, fiber, and relate
d foods and nutrients on the risk of endometrial cancer. Endometrial c
ancer cases (n = 332) diagnosed between 1985 and 1993 were identified
from the five main ethnic groups in the state (Japanese, Caucasian, Na
tive Hawaiian, Filipino, and Chinese) through the rapid-reporting syst
em of the Hawaii Tumor Registry. Population controls (n = 511) were se
lected randomly from lists of female Oahu residents and matched to cas
es on age (+/-2.5 years) and ethnicity. All subjects were interviewed
using a diet history questionnaire that included over 250 food items.
Non-dietary risk factors for endometrial cancer included nulliparity,
never using oral contraceptives, fertility drug use, use of unopposed
estrogens, a history of diabetes mellitus or hypertension, and a high
Quetelet's index (kg/m(2)). Energy intake from fat, but not from other
sources, was positively associated with the risk of endometrial cance
r. The authors also found a positive, monotonic relation of fat intake
with the odds ratios for endometrial cancer after adjustment for ener
gy intake. The consumption of fiber, but not starch, was inversely rel
ated to risk after adjustment for energy intake and other confounders.
Similar inverse gradients in the odds ratios were obtained for crude
fiber, non-starch polysaccharide, and dietary fiber. Sources of fiber,
including cereal and vegetable and fruit fiber, were associated with
a 29-46% reduction in risk for women in the highest quartiles of consu
mption. Vitamin A and possibly vitamin C, but not vitamin E, were also
inversely associated with endometrial cancer, although trends were no
t strong. High consumption of soy products and other legumes was assoc
iated with a decreased risk of endometrial cancer (p for trend = 0.01;
odds ratio 0.46, 95% confidence interval 0.26-0.83) for the highest c
ompared with the lowest quartile of soy intake. Similar reductions in
risk were found for increased consumption of other sources of phytoest
rogens such as whole grains, vegetables, fruits, and seaweeds. Ethnic-
specific analyses were generally consistent with these results. The ob
served dietary associations appeared to be largely independent of othe
r risk factors, although the effects of soy and legumes on risk were l
imited to women who were never pregnant or who had never used unoppose
d estrogens. These data suggest that plant-based diets low in calories
from fat, high in fiber, and rich in legumes (especially soybeans), w
hole grain foods, vegetables, and fruits reduce the risk of endometria
l cancer. These dietary associations may explain in part the reduced r
ates of uterine cancer in Asian countries compared with those in the U
nited States.