Many people swear by the practice of supplementing their workouts with certain products.

There are all sorts of supplements out there, but people don't know which ones make a difference and which ones are unnecessary or even harmful.

We wanted to get down to the science of it and find out what actually works to improve your performance during exercise. So we we spoke recently with Shawn Arent, an exercise scientist at Rutgers University, we asked him to fill us in.

Here's what he told us:

"I think there's some really good ones. I think creatine benefits a lot of people, it's actually also been shown to improve cognitive effects. Fish oils, I think are fantastic. I think there's really strong research evidence for the effects on fish oils on health as well as performance."*

"Caffeine - big fan of caffeine. Especially if you're looking for that little extra something with your workouts, we know it reduces fatigue and stuff like that. And then protein. Protein's a strong one because honestly more people could stand to have more protein in their diet, especially from lean protein sources. But we also know it helps with adaptation. So a protein and carb supplement, or even just a protein supplement after you work out — there's nothing wrong with that."

"But I think one of the things I see that can be a bad trend ... people will get on the treadmill, they'll do that half hour, they'll burn 250 calories, and then they'll go downstairs to the shake bar and get a 500 calorie shake. You didn't work that hard, you don't need 500 calories. So I think calorie awareness is an important thing."

"I'm a fan of supplements if they're used right ... And they're supplements for a reason. First and foremost it's about your diet. Supplements are a supplement to your diet. They're something you add in, that gives you added benefit. That's a good thing from a brain health standpoint, from a heart health standpoint, and from a muscular strength standpoint. There's real positives that go with that. And those are some of the things we should think about as part of a well-rounded fitness program."

*[Ed. note: some recent research has questioned the benefits of fish oils].

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