We’ve come a long way from the cans of Folgers that filled our grandparents’ cupboards, with our oat milk lattes, cold brews and Frappuccinos. Some of us are still very utilitarian about the drink while others perform elaborate rituals. The fourth most popular beverage in the country, coffee is steeped into our culture. Just the right amount can improve our mood; too much may make us feel anxious and jittery.

Is coffee good for me?

Yes.

In moderation, coffee seems to be good for most people — that’s 3 to 5 cups, or up to 400 milligrams of caffeine.

“The evidence is pretty consistent that coffee is associated with a lower risk of mortality,” said Erikka Loftfield, a research fellow at the National Cancer Institute who has studied the beverage.

For years, coffee was believed to be a possible carcinogen, but the 2015 Dietary Guidelines helped to change perception. For the first time, moderate coffee drinking was included as part of a healthy diet. When researchers controlled for lifestyle factors, like how many heavy coffee drinkers also smoked, the data tipped in coffee’s favor.

A large 2017 review on coffee consumption and human health in the British Medical Journal also found that most of the time, coffee was associated with a benefit, rather than a harm. In examining more than 200 reviews of previous studies, the authors observed that moderate coffee drinkers had less cardiovascular disease, and premature death from all causes, including heart attacks and stroke, than those skipping the beverage.

In addition, experts say some of the strongest protective effects may be with Type 2 diabetes, Parkinson’s disease, and liver conditions such as cirrhosis, liver cancer and chronic liver disease. For example, having about five cups of coffee a day, instead of none, is correlated with a 30 percent decreased risk of Type 2 diabetes, according to a meta-analysis of 30 studies.

The potential benefit from coffee might be from the polyphenols, which are plant compounds that have antioxidant properties, according to Dr. Giuseppe Grosso, an assistant professor in human nutrition at University of Catania in Italy and the lead author of an umbrella review in the Annual Review of Nutrition.

However, coffee isn’t for everyone. There are concerns about overconsumption. This is especially true for expecting mothers because the safety of caffeine during pregnancy is unclear. While the research into coffee’s impact on health is ongoing, most of the work in this field is observational.

“We don’t know for sure if coffee is the cause of the health benefits,” said Jonathan Fallowfield, a professor at the University of Edinburgh, and co-author of the British Medical Journal review. “These findings could be due to other factors of behaviors present in coffee drinkers.”

Does the way coffee is prepared matter?

Yes. Do you prefer a dark or light roast? Coarse grinding or fine? Arabica or robusta?

“All of these different aspects affect the taste, but also affect the compounds within the coffees,” said Neal Freedman, a senior investigator with the National Cancer Institute. “But it’s not clear at all how these different levels of compounds may be related to health.”

Roasting, for example, reduces the amount of chlorogenic acids, but other antioxidant compounds are formed. Espresso has the highest concentration of many compounds because it has less water than drip coffee.

A study in JAMA Internal Medicine examined the coffee habits of nearly 500,000 people in the U.K. and found that it didn’t matter if they drank one cup or chain-drank eight — regular or decaf — or whether they were fast metabolizers of coffee or slow. They were linked to a lower risk of death from all causes, except with instant coffee, the evidence was weaker.

The way you prepare your cup of joe may influence your cholesterol levels, too. “The one coffee we know not suitable to be drinking is the boiled coffee,” said Marilyn C. Cornelis, an assistant professor in preventive medicine at the Northwestern University Feinberg School of Medicine and co-author of the JAMA Internal Medicine study.

Examples of this include the plunge-happy French press, Scandinavian coffee, or Greek and Turkish coffee — the kind commonly consumed in the Middle East. (When poured, the unfiltered grounds settle on the tiny cup’s bottom like sludge. To peek into the future, elders in the region have a tradition of reading the sediment of an overturned cup, like a crystal ball.)

However, the oil in boiled coffee has cafestol and kahweol, compounds called diterpenes. They are shown to raise LDL, the bad cholesterol, and slightly lower HDL, what’s known as the good kind.

“If you filter the coffee, then it’s no issue at all,” said Rob van Dam, a professor at Saw Swee Hock School of Public Health at National University of Singapore. “For people with cholesterol issues, it’s better to switch to other types of coffee.” He’s been studying coffee for two decades. (And, yes, he’s had a lot of coffee in that time.)

However, other researchers say not to throw out the boiled coffee just yet. The clinical significance of such small increases in cholesterol may be questionable, given that it’s not associated with an increase in cardiovascular deaths.

Many consumers have also swapped loose grounds for coffee pods. While there are environmental concerns with single use pods, researchers believe them to hold the same benefits as, say, drip coffee. The latter applies to cold brew, too, but more research is needed.

Do all kinds of coffee have the same amount of caffeine?

No. Espresso has the highest concentration of caffeine, packing about 70 milligrams into a one-ounce shot, but is consumed in less quantities. By comparison, a typical 12-ounce serving of drip coffee has 200 milligrams of caffeine, more than instant’s 140. And, yes, brewed decaf has caffeine, too — 8 milligrams — which can add up.

When buying coffee, you never really know what you’re going to get. At one Florida coffee house, over a six-day period, the same 16-ounce breakfast blend fluctuated from 259 milligrams all the way up to 564 — which goes beyond federal recommendations.

But for some of us, knowing how much caffeine is in our coffee can be especially important. You’ve probably noticed it before. How a friend can pound quadruple espresso shots at 10 p.m. and sleep afterward, while you can’t have any past noon, or you’ll be watching “Seinfeld” reruns until dawn. Some of us have a polymorphism, a genetic variant that slows our metabolism for caffeine. It’s these individuals that Dr. Grosso recommends limit their refills. “They take a coffee, and then they have the second and the third, and they still have the caffeine of the first,” he said.

