TUESDAY, April 5 (HealthDay News) -- Some breast cancer
survivors fear that eating foods containing soy will increase the
risk of a cancer recurrence, but new research suggests that those
worries appear to be unfounded.
"We did not see any evidence that soy intake after breast cancer increases the risk of recurrence or deaths [from breast cancer]," said Dr. Xiao Ou Shu, a professor of epidemiology and medicine at Vanderbilt University Medical Center in Nashville.
"Our study indicated that soy food intake among breast cancer survivors is safe and may reduce the risk of recurrence," she said.
She emphasized she is talking about soy foods, such as tofu and
soybeans, not soy supplements.
The research is to be presented Tuesday at the American
Association for Cancer Research's annual meeting in Orlando, Fla.
Results of studies presented at meetings are considered preliminary
until published in a peer-reviewed journal.
For the study, Shu evaluated data on 9,515 women who had
participated in one of three studies of breast cancer survivors:
Life After Cancer Epidemiology, Women's Healthy Eating and Living
and the Shanghai Breast Cancer Survival studies.
Shu reviewed information from food questionnaires on the women's
soy food intake. The average time between breast cancer diagnosis
and soy food evaluation was about 14 months.
After a follow-up that averaged 7.4 years, Shu found 1,348
breast cancer recurrences and 1,171 deaths from breast cancer and
Compared to the women who ate the least soy, women in the upper
10th percentile group for soy food intake had a 35 percent reduced
risk of recurrence.
Those who ate the most soy also had a 17 percent reduced risk of
death from all causes during the follow-up, but that finding did
not reach statistical significance, Shu said.
Soy food consumption was considerably higher in the Shanghai
group than among the U.S. participants.
How much soy might be protective? "Women can get the level of
soy isoflavones that is similar to the top 10 percent consumption
level found in our U.S. study population by consuming a cup of
[soy] milk or half serving of tofu (2 oz.) per day," she said.
In the past, women who survived breast cancer tended to avoid
soy foods, said Dr. Marian Neuhouser, associate member of the Fred
Hutchinson Cancer Research Center in Seattle.
The worry, she said, was that some soy foods can act as a weak
phytoestrogen, and most breast cancers are estrogen-receptor
positive, needing estrogen to grow.
"I think this study and a previous study support the idea that soy foods are safe for women with breast cancer," she said.
She, too, emphasized that the study is on soy foods, not
supplements. Soy foods are a good source of low-fat protein, she
Soy contributes to an overall healthy diet pattern, and healthy
diet patterns are linked with lower recurrence, she said.
"If someone has a latte with soy milk, it means they aren't having a latte with whole milk, which has a lot more fat in it," Neuhouser said.
To learn more about soy, visit the
Soyfoods Association of North America.