If you were to name something in your diet that causes inflammation or health problems, things like gluten, dairy or soy might come to mind. But what about sugar?

It’s true that some people are gluten or dairy intolerant, but lots of people can also handle eating those things just fine. Sugar is a different story, says Heidi Turner, M.S., R.D.N., a medical nutrition therapist at The Seattle Arthritis Clinic.

“Sugar is the universal inflammatory,” says Turner, who specializes in anti-inflammatory diets to help reduce the pain and symptoms related to autoimmune conditions and inflammatory arthritis. “Everyone is sugar intolerant.”

Why exactly is sugar so bad for you and so hard to avoid? Here’s what you should know about the added sugar that’s lurking in your diet.

What is added sugar?

When we talk about sugar in the context of your health, we aren’t talking about those sweet strawberries you tossed on your salad for lunch. Sugar that’s naturally occurring in food isn’t an issue, says Turner.

If you eat a piece of fruit, for example, you’re not only consuming sugar (in the form of fructose), but also fiber, vitamins, minerals and phytonutrients. All of these things help feed the healthy bacteria in your gut and help your body metabolize the sugar found in the fruit. Instead of craving more and more sugar, you’ll stay satiated for a longer period without the massive blood sugar spikes from consuming a treat with a bunch of refined sugar, she says.

The real problem is added sugar that manufacturers put in food during the production process, either to sweeten it or enhance the flavor in some other way, says Michael Schwartz, M.D., director of the UW Medicine Diabetes Institute and the Nutrition Obesity Research Center.

“There aren’t really many sources of pure sugar in nature,” he says. “And so what’s different about table sugar is that we're getting a dose of it in a pure form. That is not something that we evolved to do.”

How added sugar messes up your body