You can even find out whether you are a fast or slow metabolizer through a variety of direct-to-consumer testing services, including 23andMe.

Is coffee addictive?

Evidence suggests there can be a reliance on the drink, and tolerance builds over time. Withdrawal symptoms include a headache, fatigue, irritability, difficulty concentrating, and depressed mood.

Indeed, caffeine is a psychoactive drug, and coffee is its biggest dietary source. About a half-hour after sipping a cup of joe, the caffeine kicks in, and is quickly absorbed. Blood vessels constrict. Blood pressure increases. A moderate amount of caffeine can wake you up, boost your mood, energy, alertness, concentration and even athletic performance. On average, it takes four to six hours to metabolize half the caffeine.

For those knocking back more than 400 milligrams of caffeine a day, there’s not enough evidence to assess the safety, according to the Dietary Guidelines. Higher doses can lead to caffeine intoxication, with its shakiness, nervousness, and irregular heartbeat. Caffeine is also linked with delaying the time it takes for you fall asleep, how long you stay there, and the reported quality of that shut eye.

“I think that caffeine is so common and so ingrained in our culture, and daily habits, that we often don’t think about it as a potential source of problems,” said Mary M. Sweeney, an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine.

Cutting down coffee may help with gastroesophageal reflux, too. A new study found that women drinking caffeinated beverages — coffee, tea, or soda — were associated with a small but increased risk of symptoms, like heartburn. The study’s authors predicted fewer symptoms when substituting two servings of the drinks with water.

Current available research hasn’t determined what amount of caffeine can be safely consumed during pregnancy, according to the American College of Obstetricians and Gynecologists. Caffeine does cross the placenta so some doctors may recommend pregnant women stay below 200 milligrams of coffee daily.

Extremely high doses of caffeine can be fatal. But researchers say that’s more likely to occur accidentally with caffeine powder or pills. “You don’t see a lot of people going into the emergency room because they accidentally drank too much coffee,” said Dr. van Dam.

What is a coffee bean?

Inside the red fruit of coffea lie two coffee beans. Green in color, the duo spoon together, the rich brown hue to appear only after roasting. In fact, they aren’t beans at all. “It’s like a cherry, you pick off the tree,” said Patrick Brown, a professor of plant sciences at University of California, Davis. Unlike the cherry, though, the seed is the prize, and the flesh is discarded.

In addition to caffeine, coffee is a dark brew of a thousand chemical compounds that could have potential therapeutic effects on the body. One key component, chlorogenic acid, is a polyphenol found in many fruits and vegetables. Coffee is also a good dietary source of vitamin B3, magnesium and potassium.

“People often see coffee just as a vehicle for caffeine, but, of course, it’s a very complex plant beverage,” said Dr. van Dam.

With coffea’s estimated 124 species, most of flavors remain untapped; and perhaps will be forever, with an estimated 60 percent under threat of extinction, largely from climate change, disease, pests and deforestation. What fills our mugs at cafes, the office, and on road trips are from two species: arabica and canephora, known as robusta. Arabica fills specialty cafes, and costs more than robusta, which fuels instant coffees and some espressos.

For all of the pomp swirling around arabica, the fact remains it is an extremely homogeneous little seed. Almost all of the world’s arabica coffee progeny traces itself back a few plants from Ethiopia, coffee’s birthplace, or Yemen.

Does adding milk or sugar cancel out benefits?

Doctors don’t know. One 2015 study found that those adding sugar, cream or milk had the same associated benefit as those who preferred it black. But the coffee industry has exploded since the ’90s when the older adults in the study filled out their dietary history. “It was only about a tablespoon of cream or milk, and a teaspoon of sugar,” said the study’s lead author, Dr. Loftfield, with the National Cancer Institute. “This is very different, potentially, than some of these coffee beverages you see on the market today.”

Sweet coffee and tea are the fourth largest source of sugar in the diets of adults, according to the October survey from the U.S.D.A. That includes dessert-like beverages, like Dunkin’ Donuts’ 860-calorie creamy frozen coconut caramel coffee drink, with 17 grams of saturated fat, and 129 grams of total sugars. Experts say some of these drinks bear little relation to the 2-calorie cup of black coffee of the past, worrying health officials.

“When you talk about a drink that has that load of unhealthy fats and that much sugar, can’t possibly be a healthy beverage on balance,” Dr. Jim Krieger, a clinical professor of medicine and health services at the University of Washington. “That amount of sugar alone is astronomical compared to the current recommendations of U.S. Dietary Guidelines of 50 grams of sugar a day.”

The concern is heightened, experts say, especially because an estimated 43 percent of teens are now drinking coffee — nearly doubling since 2003 — according to the research firm Kantar, driven partly by sweet drinks.

“People should worry a lot about what they put in the coffee and what the food and beverage industry puts in it,” said Laura Schmidt, a professor at the University of California San Francisco School of Medicine. “And sweetened coffee is one of the things that the beverage industry is pushing on the public now that consumers have turned away from soda for health reasons.”

Should I start pounding down more coffee?

Depends on your goals in life.

If you are enjoying the drink in moderation, doctors say continue onward, and savor those sips. And for those patients with a sensitivity to the beverage, Dr. Sophie Balzora, a gastroenterologist, weighs the benefits and risks very carefully. The clinical associate professor of medicine at N.Y.U. School of Medicine understands its cultural significance, and knows to tread lightly. As she put it: “Robbing people of their coffee seems cruel.”