High or unsteady blood sugar levels are hallmarks of diabetes, which is why regular monitoring of blood glucose is critical. But what happens when people without diabetes track their blood sugar levels throughout the day? The answer, for some, is they, too, have blood sugar spikes that creep into diabetes territory.

In other words, you may be a lot closer to developing diabetes than you think.

Nearly 70 percent of people with prediabetes will go on to develop full-blown diabetes, and many don’t realize they have it.

Researchers at Stanford University School of Medicine first had 57 people, most of whom were healthy or had prediabetes, wear blood sugar monitors for a couple of weeks. These continuous glucose monitors prick the skin superficially to monitor blood sugar periodically while a person is going about their business. People tended to have one of three patterns of blood sugar spikes: Low, moderate and intense. Even healthy people had concerning rises in blood glucose.

“There are lots of folks running around with their glucose levels spiking, and they don’t even know it,” said study author, Michael Snyder, in a news release. “We saw that some folks who think they’re healthy actually are misregulating glucose — sometimes at the same severity of people with diabetes — and they have no idea.”

Beware of Cornflakes

To look into the issue further, the research team split people into three groups: One group was to eat a bowl of cornflakes for breakfast, the second a peanut butter sandwich and the third a protein bar.

The results were fairly striking: Half the people with previously healthy blood sugar readings showed concerning spikes after eating any of the meals. And when it came to cornflakes, the vast majority of participants showed spikes.

“We saw that 80 percent of our participants spiked after eating a bowl of cornflakes and milk,” Snyder said. “Make of that what you will, but my own personal belief is it’s probably not such a great thing for everyone to be eating.”

Before you worry, remember that there’s a lot we can do to control blood sugar. The blood sugar response isn’t just a matter of genetics, as the team points out: It’s also dependent upon epigenetics — genes that are turned on and off as a result of lifestyle habits, like diet and exercise. Our gut bacteria, which are known to have strong influences on multiple facets of health, also play a role.

In fact, Snyder says his bet is on manipulating the makeup of these beneficial microbes. “Right now we have information about people who do and don’t spike, or are super-spikers, but we need to get smart about why it’s happening,” Snyder said. “I think understanding the microbiome and manipulating it is going to be a big part of this, and that’s where our research is headed next.”

More will need to be done to understand all the interactions involved in the development of diabetes, but the results suggest that just because blood sugar seems healthy between meals, it may creep into dangerous territory after a sugary or carbohydrate-dense meal. As the authors mention, nearly 70 percent of people with prediabetes will go on to develop full-blown diabetes, and many don’t realize they have it. That’s why annual glucose checks are important.

But the good news is that prediabetes can be reversed, especially if caught early. Cutting down on sugar and processed foods, increasing consumption of whole grains and exercising are the best ways to reverse prediabetes, or avoid it altogether.

The study is published in PLOS Biology.