[PHNUTR-L] Lignans could help prevent colorectal cancer, suggests study

[Kathrynne Holden, MS, RD]

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Lignans could help prevent colorectal cancer, suggests study
By Stephen Daniells
http://www.nutraingredients.com/news/ng.asp?n=68471&m=2nie616&c=xeiqgoegavfxtla
   	

16/06/2006 - Dutch scientists have reported that a high dietary intake 
of plant lignans could reduce the risk of colorectal cancer by half, the 
first such report linking lignans to this type of cancer.

Plant lignans, from sources such as flax seed, whole grain cereals, 
berries, vegetables and fruits, are metabolised in the colon by 
microflora into enterodiol and enterolactone. Previous research has 
focussed on plant lignans as reducing the risk of prostate cancer, and 
in improving menopause health.

The new retrospective study, published in the June issue of Cancer 
Epidemiology Biomarkers and Prevention (Vol. 15, pp. 1132-1136), 
indicates it is the first to report that the metabolites of lignans may 
also be beneficial for people with colorectal adenomas, growths in the 
colon and rectum that are considered by some scientists to be precursors 
for colorectal cancer.

The researchers, based in Wageningen University and the RIKILT – 
Institute of Food Safety in the Netherlands, enrolled 532 cases (at 
least one histologically confirmed colorectal adenoma, average age 59.6, 
47 per cent female) and 503 healthy controls (average age 52.8, 62 per 
cent female). Plasma enterodiol and enterolactone levels were measured.

While plasma levels of enterodiol and enterolactone did not differ 
significantly between the cases and controls, the researchers did find 
that risk associated with incident cases was significantly reduced when 
plasma levels of enterodiol and enterolactone were high.

The benefits of lignans appeared to be dose-dependent, meaning that a 
higher plasma level of the metabolites enterodiol and enterolactone was 
associated with a greater benefit.

After adjusting for possible confounders such as age, sex and antibiotic 
use, a plasma level of enterodiol of more than 3.1 nanomoles per litre 
was associated with a reduction in the risk of colorectal adenomas of 52 
per cent, compared with people with intakes of less than 0.7 nanomoles 
per litre.

A plasma level of enterolactone of more than 26.3 nanomoles per litre 
was associated with a reduction in the risk of colorectal adenomas of 37 
per cent, compared with people with intakes of less than 4.6 nanomoles 
per litre.

No such associations were observed for prevalent cases.

“Enterodiol was similarly associated with colorectal adenomas as 
enterolactone in this study, although concentrations of enterodiol were 
five to ten-fold lower. This suggests that in the human body, enterodiol 
might be more active than enterolactone,” wrote lead author Anneleen 
Kuijsten.

The authors indicate that this is the first time that such an 
association between plant lignan intake and colorectal cancer has been 
published, although they do concede that studies have reported that a 
higher intake of lignan-containing foods such as cereals, fruits, nuts 
and grains have been linked to lower risks of colorectal cancer.

“To further investigate the role of enterolignans on the development of 
colorectal cancer, more prospective studies or recurrence trials are 
needed,” concluded the researchers.

Such studies are underway, with the same researchers currently involved 
in another on-going prospective study, and are considering other 
short-term epidemiological studies.

Researcher Peter Hollman, Associate Professor Nutrition and Health, 
Wageningen University, told NutraIngredients.com that no intervention 
trials were planned and that such studies were too far away at the moment.

“We are interested in investigating the mechanisms before starting on 
any long-term or intervention studies,” said Dr Hollman.

There are 363,000 new cases of colorectal cancer every year in Europe, 
with an estimated 945,000 globally. There are about 492,000 deaths from 
the cancer each year. Only about five per cent of colorectal adenomas 
are thought to become malignant, and this process could take between 
five and ten years.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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