The study Associations between alcohol consumption and gray and white matter volumes in the UK Biobank shows that one unit of alcohol drunk a day can lead to loss of gray and white matter in the brain. It was published in Nature Communications in March 2022.[1]
The research involved 36,678 generally healthy, middle-aged adults from the United Kingdom Biobank. The UK Biobank is a biomedical database containing in-depth genetic and health information, including MRI imaging of the brain from half a million UK participants.
Here is a brief background about the brain and measures of alcohol intake.
The gray and white matter
The brain is made of neurons and supporting connective tissue. The neurons are the electrically excitable nerve cells. The main parts of the neurons, as shown below, are the cell body and the axons.
By BruceBlaus – Own work, CC BY 3.0The cell body is in gray matter. The axons connect to the other neurons in the brains’ white matter.
The white and gray matter is shown in the human brain below. The white matter is in the middle, and the gray matter is at the periphery.
The study shows that even one unit of alcohol intake daily leads to loss of gray and white matter in both men and women.
Measures of Alcohol
Unit of alcohol
A unit of alcohol is a measure to quantify the actual alcoholic content within a given volume of an alcoholic beverage. It is used in the United Kingdom to guide total alcohol consumption.
One unit of alcohol (UK) is defined as 10 milliliters (8 grams) of pure alcohol. The number of units of alcohol is known by multiplying the volume of the drink (in milliliters) by its percentage of alcohol by volume or ABV and dividing by 1,000.
Examples:
- Half an imperial pint (284 ml) of beer with 3.5% ABV contains almost one unit.
- A medium glass (175 ml) of 12% ABV wine contains around two units of alcohol.
- A small glass (50 ml) of sherry, fortified wine, or cream liqueur (≈20% ABV) contains about one unit.
- 25 ml of a spirit with 40% ABV contains one unit.
Standard Drink
For comparison, in North America, the term standard drink is used to measure alcohol content. One standard drink contains 14 grams of alcohol and corresponds to:
- 12 fl. oz. (354 ml) bottle of 5% Alcohol by Volume (ABV) beer
- Five fl. oz. (147 ml) of 12% ABV wine
- 1.5 fl. oz. (44 ml) shot of 40% ABV liquor.
Categories of alcohol intake
Back to the study [1], the authors binned the participants into:
- Abstainers
- Individuals who drank less than one unit/day
- Individuals who drank between one (included) and two (excluded) units/day (recommended maximal alcohol consumption based on the UK Chief Medical Officers’ “low-risk” guidelines)
- Individuals who drank between two and three units/day
- Individuals who drank between three and four units/day
- Individuals who drank at least four units/day.
After classifying the study subjects based on their alcohol intake, they examined the MRI of their brains from the UK Biolab. The MRI can measure the volumes of the white and gray matter of the brain.
After controlling the other variables, the result showed that the gray and white matter of the brain starts to get small with as little as one drink a day. And as the alcohol intake gets higher, the decrease is greater. Going back to what we learned earlier, that means that the cell body and the axons of the neurons are both negatively affected by alcohol.
Loss of white matter in the brain leads to impaired interconnections between the different areas of the brain.
The report shows that no particular part of the brain gets smaller compared to the others, but rather the decrease in the size affects the brain globally.
The table below shows the predicted additional age in the brain years among different levels of drinkers. The way to read this table is that a person who drinks 1-2 units a day will age their brain by two years at 50 years of age.
The CT scans of the brain below are not from the study but are presented here to show the different levels of brain atrophy (shrink). The normal brain is on your left side, and the most atrophied brain is on the left. The white is the brain tissue, and the black is water. Cerebrospinal fluid occupies the space left by the shrinking brain.
Consistency with another study
Another study in 2021 by Topiwala and colleagues, No safe level of alcohol consumption for brain health: observational cohort study of 25,378 UK Biobank participants, also showed smaller brain volumes with higher alcohol consumption. [2]
Their study shows a decrease in the sizes of the brain as alcohol use (in standard units) increases. The figure below is from their research and shows the different parts of the brain that get smaller with higher alcohol consumption.[2]
Additionally, their results show that hypertension and higher Body Mass Index make alcohol drinking worse for the brain. Their conclusion,
No safe dose of alcohol for the brain was found.
Moderate consumption is associated with more widespread adverse effects on the brain than previously recognized. Individuals who binge drink or with high blood pressure and BMI may be more susceptible.
Detrimental effects of drinking appear to be greater than other modifiable factors. Current ‘low risk’ drinking guidelines should be revisited to take account of brain effects.
Alcohol abstinence regains brain mass
Here is the good news. Three studies among alcohol users who abstained from alcohol showed that brain mass increases in size. A 1988 report showed an increase in brain mass after five weeks among alcoholics who abstained.[3]
Alhassoon et al. showed improved brain mass and working memory as early as two weeks. [4]
Pfefferbaum and his group showed that abstinence demonstrated “improvement in brain fiber tract integrity reflective of fiber reorganization and myelin restoration, indicative of a neural mechanism explaining recovery.” However, “Return to heavy drinking resulted in accelerating microstructural white matter damage.”[5]
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Related:
- Alcohol use, heat-not-burn tobacco, and cigarette smoking decrease antibody response to Pfizer COVID vaccine
- Alcohol Abuse, Covid-19, and Lung Complications
References:
- Daviet, R., Aydogan, G., Jagannathan, K. et al. Associations between alcohol consumption and gray and white matter volumes in the UK Biobank. Nat Commun 13, 1175 (2022). https://doi.org/10.1038/s41467-022-28735-5
- , , , No safe level of alcohol consumption for brain health: observational cohort study of 25,378 UK Biobank participants.
- Schroth G, Naegele T, Klose U, Mann K, Petersen D. Reversible brain shrinkage in abstinent alcoholics, measured by MRI. Neuroradiology. 1988;30(5):385-9. doi: 10.1007/BF00404102. PMID: 3211313.
- Alhassoon, O. M. et al. Callosal white matter microstructural recovery in abstinent alcoholics: A longitudinal diffusion tensor imaging study. Alcohol Clin. Exp. Res. 36, 1922–1931 (2012).
- Pfefferbaum A, Rosenbloom MJ, Chu W, Sassoon SA, Rohlfing T, Pohl KM, Zahr NM, Sullivan EV. White matter microstructural recovery with abstinence and decline with relapse in alcohol dependence interacts with normal aging: a controlled longitudinal DTI study. Lancet Psychiatry. 2014 Aug;1(3):202-12. doi: 10.1016/S2215-0366(14)70301-3. Epub 2014 Aug 5. PMID: 26360732; PMCID: PMC4750405.
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