AVONDALE, Ariz. — Dale Earnhardt Jr. says the best thing about carrot juice is it’s not prune juice.

He takes doses of both these days. Such is the compromise one makes to continue being a professional athlete two months shy of 40

“The older you get, the more you have to do to maintain a healthy weight,” Earnhardt said Friday before qualifying for Sunday’s Subway Fresh Fit 500 at Phoenix International Raceway.

Earnhardt kept having his race suit altered last season. In the brief offseason, Earnhardt lost 15 to 20 pounds.

He used what he called a 15-day “detox diet” — days when he subsisted mostly on prune juice, then carrot juice followed by strict rations of fish, chicken and steamed vegetables.

“Pretty tough,” Earnhardt recalled. “I almost didn’t make it.”

The shift to a healthier lifestyle fits a guy who has matured in his driving style and in life. He seems less prone to the edgy frustration that once gripped him after bad finishes. He can calmly dissect why things went well or poorly, as in when he described securing second place in the Daytona 500, but not maximizing his chances of overtaking winner Jimmie Johnson.

“I should have went earlier — gotten to second earlier — but I was worried about getting freight-trained like so many others,” Earnhardt said of the bunch-up of cars that restrictor-plate racing entails.

Earnhardt is in a good place right now; not raging as much, and willing to share his opinions.

Asked about the wreck at the end of Daytona’s Nationwide race — it sent a tire and other debris into the stands, injuring dozens of fans — he said this must drive NASCAR to “seek the solutions that will always make this sport safer.”

Then he was asked about NASCAR’s decision to indefinitely suspend Nationwide driver Jeremy Clements for a racially-insensitive remark. Earnhardt had a big problem with Clement’s behavior.

“It’s really unfortunate that he chose to make that decision at that time, to use that language. I don’t like it and there’s no room for that in my life,” Earnhardt said. “One person’s mistake looks bad on a lot of people and looks bad on the sport.”

Looking ahead to today’s race, he mentioned the repaving at Phoenix.

“For us to be able to put on the best race we can put on, the older surfaces, the surfaces that have a few more years on them, tend to do better,” Earnhardt explained. “The track being out here in the desert should help us — this place should age pretty quickly.”