Scientists believe that both coffee and tea confer health benefits. Studies have shown that coffee intake may improve cognitive performance and offers some protection against neurodegenerative diseases as well as certain cancers. Tea contains antioxidants, catechins and polyphenols that are believed to improve cardiovascular health, reduce systemic inflammation and provide a variety of health benefits.
So what's the difference? Is one healthier than the other? How much caffeine is optimal and is there a down side to caffeine consumption?
People are often surprised to learn that tea leaves contain more caffeine (by weight) than coffee beans. However, prepared tea tends to contain less caffeine than prepared coffee because a lesser weight is used to prepare a cup of tea than a cup of coffee.
Although tea usage is increasing, many people cling to coffee as their caffeine drug of choice. Some people really cling to it, grasping a succession of macchiatos, lattes, and Americanos all day long, like security blanket sippy cups. Unfortunately, too much caffeine can also have unwanted negative effects.
Much of the reason that caffeine acts is a stimulant is that it displaces adenosine on adenosine receptors in the brain. Adenosine has several mechanisms in the body, but in the brain, it attaches to adenosine receptors to tell you you're tired and should rest. When caffeine displaces adenosine, this message is effectively blocked. So caffeine doesn't actually give you energy- it just prevents you from getting the message that you're tired. You also have adenosine receptors in your cardiac muscles, which is why caffeine can sometimes cause a rapid heart rate.
The problem is that adenosine builds up while caffeine is blocking its receptors so that when the caffeine is finally broken down, a greater amount of adenosine floods receptors than would normally be present and then people feel extra tired. That's when many people reach for more coffee and the cycle continues.
Compounding the issue with adenosine is the fact that caffeine increases stress hormones, (cortisol, adrenaline and epinephrine) and inhibits GABA, your calming neurotransmitter. This results in a physiological state of stress and can lead to irritability and anxiety, not to mention the health effects of chronic stress and high cortisol.
Caffeine also increases the effects of serotonin (your feel-good neurotransmitter), but only while caffeine is present. So when the caffeine goes away and serotonin drops, people feel irritable and unhappy.
Over time, when the body senses that its normal feedback mechanisms aren't working properly (as a result of caffeine's chemical intervention), it attempts to compensate by altering hormone/neurotransmitter production and/or the number of receptors. The result of this is that eventually people become immune to the initial perceived benefits of caffeine and end up requiring it to stave off caffeine withdrawal symptoms. In essence, they need caffeine just to feel normal (or most severely, a stressed out, tired version of normal) and the earlier perks of occasional caffeine intake are a distant memory.
So, if both coffee and tea contain caffeine, aren't the results the same? Not exactly. You can overdo it with either and moderation is always best, but tea is different from coffee in one important way; Unlike coffee, tea contains theanine (in fact, tea is one of the only natural sources). Theanine (L-theanine, technically) is an amino acid which has the unique effect of significantly increasing alpha waves in the brain. The result is a relaxed, calm mood, but without drowsiness. (Beta waves, in contrast, are associated with high levels of stress and irritability.)
Theanine has also been found to increase GABA levels, decrease anxiety, and improve memory and may even reduce blood pressure. In other words, theanine counteracts many of the potentially negative effects of caffeine. When taken in concert with caffeine, a good number of studies have demonstrated statistically significant enhanced cognitive performance. These improvements were found to be greater than taking either theanine or caffeine in isolation. When caffeine and theanine are ingested together, various studies have identified the following cognitive improvements:
- visual information processing
- speed and accuracy of task switching
- quicker working memory
- increased accuracy in sentence verification
- faster reaction times
The benefit of tea over coffee then, is a lower level of caffeine (with fewer of the negative effects resulting from high caffeine intake), and a feeling of calm alertness with an enhanced cognitive state. Sounds pretty good, right?
So what types of tea contain theanine? They all do, but amounts can vary widely. One study tested a number of different teas and found values ranging from 5-36 mg/200 mL. In this study, black teas tended to have higher levels of theanine than green tea, but they only tested a few green teas. Conversely, another study found that green teas contained the highest levels of theanine, so it appears to be highly variable, but high mountain teas and shade-grown teas are believed to contain higher levels. (And pu-erh tea is believed to contain high levels of GABA.)
Also worth noting, they found that theanine was extracted equally well with both hot and cold water and that most of theanine is extracted during the first 5 minutes of steeping. However, when a significant amount of milk was added to the steeping tea, theanine extraction was greatly reduced, so you may want to wait and add your milk after steeping.
Caffeine content can vary greatly from tea to tea, as well. Although generally green and white teas are believed to have lower caffeine content than black teas, upon analysis, this is often not the case. One study found, "caffeine concentrations in white, green, and black teas ranged from 14 to 61 mg per serving (6 or 8 oz) with no observable trend in caffeine concentration due to the variety of tea." It is generally accepted, however, that kukicha ("stem tea") is naturally very low in caffeine, while shade-grown teas are naturally higher. White peony is also a variety with naturally lower caffeine and higher levels of antioxidants.
The caffeine content of coffee varies widely as well, with studies finding anywhere from 80-200 mg per cup (average is around 100 mg), but in most cases prepared coffee contains more caffeine than prepared tea.
In conclusion, if coffee isn't doing it for you anymore, if you're tired of feeling tired and stressed, if you're experiencing the ill effects of high caffeine intake (and caffeine withdrawal), you may want to consider switching to tea. After an initial adjustment period, you may find that tea makes you feel better and work more effectively!
And if you decide to cut out caffeine completely, we know some people (ahem, us) who have a variety of of healthy, flavorful and delicious herbal teas that will keep your hot beverage-craving mitts warm and happy all day long.
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