What Is the Association Between Dietary Carotenoids, Breast
Cancer Risk?
BRONX, N.Y.--Dietary carotenoid intake may not reduce the risk
of breast cancer, according to researchers from Albert Einstein College of
Medicine. Their case-control study was published in the October issue of the American
Journal of Clinical Nutrition (76, 4:883-88, 2002) (www.ajcn.org).
Because numerous studies have shown an inverse association between intake of
fruits and vegetables and breast cancer risk, researchers hypothesized it had
something to do with the carotenoids contained in these foods. To examine the
relationship between carotenoids--specifically, beta- and alpha-carotene, beta-cryptoxanthin,
lycopene, lutein and zeaxanthin--and breast cancer risk, researchers analyzed
data from the Canadian National Breast Screening Study, a cohort of 56,837
women. During follow-up to the end of 1993, 1,589 women were diagnosed with
breast cancer. For comparison, a subcohort of 5,681 women was randomly selected.
After exclusions for various reasons, the final analysis was based on 1,452
cases and 5,239 controls.
Researchers found no clear association between intakes of any of the
carotenoids and breast cancer risk in the study population as a whole or in
subgroups defined by smoking status; body weight; intakes of total fat, energy,
alcohol or folic acid; family history; or menopausal status. Researchers
concluded that the data they reviewed did not support any association between
dietary intakes of carotenoids and breast cancer risk. However, they noted
prospective cohort studies of carotenoids in relation to breast cancer are
scarce and further studies are warranted.
Contrarily, researchers from the New York University School of Medicine
determined that a low intake of carotenoids--whether through a poor diet or lack
of supplementation--was associated with an increased risk of breast cancer. In
their case-control study of 270 cases and 270 controls, researchers measured
blood concentrations of various carotenoids. They found an evident increase in
the risk of breast cancer for decreasing levels of beta-carotene, lutein,
alpha-carotene and beta-cryptoxanthin. The risk of breast cancer nearly doubled
among subjects whose blood levels of beta-carotene, beta-cryptoxanthin and
lutein were in the lowest quartile (Am J Epidemiol, 153, 12:1142-7,
2001).
Also in support of carotenoids' usefulness in the fight against breast
cancer, researchers from Ben-Gurion University in Beer-Sheva, Israel, conducted
in vitro research that indicated carotenoids may reduce the risk of
estrogen-dependent cancers. Lead author Joseph Levy, Ph.D., a professor at Ben-Gurion
University, and colleagues undertook this line of research based on the premise
that hormone replacement therapy (HRT) and phytoestrogen therapy may increase
the risk of breast cancer. "In light of the anti-cancer activity of
lycopene and other carotenoids, we aimed to show that these agents may protect
mammary and endometrial cells from the growth promoting effects of both types of
estrogens," the researchers wrote in their abstract.
Researchers found that phytoestrogens (specifically the soy isoflavones
genistein and daidzein) stimulated the growth of hormone-dependent mammary and
endometrial cancer cells. However, lycopene inhibited the stimulatory effects of
genistein and IGF-1 (an important risk factor for breast and other cancers).
Other carotenoids--beta-carotene, astaxanthin, phytoene and phytofluene--also
reduced estradiol- and genistein-stimulated cell growth.
Levy's study was scheduled to be presented at the American Association for
Cancer Research meeting Oct. 14 to 18, 2002, in Boston.