Despite the scientifically proved FACT that the 'straw man' argument is the first resort of the lazy researcher, I agree that a bicycle helmet provides some protection to a limited portion of the head from some specific impacts. It may prevent a scratch or bruise, for example.

But the important question is much larger than that and involves risk/cost/benefit analysis. As an example, few would disagree that IF the perfect helmet existed, a light weight helmet that contributed absolutely nothing to increasing risk of injury [a huge and theoretically impossible condition], people would be at less risk if they wore those helmets 100% of the time including when sleeping, walking, eating and especially while showering.

Like Meanwhile and Closetbikerl, I started out pro helmet since I was and am convinced of the efficacy of wearing a full face, Snell compliant helmet when riding a motorcycle.

But wearing one while cycling is like wearing one while showering, golfing, driving or crossing the street. Even if they did not increase any risks, I would feel foolish wearing one all the time. Knock yourself out. Wear a helmet. No one is saying not to. But you are kidding yourself if you only wear one while cycling and do not wear a full face Snell compliant helmet.

On a macro as opposed to an individual level, one only need look at the stats that demonstrate the loss of health benefits to the public from not riding due to mandatory helmet laws outweighs the speculative benefits from wearing one.