An MD Shares 3 Healthy Foods That Can Secretly Spike Your Blood Sugar

"We have found a lot of foods in our data set that are some of the worst glucose spikers," says Casey Means, M.D., a Stanford-trained physician and co-founder of Levels, on this episode of the mindbodygreen podcast. "But they actually are typically thought of as healthy foods." Um, what? 

"A lot of fruits are minimal spikers, but grapes seem to be gigantic," says Means. She proposes user behavior is at play here: Grapes are often eaten on their own, without any other sources of fiber or protein. "You don't often chop up grapes and put them in yogurt—you just usually pop them in," she says. "And so I think that lack of pairing makes it more problematic."

With oatmeal, it's a similar story—only, it's what people typically add to oats that provides such a spike. Loading your oatmeal bowl with mounds of brown sugar, syrup, and chocolate chips will likely result in a large surge. "Some raw cocoa powder, almond butter, chia seeds, and some walnuts could definitely change that response," Means says. 

Beans tell a trickier story. Of course, we love 'em here at mbg—they're full of fiber, protein, and important vitamins and minerals. But for some people, Means says they're a sneaky spiker. "I can eat a can of beans, which is about four servings, and have no glucose response," she says. "But there are other people who eat beans and [their glucose] spikes through the roof." 

The reason, she admits, isn't so clear, but she thinks it has something to do with the gut microbiome. She references a 2015 study in the journal Cell2 that put continuous glucose monitors on 800 healthy participants and gave them the same meals, assuming they would respond exactly the same. However, they found varying responses across the board—from no spikes to colossal spikes—and they discovered that their microbiome composition seemed to dictate those responses. 

It's not surprising, says Means: "The microbiome [does] a first pass on food," she says. "They're the ones who break down some of those early carbohydrates before it actually goes into the body. My co-founder David [Flinner] started eating huge amounts of chia every morning to get his fiber in, and over the course of the month after eating all this fiber day after day, he found that he no longer responded as much to beans."