IRETA staff member Piper Lincoln demystifies our national drinking guidelines

The questions I’ve heard most consistently (and disbelievingly) asked at alcohol education trainings are about the NIAAA’s “low-risk” drinking guidelines.  According to the guidelines, men should limit their alcohol consumption to four drinks on any day and 14 drinks per week, and women to three drinks on any day and seven drinks per week.

“How did they come up with those numbers?” the people we train want to know. “That seems pretty low.”

A few bold attendees might volunteer that they drink beyond those limits and don’t have a problem with alcohol. But now they look concerned. Everyone looks skeptical.

They start coming up with reasons that those limits only apply to certain people: people that never drink, skinny people, people that aren’t in college. Certainly not to them.

It’s human nature to downplay the risks we face, especially when those risks seem relatively small, distant, and exist because of something we’ve chosen to do. The concern is that someone who is skeptical about the numbers and doubts that they apply to him or her personally will dismiss them completely and, in so doing, throw the baby out with the bath water.

A natural tension exists between the way we think about our own individual lives and how we conceptualize the huge datasets that have informed the creation of drinking guidelines.  In this post, I’ll unpack these population-level guidelines to help make them more meaningful…instead of abstract and inapplicable to life as we live it.

“How did they come up with those numbers?”

Weekly limits are primarily based on large meta-analytic studies of alcohol consumption and heightened risk for experiencing all sorts of negative outcomes associated with drinking.

These negative outcomes are grouped into two types, acute and chronic, with acute primarily having to do with the effects of being intoxicated (an increased risk of accident, falling, overdose, assault, sexual assault, having unprotected sex, etc.) and chronic with the effects of alcohol exposure over time (developing liver and heart disease, certain cancers, stroke, gastrointestinal disorders, infection, alcohol dependence, joblessness, etc).

A natural tension exists between the way we think about our own individual lives and how we conceptualize the huge datasets that have informed the creation of drinking guidelines.

The tricky thing in developing a guideline is where to settle on a limit that comprehensively covers such a wide variety of outcomes over such a wide span of time. For example, the probability of falling increases linearly with average daily volume of alcohol consumed. Where on that straight line do we decide an acceptable amount of risk becomes unacceptable?

On the other hand, the probability of being diagnosed with coronary heart disease among people who drink moderate amounts of alcohol is actually 20% lower than that of non-drinkers, but skyrockets back up among heavy drinkers. What if the point where this switch occurs is way out of sync with the limit we decided on for risk of falls?

We do have the comfort of being within the norm of other nations’ recommendations. The 14 drink weekly limit for men in the U.S. falls in the middle of the weekly guidelines of other countries, which range primarily from 10 to 18 drinks per week. The weekly limit of seven drinks for women in the U.S. is slightly lower than other countries, which, if they give a separate guideline for women, tend to be in the 8-10 drink range.

“Why are there daily and weekly limits?”

Having both daily and weekly limits is where U.S. guidelines tend to diverge from the guidelines of other nations. Most other countries have daily or weekly limits, which look similar when multiplied or divided by seven. This is safe to do when drinking is typically spread out across the seven days of the week.

In the U.S., where drinking primarily occurs on the weekends, dividing the weekly limit across the average number of drinking days per week (1-2) does not reflect a low-risk drinking pattern. Daily limits address a specific concern in the U.S. with heavy episodic (read: binge) drinking while weekly limits address acute and chronic risk exposure.

Four and three are the number of standard drinks a man or woman of average height at a healthy BMI can drink in a two-hour period without going over a blood alcohol concentration of 0.08. Along with being the legal limit in the U.S., this level falls within the 0.06 to 0.09 range where the “positive” effects of alcohol, such as relaxation, mild euphoria, and talkativeness, become outweighed by the negative effects, such as impairment in reasoning, depth perception, and peripheral vision.

Yes, absorption rates can vary.  Accompanying alcohol with a big meal can slow down alcohol absorption, while carbonation, diet drinks, and (my favorite) cayenne pepper can speed up the process.

