Excessive alcohol consumption and alcohol dependence are known to cause cognitive impairment, including memory loss and problems with verbal fluency, verbal learning, processing speed, attention, and problem solving. problems. However, the effects of moderate alcohol consumption on brain function have not been studied. Considering that most people who drink alcohol likely fall into this category, such a study is long overdue.
A team led by Anya Topiwala from the University of Oxford recently explored the relationship between alcohol consumption and cognitive function in over 20,000 UK Biobank participants. Not only did the participants report their own alcohol consumption, but they also undertook various cognitive tests that assessed executive function, fluid intelligence, and reaction time.
The researchers went further and measured the levels of iron present in the participants’ brains and livers, with the aim of establishing whether iron levels represent a potential pathway to alcohol-related cognitive deficits. Iron is involved in many fundamental biological processes in the brain, including oxygen transport, DNA synthesis, mitochondrial respiration, myelin synthesis, and neurotransmitter synthesis and metabolism. But high levels of this element have also been found in the brains of people with neurodegenerative diseases such as Alzheimer’s and Parkinson’s.
In the largest study to date on moderate alcohol consumption and iron accumulation, researchers recruited 20,965 participants who had completed their UK Biobank questionnaires and had undergone MRI brain imaging. Around 7,000 of them also underwent liver analysis, with both types of analysis used to identify iron levels in cells. The average age of the participants was 55 years old and 48.6% were women. Although 2.7% classified themselves as non-drinkers, the average consumption was around 18 units per week, which translates to around 7½ cans of beer or 6 tall glasses of wine.
This level of alcohol consumption, classed as moderate, was higher than the current UK low-risk guidelines (
The team found that drinking more than seven units of alcohol per week was associated with higher iron markers in several brain nuclei, including the bilateral putamen, caudate and substantia nigra. These basal ganglia and the substantia nigra in the midbrain are associated with the control of motor movements, procedural learning, eye movements, cognition, emotions, and other functions.
The significantly higher levels of accumulated iron in these areas of the brain had also been identified in previous research on people with alcohol-related disorders, also known as alcohol dependence, but in the present study , the result was observed in people who were only moderate consumers of alcohol.
In addition, higher alcohol consumption was associated with increased levels of iron in the liver, which is considered a good indicator of iron levels in the body in general, and the researchers found that iron levels were also the best indicators of liver damage. Alcohol suppresses the production of hepcidin, an important hormone in the liver that regulates iron balance. As a result, alcohol consumption leads to increased absorption of iron from digested food and can lead to imbalances in iron levels in body organs such as the brain.
High levels of iron in certain brain regions were also associated with poorer performance on cognitive tests, such as lead-making tests that assess executive function and fluid intelligence tests that assess reason and logic. Reaction times were also slower in cases where certain brain regions had higher iron levels.
There are some limitations to this large study of moderate alcohol consumption and iron accumulation. Alcohol consumption was self-reported and may have been underestimated by participants. Additionally, MRI-derived measurements are indirect representations of brain iron and could confuse other brain changes seen with alcohol consumption that have changes in iron levels.
In conclusion, Topiwala says, “In the largest study to date, we found that drinking more than 7 units of alcohol per week was associated with iron accumulation in the brain. Higher brain iron is in turn linked to poorer cognitive performance. The accumulation of iron in the brain could therefore be at the origin of alcohol-related cognitive decline.
Given the prevalence of moderate alcohol consumption in the world today, even small links between alcohol and reduced brain function could have substantial impacts on entire populations. Thus, these results support the introduction of interventions aimed at reducing alcohol consumption in the general population.
The research is published in the journal PLoS medicine.
By Alison Bosman, Terre.com Personal editor