How Much Caffeine You Should Actually Have—and When
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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

By SUMATHI REDDY
Thu, Jan 11, 2024 9:54amGrey 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 than 400 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 metabolise 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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Ben Broca launched a company last December that offers AI tools to entrepreneurs. He’s already added 10,000 paying customers and is on track to bring in $10 million in revenue this year.

One thing he hasn’t added: any other employees.

The 40-year-old is part of a class of entrepreneurs who are launching, and then often running, new companies on their own. Artificial intelligence tools answer Broca’s emails, help write and debug code, field requests from customers, sign up new subscribers and grant refunds when issues arise.

Broca relishes his ability to make whatever decisions he wants on his own, often from his sun-drenched Sausalito, Calif., living room. “I think compromises make lukewarm results,” he said.

Once upon a time, running a business of a certain size required a team. AI is turning that assumption upside down, and more aspiring entrepreneurs are going it alone.

Ben Broca sitting in his home office.
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An analysis by the payments company Stripe shows there are thousands of solo operators on the company’s platform that are generating over $1 million in revenue, with their ranks doubling between 2023 and 2025. The number of solo operators crossing the $10 million threshold nearly tripled in that same span.

In the past, people without business contacts or particular savvy might not have known how to get their ideas off the ground, said Ernie Tedeschi, Stripe’s chief economist. “Now, AI can be a built-in business partner,” he said.

AI’s ability to handle various administrative tasks makes it potentially useful for launching solo businesses in many fields. But the technology’s ability to also handle key tasks in tech, like coding, make that field a particular hot spot.

Analyzing Census Bureau data, Bank of America Institute economist Taylor Bowley found that among all industries, new business applications in the information sector have seen the biggest percentage increase—nearly 45%—over the past year. At the same time, the rate of information-sector applicants saying they plan to hire workers has experienced the sharpest decline of any measured industry.

This Census dataset doesn’t track solo-operated businesses. But the numbers broadly show—in tech and beyond—that applications are flat among businesses likely to hire workers, but generally rising elsewhere. Economists say that’s a strong sign that solo operators are on the upswing.

“The bar for getting started has never been lower,” said Julian Weisser, who runs a San Francisco-based accelerator for solo founders working in tech. The accelerator—which offers founders seed money and mentorship in exchange for an equity stake—attracted 4,500 applicants for 10 slots made available in its most recent cycle, nearly five times the number it drew when it launched last May.

Going it alone with AI can still be surprisingly expensive. Broca said he was losing money on many customers’ accounts while paying to access Anthropic’s Claude to run his clients’ requests—that AI company, as well as others, charges based on usage. He has since switched to free open-source AI models from China.

Broca said he has raised $30 million from investors and, at the same time, has saved millions in salary since he hasn’t needed a team of software engineers.

Another risk: If it’s easy for one entrepreneur to launch an AI-assisted business, copying them can be easy, too. This creates anxiety for founders like Troy Johnston, who runs an AI-assisted business alone in Orlando, Fla.

“Everybody has the sword and we all have the ability to unsheathe Excalibur now,” said Johnston, 40, who used AI to code an app that helps people get the most out of credit card benefits. The company makes around $3,000 a month in profit, with no employees, and is continuing to grow.

Headshot of Troy Johnston.
Troy Johnston said AI’s power and ease of use is an incredible boon for entrepreneurs like him—and also a double-edged sword. Luann Koerper

What one-person businesses will mean for the labor market remains to be seen. Polling has shown Americans are worried that AI will replace jobs, and top economists are wrestling with that possibility, too. But AI is also creating lots of new jobs, and the go-it-alone entrepreneurs show how the technology can both open doors and limit employment opportunities.

“If everyone’s hiring less, but you get four times more firms, what does that do to head count?” said Rembrand Koning, an associate professor at Harvard Business School who studies entrepreneurship. He co-authored a recent study that found that among 50,000 startups the researchers examined, those focused on AI tended to operate with 25% fewer employees.

Koning also believes a soft hiring environment that’s left some people mired in long job searches has encouraged more to try their hand at launching businesses.

Some founders cite different motives. “It’s a perfect storm of post-pandemic burnout and a re-evaluation of one’s priorities, and also booming AI and a sense of what’s possible,” said Samir Ahmad, 39, who lives in Breinigsville, Pa.

Two years ago, Ahmad decided to leave the corporate job he had worked at Verizon for almost two decades to start a solo coaching and consulting business. He had been seeing social-media posts touting the ease and virtues of AI, which he used to chart a business plan and help with marketing. “It was like my chief of staff, a second in command,” he said.

The business ultimately petered out within months, though, and Ahmad is now back to a full-time corporate role with a utility company.

For Claire Vo, 41, AI helped her turn a passing impulse into a business. She was working full-time as a tech executive when she tapped AI in late 2023 to help code an app that would help her manage documentation and design for new products, with customers ranging from financial services to healthcare firms.

“I was copying and pasting from ChatGPT,” said Vo, who lives in San Francisco.

Claire Vo smiling into the camera while recording a podcast.
Claire Vo used AI to code an app that’s on track to make seven figures in profit this year. Claire Vo

She put the app online for $1 a month, and within weeks people downloaded it thousands of times. Nearly three years later, Vo’s company—which she ran solo for nine months before hiring an engineer—now has 100,000 users and is on track to make seven figures in profit this year. AI handles the company’s marketing, sales and customer support.

While AI is a shortcut, Vo said her network and credibility in the industry were key. “I think people over-index on how easy AI is and under-index on how much I did to get to this point,” she said.

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