 “Why do men and women have different limits?”

restrooms

Women tend to be smaller, but also have different body compositions and different metabolic enzymes
Source: Wikimedia Commons

Size does matter, but the story is a little more nuanced than that. Alcohol is mostly soluble in water, so it is water weight, not total weight, which affects blood alcohol concentration.

Here is where the gender differences begin: men typically contain about 70% liquid while women typically contain only 60%. Even at the same total weight, a woman has less water in her body in which alcohol can disperse, leading to higher overall concentrations in her blood.

Men also have more of the enzyme that metabolizes alcohol in their stomach and liver, called alcohol dehydrogenase, and the enzyme which further metabolizes alcohol’s even more toxic byproduct, called acetaldehyde (similar to formaldehyde, and the cause of headaches, vomiting, and facial flushing when too much of it builds up in the body). The toxic effects of alcohol and acetaldehyde last from the moment of ingestion until metabolism.

Acetaldehyde. Source: Wikimedia Commons

Acetaldehyde: the stuff hangovers are made of. Source: Wikimedia Commons

Women have an increased level of exposure to harm because it takes longer for alcohol to be fully metabolized by the body.  However, the research setting their weekly limit at 50% of men’s in our national guidelines is based on an old study that other countries no longer consider when setting their guidelines. Canada’s limits, for example, put women at 10 drinks per week.

Water and enzymes also explain why the effects of alcohol change as we age and across different genetic backgrounds.

Both men and women experience decreased water content as they age and the amount of alcohol dehydrogenase present in the liver also decreases, although the decrease is much more dramatic in men than women. This is why both men and women over the age of 65 are recommended to stick to the women’s limits.

East Asians and American Indians tend to have a slightly different, less efficient, form of the enzyme which processes acetaldehyde. A build up of acetaldehyde is what causes the reaction called “Asian flush.”

“I am not an average person, so do those numbers still apply?”

People (in America, anyway) hear the word “average” and immediately think “I’m not average. I’m above average!” While that has a certain ironic ring in the context of a discussion about risky drinking, the truth is you are probably more similar to the “middle person” that a statistical average represents than you are dissimilar.

And the research is based on measuring the average risk level present in groups of people who share drinking habits. So you might think of yourself as more similar than dissimilar to other people who drink in similar patterns as you.

“Are you saying I’m an alcoholic?”

hangovers

Easy-to-read NIAAA publication on physical health and alcohol consumption

While drinking beyond the guideline limits does not automatically mean you have an alcohol use disorder, mild, moderate or otherwise, it does put you in a higher risk category for having or developing one.

In a national survey of 43,000 adults conducted by the National Institutes of Health, 37% of respondents drink within the low-risk limits. Only 1 in 50 of those adults has alcohol dependence or abuse problems. The survey also found that of the 19% of adults who drink more than either the daily or weekly limits, about 1 in 5 have alcohol dependence or abuse problems. Of the 9% of adults who drink more than both the daily and weekly limits, 1 in 2 has alcohol dependence or abuse problems.

Since an alcohol use disorder is just one of the many negative health outcomes that are more likely to develop with risky drinking patterns, it might make sense to join the 35% of folks in this survey who never drink alcohol.

“Alcoholism doesn’t run in my family, so I’m safe.”

It might make sense down the road to have more individualized low-risk guidelines that take into account your unique risk considerations surrounding alcohol use, say, a family history of osteoporosis where falls are a major concern.   Or, of course, a family history of substance use disorders, one of the harms associated with drinking alcohol.  Genetic profiling may someday significantly impact the way we think about individual and population-level health.

Until then, the guidelines are meant to cover as many people as possible, but are at least somewhat tailored to gender and our national drinking culture.

Recommended Resources

NIAAA Rethinking Drinking website

Beyond Hangovers: Understanding Alcohol’s Impact on your Health by the NIAAA

Down Your Drink (UK)

SBIRTwiki

SBIRT on ireta.org

lincolnPiper Lincoln joined the staff as a Research Associate in September 2012. She holds a M.S. in Behavioral Decision Research and B.S. in Decision Science from Carnegie Mellon University. Piper works on applied research and data evaluation.