As summer iced coffees turn into seasonal fall lattes, it can be easy to reach for an extra cup of coffee throughout the day for a jolt of energy, a mood boost or a sugary afternoon treat.

Along with a temporary pick-me-up, research has continued to show the longer-term health effects of coffee include a decreased risk of cancer, heart failure, Type 2 diabetes and even death. But there are a few caveats: Studies have also shown that high coffee consumption is linked to increased risk of dementia and stroke, as well as a higher risk of death from cardiovascular disease among coffee drinkers with hypertension.

So where’s the line between reaping the benefits of a morning cup of coffee and taking it too far?

NBC News reviewed the research and spoke with four doctors and nutritionists, who generally agreed that although coffee is safe and healthy, people with pre-existing health conditions may feel more of its negative side effects. 

And though there is “strong and consistent” evidence that moderate coffee consumption isn’t harmful, that doesn’t mean coffee should be consumed for health benefits, said a member of the American Society for Nutrition, Tricia Psota, a dietitian with Nutrition on Demand.

“I would never recommend that individuals who don’t consume caffeinated beverages start incorporating them into their day for any reason,” Psota said.

How much coffee is bad for you?

The Food and Drug Administration recommends people cap their daily caffeine intake at 400 milligrams, or about four or five 8-ounce cups of coffee. Most people are unlikely to experience serious side effects of caffeine — like erratic heartbeat, vomiting, seizures, diarrhea and even death — unless they consume 1,200 milligrams, or about 12 cups, in a day, according to the FDA. 

But even consuming 400 milligrams of caffeine daily can sometimes come with undesirable side effects, including jitteriness, anxiety and trouble sleeping, Psota said.

While some people can easily down four to five cups a day, she said, others may just have lower caffeine tolerances and be more susceptible to the side effects. Psota said she has found her own body can’t tolerate more than one or two cups of coffee a day.

“I’ve noticed that on days when I might not have slept as well the night before and go beyond that point, I just feel jittery and uncomfortable,” she said. “So for me, I definitely stay below that FDA recommendation.”

For pregnant or breastfeeding people, Psota recommends no more than 200 milligrams, or about two cups of coffee a day, because the caffeine can pass on to the infant through breast milk. Research has shown that caffeine consumption during pregnancy can lead to lower birth weights among newborns, though a 2021 study found that pregnant people who consumed moderate amounts of caffeine were at lower risk for gestational diabetes than people who didn’t consume caffeine.

A daily cup of coffee might also be riskier for people with cardiovascular disease or diabetes if they add sugar or cream, said Nikki Cota, a dietitian at the Mayo Clinic in Arizona. Cota said she has seen elaborate caffeinated beverages from coffee shops that contain up to 50 grams of sugar — which is how much added sugar the FDA recommends for the entire day for people eating 2,000 calories a day.

Though she drinks two 12-ounce coffees a day, Cota said, she usually makes them herself to control the added sugar.

“Watch out for that pumpkin spice latte with the sugar and the calories,” she said.

When should you stop drinking coffee?

Some people might feel more of coffee’s negative side effects as they age, as the body’s ability to tolerate certain chemicals and foods evolves over time, said the spokesperson for the Academy of Nutrition and Dietetics, Jessica Sylvester, a dietitian at the Florida Nutrition Group.

“Within those milligram or cup of coffee recommendations, if you start feeling overly tired and the caffeine is not helping, then you’ve got to stop,” Sylvester said. “If your heart starts beating incredibly fast, you’ve got to stop. It’s different for each person.”

Sylvester said that she has formed a habit of starting her mornings with a double shot of espresso in almond milk — but that over time, she has become less likely to finish the drink and often sips it into the afternoon.

“I used to be able to drink more than that, and I can’t anymore,” she said. “I get headaches, and it doesn’t work out.”

Coffee can also pose risks for younger people, especially teenagers. Dr. David Buchholz, a pediatrician at the Columbia University Irving Medical Center, said no amount of caffeine is healthy for adolescents. But in recent years, he said, brands have increasingly marketed caffeinated energy drinks to children. 

In terms of coffee, Buchholz said he sees patients start to develop the habit in their teenage years, when they have more control over their diets and are managing heavier workloads and schedules. Buchholz said he wouldn’t recommend more than 100 milligrams a day, or about one 8-ounce cup of coffee, for teenagers.

“If a teenager is drinking one cup of coffee and they’re OK with it, their family is OK with it, they’re not having any side effects, there’s probably no harm,” he said. “But various people have different sensitivities, so if that person is complaining about an inability to sleep at night, the first thing I would do is avoid caffeine.”