Dietary Change May Prevent the Most Serious Form of Prostate Cancer
WA, 6 August 2002
Suggests Promising New Insights for Men With Early-Stage Disease
fat-laden diet and high calcium consumption are both well-known
suspected risk factors for prostate cancer. However, new findings
from the Fred Hutchinson Cancer Research Center suggest that fat
and calcium themselves may not cause prostate cancer, as previously
thought, but instead may fuel its progression from localized to
high intake of dietary fat and calcium is associated with an increased
risk of clinically significant, advanced prostate cancer, it has
no apparent impact on risk of early-stage disease, according to
findings by Alan Kristal, Dr.P.H., and colleagues in Fred Hutchinson's
Public Health Sciences Division.
of this population-based, case-control study appear today in Cancer
Epidemiology, Biomarkers and Prevention, a journal of the American
Association for Cancer Research. The National Cancer Institute and
Fred Hutchinson funded the research.
findings clearly show decreased risk for late-stage disease in men
with diets that are low in fat and moderate in calcium, perhaps
because these diets slow progression of prostate cancer into more
aggressive disease. For men diagnosed with early-stage prostate
cancer, this finding could be important because it suggests that
moderating fat and calcium consumption may reduce the risk of cancer
recurrence following treatment," said Kristal, a member of Fred
Hutchinson's Cancer Prevention Research Program.
study looked at the associations of total calorie, fat, calcium
and vitamin D intake on prostate-cancer risk among 1,200 Seattle-area
men ages 40 to 64; more than 60 percent of the participants were
under age 60. Half of the men had been recently diagnosed with prostate
cancer and the other half were healthy, randomly selected Puget
Sound-area residents who served as a comparison group. The men were
interviewed about their dietary habits three to five years prior
to diagnosis (or an equivalent time frame among the control group).
They also completed a detailed dietary questionnaire that asked
how much and how often they consumed certain foods and dietary supplements.
previous studies have examined similar dietary factors on overall
prostate-cancer risk, few studies have looked specifically at risk
comparing early with advanced disease.
there is no effective treatment for advanced prostate cancer, localized
disease can be treated with either prostatectomy or radiation therapy.
While almost all men diagnosed with early-stage prostate cancer
survive for more than five years, only 34 percent of men diagnosed
after the disease has spread to distant organs are alive after five
years, according to the American Cancer Society.
more and more men are diagnosed with early stage disease due to
the widespread use of the PSA (prostate-specific antigen) screening
test, it becomes increasingly important to consider how dietary
or lifestyle changes could decrease their risk of cancer recurrence,"
said Kristal, also an associate professor of epidemiology at the
University of Washington School of Public Health and Community Medicine.
and colleagues found that men who ate lower-fat diets, with fat
accounting for no more than 30 percent of their daily calorie intake,
had half the risk of late-stage cancer than men who consumed more
fat. However, there were no associations of fat intake with early-stage
fats (found in meat and dairy fat) and monounsaturated fats (found
in certain oils, such as olive and peanut) were associated with
an increased risk of advanced prostate cancer. Polyunsaturated fats
(found in certain oils, such as safflower and canola) were not.
Consumption of omega-3 fatty acids (found in fatty fish such as
salmon and mackerel) also did not have an impact on overall prostate-cancer
risk, contrary to experimental studies in cell cultures that have
suggested there may be a protective effect.
U.S. Department of Agriculture's Dietary Guidelines for Americans
recommends no more than 30 percent of total daily calories from
fat. For example, a person who needs 2,000 calories a day based
on their height, weight and activity level would want to aim for
no more than 600 calories from fat, or 65 grams (1 gram of fat has
9 calories, compared to only 4 calories in a gram of carbohydrate
reason that low-fat diets could reduce the risk of prostate cancer
is because they reduce blood levels of circulating male hormones
such as testosterone. Growth of the prostate, and perhaps growth
of prostate cancer, is fueled by male hormones.
researchers also found the risk of advanced prostate cancer was
112 percent higher -- more than double -- among men who consumed
the most calcium (more than 1,200 mg per day, equivalent to four
or more glasses of milk) as compared to those who got the least
(fewer than 500 mg). It didn't matter whether the calcium came from
food or supplements. "For regional/distant disease, there were consistent
trends for increased, independent risks from
both dietary and supplemental calcium," the researchers wrote.
mechanism underlying the effect of calcium on prostate-cancer risk
isn't clear, although there are relatively consistent findings from
previous studies suggesting that dairy products or calcium-supplement
intake are associated with risk. Some scientists hypothesize that
a high intake of calcium may suppress blood levels of the active
form of vitamin D, a hormone that may protect against prostate cancer
by preventing the development of cancerous cells.
only dietary risk factor that appeared to carry equal weight among
men with both early and advanced prostate cancer was the amount
of total calories consumed, regardless of fat. "Total energy intake
was significantly associated with risk for both localized and advanced
disease," Kristal said. Men who ingested the most calories each
day more than doubled their risk of localized prostate cancer (a
115 percent increased risk) and nearly doubled their risk of advanced
prostate cancer (a 96 percent increased risk) compared to men who
ate the fewest.
interpretation of these results is that high energy intake increases
prostate cancer risk overall, while high dietary fat and calcium
intakes increase the risk of more clinically significant, advanced
stages of the disease," the researchers wrote. "These results are
consistent with general dietary guidelines to moderate consumption
of total energy and fat, and they motivate further research to consider
the potential benefits and risks of high calcium intake."
important implication of this research, Kristal said, is that men
who have been diagnosed with early-stage prostate cancer may benefit
from a diet low in fat and calories. "While there is an increasingly
popular message that fat intake is not important for health," he
said, "there is no doubt that high-fat diets are associated with
high calorie intake and obesity. A low-fat diet may well be important
for the thousands of men who are diagnosed each year with early-stage
recommendations for calcium consumption are more complex, because
calcium also helps prevent osteoporosis and colon cancer.
U.S. Recommended Daily Intake of calcium for men over age 50 is
1,200 mg. While the most well-known dietary sources of calcium include
milk, dairy products, salmon and dark, leafy greens, men -- particularly
those taking calcium supplements -- also should be aware of the
additional calcium content in fortified foods, from cereals to juices.
A small bowl of fortified cereal, for example, can contain up to
1,000 mg of calcium.
diagnosed with early-stage prostate cancer may wish to moderate
their calcium intake, though the optimal level is simply not known,"
Kristal said. "Much more research is needed on factors that may
prevent cancer recurrence in men treated for early-stage disease."
Fred Hutchinson Cancer Research Center, home of two Nobel Prize
laureates, is an independent, nonprofit research institution dedicated
to the development and advancement of biomedical technology to eliminate
cancer and other potentially fatal diseases. Fred Hutchinson receives
more funding from the National Institutes of Health than any other
independent U.S. research center. Recognized internationally for
its pioneering work in bone-marrow transplantation, the center's
four scientific divisions collaborate to form a unique environment
for conducting basic and applied science. Fred Hutchinson is the
only National Cancer Institute-designated comprehensive cancer center
in the Pacific Northwest and is one of 41 nationwide. For more information,
visit the center's website at www.fhcrc.org.
Hutchinson Cancer Research Center.