Alcohol and cancer

Doug Sellman writes:

University of Otago’s Professor Jennie Connor has had two prestigious publications in the past month highlighting the fact that alcohol causes cancer in moderate drinkers in New Zealand.

Not quite correct. To quote a paper from the US National Institute on Alcohol Abuse and Alcoholism:

To date, no experimental evidence indicates that alcohol by itself can cause cancer-that is, that alcohol can act as a complete carcinogen. Over the past few decades, however, several animal studies have indicated that alcohol can have a cocarcinogenic, or cancer-promoting, effect. This means that when alcohol is administered together with other known cancer-inducing agents (i.e., carcinogens), it promotes or accelerates cancer development.

What the research shows is:

Alcohol consumption has been linked to an increased risk for various types of cancer.

I don’t know anyone who disputes this. There are of course scores of things that increase the risk of cancer from sausages to red meat to sunlight.

The really important point that Connor makes is that many of the cases of these alcohol-related cancers occur in moderate drinkers, ie they are not confined to people with severe alcoholism.

Again I don’t know anyone who disputes that overall there is a non-zero increased risk of cancer with even a moderate level of drinking. But there are also increased health benefits (as well as enjoyment).  To quote the Harvard School of Public Health:

It’s safe to say that alcohol is both a tonic and a poison. The difference lies mostly in the dose. Moderate drinking seems to be good for the heart and circulatory system, and probably protects against type 2 diabetes and gallstones. Heavy drinking is a major cause of preventable death in most countries. In the U.S., alcohol is implicated in about half of fatal traffic accidents. (1) Heavy drinking can damage the liver and heart, harm an unborn child, increase the chances of developing breast and some other cancers, contribute to depression and violence, and interfere with relationships.

Alcohol’s two-faced nature shouldn’t come as a surprise. The active ingredient in alcoholic beverages, a simple molecule called ethanol, affects the body in many different ways. It directly influences the stomach, brain, heart, gallbladder, and liver. It affects levels of lipids (cholesterol and triglycerides) and insulin in the blood, as well as inflammation and coagulation. It also alters mood, concentration, and coordination.

They note:

Even moderate drinking carries some risks. Alcohol can disrupt sleep. Its ability to cloud judgment is legendary. Alcohol interacts in potentially dangerous ways with a variety of medications, including acetaminophen, antidepressants, anticonvulsants, painkillers, and sedatives. It is also addictive, especially for people with a family history of alcoholism.

So heavy drinking is bad overall for health. Moderate drinking has some health benefits and some health risks.

The benefits and risks of moderate drinking change over a lifetime. In general, risks exceed benefits until middle age, when cardiovascular disease begins to account for an increasingly large share of the burden of disease and death.

So whenever an activist focused just on the risks without the benefits, they are not wanting you to understand the full picture – just as anyone promoting just the benefits without the risks does the same.

Sellman continues:

It is clearly important for this information to be widely publicised to all who consume alcohol in New Zealand. However, it won’t be the alcohol industry that engages in this work. A responsible industry of any product that is causing 250 cancer deaths each year would quickly warn its customers about the risk.

Actually what is important is both the benefits and risk be publicised. And this is what public health professionals should do – provide a balanced view, rather than be zealous campaigners.

Now what I find interesting is that when Connor and Sellmam provide data like this:

  • There were 243 cancer deaths attributable to alcohol in 2007.
  •  126 of these cancer deaths were in men, 117 were in women.
  •  This represents 4.2% of all cancer deaths, i.e. 1 in 25.
  •  60% of all alcohol-related cancer deaths in women were due to breast cancer.
  •  This represents 14% of all breast cancer deaths, i.e. 1 in 7.
  •  There is no level of drinking that does not increase your risk of cancer to some extent, but heavier drinkers are more affected than light drinkers.

They don’t provide what the public would find the most useful information to make an informed choice. What is the overall increased risk of getting cancer from moderate alcohol consumption. Is it 25%, 15%, 10%, 5%, 2% etc? Knowing this allows us to make an informed choice. If moderate drinking increased my risk of cancer by say 25% I’d be quite likely to stop drinking as that risk is not worth the health benefits it provides and/or the enjoyment from it.

What would also be useful if quantifying the overall increased risk from moderate drinking compared to other risks, such as processed meat. Also is the risk of dying from cancer from moderate drinking say more or less than the risk of dying in a car crash?

An article in the British Medical Journal provides the information that I would want to make an informed choice:

Compared with non-drinkers, light to moderate drinkers had relative risks of total cancer of 1.02 (95% confidence interval 0.98 to 1.06) and 1.04 (1.00 to 1.09; Ptrend=0.12) for alcohol intake of 0.1-4.9 and 5-14.9 g/day among women

That is a 2% and 4% increased risk.

Corresponding values for men were 1.03 (0.96 to 1.11), 1.05 (0.97 to 1.12)

A 3% and 5% increased risk.

But these are affected by if you smoke. The combination of tobacco and alcohol is a bad one. They find for non-smokers:

For a priori defined alcohol related cancers in men, risk was not appreciably increased for light and moderate drinkers who never smoked

And women:

However, for women, even an alcohol consumption of 5-14.9 g/day was associated with increased risk of alcohol related cancer (relative risk 1.13 (95% confidence interval 1.06 to 1.20)), driven by breast cancer.

So a 13% increased risk of alcohol related cancers for women, but the important stat is the overall increased risk of any cancer which is 4%. Their conclusion:

Light to moderate drinking is associated with minimally increased risk of overall cancer. For men who have never smoked, risk of alcohol related cancers is not appreciably increased for light and moderate drinking (up to two drinks per day). However, for women who have never smoked, risk of alcohol related cancers (mainly breast cancer) increases even within the range of up to one alcoholic drink a day.

Now if Connor and Sellman were providing this context, I doubt anyone would object. Knowing moderate drinking increases overall risk of cancer by around 2% to 4% amongst non smoking women and minimally amongst non smoking men is useful information to have.

But you balance that up against the fact that non drinkers tend to die before moderate drinkers. Again there are benefits and risks from moderate drinking and I think we should regard with suspicion those that promote the risks only, just as much as those who promote the benefits only.

UPDATE: Eric Crampton has also blogged on this, providing some very useful data about overall health impacts.

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