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Phytosterols, cholesterol-like molecules derived from plants, are increasingly well known to consumers due to their scientifically proven ability to reduce cholesterol levels. As consumer awareness has increased, the number of products containing plant sterols or plant stanols and their esters has increased.
And it is this cholesterol-lowering ability, say the authors of the new study, which may offer protecting against the risk of developing colorectal cancer. Studies have suggested that high circulating cholesterol levels are linked to increased bile acid secretion, particularly cholic acid, which may act to induce cancer.
This point is however controversial and insufficient studies have been performed to support or reject the link between hypercholesterolaemia and cancer of the colon.
The research study
The new research, published in the Journal of Nutritional Biochemistry (Vol. 17, pp. 396-401), adds to a very limited number of other animal studies that have suggested a link between stanol/sterol intake and a reduced risk of colorectal cancer.
“Our results implicated that plant sterol and stanol esters may possess capabilities to protect or delay cancer development in the colon,” said lead author Xiaoming Jia, from McGill University in Canada.
The researchers from McGill, the National Research Council of Canada, and the State University of New York, divided 70 hamsters into seven equal groups. The first group ate a control diet with no cholesterol (Con); the second group ate the control diet plus 0,25 percent cholesterol (Ch-con). The other five groups ate the Ch-con diet supplemented with 1 percent phytosterols (Ste), 1 percent phytostanol (Sta), 1.76 percent sterol ester (esterified to fish oil, SteF), 0.71 percent stanol esters (esterified to ascorbic acid, 0.7 StaA) and 1.43 percent stanol esters (1.4 StaA).
After five weeks on the respective diets, the degree of colon cell proliferation was measured using a dye to identify the new cells.
No difference was found between the control group and the Ch-con group, a result that suggests that cholesterol may not increase the risk of cell proliferation in the colon, and thus increase the risk of colon cancer.
However, animals given the 0.7 StaA supplement (provided by Forbes MediTech) reduced the rate of proliferation, compared to those fed the control plus cholesterol diet by about 25 percent.
Interestingly, the 1.4 StaA supplemented hamsters did not benefit in a dose-dependent manner.
The level of proliferation of the hamsters supplemented with SteF was also lower by 13.9 percent, however this was ‘borderline’ in terms of being statistically significant.
Free stanols and sterols did not produce an effect.
Mechanism unclear
The mechanism behind the benefits of the stanol ester with ascorbic acid is not clear, the researchers said. Ascorbic acid, also known as vitamin C, is a known antioxidant that reduces the presence of oxidative stress, and, at a dose of 0.7 percent, may have enhanced the antitumour property of the stanols.
At the higher dose (1,4 percent) the researchers propose that the anti-oxidant was now acting as a pro-oxidant, and therefore inhibiting the phytostanols.
“Since ascorbic acid was not tested separately in the current study, it is impossible to elucidate whether the enhanced inhibitory effect of stanol esters was simply a result of increased bioavailability of phytostanols or due to a synergistic action of the phytostanols and ascorbic acid,” wrote Jia.
Further study needed
The evidence and understanding of this apparent protective effect is limited and it must be stressed that significant further study is needed, a point emphasised by the researchers.
“Dietary supplementation of stanol esterified with ascorbic acid at the lower dose significantly inhibited colon cell proliferation rate, and sterol esterified with n-3 PUFA in fish oil showed a trend of inhbiting colonic cell proliferation,” concluded the researchers.
There are 363 000 new cases of colorectal cancer every year in Europe, with an estimated 945 000 globally. About 492 000 deaths occur from the cancer each year. According to the European School of Oncology, 80 percent of colorectal cancers may be preventable by dietary changes.
Source: Decision News Media
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