Link Between Good Cholesterol and Lower Risk of Colon Cancer

Summary
This study attempted to explore a possible relationship between various parameters of blood cholesterol and a risk of bowel cancer. The cholesterol parameters studied included total cholesterol, high density lipoprotein (HDL) cholesterol (or “good” cholesterol) and other molecules known as lipoproteins. Results showed that the risk of colon cancer was reduced when there was a rise of HDL and a lipoprotein called apoA. This relationship did not hold true for cancer of the rectum however. The authors conclude, “These findings show that high concentrations of serum HDL are associated with a decreased risk of colon cancer. The mechanism behind this association needs further elucidation.”

Introduction
Over the years, many studies have shown that a rise in different types of blood cholesterol may contribute to an increased risk of colon and rectal cancer. However, results from these studies have not always been consistent. Also, there has been little evidence that shows whether lipoproteins and HDL cholesterol are protective in bowel cancer. Studies have speculated that cholesterol in the body can cause several pathological processes that may give rise to bowel cancer. Similarly the risk of high blood cholesterol — especially the bad components like triglycerides, total cholesterol, etc.– is raised by bad lifestyle habits, like too much fatty food consumption, obesity, lack of exercise and alcoholism. This study was planned to explore the benefits that high good cholesterol can provide in protecting against bowel cancer.

Methodology
* For this study a total of 520,000 people were followed from 10 different countries from Western Europe.
* Among these people a total of 1,238 cases of bowel cancer that affected either the rectum or the colon were detected. For each of these cases, matching people with the same age, sex and region, but without cancer, were selected for analysis.
* For both the set of cancer-affected people and matching controls, a complete analysis of other parameters like weight, smoking, alcohol consumption, duration of physical exercise, dietary habits, educational status, etc., were recorded. Blood was taken for examination of various cholesterol parameters.

Results/Key findings
* Preliminary analysis revealed that those with bowel cancer weighed more than normal, exercised less and had a higher level of education.
* HDL was highly correlated with apoA levels but LDL (or “bad” cholesterol) was highly correlated with apoB, another type of lipoprotein. Results showed that a high level of good cholesterol and lipoprotein apoA meant a reduced risk of cancer of the colon.  This beneficial relationship of HDL and apoA did not translate over to cancer of the rectum.
* On following the patients for more than two years, the benefits of HDL cholesterol remained, while that of apoA was not found.

Next steps/Shortcomings
Authors agree that one of the shortcomings of this study was the one point examination of the blood cholesterol levels. They admit that effects of rising or falling levels of cholesterol on risk of bowel cancer were not explored. They admit that some of the cases of cancer may have been a silent disease at the start of the study and this may have altered their dietary patterns. Finally, the authors write that this study was conducted over a short period of time and longer studies are warranted.

Conclusion
This study’s “findings show that high concentrations of serum HDL are associated with a lower risk of colon cancer.” Authors agree that the short duration of this study should be kept in perspective before coming to concrete conclusions. Long-term benefits of HDL cholesterol need to be studied in detail. This is, however, the first large study on bowel cancer and the benefits of HDL cholesterol and apoA that, no matter how small, cannot be overruled. The authors suggest that apart from modification and stoppage of other risk factors for bowel cancer — like an improper diet, smoking, alcoholism, lack of exercise and obesity — raising HDL cholesterol may also be considered as an intervention.

For More Information:
Blood Lipid and Lipoprotein Concentrations and Colorectal Cancer Risk in the European Prospective Investigation into Cancer and Nutrition
Publication Journal: Gut, March 2011
By Fränzel J. B. van Duijnhoven; H. Bas Bueno-De-Mesquita; National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands, and the University Medical Center, Utrecht, The Netherlands

*FYI Living Lab Reports Are Summaries of the Original Research.

 


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