According to a nutritionist, you shouldn’t drink coffee on an empty stomach:

Wake up, hit snooze several times, drag me to the kitchen to make coffee, then wait for the sweet, sweet caffeine to hit my veins. Here’s how a typical morning for me used to go. I’m a walker, essentially, but first, a coffee cliché. But I mean, for a reason, that sentence is all over T-shirts/mugs/café letter boards, right? So when I mentioned my daily routine during a recent nutrition consultation with Carlyn Rosenblum, MS, RD, I did not expect that particular habit to be her first critique. Here’s what she had to say prior to breakfast about drinking coffee on an empty stomach.

Wait, why am I not supposed to be drinking coffee in the morning?

“There are a few reasons why coffee, especially for women, is not a great first thing in the morning,” says Rosenblum. Second, it raises cortisol, which can have a detrimental effect on ovulation, weight, and hormonal balance. The so-called stress hormone fluctuates throughout the day, but is normally high throughout the morning and low throughout the evening, which, among other things, helps control energy and makes you feel alert. “When cortisol is high, drinking caffeine first thing in the morning blunts the production of the hormone and shifts the timing of the cycle,” Rosenblum explains. This can cause cortisol to be released at times when it normally decreases (like at night). “Studies also show that consuming caffeine can actually cause you to produce more cortisol when cortisol is high,” she says. Although the logic behind this is not well known, part of the explanation may be due to the influence of coffee on some vitamins and minerals.

And remind me again why it’s bad with high cortisol?

“Cortisol is necessary for our health, but the problem is that our body continually produces cortisol when we are constantly stressed out,” Rosenblum explains. This can lead to elevated blood sugar, which then contributes to the increased development of insulin hormones, leading to insulin resistance. Excess cortisol can lead to symptoms such as weight gain, sleep disorders, and decreased immune response.

Why should I avoid drinking coffee on an empty stomach?

“Drinking coffee first thing in the morning can also create gut health issues,” Rosenblum says. While study results are mixed on how coffee affects your gut microbiome (one recent study suggests it might actually be beneficial), it does stimulate acid production in the stomach. If you’re prone to acid reflux or other GI issues, it’s worth paying attention to your symptoms to see if coffee exacerbates them. Rosenblum recommends eating a breakfast of calcium-rich foods (like yogurt, almonds, spinach, kale or chia seeds), which help neutralize both the acidity of the coffee and your stomach acid. She also notes that cold brew has about 70 percent less acid than hot coffee.

So, when should I drink coffee?

If you wake up on a relatively standard schedule, your best bet is to pour yourself a cup after breakfast, between 9:30 a.m. and noon, a window when your cortisol levels are typically low. (It’s tied to activity, so if your “day” starts significantly earlier or later than average, adjust accordingly.) At that point, coffee will actually give you a needed boost, evening out a potential energy slump.

But if cortisol is high in the morning, why do I still feel groggy?

Rosenblum posits a few potential reasons. One, your coffee habits: If you’re accustomed to drinking coffee first thing in the morning, your body may have come to use the caffeine as a crutch and thrown off its natural wake-up mechanisms. Two, dehydration: You lose water while you sleep, so you might be waking up dehydrated, particularly if you didn’t drink enough water during the day. And three, poor sleep habits: Most people need seven to eight hours of sleep, so if you’re falling significantly short, you’re going to feel it no matter what. She also notes that sleep quality is as important as quantity, and recommends promoting restful sleep by powering off electronics 60 minutes before bed, drinking herbal tea, taking an Epsom salt bath, or writing in a gratitude journal before turning in. “Also, our adrenal glands (which produce cortisol) like consistency,” says Rosenblum. “Try going to bed and waking up at the same time every day.”

For the past two months, I’ve been holding off on my daily cold brew until I get to work. It could be the placebo effect, but I do feel like my energy’s a little more even-keeled throughout the day. Not gonna lie, though—it’s still rough getting out of bed, at least I have a mid-morning coffee break to look forward to.