Is caffeine bad for you? It may depend on your genes. More specifically, it may depend on one gene—called CYP1A2—that determines how your body metabolizes the caffeine found in fan favorite beverages like tea, coffee, and soda.
Caffeine is a bitter, white substance that’s found naturally in more than 60 different plants , including coffee beans, tea leaves, and kola nuts, which are used to make soda. Caffeine acts as a natural stimulant and for this reason, the FDA has it listed as both a food and a drug.
To get specific, caffeine targets the central nervous system and makes you feel more awake, energized, and alert. It’s often described as a cognitive and physical performance enhancer. Everyone seems to react to caffeine differently; some get jittery and anxious from a few sips of coffee while others can drink cup after cup without blinking an eye. Recently, researchers discovered these variations in caffeine tolerance can be traced back to genetic differences, which brings us to the CYP1A2 gene.
The caffeine you ingest passes through the stomach and small intestine, entering the bloodstream in a little as 15 minutes . Your caffeine levels peak about 1-hour after consumption and then start to decrease gradually. The speed of this decline depends on your CYP1A2 gene, which controls an enzyme (also called CYP1A2) that is in charge of breaking down any caffeine that enters the body.
You have two copies of the CYP1A2 gene—one inherited from each of your parents—and each can be either a “fast” or “slow” version of the gene. If you have two “fast” versions, you’re considered a fast caffeine metabolizer. According to Dr. Tiffany Lester, M.D. , physician and medical director at Parsley Health San Francisco , “These are the people that can have an espresso and go right to sleep!”
In contrast, if you have one or two versions of the “slow” version of CYP1A2, you’re labeled a “slow” caffeine metabolizer, meaning you clear caffeine from your system about four times slower than your quick metabolizing counterparts, says Dr. Lester.
Based on your reaction to caffeinated beverages, you probably already have a hunch as to whether you’re a fast or slow caffeine metabolizer. But how do you test it to know for sure? You can test for the caffeine gene through a simple saliva or blood test that analyzes your DNA.
“I don’t typically test for CYP1A2 in isolation,” explained Dr. Lester. In other words, it doesn’t influence health in a significant enough way that she would go out of her way to order the test for every single one of her patients. “It usually comes up if a patient has done a 23andMe or other direct-to-consumer genetic test,” she continued.
The CYP1A2 gene made headlines a few years ago when a study, published in the Journal of the American Medical Association, showed that slow metabolizers who drink more than four cups of coffee per day have an increased risk for heart disease .
So if you’re a slow caffeine metabolizer, should you be cutting out caffeine from your routine entirely? “No way!” said Dr. Lester. In fact, Dr. Lester is a slow caffeine metabolizer herself and still enjoys her daily dose of caffeine.
That said, knowing that she has this genetic variant has helped her consume caffeine more strategically. “For someone like me who does have that genetic variant, I do not have caffeine after 8 a.m. otherwise it will be difficult for me to fall asleep at night,” she said.
It’s all about evaluating your relationship with caffeine and figuring out what’s best for your lifestyle and genetics. Parsley Health’s health coaches are experts in helping members determine what works best for them—and how to still enjoy caffeine if they choose.
According to Dr. Lester, if you’re dependent on caffeine to function and get through the day—and you’re still tired even after getting plenty of sleep—it could be a sign that you have underlying adrenal fatigue . “In that case, cutting out caffeine entirely for a period may be the best option to discuss with your doctor,” she explained.
Even if you’re a fast caffeine metabolizer, you can still experience side effects of too much caffeine such as:
According to Mayo Clinic, a healthy caffeine intake can be up to 400 milligrams (mg) a day. If you’re consuming more than that, it might be worth cutting down your caffeine intake, especially if you’re a slow caffeine metabolizer or are experiencing any of the side effects of too much caffeine listed above.
It’s possible to be a fast caffeine metabolizer and still have negative reactions to moderate or even low amounts of caffeine. This could indicate an underlying health concern, such as estrogen dominance .
Estrogen and caffeine are both broken down in the liver by the CYP1A2 enzyme. “Women that have estrogen dominance often do not have an abundance of this enzyme and therefore should not consume caffeine as they will also have a hard time detoxing it,” explained Dr. Lester. The good news is that once you balance your hormones with the help of a doctor, it’s likely you’ll be able to tolerate caffeine again.
If you’ve decided to pull back on your caffeine intake for any reason, the first step is to figure out how much caffeine you’re actually consuming. Not every beverage contains the same amount of caffeine. For example, an 8-ounce cup of coffee has about 95 to 200 mg of caffeine compared to a cup of green tea, which has about 14 to 60 mg in an 8-ounce serving.
Meanwhile, energy drinks can have anywhere from 60 to 250 mg of caffeine per serving. As Dr. Lester explained, “Each of these beverages have different amounts of caffeine with tea being the lowest. So, for example, someone with anxiety may not be able to tolerate an espresso but can happily drink a matcha latte!”
Caffeine can also be hiding in places you might not expect. Kombucha and chocolate are two hidden sources of caffeine that you might not be taking into account. When you’re cutting back on caffeine, Dr. Lester recommends going slowly or you might experience caffeine withdrawal symptoms like headaches, irritability, and fatigue . “A general rule is to go by halves. Cut down gradually by halving your intake every 3 days until you’re completely off any caffeine source,” she said.
Cutting back on caffeine isn’t always easy. Caffeine is the most common “drug” in the world and after water, coffee is the most popular beverage on earth. About 1.6 billion cups of coffee are consumed every single day worldwide; in other words, it’s deeply ingrained in our culture and our daily routine. Turning to other caffeine-free drinks can help you ease the transition.
The most obvious choice is the caffeine-free version of your favorite coffee or tea-based beverage. But proceed with some caution. Many companies use harsh chemicals to remove caffeine that you’ll want to avoid. In this case, opt for organic options or buy from companies that are transparent about the process they use.
Naturally caffeine-free options include herbal teas like chamomile, peppermint, rooibos, and hibiscus. You can also find herbal chai—made from rooibos or herbal tea instead of black tea—that tastes like your favorite chai without the stimulating effects.
An ancient Ayurvedic tradition, golden milk is a creamy, lightly sweet beverage that contains turmeric powder and steamed milk—and oftentimes honey and cinnamon, vanilla, and other spices. You can find golden milk or turmeric lattes in many coffee shops and cafes and it is naturally caffeine-free.
In the end, there’s no cut and dried equation for how much caffeine you should consume. Instead, it’s up to you to be mindful and know how much caffeine is too much for your health and sleep quality. The good news is that even if you’re a slow caffeine metabolizer, you can enjoy your morning coffee as long as you’re wise about your consumption.
Gretchen Lidicker is a writer, researcher, and author of the book CBD Oil Everyday Secrets: A Lifestyle Guide To Hemp-Derived Health & Wellness. She has a masters degree in physiology and complementary and alternative medicine from Georgetown University and is the former health editor at mindbodygreen. She's been featured in the New York Times, Marie Claire, Forbes, SELF, The Times, Huffington Post, and Travel + Leisure.