New research published in journal alcohol and alcoholism The findings suggest that moderate to heavy drinking tends to be associated with increased inflammation in the body, even in people who maintain a nutritious diet. This study provides evidence that eating well alone may not be enough to counteract the harmful physical effects of frequent alcohol consumption.
Scientists Kailyn Roeder and Jimicae Beck-Courtney wanted to better understand how two common lifestyle factors, diet and alcohol intake, interact to influence chronic systemic inflammation. Jimikaye Beck Courtney is an assistant professor and A. Donald and Billy J. Stallings Research Fellow at the University of North Carolina at Chapel Hill.
“I studied nutrition as an undergraduate and began researching alcohol consumption during my postdoctoral research,” Courtney said. “Through these experiences, I became interested in the intricacies of how both nutrition and alcohol consumption influence health outcomes.”
“For example, although past research has shown that moderate alcohol consumption may protect against cardiovascular disease, the U.S. Surgeon General just recently recommended that any alcohol consumption increases the risk of cancer.”
Chronic systemic inflammation is a persistent low-level immune response. This constant activation of the immune system can induce oxidative stress, which can ultimately damage healthy tissue. This persistent damage is the basis for a variety of serious health conditions, including cardiovascular disease, cancer, diabetes, and non-alcoholic fatty liver disease.
“First author Kailyn Lowder is an EXSS master’s student at UNC-Chapel Hill with a background in nutrition and researching inflammation in cancer,” Courtney noted. “We were interested in investigating whether alcohol use has a negative impact on inflammation, given the health of a person’s diet.”
To answer these scientific questions, researchers recruited 91 adults between the ages of 21 and 44. All participants had a Body Mass Index of 25 or higher and were classified as overweight or obese. Body Mass Index is a standard measurement tool that uses a person’s height and weight to estimate total body fat.
The selected sample was primarily White, non-Hispanic, and female. The study had an intensive longitudinal design, with researchers closely following participants over a relatively short period of 21 consecutive days.
At the beginning of the study, participants filled out an initial survey detailing their typical drinking habits over the past month. Based on this retrospective information, the researchers divided the participants into four different groups. These categories include non-drinkers who consume zero alcohol, light drinkers who consume up to three drinks per week, moderate drinkers who consume up to 14 drinks per week for men and seven drinks per week for women, and heavy drinkers who exceed these moderate limits.
For 21 days, participants completed a smartphone survey every morning to report their exact alcohol intake. Participants also completed a very detailed dietary recall interview at the beginning and end of the study.
The researchers used this food data to calculate a total Healthy Eating Index score for each person. A higher score indicates a healthier diet, rich in whole grains, fruits, and vegetables, and low in saturated fat.
At the end of the 21 days, participants returned to the laboratory for a follow-up blood draw. The researchers analyzed blood samples for specific inflammatory markers known as cytokines. Cytokines are proteins released by the immune system in response to stress or injury.
Small amounts of cytokines are a normal part of the body’s defense system. But when it’s persistently elevated, known as chronic low-grade inflammation, it can contribute to the development of heart disease, cancer, and diabetes.
Specific cytokines measured included C-reactive protein, tumor necrosis factor alpha, interleukin-6, and interleukin-1 beta. C-reactive protein is one of the most commonly used clinical markers of inflammation because it can be measured with routine blood tests. Elevated levels of C-reactive protein are associated with increased risk of cardiovascular disease, diabetes, and other chronic diseases.
By closely examining 21 days of daily drinking records, the researchers found no significant association between average daily alcohol consumption and levels of inflammatory proteins in the blood. However, when scientists looked at categories of habitual drinking based on overall behavior over the past month, habitual alcohol consumption appeared to have a negative impact on certain inflammatory markers. This particular relationship remained even after accounting for how well the participants ate.
Scientists have found significant differences based on biological sex regarding levels of C-reactive protein. Women in the moderate and heavy drinking categories had significantly higher levels of C-reactive protein compared to women who drank only light amounts. Interestingly, there were no such differences among the male participants in this study.
