How much time will it take for the alcohol you consumed to affect your brain?

Krishna: That depends! On the strength of your drink , how fast you drink it and how well your system absorbs alcohol and metabolizes it.

However, generally speaking, just one drink can quickly go to your head. Researchers tested this well-known adage. Only six minutes after consuming an amount of alcohol equivalent to three glasses of beer or two glasses of wine, leading to a blood alcohol level of 0.05 to 0.06 percent, changes have already taken place in the brain cells, as the scientists have now shown using magnetic resonance spectroscopy (1).

This is what the research paper on this says:

On average, Eth was detected first at 5.79 and 8.64 mins upon per os ingestion within the fronto-mesial and cerebellar volume of interest, respectively, leaving a 2.85-min offset, mainly caused by the subsequent collection of supratentorial and infratentorial data. In addition, supratentorial and infratentorial Eth concentrations culminated at different times. Besides the subsequent acquisition of fronto-mesial and cerebellar MRS data for Eth kinetics, there is much dispersion in time, because of interindividually different ingestion and absorption rates. These individual disparities defy data correction in time through postprocessing. Thus, varying onsets of fronto-mesial and cerebellar Eth peaks rather reflect intrinsic physiology of each individual than true effects of spatially distinct Eth kinetics.

During the experiment, the concentration of substances such as creatine (energy metabolism), which are attributed with protecting cells, decreases as the concentration of alcohol increases(2,3).

Choline, a component of cell membranes, was also reduced. That probably indicates that alcohol triggers changes in the composition of cell membranes(2,3).

Follow-ups on the next day showed that the shifts in brain metabolites after moderate consumption of alcohol by healthy persons are completely reversible(2,3).

This study found no differences between the results of male and female individuals – the brains of female and male subjects reacted to alcohol consumption the same way (2,3).

Footnotes:

1. https://journals.sagepub.com/doi/10.1038/jcbfm.2009.12
2. http://Armin Biller, Andreas Bartsch, György Homola, Laszlo Solymosi, Martin Bendszus. The results of the study were published in the Journal of Cerebral Blood Flow and Metabolism. Journal of Cerebral Blood Flow and Metabolism 2009
3. From The Glass To The Brain In Six Minutes

(Both 1 and 2 references are same)