Coffee & Tea: Healthy or Harmful?

Do you start every morning with a mug of coffee or tea? If so, welcome to the billion-member morning brew club! Drinking coffee and/or tea has been a standard ritual for thousands of years, but for such a popular, and historic drink, not many people understand the health implications. Are these caffeinated beverages benefitting our health? Harming it? Both? Neither? Tune in to find out.

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Transcript

Welcome to Nutrition Bites. The no nonsense podcast where you get the truth about food so you can eat what you want and be healthy. I’m your host Maggie and welcome to the series! Almost all of us start our days with something caffeinated. Whether it’s a hot mug of tea or iced coffee, a morning beverage is a global tradition. But what do we really know about these pick-me-up drinks? On the menu today, coffee and tea. 

Halfway through the pandemic I succumbed to the social media behemoth TikTok. As a millennial, I did feel a bit embarrassed, and slightly creepy, browsing this app, but the algorithm sucked me and I’ve been stuck ever since. Soon my feed was filled with adorable farm animals, pop culture comedians, and of course, plenty of food. One big trend I’ve noticed this summer has been home-made iced coffees and teas. But these aren’t your regular iced beverages, they’re cool iced beverages. Everyday kitchens now rival Starbucks stores. You can easily make an iced coffee latte with caramel drizzle and oat milk froth at home. Or an upgraded iced tea flavoured with a splash of guava juice and a sprig of fresh mint. As amazing as these look, I’m far too lazy to tap into my inner barista and whip up something unique. Just hand me a hot black coffee and I’m good to go. But these trends got me thinking. For something billions of people consume every day, I know shockingly little about the health effects of drinking coffee and tea. Are they benefitting our health, harming it, both, neither? It’s about time we find out.

Coffee is a beverage prepared by brewing roasted coffee beans - which are actually not beans at all, but seeds from a fruit called a coffee cherry. In its purest form coffee is predominantly water, with some caffeine, a few vitamins and minerals, and a pretty sizable serving of phytochemicals. These protective compounds are produced by plants but also have potential benefits for our health. The type of coffee bean and where it was grown, the roasting style, grind, and brewing method all affect the exact cup of coffee you get - from taste to variety of phytochemicals. And it’s a similar story with tea. 

Tea is a beverage prepared by pouring hot water over plant leaves. Black, green, white, and oolong tea all actually originate from the same species of plant. While herbal teas are a bit different - they are made from the roots, flowers, or leaves of a variety of different plants. So when I refer to tea in this episode, I mean the OG one made from the actual tea plant. Like coffee, tea is mostly water, with a little caffeine, a sprinkling of minerals, and a variety of phytochemicals. And similar too, different processing techniques, harvesting times, and brewing methods affect the type of tea and phytochemicals you’ll end up drinking.

The presence of these phytochemicals in tea and coffee is the reason why many scientists think these drinks are beneficial for our health. These molecules are thought to help reduce inflammation, moderate metabolism, and a whole other bunch of good-for-you actions. Some of these phytochemicals also act as antioxidants - substances that stop chemical reactions that can damage our cells. Fruits and vegetables are the best source of antioxidants, but coffee can also act as a really important source. In fact, this drink serves as Americans #1 source of antioxidants. Which really just means they don’t eat enough fruits and veggies.  In coffee, there are hundreds of phytochemicals that are thought to have beneficial actions. The same goes for tea, however, there is one family of molecules called catechins that have reached biochemical Kardashian-level fame. And the Kim K of this group is a molecule called epigallocatechin gallate (or EGCG for short). EGCG is found across all different types of tea, but green tea has the highest levels, which makes it the tea of choice for health research. 

