When you wake up groggy, your first instinct might be to reach for the coffee pot. A kick of caffeine is the fastest way to wake up and face the day. But a new study has shown that eating before drinking coffee can help keep your blood sugar steady and avoid spikes.

Researchers from the Univ. of Bath found that a rough night’s sleep can upset your metabolism. And, a cup of coffee on an empty stomach could worsen your blood sugar control. Regardless of how well a person slept in the study, their bodies reacted the same to breakfast without coffee. But, people who slept poorly had a 50 percent higher blood sugar spike to food if they drank coffee before eating versus if they drank coffee after eating.

In the study, they had 29 men and women sleeping from 11 pm to 7 am. They put all the people through three different tests with a week between each test to make sure they got results from everyone. They got a good night’s sleep and a drink that simulated breakfast. Then they got a bad night’s sleep where they were woken up every hour by a text message that they had to respond to and stay awake for five minutes and then given the breakfast drink. And in the third, they had the same rough night’s sleep and a cup of coffee before the breakfast drink.

“Our blood sugar control is impaired when the first thing our bodies come into contact with is coffee,” said Dr. James Betts, who oversaw the research, “especially after a night of disrupted sleep. We might improve this by eating first and then drinking coffee later if we feel we still feel need it. Knowing this can have important health benefits for us all.”

“There is a lot more we need to learn about the effects of sleep on our metabolism,” agreed Dr. Harry Smith, who led the research, “such as how much sleep disruption is necessary to impair our metabolism and what some of the longer-term implications of this are, as well as how exercise, for instance, could help to counter some of this.”

They did see that a single poor night’s sleep didn’t appear to negatively affect people when they ate breakfast without coffee. While losing sleep does impact the metabolism, that alone doesn’t seem to do much in the short term without other factors — like the coffee. The first two versions of the tests had the same results. The people’s blood sugar results were the same. Other studies have found that persistently getting too little sleep can harm your metabolism.

The people in the test were drinking black coffee. However, the researchers thought that milky coffee would still have negatively impacted blood sugar. “Milk would have complicated the comparisons by providing additional nutrients,” said Dr. Betts. “I suspect the effect of caffeine per se would be the same had milk been included because the physiological effects of caffeine are quite potent.”

We would like the study to be performed again with people who have blood sugar concerns. The study was small, and none of the participants had any underlying medical issues. We would like to know how this would impact people who already worry about their blood sugar. Until then, it seems better to wait until after breakfast to reach for your morning brew.