In the largest study to date examining the relationship between lipids and colorectal cancer (CRC), a European study has found a strong inverse relationship between HDL cholesterol and colon cancer. Previous smaller studies investigating the relationship had been inconclusive.
In a paper published in Gut, Fränzel JB van Duijnhoven and colleagues report on a nested case-control study from the large European Prospective Investigation into Cancer and Nutrition (EPIC), which includes more than 500,000 participants. The new study focuses on 1238 cases of CRC and the same number of matched controls. After adjusting for other known risk factors, the investigators found a significant inverse association between HDL and apoA and colon cancer. No association was found with rectal cancer.
The authors speculated that a protective role for HDL in colon cancer may involve the effects of HDL on inflammatory pathways or oxidative stress, but they acknowledged that “it still remains to be established whether low HDL concentrations are just correlated with other truly detrimental pathways, whether they are intermediate factors in the colon carcinogenic process or are a true risk factor initiating a mechanistic path on the road to colon cancer.”
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Here is the press release from the BMJ Group:
High levels of “good” cholesterol may cut bowel cancer risk
[Blood lipid and lipoprotein concentrations and colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition 2011; doi 10.1136/gut.2010.225011]
High levels of “good” (high density lipoprotein) HDL cholesterol seem to cut the risk of bowel cancer, suggests research published online in Gut.
The association is independent of other potentially cancer-inducing markers of inflammation in the blood.
The researchers base their findings on participants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. This is tracking the long term impact of diet on the development of cancer in more than half a million people in 10 European countries, including the UK.
Some 1,200 people who developed bowel and rectal cancers – 779 bowel and 459 rectal cancer – after agreeing to take part in EPIC were matched with another 1,200 participants of the same age, gender, and nationality.
Blood samples taken when they joined the study, and the dietary questionnaires these participants had completed, were compared to see if there were any discernible differences between the two groups.
The analysis showed that those who had the highest levels of HDL cholesterol, and another blood fat, apolipoprotein A, or apoA – a component of HDL cholesterol – had the lowest risk of developing bowel cancer.
Each rise of 16.6 mg/dl in HDL and of 32 mg/dl in apoA reduced the risk of bowel cancer by 22% and 18%, respectively, after taking account of diet, lifestyle, and weight.
But HDL and apoA levels had no impact on the risk of rectal cancer.
After excluding those who had only been monitored for two years, as they may have already been undergoing cancerous changes when they joined the study, only levels of HDL were associated with a reduction in bowel cancer risk.
The association remained intact, irrespective of other indicators of inflammation, insulin resistance, and oxygen free radicals levels, all of which are associated with the development of cancer.
The authors explain that low HDL levels have been linked to higher levels of proteins involved in inflammation, while higher levels of proteins that dampen down the inflammatory response have also been linked to high HDL levels.
The pro inflammatory proteins boost cell growth and proliferation while curbing cell death, so HDL may alter the inflammatory process in some way, they suggest.
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