How Much Caffeine You Should Actually Have—and When - Kanebridge News
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How Much Caffeine You Should Actually Have—and When

Figure out the right amount of caffeine to boost alertness without disrupting your sleep

Thu, Jan 11, 2024 10:49amGrey Clock 3 min

Caffeine can give us a boost, but too much can mess with our sleep and make us feel jittery. So how do we know what’s the right amount?

Generally, government and health groups recommend that healthy adults consume no more than400 milligrams of caffeine a day. That comes out to about four, 8-ounce cups of coffee, says Jennifer Temple, a professor of exercise and nutrition sciences at University at Buffalo School of Public Health and Health Professions.

(No, that 20-ounce Starbucks Venti doesn’t count as one cup of coffee.)

And believe it or not, we are doing pretty well on this target. The average American adult consumes about 200 milligrams of caffeine a day and in Europe, it is 270 milligrams, according to a 2017 review study.

But not everyone is optimising their caffeine intake to maximise how it can help them—by sharpening concentration for work or giving them a boost before a run—without hurting their sleep or overall health.

Here’s how to think strategically about getting the most out of your daily dose.

Optimising the boost

Caffeine can help you focus and keep you alert.

About 100 to 150 milligrams—or one to 1.5 cups of coffee—is a ballpark amount that will deliver a boost, says Astrid Nehlig, an emeritus research director at the French National Institute of Health and Medical Research, who has studied caffeine’s impact on brain activity, though it varies from person to person.

The effects generally kick in about five minutes after consumption and increase to become optimal for between roughly 15 and 120 minutes, Nehlig says.

Caffeine has been linked to physical benefits, too. People walked more on days they drank coffee than on days they didn’t, according to a 2023 study of 100 people in the New England Journal of Medicine. Participants took an average of 1,000 more steps on days when they drank caffeinated coffee than when they didn’t.

Other studies have suggested that caffeine can sometimes help us work out harder, such as when we have it before high-endurance exercise like long runs or swims, or sports that require a sustained effort, like soccer, Nehlig says.

The same boost hasn’t been found with shorter efforts, such as a sprint. Caffeine doesn’t act directly on muscles but rather reduces your rate of perceived exertion and the time it takes you to feel exhausted.

The downsides

Caffeine’s main negative for your health is that it can disrupt your sleep.

The NEJM study that found that people walk more on days when they drink caffeine also found a downside. On days when study participants could drink as much caffeinated coffee as they wanted, they slept on average 30 minutes less than on days they didn’t drink any.

The impact on sleep varies greatly depending on how fast you metabolize caffeine, says Gregory Marcus, a cardiologist and professor of medicine at University of California, San Francisco and first author of the NEJM study.

On average, it takes about 4.5 hours for half of the caffeine consumed to pass through your system. However, genetic differences make some people metabolise it slowly or quickly, doctors and researchers say. The population is roughly split between fast and slow metabolisers.

The sleeping and walking study tested whether participants were slow or fast metabolisers of coffee. Those that were slow metabolisers slept nearly an hour less on the nights they drank caffeinated coffee, while the fast metabolisers didn’t experience any impact on sleep.

Where to get your caffeine

The best source of caffeine is unsweetened coffee or tea, says Dr. Frank Hu, professor of nutrition and epidemiology at Harvard T.H. Chan School of Public Health. These drinks have other beneficial ingredients, such as polyphenols, which have antioxidant effects which reduce inflammation.

The caffeine content in coffee and tea can vary, but soda can’t have more than 71 milligrams per 12 ounces, per Food and Drug Administration regulations.

Adults get most of their caffeine from coffee, but the market for energy drinks is growing. Pay extra attention to the caffeine in these drinks, because some contain very high levels.

Getting caffeine from soda or energy or sports drinks makes it more likely you are also getting a high dose of sugar and empty calories, says Hu.

Extra caution

Kids under 12 should avoid caffeine, while 12- to 18-year-olds should have no more than 100 milligrams a day, according to the American Academy of Pediatrics. Pregnant women are advised to have no more than 200 milligrams of caffeine a day.

People with chronic conditions like high blood pressure, diabetes or heart disease might want to be more cautious about their caffeine consumption, Hu adds. The NEJM study found that on the days when participants consumed caffeine, they had more abnormal heart rhythms in the lower chamber of the heart, which is associated with a greater risk of developing heart failure.

And people who get migraine headaches should try to drink no more than 100 milligrams of caffeine a day, the equivalent of a mug of coffee, says Dr. Amaal Starling, a headache specialist and neurologist at Mayo Clinic in Scottsdale, Ariz. She advises her patients who have daily or severe headaches not to drink any caffeinated beverages or switch to decaffeinated coffee.


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I.M. Pei was the confident visionary behind such transformative structures as the Bank of China Tower in Hong Kong and the Louvre Pyramid in Paris, but he was also humble, and for years resisted a retrospective of his work.

