Attempting challenging puzzles and reading up on the theory of relativity aren’t the only ways to keep your brain at its finest.

The right diet can do wonders, improving the brain’s function and even helping reverse brain damage. Meanwhile, the opposite is also true. Poor diet choices not only hurt the waistline, but have a nega- tive effect on the brain.

“When it comes to the brain, sugar is public enemy number one,” said Dr. Daniel Amen, a clinical neuroscientist and brain imaging expert who is also the founder of Amen Clinics (www.amenclinics. com) and author of the New York Times bestseller “Change Your Brain, Change Your Life.”

Sugar is pro-inflammatory, increases erratic brain-cell firings and is addictive, said Amen, He doesn’t hold back his disdain.

“Sugar is insidious, sort of like heroin,” he said. “It will make you want it over and over again. It’s like dating the bad boys. You fall in love with something that beats you up.”

Sugar has company on Amen’s list of unfriendly brain foods, including a few surprises, such as corn, which has one of the worst fatty-acid profiles of any vegetable. Others on the avoid-at-all-costs list include artificial dyes, especially red dye; foods with trans fats, such as cookies, cakes and pie crusts; and low-fiber foods, which include many fast-food choices.

Fortunately, there are also great food options that can heal the brain and even help reverse brain damage.

• Healthy fats. Surprisingly, fat is not the enemy. That’s because there are good fats and bad fats. Some examples of good fats are olives, sunflower seeds and flax- seed. Amen also pointed out that 60 percent of the solid weight of the brain is fat.

• Fish. Salmon, halibut, sardines, mackerel and other fish are loaded with healthy oils and healthy fat.

“People who eat grilled or baked fish once a week have more grey matter in their brain,” Amen said. “You may not want grey in your hair, but grey in your brain is awesome.”

• Avocados. This nutrient-dense fruit is loaded with healthy omega 3 fatty acids, which build brain- cell membranes, reduce brain inflammation and promote new brain-cell formation.

• Raw nuts. Go easy on the amount because they pack a lot of calories, but raw nuts are very healthy for the brain.

• Chocolate. Here’s another surprise. Chocolate has been shown to decrease cravings and increase blood flow to the brain. It’s what usually is added to chocolate, like sugar and dairy products, which makes it bad.

• Colorful vegetables. Green is great, but with vegetables you can branch out into such choices as yellow squash, purple carrots and orange bell peppers.

“You want things that are high in fiber, that are colorful, that are really medicine for your brain,” Amen said. “Anytime you prepare to eat something, don’t just think about the pounds you might put on. Ask yourself: Is this good for my brain or is it bad for my brain?”