Thursday 4 January 2018

Alcohol raises the risk of developing cancer.

Credit: National Institutes of Health

Alcohol can cause cancer by permanently damaging stem cell DNA, a new study has found.

Links between drinking and cancer are well-documented, however, the science behind this correlation has remained fairly ambiguous until now.

Also Read:Even light drinkers at risk of cancer

Researchers from the Medical Research Council’s lab of molecular biology at Cambridge University found that alcohol severely damages the DNA of stem cells in the blood and can subsequently lead to the formation of tumours.
A new study looking at blood stem cells uncovered fresh details surrounding the mechanisms by which alcohol raises the risk of developing cancer.

Alcohol is known to raise the risk of no fewer than seven types of cancer. These are mouth, upper throat (pharynx), voice box (laryngeal), esophageal, breast, liver, and bowel cancer.

Though the links are established, exactly how alcohol works to induce malignancy is not as well-understood. Several mechanisms are thought to be at work.

Also Read: Scientists find that for first time Brain stimulation enhances long-term memory.

Most previous studies have only examined cells in the laboratory, looking at changes in them after exposure to alcohol (ethanol).


When alcohol is broken down in the body it produces a toxic chemical known as acetaldehyde.
The study’s authors conducted their research on a group of mice, who were given ethanol and were subsequently examined to see what effect the acetaldehyde had on their cellular structures.
By conducting chromosome analysis and DNA sequencing, they were able to uncover the level of genetic damage that had been caused as a result of the ethanol.
They found that the chemical gave rise to permanent mutations in the mice’s DNA sequences which could lead to various forms of cancers.
Recently, researchers from MRC Laboratory of Molecular Biology in Cambridge, United Kingdom, set out to gain a clearer picture of the alcohol-cancer relationship using whole animals.
Their study, which was funded by Cancer Research U.K., is published this week in the journal Nature.

Acetaldehyde and blood stem cells

The team fed diluted ethanol to mice and then used chromosome analysis and DNA sequencing to measure any damage caused by acetaldehyde, a chemical produced when alcohol is processed. They focused their attention on a specific cell type: blood stem cells.

Blood stem cells, found in blood and bone marrow, are immature blood cells that can develop into any type of blood cell, including white blood cells, platelets, and red blood cells. It is important to understand how alcohol damages these cells, as faulty stem cells are known to cause cancer.
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As alcohol is broken down in the gut, bacteria convert it into large quantities of acetaldehyde, a chemical that has previously been shown to cause cancer in animals.

Following the analysis, the researchers found that acetaldehyde could, in fact, damage and break DNA within blood stem cells. Chromosomes became rearranged, and the DNA sequence was permanently changed in stem cells.

Lead study author Prof. Ketan Patel says, "Some cancers develop due to DNA damage in stem cells. While some damage occurs by chance, our findings suggest that drinking alcohol can increase the risk of this damage."

Self-defense mechanisms

Alongside new insights into the damage that ethanol causes to stem cells, the scientists uncovered new information about the protective mechanisms employed by our bodies in response to alcohol.

Enzymes called aldehyde dehydrogenases (ALDHs) form the first line of defense against alcohol-related damage. ALDHs break alcohol down into acetate, "which our cells can use as a source of energy."

Millions of people — many East Asians, for instance — have low levels of ALDH or faulty copies of the enzymes. This means that toxic acetaldehyde builds up in the body. These individuals will experience tell-tale flushed cheeks and potentially feel ill.

When the researchers investigated mice without ALDH, they found that alcohol caused four times as much damage to DNA when compared with mice that could produce ALDH.

Beyond ALDH, the body has a range of other secondary mechanisms that can repair various types of DNA damage. But these mechanisms do not always work; some people have mutations that render them ineffective.

Our study highlights that not being able to process alcohol effectively can lead to an even higher risk of alcohol-related DNA damage and therefore certain cancers."

Prof. Ketan Patel

"But," he continues, "it's important to remember that alcohol clearance and DNA repair systems are not perfect and alcohol can still cause cancer in different ways, even in people whose defense mechanisms are intact."

Alcohol is known to give rise to cancer, and studies such as this help us to understand why and will, eventually, help to prevent or slow alcohol-related cancers.


Recent figures estimate that 21,000 cases of cancer in the UK could be avoided if nobody drank alcohol.
“Some cancers develop due to DNA damage in stem cells,” explains lead author Ketan Patel.
“While some damage occurs by chance, our findings suggest that drinking alcohol can increase the risk of this damage.”
The study, which was published in the journal Nature, also looked at how the body defends itself against alcohol.
Enzymes known as aldehyde dehydrogenase (ALDH) break down aldehyde, however, millions of people worldwide lack these key enzymes or possess faulty ones.
Scientists looked at the effect aldehyde had on mice with and without these critical ALDH enzymes and found that those who didn’t have them suffered from four times as much damage to their DNA.
“Our study highlights that not being able to process alcohol effectively can lead to an even higher risk of alcohol-related DNA damage and therefore certain cancers,” added Patel.
“But it’s important to remember that alcohol clearance and DNA repair systems are not perfect and alcohol can still cause cancer in different ways, even in people whose defence mechanisms are intact.”
According to Cancer Research UK, who part-funded the research, recent studies reveal that alcohol is responsible for 12,800 cancer cases in the UK each year, 4,800 of which are bowel cancers.
As Prof. Linda Bauld, from Cancer Research U.K., says, "This thought-provoking research highlights the damage alcohol can do to our cells, costing some people more than just a hangover." 


Article Summary

  • According to a recent extensive review of multiple research studies, alcohol consumption has been conclusively shown to be the direct cause of 7 types of cancer – including those of the oropharynx, larynx, esophagus, liver, colon, rectum, and breast.
  • What is more than a little troubling is that even people consuming low to moderate amounts of alcohol seem to be at risk. People who smoke and drink at the same time are at even greater risk of getting cancer.
  • People who consume 3.5 or more drinks daily have at least 2-3 times greater risk of developing cancers of the mouth (not including the lips), pharynx, and larynx than non-drinkers.
  • Alcohol consumption is an independent risk factor for, and a primary cause of, liver cancer. Women who drank more than 3 alcoholic drinks daily had 1.5 times the risk of developing breast cancer when compared to non-drinkers.
  • There is a clear association between alcohol consumption of more than one drink daily and higher colorectal cancer risk.
  • There’s some evidence to suggest that drinkers who give up alcohol can reverse their risk of laryngeal, pharyngeal, and liver cancer. Their risk stays reduced the longer they avoided alcohol.
  • While abstaining from alcohol is the safest bet, here are some tips to lower your alcohol-related cancer risk:
    1. Have some alcohol-free days every week to cut down on the total amount of alcohol you consume
    2. Swap every second or every third alcoholic drink for a healthier beverage such as water
    3. Choose smaller servings (e.g. get singles not doubles and use smaller glasses)
    4. Substitute with less alcoholic versions of drinks
    5. Don’t keep a stock of alcohol at home
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Sources:American Cancer Society,National Cancer Institute,Colorectal Cancel Alliance, Nature, Cancer Research UKMediline Plus, NCBI


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