Scientists are still trying to figure out exactly how and why alcohol can promote cancer. There are a variety of possible explanations.
One explanation is that alcohol itself is not the primary trigger for cancer. We know that metabolizing, or breaking down, alcohol results in harmful toxins in the body. One of these toxins is called acetylaldehyde. Acetylaldehyde damages the genetic material in cells-and renders the cells incapable of repairing the damage. It also causes cells to grow too quickly, which makes conditions ripe for genetic changes and mistakes. Cancer can develop more easily in cells with damaged genetic material.
In addition, recent animal studies have shown that as cells try to break down alcohol, they cause the body to produce additional amounts of a protein called vascular endothelial growth factor (VEGF). VEGF promotes the growth of blood vessels and organ tissue. But, the flip side of having too much VEGF is that it allows blood vessels to grow in cancer cells that would die on their own. This allows the cancer cells to develop into tumors.
We also know that alcohol can damage the liver, causing cirrhosis. Cirrhosis results when too much scar tissue builds up within the liver and leaves it unable to perform its vital functions. One of the many complications that can result from cirrhosis is liver cancer.
Hormones may be the link between alcohol and breast cancer. Alcohol can increase the amounts of some hormones in the body, including estrogen. An excess of estrogen may lead to breast cancer.
Finally, genetics may play a role in preventing some heavy drinkers from developing cancer. A European research team examined 9,000 people with similar lifestyle habits to determine why some of them developed mouth and throat cancers, and some did not. Of the participants who were heavy drinkers, those who did not develop cancers had a particular genetic alteration that enabled them to break down alcohol about 100 times faster than in those without it. The study suggested that this gene is the reason why some people are less likely to develop cancer in response to heavy drinking.