Define "survival situation".

If I'm stuck in a stranded vehicle and the best plan is to stay there for at least the next day or so then I wouldn't mind enjoying a little drink in the company of good friends. Since we're stuck anyway we might as well enjoy ourselves, right?

If I need to be at or above 100% mental and physical capacity I don't touch alcohol.

About the "liquid bread" analogy: It would be very interesting to see some qualified judgement about how many beers you should drink (along with plenty water) to optmimize performance. Following the guidance in my old friend the Swedish army survival manual http://www.bushcraftuk.com/downloads/pdf/h_overlevnad.pdf about 500 kcal per day (preferably carbohydrates) is a nice tradeoff for adequate performance in a low food situation. So a little more than two pints per day should do nicely, energy wise, sipped a little now and then throughout the day. I'm not so sure I like the idea on combining a pint with advanced navigation skills on an empty stomach, though...

Oh, about the Swedish survival manual: It is written in 1988. I'm sure our knowledge about how cognitive and bodily functions are impared in a low food/no food situation has improved since then, but I can't find it. I'm interested in what to do when faced with little food and you still need to do physical labour and/or generate body heat so you don't freeze to death. If anyone has material on that subject I'd love to hear about it.