Is caffeine harmful or helpful to your health?

Before I can even begin to talk about caffeine, I need to admit my bias. I’ve loved coffee since I was a kid. It used to drive my mother crazy when she would catch me drinking from her mug when I was just seven years old. Now, at almost 43, I still drink two cups every day, in the morning (never in the afternoon). With half and half, because dairy is the best, and I will die on that hill.

Now that I have my disclosures out of the way, I want to do a little mythbusting, because one day you read that coffee is going to kill you and the next day it’s going to help you live a long and productive life. Which is it??

I’ve posted about the myth of coffee dehydrating you on my Instagram, so today I’m going to dig deeper into the physiologic outcomes related to coffee consumption, and then I’ll get more specific about caffeine. 

But first, coffee. 

Let’s start with the great news! In their exhaustive umbrella review of observational and interventional meta-analyses on coffee consumption, Poole and colleagues (2017) found in 218 studies that coffee was associated with more benefit than harm for a range of health outcomes across exposures, and up to three to four cups per day was associated with reduced all-cause mortality, incidence and death from cardiovascular disease, a lower risk of cancer, as well as some neurological, metabolic, and liver conditions. In general, there were no differences in sex, except for two specific female cohorts. There was increased risk of low birth-weight babies from mothers who drank coffee during pregnancy, and increased fracture risk in women with osteoporosis.Interestingly, the researchers found similar effects in both caffeinated and decaf coffee. 

What’s behind coffee’s beneficial effects? 

The answer to this question takes me back to the days of teaching food science to aspiring dietitians at Simmons University, where we would spend a week discussing the benefits of plant-derived beverages like coffee and tea. Coffee contains many bioactive compounds (i.e., chlorogenic acid and diterpenes such as cafestol and kahweol) that act as antioxidants and antiinflammatory agents, and can potentially aid the liver in its natural detoxification process. And, they are in physiologic doses that are extremely beneficial! Another of the potent bioactives in coffee is caffeine. 

Are coffee biohacks legit?

There’s been a lot of hype from podcasters and influencers about the supposed benefits of waiting to drink coffee for at least an hour after waking up, or only after you get full sun in your eyes, or after a tall drink of water and breakfast. But is this advice based on any data or evidence? 

Many of us in the nutrition space have thrown shade on these tips, tricks, and hacks because we kn0w the data isn’t there to support these claims, and now we have an outstanding review done by an epic team of nutrition scientists mythbusting all of the most popular questions about caffeine and health. I’m going to keep it short and sweet here, but you should definitely go read the full paper. It’s incredibly comprehensive and well worth your time.

Here’s a summary of the major takeaways from the review:

Does caffeine dehydrate you? 

Nope. As I mentioned in my instagram post, the typical consumption of caffeine (i.e. usually in a beverage) has little to no effect on hydration if you keep it to <400 mg./day, or <4 cups of coffee).

What about during exercise? 

Again, nope. Sweat, lack of fluid replacement, and genes cause most of the dehydration during exercise and, contrary to depleting you, caffeine has actually been shown to be one of the ergogenic aids that increases performance. This appears to be true even for habitual coffee drinkers.

Does caffeine help you lose weight? 

Probably not. The studies on this are kind of all over the place, but generally don’t support fat loss.

Is there a relationship between caffeine and mental health? 

It’s complex. Caffeine’s association with mental health is pretty individualized and depends very much on dose. Moderate caffeine intake can improve mood and sometimes offers temporary relief from certain depressive symptoms. But, excessive consumption of caffeine can worsen anxiety, mess up your sleep if you consume it too late in the day (which is why I don’t drink coffee in the afternoon), and can impair some mental health outcomes. You’ve got to figure out this dose for yourself because everyone metabolizes coffee a little differently.

Are there sex differences regarding caffeine’s effects? 

Yes and no. The evidence around sex differences are mixed. As far as performance outcomes go, there doesn’t seem to be a difference between males and females. but, like the coffee data above, there is an association between maternal caffeine consumption and negative pregnancy outcomes. So mamas to be, lay off the caffeinated stuff. Also, there seems to be a connection between high doses of caffeine (>400 mg. of caffeine, or >4 cups of coffee per day) and increased risk for fractures in women.

Does caffeine work for everyone? 

Probably. Non-responders to caffeine are quite rare, but there is a tremendous amount of variability in how people respond to caffeine overall. We all know that wild child who can have a double espresso shot after dinner and fall fast asleep an hour later. This likely has to do with a gene that metabolizes caffeine, as well as how often you consume it, and whether or not you have other food and drinks in your system. 

Is caffeine addictive? 

This one’s tricky. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) caffeine withdrawal is an officially recognized diagnosis, as are caffeine-induced disorders and caffeine intoxication. However, the manual stops short of including it as a substance use disorder. “Addiction” has very specific criteria (which is why we are careful about using it in the scientific and clinical world), and includes: 1) a persistent desire or unsuccessful effort to limit use; 2) continued use despite knowledge of potential harm; and 3) withdrawal. While withdrawal is certainly something you can experience if you stop drinking your coffee cold turkey, the other two diagnostic criteria are probably pretty rare for someone just looking for an afternoon latte fix.

Can too much caffeine kill you? 

Probably not. However, caffeine can be fatal in cases of overdose. These circumstances are quite rare, and generally don’t apply to coffee and tea drinkers. However, an increasing number of cardiovascular adverse effects, emergency room visits, and deaths have been linked to energy drinks. Whether it’s due to the caffeine or something else is unclear.

Will you harm your adrenals if you drink coffee first thing in the morning? 

Hell no. And I’m going to quote the study review here. The researchers state, “A significant drawback in the argument related to cortisol is that a similar effect occurs with intense resistance exercise performed soon after waking. Following this line of reasoning would imply that this type of early morning exercise should be avoided; however, this notion makes no scientific or pragmatic sense. There is also no evidence that caffeine ingestion upon waking is somehow responsible for an afternoon ‘crash’ or that delaying consumption would somehow prevent this if it did occur.”

So, there you have it. Enjoy coffee – or a caffeinated beverage of your choice – whenever you feel like it in the morning, but not too much, and not if you’re pregnant. 

Cheers!