Higher consumption of some soy products, grains and vegetables linked to reduced

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29 Sep 2005

 

A diet higher in plant-derived compounds known as phytoestrogens is

linked with a lower lung cancer risk, according to a study in the

September 28 issue of JAMA.

 

Phytoestrogens are plant-derived nonsteroidal compounds found in soy

products, grains, carrots, spinach, broccoli, and other fruits and

vegetables, according to background information in the article. They

have weak estrogen-like activity. The three main classes of

phytoestrogens are isoflavones, lignans, and cumestrans. A fourth

group of plant-derived steroidal compounds believed to have

estrogenic properties are the phytosterols. Phytoestrogens have been

shown to have a protective effect against some solid tumors, but

there has been little epidemiologic research focused on dietary

intake of phytoestrogens and lung cancer risk.

 

Matthew B. Schabath, Ph.D., and colleagues at the University of Texas

M.D. Anderson Cancer Center, Houston, analyzed data from an ongoing

case-control study to examine the relationship between dietary intake

of phytoestrogens and the risk of lung cancer. The study included

1,674 patients with lung cancer (cases) and 1,735 matched healthy

controls. From July 1995 through October 2003, study participants

were personally interviewed to obtain information on demographics,

socioeconomics, and smoking history. Women were asked whether they

had taken hormone therapy in the previous six months. A food

frequency questionnaire was used to collect dietary data on intake of

12 individual phytoestrogens.

 

" Our main findings were that patients with lung cancer tended to

consume lower amounts of phytoestrogens than controls, that there

were sex-specific differences both in intake and in protective

effects, and that the apparent benefits were evident in both never

and current smokers but less so in former smokers, " the authors

report.

 

Reduction in lung cancer risk tended to increase with increasing

phytoestrogen intake. " The highest quartiles of total phytosterols,

isoflavones, lignans, and phytoestrogens were each associated with

reductions in risk of lung cancer ranging from 21 percent for

phytosterols to 46 percent for total phytoestrogens from food sources

only, " the authors write.

 

Sex-specific effects were also apparent. " For men, statistically

significant trends for decreasing risk with increasing intake were

noted for each phytoestrogen group, with protective effects for the

highest quartile of intake ranging from 24 percent for phytosterols

to 44 percent for isoflavones, while in women, significant trends

were only present for intake of total phytoestrogens from food

sources only, with a 34 percent protective effect for the highest

quartile of intake, " the authors report.

 

The apparent benefits of high phytoestrogen intake were evident in

both current smokers and those who had never smoked, but less

apparent in former smokers.

 

In women, statistically significant joint effects were evident

between hormone therapy use and phytoestrogen intake. " Specifically,

high intake of the lignans [metabolites] enterolactone and enterodiol

and use of hormone therapy were associated with a 50 percent

reduction in risk of lung cancer, " the authors report.

 

" In summary, these data provide further support for the limited but

growing epidemiologic evidence that estrogens and phytoestrogens are

associated with a decrease in risk of lung cancer, especially in

never and current smokers, " they conclude. " However, confirmation of

these findings is still required in large-scale longitudinal

studies. "

 

Editor's Note: This study was supported by the Flight Attendant

Medical Research Institute and Public Health Service grants from the

National Cancer Institute, National Institutes of Health, Department

of Health and Human Services. Dr. Schabath was also supported by a

cancer prevention fellowship, National Cancer Institute grant.

 

Editorial: Reducing the Risk of Lung Cancer

 

In an accompanying editorial, Lawrence J. Dacey, M.D., M.S., and

David W. Johnstone, M.D., of Dartmouth-Hitchcock Medical Center,

Lebanon, N.H., urge physicians and other health professionals to talk

with their patients about the importance of diet in cancer

prevention.

 

" … patients should be informed that they may further reduce their

risk of developing cancer by adopting a diet rich in fruits and

vegetables, " they write. " Clinicians who actively and aggressively

educate their patients and follow up on their efforts to modify their

cancer risks will help lessen the great personal suffering and

societal burden inflicted by lung cancer. "

 

Nina S. Godtfredsen, M.D., Ph.D.

duegodt

JAMA and Archives Journals

http://www.jamamedia.org