Pei, a Chinese-American architect who died in 2019 at 102 , would always protest any suggestion of a major exhibition, saying, “why me,” noting, too, that he was still actively at work, recalls his youngest son, Li Chung “Sandi” Pei. A decade ago, when Pei was in his mid-to-late 90s, he relented, finally telling Aric Chen, a curator at the M+ museum in Hong Kong, “all right, if you want to do it, go ahead,” Sandi says.

A sweeping retrospective, “I.M. Pei: Life Is Architecture,” will open June 29 at M+ in the city’s West Kowloon Cultural District. The exhibition of more than 300 objects, including drawings, architectural models, photographs, films, and other archival documents, will feature Pei’s influential structures, but in dialogue with his “social, cultural, and biographical trajectories, showing architecture and life to be inseparable,” the museum said in a news release.

As a Chinese citizen who moved to the U.S. in 1935 to learn architecture, Pei—whose full first name was Ieoh Ming—brought a unique cultural perspective to his work.

“His life is what’s really interesting and separates him from many other architects,” Sandi says. “He brought with him so many sensibilities, cultural connections to China, and yet he was a man of America, the West.”

Facade of the Bank of China Tower in Hong Kong in a photograph commissioned by M+ in 2021.
© South Ho Siu Nam

Pei’s architectural work was significant particularly because of its emphasis on cultural institutions—from the East Building of the National Gallery of Art in Washington, D.C., to the Museum of Islamic Art in Doha, Qatar—“buildings that have a major impact in their communities,” Sandi says. But he also did several urban redevelopment projects, including Kips Bay Towers in Manhattan and Society Hill in Philadelphia.

“These are all places for people,” Sandi says. “He believed in the importance of architecture as a way to bring and celebrate life. Whether it was a housing development or museum or a tall building or whatever—he really felt a responsibility to try to bring something to wherever he was working that would uplift people.”

A critical juncture in Pei’s career was 1948, when he was recruited from the Harvard Graduate School of Design (where he received a master’s degree in architecture) by New York real estate developer William Zeckendorf.

With Zeckendorf, Pei traveled across the country, meeting politicians and other “movers and shakers” from Denver and Los Angeles, to Philadelphia, Washington D.C., Boston, and New York. “He became very adept at working in that environment, where you had to know how to persuade people,” Sandi says.

During the seven-year period Pei worked with Zeckendorf, the developer fostered the growth of his architecture practice, supporting an office that included urban, industrial, graphic, and interior designers, in addition to architects and other specialists, Sandi says.

When Pei started his own practice in 1955, “he had this wealth of a firm that could do anything almost anywhere,” Sandi says. “It was an incredible springboard for what became his own practice, which had no parallel in the profession.”

According to Sandi, Chinese culture, traditions, and art were inherent to his father’s life as he grew up, and “he brought that sensibility when he came into America and it always influenced his work.” This largely showed up in the way he thought of architecture as a “play of solids and voids,” or buildings and landscape.

“He always felt that they worked together in tandem—you can’t separate one from the other—and both of them are influenced by the play of light,” Sandi says.

View of the National Center for Atmospheric Research, on the mesa, in a photograph commissioned by M+ in 2021.
© Naho Kubota

Pei also often said that “architecture follows art,” and was particularly influenced by cubism, an artistic movement exploring time and space that was practiced in the early 20th century by Pablo Picasso, Georges Braque, and the sculptor Jacques Lipchitz, among others. This influence is apparent in the laboratory at the National Center for Atmospheric Research in Boulder, Colo., and at the Everson Museum of Art in Syracuse, N.Y. “Those two buildings, if you look at them, have a play of solid and void, which are very cubistic,” Sandi says.

Yet Sandi argues that his father didn’t have a specific architectural style. Geometry may have been a consistent feature to his work, but his projects always were designed in response to their intended site. The resulting structure emerged as almost inevitable, he says. “It just was the right solution.”

Pei also intended his buildings “not only to be themselves a magnet for life,” but also to influence the area where they existed. “He never felt that a building stood alone,” Sandi says. “Urban design, urban planning, was a very important part of his approach to architecture, always.”

After he closed his own firm to supposedly “retire” in the early 1990s, Pei worked alongside Sandi and his older brother, Chien Chung (Didi) Pei, who died late last year, at PEI Architects, formerly Pei Partnership Architects. Pei would work on his own projects, with their assistance, and would guide his sons, too. The firm had substantial involvement in the Museum of Islamic Art, among other initiatives, for instance, Sandi says.

Working with his father was fun, he says. In starting a project, Pei was often deliberately vague about his intentions. The structure would coalesce “through a process of dialogue and sketches and sometimes just having lunch over a bottle of wine,” Sandi says. “He was able to draw from each of us who was working on the project our best efforts to help to guide [it] to some kind of form.”

The M+ retrospective, which will run through Jan. 5, is divided into six areas of focus, from Pei’s upbringing and education through to his work in real estate and urban redevelopment, art and civic projects, to how he reinterpreted history through design.

Sandi, who will participate in a free public discussion moderated by exhibition co-curator Shirley Surya on the day it opens, is interested “in the opportunity to look at my father anew and to see his work in a different light now that it’s over, his last buildings are complete. You can take a full assessment of his career.”

And, he says, “I’m excited for other people to become familiar with his life.”