When Scott McCarron returned to his locker after a round in the 2018 Boca Raton Invitational, a bottle of CBD oil pills had been placed in the cubby by Functional Remedies EndoSport. It's not unusual for professional golfers to have various products given to them to sample, but this one in particular was intriguing to the No. 1-ranked player on the PGA Champions Tour.

McCarron didn't know a great deal about CBD oil, but he knew enough from research and talking to other athletes who had taken cannabidiol (CBD), a supplement derived from the hemp plant, to realize that it might be able to help with some of his ailments.

"I went and tried it about two weeks later when I went home. I measure my sleep with a device called WHOOP," McCarron said. "That's a sleep and strain device. Major League Baseball, NFL and Olympic athletes use the device. For the first time in about two years that I'd been wearing the device, I was taking the CBD oil, started on Monday and had sleep in the green, which is fantastic sleep, for seven days straight the first time I took this CBD oil at night to help me sleep."

McCarron has now been using the products for nearly two years and is among a growing list of PGA Champions Tour players using CBD oil for various reasons, including sleep, recovery, anxiety and inflammation. Through word of mouth of the perceived benefits, the products have spread on the Champions Tour.

Despite its open popularity among the senior players, it has taken longer to surface as an acceptable practice to discuss publicly with the PGA Tour players. That is rapidly changing, though, as the perception of and education about the product are growing as well.

What used to be a taboo topic, and a product quite a few players on the Tour were using but were reluctant to talk about, has become a growing industry -- now diving into sponsorships and ambassador programs with high-profile players from both tours, including McCarron, Bubba Watson, David Toms, Vaughn Taylor, DJ Trahan, Kenny Perry, Tom Kite and Scott Piercy, among others.

Part of the reason CBD oil has been more popular early on in the Champions Tour is because the players are older, with rapidly changing bodies, and are looking for ways to continue competing at a high level with their grueling schedules.

A big reason the senior players are more open to discussing CBD use than their younger counterparts on the PGA Tour, however, is because they are not drug-tested in the same way as the under-50 crowd on the PGA Tour.

CBD is derived from the hemp plant, which is a strain of cannabis, but it is grown and used to make the products because it typically contains less THC, the psychoactive ingredient that causes a high, than the marijuana plant.

Scott McCarron said CBD oil has changed his sleep, improving it. He sees the benefits other Tour pros are now seeing, too. AP photo/Nam Y. Huh

THC is a substance banned by the World Anti-Doping Agency, and because the CBD products are not regulated by the FDA, there is a level of uncertainty about what is actually in the product. It raises questions about whether the THC levels are low enough to keep the Tour players from failing a drug test and if the listed ingredients are actually what make up the CBD oil.

"I think everybody [on the Tour] was taking a wait-and-see approach," McCarron said. "They want to make sure it is legal and there is nothing in it. One of the things with the Tour, to their credit, they put out a statement saying it's not illegal to take this substance, but you better make sure you know what's in it.

"There's so many CBD companies out there right now, that you might not know what's in it. So if you're on the PGA Tour, you better do your homework and make sure there's nothing in it that can give you a positive test."

That's why Steve Patterson, the director of sales at Functional Remedies EndoSport, was apprehensive at first about whether the Tour players would accept it when the company decided to go beyond the Champions Tour in the fall of 2018.

The company now has 50 players on the Tour who are using their products, which include a salve to rub on the skin, oil to take orally and pills.

"The players are comfortable with a low THC count. That was the main thing I had a hesitancy about, what is their response to putting something in their bodies that's new?..." Patterson said. "But it's also a natural product, so then word of mouth, it really took off. That's where the popularity and acceptance has come in."

The PGA Tour's stance on CBD, according to Andy Levinson, the senior vice president of tournament administration, is that it falls under the same category as permitted supplements. The Tour warns its players that any supplement is to be taken at their own risk and that there are potential pitfalls to taking products that could contain ingredients not listed on the package.

"There's very, very little FDA regulation over the supplement industry as a whole, so if a player wants to take any supplements, whether it's CBD, or a multivitamin, or a protein powder, they need to understand that there is risk associated with that regardless of the manufacturer, because there is very little FDA regulation over the industry," Levinson said. "There is no guarantee that what is on the label is actually contained in the product."

Because the CBD products are considered supplements and not a drug, the manufacturers are not allowed to make any medicinal claims of benefits, either. The players have noted that they have seen improvements in sleep, recovery, anxiety and focus, and that's where the word-of-mouth testimonials have benefited the companies.

Those testimonials started to spread quietly, as more and more players were using the products but were still mainly unwilling to talk about it publicly -- until some bigger names came out and openly endorsed a few products.

