Caffeine is on the International Olympic Committee's list of banned substances. It is a punishable offence to take it in excess. Yet those of us who have drunk coffee in permissable moderation to delay glycogen depletion in a marathon, the hitting of the so-called wall, are clean in the eyes of sporting law.
"Are you not morally taking drugs to help you compete?" Dr Dawson pondered. "Is that not manipulating drugs for performance enhancement? Is it right to use creatine monohydrate, which is not banned but boosts power in explosive sports? It's all about what you as an individual perceive as correct. The lines are very blurred.
"If you are a female athlete and you go to a big meet and you don't want to have a period, you're allowed to take two packets of the pill. That is using a female hormone to manipulate your body effectively to help you. Well, shoot, what's the big jump from there to a male athlete taking a male hormone to manipulate his body? Where does anyone draw the line?
"To me, if you elect to take a performance-enhancing aid, just because it's not banned doesn't mean it's right. Morally, you've already accepted the use of performance-enhancing agents, outwith your natural training, to improve your sport. It's not a huge step from there to legitimising the use of drugs in sport because you've already accepted the premise."
Doug Walker has crossed no line between sporting heroism and sporting villainy this week. He has failed a drugs test - innocently so, the European 200m champion insists. Metabolites of nandrolone, a banned anabolic steroid, are understood to have been found in a urine sample he provided last month. How they came to be there has yet to be explained. But what Walker's case has highlighted already is the difficulty of defining the line between what is acceptable and what is not in pursuit of sporting performance enhancement.
The issue was literally brought home to those who subscribe to Athletics Weekly when Wednesday's edition thudded on the doormat with a 96-page guide to "power and performance supplements". The brochure advertises some products endorsed by Walker that are not banned, and others that are banned. It also includes an advert for the World Anabolic Reference Guide, a volume that will be of professional interest to Dr Dawson.
A first-team rugby player with the Portobello club in his younger days, he is the resident doctor at a clinic run by Durham Health Authority for sportsmen and sportswomen who use drugs. The Discus clinic (Drugs in Sport Clinic and Users' Support) has been held weekly in Chester-le-Street for four years. "It's about harm minimisation," Dr Dawson said. "My basic stance is I do not believe anyone should take drugs to enhance performance. I think it's wrong. But it's not my place to put a moral judgement. As a physician, it would be unethical.
"We know that drug use in sport has been on the go since times BC - from people using magic mushrooms, to Abyssinian asses' hooves to testes to strychnine in the 19th century to anabolic steroids in the 1950s. It's naive of us to think we'll stamp it out simply by urine testing. The Chinese swimmers were only caught by accident and the same with the Tour de France cyclists. For all our super-dooper testing, the major catches have been made by accident - by customs officials.
"If you want to `cheat' now you can use insulin, growth hormone and erithopoeitin, all of which are undetectable. One of the common things is insulin used in combination with creatine. It improves power output and, again, it's undetectable. The athletes, in general, will always stay one step ahead of the testing programme."
Those athletes, however, who fail to negotiate the testing programme, innocently or not, enter the grey area in which Doug Walker may find himself. Randy Barnes, the Olympic shot-put champion, was banned for life last year after testing positive for nandrolone. A member of the Irish rugby team who tested positive for it after a Five Nations match last season has escaped punishment. So has the Czech tennis player Petr Korda.
A British boxer has even fought a successful defence based on oral sex. He claimed to have ingested nandrolone from his partner the night before his test. The offending substance, apparently, can be found in pregnant women.