But whether green or black, white or oolong, tea has always had a pretty steady status as a healthy drink. Coffee on the other hand, has had to deal with a touch more controversy. Back in the 80s and 90s scientists thought that regular coffee consumption contributed to cardiovascular disease. Studies at that time associated daily coffee drinkers with poor heart health, but the researchers didn’t account for the fact that many of their participants also smoked cigarettes. Later on they re-evaluated the data and found that coffee on its own was perfectly OK. But around this time, coffee lovers were battling another negative association: cancer. Acrylamide is a molecule found in foods processed at high temperatures like french fries, potato chips, and roasted coffee beans. Research in animals has found acrylamide to be carcinogenic, which led coffee to be added to the World Health Organisation’s list of possible carcinogens. Plenty of research since then has shown that the levels of acrylamide in coffee do not have a cancerous effect on humans, however the drink still remains on the WHO’s naughty list. But funnily enough, decades of research hints that the exact opposite may be true.

Observational research has shown that drinking the equivalent of 4 cups of black coffee a day is associated with a decreased risk of cancer. Similar associations are made with consumption of green tea - at least for those who can throw back 10 cups a day. So basically, people with a caffeine dependency and extra strong bladder. Another strong association for these drinks is with our heart health. Observational research across hundreds of thousands, if not millions, of people has shown that habitual coffee and tea drinkers have a reduced risk of cardiovascular disease. That includes stroke and heart attacks. Now most of the research has been done in coffee, but observational studies with green tea drinkers find similar results. Consume 3 cups a day of either beverage, a reasonable goal for any exhausted adult, and you may get a serving of heart protection along with that caffeine boost.

The brain is another area of the body where both coffee and tea have positive health associations. Observational studies have once again found that those who regularly drink coffee are less likely to be depressed than those who abstain. At least for those who drink 4 cups of coffee per day. A cool result, though I can’t help but wonder if this effect is because it’s hard to be depressed when you’re constantly wired. In the case of tea, the positive effects on the brain are a bit different. Present in all types of tea is a unique amino acid called L-theanine which exerts a relaxing effect on our brain. And multiple studies have shown that L-theanine, and tea consumption in general, can reduce subjective and objective measures of stress. No wonder the Brits love to offer a cuppa when someone is stressed (or at least that is what watching multiple BBC miniseries has taught me). 

Observational research has also shown that high volumes of coffee and green tea may be the nutrition equivalent of carrying around a lucky rabbit’s foot. Studies show that those who average 5 cups of coffee a day, or 4 cups of green tea, seem to have a lower risk of early death. As opposed to, old death I guess? But the good news doesn’t stop there. Other long-term studies show habitual coffee and green tea drinkers may have a reduced risk of developing Type 2 Diabetes and dementia. While straight java enthusiasts can look forward to a potential reduced risk of Parkinson's disease, kidney injury, and gallstones (although the research is pretty limited here). All together both these beverages seem incredibly healthy for us. But just like with any good Disney movie, in the field of nutrition, there’s always a catch.

The biggest drawback to all these health benefits is that the vast majority of research on coffee and tea is done via observational studies. With this type of research you can really only draw associations not conclusions. And unfortunately, it seems like scientists may be stuck with doing this type of research. Most chronic diseases take decades to develop, and drinking coffee is tea is a regular habit for billions of people. Both these factors make running clinical trials difficult - which means conclusive evidence is hard to come by. 

But even if we had the hard truth at our fingertips, both coffee and tea also have their own disadvantages. Drinking coffee can temporarily increase both your blood sugar as well as LDL cholesterol (often called the “bad” cholesterol). Although what’s interesting about the cholesterol discovery is that it’s unique to unfiltered coffees, like what you get with French press. That’s because coffee grounds contain a unique substance called diterpenes which raise cholesterol. But if you make your brew using a filtered method, like classic drip, pour over, moka pot, or aeropress, you remove the diterpenes and don’t get the cholesterol raising effect.