“We were a bit surprised to find that men showed no difference in inflammation (especially C-reactive protein (CRP)) regardless of alcohol consumption, whereas women had increased inflammation even when they drank moderately (four to seven drinks a week),” Courtney said. “This was surprising given previous research suggesting that moderate alcohol intake may reduce risk. In general, the results varied by inflammatory biomarker, showing how complex the relationship between nutrition, alcohol intake, and inflammation is.”
The authors note that women generally produce less of the enzymes needed to metabolize alcohol in their stomachs and livers, and tend to have less lean body mass than men. These inherent biological differences mean that women typically experience higher blood alcohol levels for the exact same amount of alcohol, which may explain their heightened inflammatory response.
When scientists looked at tumor necrosis factor alpha, they found that heavy drinkers, regardless of biological sex, had significantly higher levels of this inflammatory protein compared to light drinkers. Researchers found no significant association between type of drinker and interleukin-1 beta. For interleukin-6, female gender moderated the association among moderate drinkers, but the differences between specific drinking groups were not statistically significant enough to draw firm conclusions.
Regarding overall diet, the researchers found that higher scores on the Healthy Eating Index were associated with slightly lower levels of C-reactive protein, tumor necrosis factor alpha, and interleukin 1 beta. Increased whole grain intake was associated with decreased interleukin-6, and increased saturated fat intake was associated with increased interleukin-6. Consuming a high-quality diet had a small protective effect on inflammation, but it could not counteract the large spike in inflammation seen in the moderate and heavy drinking categories.
“Inflammation increases your risk of disease, and no matter how healthy the rest of your diet is, alcohol consumption can worsen inflammation,” Courtney told Cypost. “It’s worth noting that our study focused specifically on overweight or obese adults, so these results may not apply equally to everyone. If you’re unsure of what this means for you personally, it’s worth talking to your doctor. That said, if you have a body mass index > 25 If you are an overweight or overweight adult based on kg/m2, our findings suggest that it may be worth avoiding three or more alcoholic drinks per week.”
Courtney also outlined some limitations and potential misconceptions about the findings. “Important for readers is that although women who drink light (one to three drinks per week) have lower CRP than women who drink moderately or heavily, they do not have lower CRP than non-drinkers,” Courtney said. “In other words, these findings should not be interpreted as suggesting that light drinking is better than non-drinking when it comes to inflammation.”
The researchers note that the findings may not apply to the broader general population or people with different body compositions. “As well, this was a sample of disease-free adults who were overweight or overweight based on body mass index,” Courtney noted. “Because being overweight and obese increases inflammation, the effects of alcohol intake and nutrition on inflammation may differ between normal-weight adults and adults who already have diseases such as high blood pressure or diabetes.”
Additionally, the dietary data covered only two days of the entire three-week study period. Dietitians usually recommend collecting dietary data over at least three to four days to get an accurate picture of a person’s habitual eating patterns. Another potential misconception may arise from reliance on self-reported data on alcohol consumption.
“My overarching goal in research is to help people live healthier and happier lives, for example by helping them make informed decisions about whether drinking alcohol is a good decision for their health and well-being,” Courtney said. “As a next step, we are continuing to investigate the effects of alcohol use and other lifestyle factors, such as nutrition and physical activity, on inflammation with the aim of achieving long-term goals.”
Future research should aim to include larger and more diverse groups of people over longer periods of time. The scientists suggest that future studies could use objective measures of biological alcohol exposure, such as wearable alcohol sensors or breathalyzers, to eliminate the potential inaccuracies of self-reporting.
“As with any research, there is always a need for replication and further investigation,” Courtney said. “In the meantime, guidance from medical institutions and the U.S. Surgeon General on alcohol use remains the best source of information for making informed decisions about drinking. In that regard, we would like to highlight the efforts of first author Kailyn Roeder on this study. She is the one who initiated this particular research question. She is an MD/PhD student, and we believe she is a future leader in medicine and research.”
The study, “Moderate-to-severe habitual alcohol use appears to be detrimentally associated with inflammation, even when accounting for human diet quality: Results from an observational intensive longitudinal study,” was authored by Kailyn Lowder and Jimikaye Beck Courtney.
