It seems like such a no-brainer. You get out your bike to go for a ride and you put on your helmet, a highly engineered and carefully scrutinized piece of equipment designed to protect you from serious brain injury, even death.

Helmets are lighter, more comfortable, more versatile and more stylish than ever.

But helmet use at the recreational level does not enjoy a consensus. For something that seems so obvious — helmets protect the brain in a fall or collision — it may surprise you that helmet use has been studied and studied again for decades.

Some studies suggest motorists give cyclists without helmets more room when they drive past. Other studies suggest we take more chances and perhaps ride more recklessly when wearing a helmet. And other studies seem to show that making helmet use mandatory would discourage many would-be bike riders from getting out there.

And then there are the people who just don’t think bike riding is all that dangerous of an activity. In 2014, 726 cyclists were killed in accidents in the United States, according to the Governors Highway Safety Association.

Take Mel Melvin, who gave up driving altogether while in college, and these days uses his bike for everything from riding to work to going out to dinner. If you ask him, he’s neither reckless nor foolish. But he made the conscious decision to not wear a helmet, and he hasn’t looked back.

“I don’t wear a helmet because I don’t feel cycling is a dangerous enough activity to warrant wearing a helmet. I’ve been car-free for 28 years and I’ve never been hit by a car and I’ve never had an incident with a car,” said Melvin, who has a master’s degree in history and does environmental consulting.

Sometimes his helmet-free ways trigger unsolicited responses from friends, loved ones and even strangers, ranging from advice to outrage.

“People say I’m reckless or I’m completely disregarding my well-being by not wearing a helmet,” Melvin said. “I don’t discourage anyone from wearing a helmet. I just don’t believe it’s dangerous enough to do so. At times, I feel people are judging me that I don’t care about myself. I just feel it’s a rational decision. I’ve never seen any data that suggests that cycling is that dangerous that you need to be wearing a helmet.”

That’s not how Steven Maviglio sees it.

“Every time I see someone without a helmet, I think they’re risking their life,” said Maviglio, a longtime political consultant. “Accidents can happen anywhere, and the chances of surviving an accident are much better when you’re wearing a helmet.”

Maviglio points to a personal incident in which his helmet saved him: Riding on the bike trail a couple of years back, he crashed and landed on his head. The helmet absorbed the blow.

“Once a week, there’s something in the near-miss category where I have to think about my safety,” said Maviglio, who rides 3 miles to work, rain or shine.

Like Maviglio, many others wouldn’t consider going for a ride without a helmet, even if it’s a slow-paced excursion to the store or a cruise around the neighborhood. When we asked the question on Twitter, most responses were decidedly pro-helmet. A pediatrician weighed in. So did a neurologist. Parents said they wore helmets to set an example for their kids, who are legally required to wear a bike helmet up to age 17.

“Always. I cringe when I see others without them,” tweeted Susan Berg, a recreational cyclist who lives in Citrus Heights and is the mother of two teenagers, both of whom wear helmets.

In a follow-up interview, she said, “I can’t think of a situation where you wouldn’t be safer wearing a helmet. It would be like driving in a car on the freeway without wearing a seat belt.”

Despite occasional forays by politicians seeking to make helmets mandatory for all, California and most other places in the United States continue to leave it as a choice for adults. Part of the problem with the debate is that bicycle riding is such a varied activity and bikes range from lightweight racing machines to beach cruisers.

When we look for answers abroad, the helmet question becomes even more complicated. In Denmark and the Netherlands, tens of thousands of people ride their bikes for transportation of all kinds. Americans who visit are often alarmed that almost no one wears a helmet and there seems to be no great helmet debate.

Are cyclists there safer because the cycling infrastructure is better? Because motorists are more considerate and aware? Because riding a bike is more ingrained in the culture? It’s probably a combination of those factors.

In the United States, cycling advocates point to Amsterdam and such cities, where folks ride their bikes and feel absolutely safe in doing so, as a bicycle riding utopia. In the Netherlands, a quarter of all trips are made by bicycle, according to a report by the Organization for Economic Cooperation and Development.

Dave Snyder, executive director of the California Bicycle Coalition, opposes mandatory legislation, in part because bike riding comes in so many forms. Per capita bicycling injuries have been dramatically reduced in recent years, in part because of more bike lanes and, as cycling increases in popularity, greater visibility of bikes around town.

His organization has gone on record in opposing mandatory helmet laws, pointing out that bicycling rates dropped or stagnated in Australia and New Zealand when laws were passed requiring cyclists to wear helmets.