This article was first published inÂ
“Moderation in everything” is a popular slogan. It seems to go hand in hand with the cornerstone of toxicology, namely Paracelsus’s famous dictum that “only the dose makes the poison.”
We use it justify eating just a few potato chips instead of the whole bag, a spoonful of ice cream instead of the whole container, and a glass of wine instead of half a bottle.
Ah, the wine. There may be a snag here. It’s the alcohol. A known carcinogen. The International Agency for Research on Cancer (IARC) places ethanol in “Group 1,” reserved for such substances as tobacco, asbestos and radioactive materials that are “known to cause cancer in humans,” and the World Health Organization has concluded that the only safe amount of alcohol to consume is zero. No “moderation” here. Not a comforting thought.
But what about all those studies, and there have been many, that have documented a J-shaped curve when alcohol consumption is plotted against cardiovascular disease? Compared with zero alcohol, risk decreases until the consumption of 10 grams of alcohol a day is reached, roughly that found in a glass of wine, and then increases sharply.
These studies have comforted many who enjoy having that glass of wine with dinner and even prompted some to take up the habit. Various studies have buttressed the argument for red wine by pointing out that it contains numerous polyphenols, resveratrol in particular, that act as antioxidants and prevent the formation of oxidized cholesterol, the villain implicated in the formation of artery-blocking plaque. Others point out that alcohol can raise levels of HDL, the so-called “good cholesterol,” reduce levels of inflammatory proteins, release vasodilating nitric oxide and impair the ability of platelets to aggregate and form blood clots. But as is often the case with science, closer scrutiny of the data can alter the picture.
The bane of observational studies are confounders, variables other than the one being studied that may affect the results. Is there any reason that people who drink a glass of wine a day may be protected from cardiovascular disease other than the wine? Is it possible that they consume more fruits and vegetables and less meat as in the Mediterranean diet? Or that, like the French, have their main meal at noon and consume fewer calories overall? Is it possible that abstainers appear to be at greater risk because they have chosen to abstain due to already having some medical condition? So, maybe the reduced early mortality in moderate alcohol consumers isn’t due to alcohol but to some other factor. But that isn’t even the main issue with alcohol. The issue is that the evidence is clear that alcohol is a carcinogen and that any benefit it may provide in reducing cardiovascular risk is outweighed by the risk of cancer.
In the body, ethanol is converted to acetaldehyde, the active carcinogen capable of disrupting DNA. Indeed, the IARC classifies both ethanol and acetaldehyde as substances known to cause cancer in humans. But the IARC just determines whether a substance is capable of causing cancer without taking extent of exposure into account. That raises the question of whether there is a threshold effect for alcohol’s carcinogenicity. In other words, is there an amount of alcohol that can be ingested without a risk of triggering cancer?
The World Health Organization has amassed a significant amount of epidemiological data that seems to indicate that no amount of alcohol can be considered to be safe. Even “light” consumption — which is defined as less than 1.5 litres of wine, 3.5 litres of beer or half a litre of spirits a week — has been linked to an increased risk of cancers of the esophagus, liver, colon and breasts. How large is this risk? Based on numerous epidemiological studies, WHO estimates that the lifetime risk of cancer for people who have one drink a day is roughly one in 100. That is not insignificant considering that millions of people fall into the “one-a-day” category. Even if alcohol intake were to slightly reduce the risk of heart disease, the overall impact of alcohol’s effect on health is negative, especially given that in addition to cancer it increases the risk of hepatitis, fatty liver disease, pancreatitis, acid reflux, obesity and osteoporosis.
If all that isn’t enough of a deterrent, some recent studies also link alcohol consumption with accelerated aging. The DNA in our cells is the master molecule of life, controlling the production of all the proteins that are critical in biochemical processes. As we age, some of the genes in our DNA may be “switched off” and stop producing important proteins. This can happen through “epigenetic changes” that do not alter the basic structure of DNA but modify it by attaching to it small fragments called “methyl groups.” Such a modification can prevent a gene from being expressed. “Blood DNA methylation” can be profiled via laboratory tests, and researchers have shown that in young adults, methylation, and consequently aging, is accelerated by drinking alcohol, particularly binge drinking. If that still isn’t worrisome enough, brain-imaging data has also shown that alcohol can cause brain shrinkage. It isn’t clear, though, what that means since Einstein’s brain volume was at the lower end of normal and he did pretty well with it.
Alcohol presents other risks as well. An average of 37 people die every day on American roads from alcohol-related accidents. There is good evidence that the 0.08% alcohol limit in blood for intoxication is too high because reaction time and judgment are impaired even at this level. Then there are also deaths caused by alcohol-related violence and those linked to communicable diseases. Consider that alcohol consumption has been shown to raise the risk of HIV transmission because it increases the frequency of unprotected sex.
Does this mean that we should all become teetotallers? In terms of health, yes. But obsessing about every risk in life is also risky. Stress causes illness, and enjoyable activities alleviate stress. If you enjoy that glass of wine with dinner, go for it. Recognize, though, that there is an associated risk. So, I wouldn’t go for two.
And a final thought. Given the extensive attention the media has given to the contention that “no amount of alcohol is safe,” I was surprised how few in my class of undergraduates knew that alcohol is a carcinogen. I encountered the same scenario at a public lecture. They just didn’t know. But now, you do.
