Vis tegen darmkanker.*
Uit een studie onder meer dan 22.000 mensen die bijna 20 jaar gevolgd werden blijkt dat het eten van vis de kans op darmkanker doet afnemen. Een keer vis per week en de kans wordt 10% kleiner, bij 2-4 keer per week vis is dat 20% en als je een echte visliefhebber bent en 5x per week vis eet wordt de kans op darmkanker met 40% gereduceerd. Van deze 22.000 mensen blijkt slechts 11% 5x per week vis te eten, 10% eet minder dan 1x per week vis , 31% minder dan 2x per week en toch het merendeel, 48% tussen de 2 en 5 keer.
A
prospective study of fish, n-3 fatty acid intake, and colorectal cancer risk in
men
Men
who ate fish five times a week or more had a 40 percent lower risk of developing
colorectal cancer compared to men who ate fish less than once a week, according
to a new analysis of data from 22,071 participants in the Physicians' Health
Study (PHS).
The
researchers say the reduction in colorectal cancer risk is substantial in
comparison to other dietary components, and while they don't suggest that
everyone starts eating fish daily simply because of these results, they say the
health benefits of fish consumption have already been proven.
"We
already know that eating fish can reduce the risk of sudden cardiac death, and
this might provide another reason to add fish to your diet," said Megan
Phillips, a doctoral student at the Harvard School of Public Health and the lead
author of this study.
The
researchers believe the health effects of fish consumption in relation to
colorectal cancer may lie in their content of the n-3 fatty acids that can
inhibit the cyclooxygenase-2 (COX-2) enzyme. This enzyme acts as a mediator of
inflammatory responses thought to be associated with cancer development.
The
PHS was designed as a randomized, double blind, placebo-controlled clinical
trial to examine the effect of aspirin and beta-carotene supplements on
development of cancer and cardiovascular disease, and the participants filled
out a one-time food questionnaire 12 months after starting the study. In this
analysis, investigators were also trying to determine if fish consumption had a
different effect on men who received aspirin for five years compared to men who
weren't randomized to use aspirin, which is also a COX-2 inhibitor. "We
thought that maybe for men who received aspirin, it wouldn't matter whether they
ate fish or not," Phillips said.
The
researchers looked at four different categories of fish consumed- tuna fish,
dark meat fish (salmon, sardines, bluefish, etc.), a general fish category, and
shellfish including shrimp, lobster and scallops- and asked how many times the
participants ate them on average during the previous year. They found almost 10
percent ate fish less than once a week, 31 percent ate it less than two times a
week, 48 percent ate fish less than five times a week, and about 11 percent ate
it five times or more a week. They then compared these figures with incidence of
colorectal cancer that later developed in the men. (The average follow-up was
19.4 years).
They
found that compared to men who ate the least amount of fish, the risk of
developing colorectal cancer was 40 percent lower in men who ate the most fish,
was 20 percent lower in men who ate fish 2-5 times a week, and 13 percent lower
among participants who ate fish less than two times a week.
The
relationship between fish consumption and colorectal cancer was similar for men
randomized to aspirin and those who weren't, possibly because the researchers
only had information on aspirin use during the first five years in the trial,
and "it may take more years of aspirin use to see an effect," Phillips
said.
While
she said the results are promising, Phillips also noted that they are based on
the assumptions that the pattern of fish consumption observed in the sole food
questionnaire represented a diet that the men subsequently followed for many
years.
In addition, men who consumed more fish may also have a healthier lifestyle perhaps including better cancer screening. Although this study controlled for some of these factors such as cigarette smoking, vigorous exercise, and multivitamin use, the investigators do not have information on colorectal endoscopies. Thus, these findings need additional confirmation through other prospective studies with more complete information and a definitive answer might require a randomized trial, said senior author Jing Ma, M.D., Ph.D., a researcher at the Brigham and Women's Hospital-based Channing Laboratory and associate professor of medicine at Harvard Medical School. (Nov. 2006)