The biggest was Bubba Watson, who announced a partnership with cbdMD in April and displays the company's logo on both sides of his visor in tournament play.

Similar to Functional Remedies, cbdMD manufactures its own products, which allows it to monitor the THC levels, and it gave Watson a level of comfort to openly use the products.

"Just because of, I'm getting older," Watson told TheStreet. "The inflammation in my body, waking up with better sleep. That was the two things I focused on. With a 7-year-old and a 4-year-old at the house, and playing golf all day, I needed some energy fast.

"For me, it was all about sleep and trying to get the body right."

There are still misconceptions about the products that have made some Tour players hesitate to publicly announce they use CBD oil in any form. For example, the product is derived from hemp, not marijuana. Also, hemp is produced for high CBD content and marijuana for high THC content.

That's the challenge some companies are still facing. But as more and more players are seeing an impact with the natural remedy, more golfers are willing to use it. And as education about the products continues to spread, and as the companies are doing more to ensure they meet the standards for each sport's governing body, that hesitancy is likely to fall as well.

"We're also working on getting what is called NSF for sports certification. Once we get it, we'll be in baseball in particular, because those guys are so paranoid about putting anything in their body," Patterson said. "But once you get the certification, it's basically a vetting process. When you have the logo, players know that your products are safe, they're not contaminated, and they feel comfortable taking them."

Levinson is quick to note that no cannabis product has NSF certification for sports, but he says that if a company were able to obtain it, that is considered the gold standard by the PGA Tour in terms of consistency and knowing what is in the product.

It would be a vote of confidence for the brand to achieve the certification, and the PGA Tour only considers supplements that are NSF-certified for sports for any marketing partnerships or business-related relationships, let alone recommending them for players.

"The risk here [currently] is that you really don't know what's in a product," Levinson said. "Taking a supplement that you really don't know what's in it may or may not be better for you. There's no substantive science behind the claimed benefits of these products, whether it's inflammation or anti-anxiety, or what have you.

"Without FDA regulation, a lot of these companies are able to make these pretty broad claims about the health benefits without any science behind it whatsoever."

McCarron was comfortable using the product before many others were and didn't need the certification or studies after doing his own research. He acknowledges the lack of long-term studies on effects and impact CBD oil can have, but he has also seen the effects of other medicines and remedies his fellow professional golfers have used to help heal their bodies and minds.

Players using Ambien to sleep and ibuprofen to control their pain are now turning to CBD products as a more natural way to feel relief.

"You would take Advil like candy sometimes, not knowing the effects or what it could do to your kidney and liver," McCarron said. "I hardly take any anti-inflammatories anymore because I don't feel like I need to. That's a huge positive for athletes, because taking a little bit of Advil or Aleve, that's fine, but if you're dependent on it to function every day, that's a problem."

It's a problem many athletes face, including golfers at every level.

McCarron even believes CBD could help the average golfer who deals with the anxiety that comes from playing the sport recreationally. Alcohol is the drug of choice for the everyday golfer, and McCarron thinks there is a borderline abuse issue stemming from golfers thinking they need to drink while playing to cut the anxiety.

Naturally, the products are being aimed at the average golfer as well. Functional Remedies is now selling its products in 125 golf shops, with 12 sales representatives selling to golf courses around the country.

Stress and anxiousness are amplified at the professional level, which is why some of the athletes are taking CBD.

"Between the mental focus and overall clarity necessary to play a solid round, golf is a challenging sport," said cbdMD director of public relations Dillon Kivo. "That's where CBD can come into play. Again, although research is still in the early stages, there seems to be support behind the idea that CBD can be utilized to help aid mental functions, as well as work to reduce overall stress. The idea is that CBD helps calm some of those intense bodily responses that may result in further health complications, all while working to naturally relax the mind and body."

Those claims are still unfounded scientifically, but the proof may just be in how many golfers continue to get on board with using the products and openly touting how their bodies feel.

The Champions Tour might have been the guinea pig, but as the products are becoming more widely accepted, and as players gain more knowledge about what they're putting into their bodies and the potential impact it could have on their performance and recovery, we are heading to a point where more and more Tour players will be comfortable publicly saying they are utilizing a form of CBD.

"What the perception was, when someone said CBD initially, [was] is it THC, is this marijuana, is it legal?" McCarron said. "I think there was a misconception of what it really was, a hemp oil. I think there was a lot of buzz about it, but people weren't really sure. I wasn't really sure what to think of it. But when you find out what's really in it, what isn't in it, that it's natural and that the levels of THC are so minute, I think it's going to continue to take off."