Tea’s biggest drawback is its effects on iron absorption. You may have heard the word tannins before - particularly if you’ve chatted with a wine snob, or maybe are the wine snob yourself. These compounds provide a bitter taste to wine, and do the same in tea. In addition to providing a flavour sensation, tannins also act to inhibit the absorption of iron - particularly the type found in plant-based foods like spinach, beans, and oats. Some studies estimate that tea can reduce the absorption of dietary plant-based iron by up to 70%. Fortunately you just have to wait at least 30 min between drinking tea and eating an iron-rich plant-based meal in order to avoid this absorption dilemma.

Apart from these small challenges with coffee and tea, there’s really nothing else negatively unique about these beverages. But one factor that is both an up and downside, is caffeine. Now episode 15 of the podcast is dedicated entirely to caffeine, but the quick and dirty summary of this psychoactive molecule is as follows. At low doses caffeine can increase alertness, energy and our ability to concentrate. But at high doses, it causes blood pressure to rise, anxiety to increase, restlessness, and insomnia. The recommended max intake of caffeine is 400 mg. That equals around 3 - 4 cups of drip coffee, or 8 cups of black tea, or 11 cups of green tea. Now unless you have a bladder of steel, it’s unlikely you’ll over consume caffeine from too much tea. More than 4 cups of coffee on the other hand, well that’s just a regular Tuesday for many folks. While you can develop a tolerance to caffeine, meaning you avoid the anxious jitters of a cup too many, tolerance also means painful withdrawal symptoms if you don’t get your fix. 

And this is where the benefits vs drawbacks of these caffeinated beverages face off a la dramatic spaghetti Western. To get all the big chronic disease prevention advantages, you need to regularly consume high volumes of coffee or tea. Want to decrease your risk of depression - that’ll be 4 cups of coffee every day. Cancer? 10 cups of green tea. Yet these volumes generally means you’re maxing out or going above the recommended caffeine intake. Pretty conflicting right? This caffeine drawback is likely why no doctor recommends upping your coffee or tea intake if you’re at risk for a chronic disease. Sure the phytochemicals are good for us, but you can improve your heart health, brain health, and cancer risk doing other things. At the same time though, the general view of coffee and tea by health professionals is that these beverages can be part of a healthy lifestyle. So long as you’re not treating them as drinkable desserts. 

Over the years black coffee and tea have slowly morphed into sugar and cream-laden concoctions. Sure you can blame Starbucks for popularising this trend, but even at-home drinks can still seem more like desserts rather than simple caffeinated water. According to a 2021 survey by the US Department of Agriculture, sweetened coffee and tea are the fourth largest source of sugar in the diets of US adults. And it makes sense. One grande order of the popular caramel macchiato latte from Starbucks averages 150% of the recommended added sugar intake for an adult. Similarly, one signature bubble tea from the global chain ChaTime, fulfils a day’s added sugar quota. Even the iconic Canadian order of a medium double-double at Timmies, which translates to a coffee with two creams and two sugars, contains 80% of an adult woman’s saturated fat intake and over 100% of added sugar. And sadly. Every teaspoon of sugar stirred into your English breakfast brew contains a quarter of your daily added sugar. So instead of being a relatively nutrient-free beverage, coffee and tea can easily become vehicles for excess sugar and saturated fat - without us really knowing it. And ironically, too much of these nutrients puts us at risk for the same chronic diseases coffee and tea are thought to help prevent. So let’s listen to the words of Amy Winehouse and go back to black. 

Although many people don’t consume coffee or tea specifically for long-term health benefits, a lot of research is pointing in a favourable direction. Of course, balancing caffeine intake and what we put in our drinks complicates things. Though it’s still kind of nice that our daily pick-me-up coffees and teas may also be improving our health. It’s like the nutrition equivalent of a 2-for-1 sale. But regardless of if these morning brews actually do anything more than help wake us up, consuming them can be part of a healthy diet. And beyond what coffee and tea does to our body, they are both drinks that taste good, act as social lubricant, and provide a great excuse to take a break. So if you haven’t already, go ahead and put on the kettle.  

That’s been the bite for today. Stay hungry.