What began as a public health campaign in the United Kingdom is now the subject of a recent trend: alcohol-free challenges. You may have seen friends and family members participating in month-long challenges like Dry January and Sober October as a way to reset or reevaluate their relationship with drinking. After a booze-free month, people often feel improvements in overall well-being, according to recent research.  But little is known about what happens internally to social drinkers when they abstain from alcohol for a month.
InsideTracker’s Inside Impact: Sober October Study followed 30 light to moderate consumers of alcohol for 31 days. Participants completed a blood draw before and after abstaining from alcohol and completed a questionnaire about how they felt after the challenge. Results showed that even this short-term break in alcohol consumption can impact markers of health.
According to the Inside Impact: Sober October Study, here are four things that can happen when you participate in a month-long alcohol-free challenge like Dry January or Sober October.
1. Improvements in sleep quality, mood, energy, and hydration
Just as the study investigators hypothesized, more than 50% of study participants reported feeling improvements in one or more of the following characteristics: sleep quality/duration, athletic performance, post-exercise recovery, stress/mood, energy level, hydration level, which was met based on a post-study survey.
And these findings align with the current scientific literature on the impact of alcohol cessation on health measures.
- Sleep quality and duration: Studies show that having an alcoholic beverage within a few hours of bedtime may negatively impact your sleep quality and duration. In particular, alcohol can disrupt REM sleep, which is particularly important for learning and memory consolidation. 
- Athletic performance: Consuming alcohol-containing beverages can negatively impact both aerobic and aerobic athletic performance. 
- Post-exercise recovery: Repairing and producing new muscle protein post-exercise is essential for recovery. Excessive inflammation hurts this process, and while exercise does lead to some acute inflammation, drinking also increases proinflammatory molecules and can impair post-exercise recovery. 
- Stress and mood: Alcohol can disrupt the chemical messengers in the brain that impact stress and mood. 
- Energy level: Alcohol consumption is associated with increased fatigue. 
- Hydration level: Alcohol is a diuretic and inhibits antidiuretic hormone, which increases fluid loss and can lead to dehydration. 
Key takeaway: Evidence suggests that even short-term abstinence from alcohol can lead to improvements in perceived sleep, energy, mood, and athletic performance.
2. A decrease in high-density lipoprotein (HDL) cholesterol
As a group, participants saw significantly decreased HDL cholesterol levels (-9%), and these findings remained significant in the compliant group (-9%), females (-7%), and males (-14%). High-density lipoprotein, also known as the “good cholesterol” is a protective form of cholesterol that helps to remove harmful particles from the bloodstream before they can cause damage to blood vessels, and are therefore cardioprotective.
While many people are looking to raise their HDL levels, this finding that alcohol abstinence decreases HDL is consistent with previous studies and coincides with studies that show that moderate alcohol consumption is associated with increased HDL cholesterol levels. [8-10]
Key takeaway: The Inside Impact: Sober October Study found that a month-long alcohol abstention was associated with significantly decreased HDL cholesterol levels.
3. A decrease in neutrophil to lymphocyte ratio (NLR)
Results showed significantly decreased neutrophils (-11%) and increased lymphocyte counts (+9%), among study participants.
Neutrophils and lymphocytes are two of the five components of white blood cell counts.
Neutrophils make up the largest share of your white blood cell count, contributing 60-70% of the total. Neutrophils are the immune system’s first responders; they recruit white blood cells to rid the body of pathogens that shouldn’t be there.
Lymphocytes represent around 20-40% of circulating white blood cells. Like neutrophils, lymphocytes also help to fight off foreign pathogens. But lymphocytes also become memory cells—meaning they can remember the pathogens they’ve fought and prevent further diseases from them. This is also known as adaptive immunity.
Consuming alcohol-containing beverages can suppress the body’s immune response. In fact, clinical studies have shown that overconsumption of alcohol is associated with increases in infectious diseases. 
The relationship between the two—known as the neutrophil-to-lymphocyte ratio—is a way to evaluate the balance between systemic inflammation (neutrophil count) and adaptive (longer-term) immunity (lymphocyte count). Emerging evidence links the NLR to measures of longevity (like mortality and disease risk). In the general population, increased NLR is associated with overall mortality and mortality due to heart disease, lower respiratory disease, influenza/pneumonia, and kidney disease. 
Key takeaway: The Inside Impact: Sober October Study found that a 30-day alcohol abstention was associated with decreased NLR, which is beneficial for immune function and additional health outcomes.
4. An improved resting heart rate (RHR)
In addition, 22 of the study’s 30 participants wore fitness trackers such as a Garmin smartwatch, Apple Watch, or FitBit, that collected heart rate data. A preliminary analysis showed statistically significant changes in the seven-day average RHR of participants, which moved from 57.5 bpm to 55.5 bpm—a 3.5% reduction (p=0.003).
This finding is consistent with previous studies showing higher breath alcohol concentrations (BAC) are associated with increased RHR, as assessed using an electrocardiogram (ECG). 
Key takeaway: The Inside Impact: Sober October Study found that a 31-day alcohol abstention was associated with decreased RHR.
So you’ve completed an alcohol-free month. What’s next?
You may experience both subjective (i.e I feel more rested, I feel more motivated) and objective changes by participating in alcohol-free challenges like Sober October and Dry January. Tracking how you feel and leveraging blood analysis can help you to understand how your habits impact your health. Abiding in or abstaining from alcohol consumption is truly a personal choice. Some study participants reported that they would resume drinking after the study, although with modifications, and two participants even noted that they would continue on their sober curious journey.
Being able to evaluate and iterate on the habits that best suit your physical and mental health is key to maintaining your well-being—which may or may not include alcohol.