Alcohol reduces the risk of dementia. 23 year follow-up of Whitehall II cohort study

Your title is completely false. This was a correlation study. It did not prove any causal link. The study does NOT say that alcohol reduces the risk of dementia. It says that the instances of dementia were higher in people who abstained from alcohol in mid-life, but were also greatly increased in people drinking more than 14 units a week. They even state that the increase was partly explained by cardiometabolic disease over the follow-up. Not only that, the entire conclusion of the study was that some country's weekly limits for harmful alcohol consumption were too high, and they should be lowered. This is because the risk of dementia went up when drinking more than 14 units a week, which is lower than some thresholds. It literally says all this shit in the abstract...

They even state later on that heavy consumption of alcohol led to a fourfold increase in dementia risk. 4X the instances of dementia in people drinking more than 14 units of alcohol a week. That's huge! Then you get to the section on the increased risk in abstinent users, and you get a clear picture as to why that might be.

Moderate alcohol consumption has been hypothesised to benefit cardiovascular health through favourable impacts on lipid profile, inflammation level, endothelial function, and insulin sensitivity. In agreement with this, a meta-analysis of interventional studies (alcohol use versus a period of no alcohol use) reported that moderate alcohol consumption had favourable effects on levels of high density lipoprotein cholesterol, apolipoprotein A1, adiponectin, and fibrinogen,38 potentially underlying the apparent neuroprotective effects of moderate alcohol consumption.

So moderate alcohol consumption might improve some cardiovascular, metabolic, and inflammatory levels. Those improvements could be correlated with lower risks of dementia. Alcohol is not directly reducing the risk, nor is this causal link proven in any way. You could certainly just eat healthy and exercise, and get much better improvements without alcohol. They also state the following:

Our analyses using repeat data on alcohol consumption across midlife suggest that former drinking might not explain the excess dementia risk in abstainers, although we cannot exclude the possibility that those who report alcohol abstinence in midlife were heavy drinkers in young adulthood or misreported their alcohol consumption. We accounted for several sociodemographic and health related characteristics in the analysis, but residual confounding cannot be excluded as an explanation for the higher risk of dementia among abstainers. Indeed, this group is particular in that it is composed mainly of women from the lower socioeconomic group with higher prevalence of cardiometabolic risk factors and disease at baseline, a pattern that has also been observed in other studies.

So there are other possible confounding variables that they cannot rule out. The data not only is correlational only, it is far from sound enough to make a definitive assessment of a causal link. They then clearly state:

The present findings on alcohol abstinence should therefore not motivate people who do not drink to start drinking given the known detrimental effects of alcohol consumption for all cause mortality and diseases such as neuropsychiatric disorders, cirrhosis of the liver, and cancer.

Listen, I drink alcohol myself. I brew my own beer and eventually will probably start my own microbrewery. So I am not against it by any means. Having a beer with colleagues or friends is a very beneficial social thing, and comes with its own benefits in moderation. However, in no way shape or form am I under the impression that the direct effects of alcohol are healthy in any way. They aren't. Period. There is no debate about that. ZERO. Alcohol is a direct neurotoxin, and its main metabolite acetaldehyde is a carcinogen. However, moderate consumption of alcohol in healthy people does not seem to have serious health effects that need to be worried about. The key here is moderate. But let's not start going around trying to make people think it is healthy and beneficial, or to seed doubt in the science behind its risks.