The Best Time to Drink Coffee for Productivity (And When Not to Do It)

“When your adrenaline goes up, it promotes the release of sugar stores from your liver, and then you crash,” Ackerman says. “And if you don’t eat anything, you can get hypoglycemia, which can make you really shake on top of everything else.”

The key, Ackerman says, is to eat fewer complex carbohydrates and proteins. This could be anything from granola to peanut butter bread. The extra energy from food will prevent your body from crashing mid-morning.

I learned from Ackerman that this is the reason for my mid-morning shakes. It wasn’t caffeine. It was adrenaline and hypoglycemia. I’m not much of a breakfast fan, but on Akerman’s advice, I now eat a handful of peanuts every morning before my morning smoothie, to avoid an unexpected sugar crash.

Moderate your caffeine dose

Some people process caffeine quickly and well. Some people don’t. Some people are also larger than others. But the general rule of US Food and Drug Administration is that 400 milligrams of caffeine per day is the highest dose proven to be safe for most people.

This could amount to four 8-ounce cups of drip coffee or three double shots of espresso. If you are pregnant, a safe dose may be half this amount.

But people can also vary greatly in their ability to metabolize caffeine. “There’s actually a genetic test you can take — it’s the CYP1A2 gene — that can tell you whether you’re metabolizing caffeine slowly or rapidly,” Zumpano says. But for the most part, she says, the key is listening to your body. If you’re experiencing rapid heartbeat or palpitations, you’ve probably consumed too much caffeine.

The same is true, she says, if you feel a deflating mix of stress and exhaustion in the afternoon, a common feeling that’s often the result of high stress levels fueled by adrenaline or cortisol plus a post-lunch sugar drop.

“I’m a cardiac dietitian,” says Zumpano. “So I see a lot of people who have arrhythmia, tachycardia, atrial fibrillation — all of these things are exacerbated by caffeine. Caffeine is one of the first things I stay away from, and it actually regulates their heart rhythm.”

Stop drinking coffee in the late afternoon

I know, I know. In France, it is civilized to have a small cup of coffee after dinner.

But Europeans also tend to have a different circadian rhythm than Americans, Zumpano points out, with downtime in the afternoon. They also don’t drink their coffee from a 10-ounce cup.

As a general rule, Ackerman and Zumpano say, most people should stop drinking coffee by 3 p.m., or maybe even at noon. This will depend on how much coffee you drink each day and how quickly your body metabolizes caffeine. Although many people are still able to sleep after consuming caffeine late in the day, Zumpano says, it often has a calming effect on the quality of your sleep. Cortisol slowly leaves your body.

“I have these patients who say, ‘I can have caffeine anytime, and it doesn’t affect my sleep,'” Zumpano says. “And I say, ‘Why don’t we try to get rid of it?’ And they say, ‘Oh my God, I’m sleeping so much better. I sleep through the night. I didn’t know that was possible.'”

Don’t turn to tea late in the day

Ackerman, the neurologist, also warns against switching to afternoon tea, a fairly common habit among those who don’t want caffeine levels to skyrocket in the afternoon.

Tea generally contains less caffeine than coffee. On average, a cup of tea contains one-half to three-quarters as much caffeine as a dripping mug. But the reason you feel nice isn’t because of a lack of caffeine. Instead, tea releases caffeine much more slowly. The phenols in tea slow the rate at which the body processes caffeine, resulting in a more luxurious and civilized feeling.