Ask a Dietitian: Should you drink coffee on an empty stomach?

Welcome to Ask A Dietitian, a series where Yahoo Canada digs into food trends and popular nutrition questions with registered dietitian Abbey Sharp.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.

A morning coffee is a part of a daily routine for many, and for some, it'll be the first thing they consume each day.

But is it healthy to do so?

Discourse on whether or not to drink coffee on an empty stomach isn't new, but it has recently been trending on TikTok. Some claim it curbs appetite and helps with weight loss, while others say it spikes cortisol levels and prevents weight loss.

To find out what science says about coffee and empty stomachs, Yahoo Canada spoke with registered dietitian Abbey Sharp.

Context

• Coffee is an acidic drink with a pH value of around 5 — placing it somewhere between water and vinegar. Milk has a pH value of 6, making a coffee drink slightly diluted when mixed.

• Impact of coffee on an empty stomach and belly fat has been trending on TikTok. User @alice.veneziani claimed in one video that every time a person drinks coffee,"You're raising your cortisol levels, therefore raising your insulin levels, therefore putting on body fat."

• Dietitian Abbey Sharp said she has "no concerns" over coffee leading to belly fat.

How does coffee impact an empty stomach?

There are several claims wellness influencers often make when it comes to coffee on an empty stomach: it's impact on cortisol levels and the acidity impact on the gut.

Dietitian Sharp wants to set the record straight.

Impact on cortisol

Coffee's impact on cortisol levels, according to Sharp, is "probably one of the least of my professional concerns."

Sharp explained it's true that cortisol is naturally highest when you wake up, and it's true that elevated cortisol is associated with increased belly fat. Since coffee is a stimulant, it is also true it can increase cortisol levels.

"However, the evidence suggests that when we regularly consume coffee, our body adapts and we don't get any kind of concerning spike in cortisol," Sharp said.

"And actually, some studies find no cortisol increase at all."

Sharp added it's different for those who aren't regular coffee drinkers.

"If you've never had coffee before and you just drank a couple of cups of it out of the blue, then your heart rate might increase, you might get a little jittery.

"Most humans who consume coffee in the morning, it's a bit of a ritual. And so eventually, your body adapts and no longer puts itself into that fight or flight mode.

This means the spike in blood sugar levels out for those who are used to it.

Sharp added, however, for those who are prone to anxiety or are cortisol-sensitive, it might make sense to "experiment" with consuming coffee after a meal, or at different times of the day.

Though there's isn't "any strong research that has compared coffee on an empty stomach to coffee with food," it makes sense, "hypothetically," that food in your stomach would "buffer the cortisol effect."

Impact on the gut and digestion

Cortisol aside, Sharp said her "bigger concern as a dietitian" is coffee's impact on the gut — but not in the way that many say on social media.

"It's not because it ruins the gut lining, or causes leaky gut, as so many influencers say," Sharp claimed.

She added many influencers will say coffee ruins your gut because it's acidic, and though it is acidic, it's not enough to cause damage.

"Considering that influencers are always swearing by their lemon water to support gut health, the pH of coffee is actually not the concern."

She explained our gut has protective defense mechanisms that protect against harsh things.

"We do know that things like alcohol, smoke, cigarette smoke, et cetera, those can damage the lining of the gut. But, research has shown consistently that this is not the case for coffee.

However, it can cause digestion issues in some.

Sharp said coffee contains a "unique combination" of caffeine and polyphenols, which stimulate gastrin and hydrochloric acid — both of which may cause symptoms of indigestion and GERD (acid reflux).

"We do have a meta analysis that found no association between coffee and GERD, so I do think this is a highly individual experience," she added.

Because it's a stimulant, it can also cause loose bowels, as depicted in one humerous TikTok.

Sharp repeated there is no strong research on coffee on an empty stomach versus a full one, but again, "it does make sense to have something on board to buffer the effects."

So, should you have coffee on an empty stomach?

According to Sharp, whether or not you should drink coffee first thing in the morning is individual.

"For some, having a little milk in their coffee would be enough; for others, black coffee is just fine; for others, maybe you need an entire meal in order to not have indigestion or diarrhea," she claimed.

"Generally speaking, I think the average person will do better with something in their stomach."

She recommends experimenting and monitoring your symptoms at home. Some things to look out for include:

• symptoms of anxiety

• heightened heart rate

• feeling jittery

• gastrointestinal symptoms

• needing to rush to the bathroom

• heartburn or other indigestion symptoms

• gas pains

Sharp also recommends experimenting with what you put in your coffee.

"For some people who do find that they get symptoms from coffee, there may actually be an intolerance to the dairy, or any kind of non-dairy milk they may be adding to it," Sharp advised.

A dietitian can also help people find a systematic way to rule out intolerances.

An expert's recommendation on coffee

According to Sharp, there are many benefits in coffee, including that it "may be favorable to healthy gut microbiome."

There is also research, she added, that coffee may reduce the risk of depression by 13 to 20 per cent — it increases dopamine. There's also evidence that it helps with mental and physical performance.

"We also have some research that caffeine intake is associated with reduced risk of different neurodegenerative diseases like Alzheimer's, Parkinson's, dementia, general cognitive decline."

However, Sharp said for those who don't drink coffee regularly — they don't need it.

"We know that some coffee has a lot of these benefits, but too much can also be detrimental, especially when it comes to anxiety and general daily performance," she added.

"If it's a pleasurable part of your ritual, like it is for so many people, I think there's a lot of benefits. But I would never go out and say, 'I want you to start drinking coffee.'"

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