Some teas and herbal infusions have long been appreciated for their alleged health benefits, but what does research have to say?
"Tea began as a medicine and grew into a beverage," writes 19th-century Japanese scholar Okakura Kakuzo in his infamous publication The Book of Tea.
In it, he speaks at length about the history of tea and the philosophy of the traditional Japanese tea ceremony.
Kakuzo was correct: modern research about the history of tea-drinking in the world confirms that this beverage was originally consumed less for pleasure or as a mindfulness aid, calling for the drinker to take slow sips and be in the moment.
Instead, as shown by Prof. Victor Henry Mair — from the University of Pennsylvania in Philadelphia — in The True History of Tea, early in its history, the tea plant (Camellia sinensis) became popular for its medicinal properties.
The tea plant's main varieties — Camellia sinensis sinensis and Camellia sinensis assamica — are responsible for most of the tea brews that we are accustomed to: black tea, green tea, white tea, and oolong tea.
There are many other types of teas and infusions using various other plants, such as Aspalathus linearis, which is better known as "rooibos" or "redbush." In this Spotlight, we'll give you an overview of the top five teas that can benefit your health.
1. Green tea
A favorite with tea drinkers everywhere, green tea has been praised for its medicinal properties for years. Some recent studies have now confirmed some of these benefits, suggesting that green tea may protect various aspects of our health.
Green tea can increase cognitive functioning.
To begin with, this beverage has been found to enhance cognitive functioning, with one study connecting it to better working memory, the type of we use on a day-to-day basis.
Researchers from the University Hospital of Basel in Switzerland found that healthy people who agreed to consume a soft drink containing 27.5 grams of green tea extract exhibited more intense activity in brain areas linked to working memory.
Therefore, participants who had ingested the green tea extract had better connectivity between the frontal and parietal lobes of the brain, which are two regions involved in aspects of learning, memory processes, and decision-making.
The health benefits brought about by green tea have been linked with their content of polyphenols, which are micronutrients with antioxidant properties. As antioxidants, these substances can protect against the action of free radicals, which induce the type of cellular damage consistent with aging.
A 2017 study that was published in the Journal of the American Chemical Society found that one such polyphenol found in green tea — called epigallocatechin gallate — may lower the risk of Alzheimer's disease by interacting with the "building blocks" that form beta-amyloid plaques.
A buildup of these plaques in the brain is typical of this condition and impairs brain cell signaling. Epigallocatechin gallate, this study suggests, could stop beta-amyloid from forming into plaques, potentially helping to keep Alzheimer's at bay.
Research that was led by the Los Angeles Biomedical Research Institute in California has shown that epigallocatechin gallate can disrupt the metabolism of pancreatic cancer cells, thereby impairing their growth.
2. Jasmine tea
What we refer to as "jasmine tea" is a type of beverage that usually has green tea at its base, to which jasmine flowers are added for an enriched aroma.
Jasmine tea is an important component of the diet of one of the longest-living populations in the world.
But the benefits of jasmine tea aren't solely due to the antioxidant effects of the tea plant, since jasmine blooms also bring their own medicinal properties to the mix.
In the book Ikigai: The Japanese Secret to a Long and Happy Life, authors Héctor García and Francesc Miralles note that the inhabitants of a healthy, long-lived community in the Okinawa Prefecture of Japan are avid drinkers of Sanpin-cha, a special blend of green tea and jasmine.
"Okinawans drink more Sanpin-cha — a mix of green tea and jasmine flowers — than any other kind of tea," they write, suggesting that this blend may play a role in keeping the inhabitants of Okinawa healthy and mentally agile well into old age. This may be because, like the tea plant, jasmine flowers contain antioxidants — which may protect cells from age-related damage.
Jasmine itself has been linked with improved physical well-being and is said to reduce the impact of stress. That is why some researchers have experimented with compounds derived from this plant in the search of better therapies.
For instance, Prof. Eliezer Flescher — from Tel Aviv University in Israel — noticed that methyl jasmonate, which is a compound obtained from jasmonic acid, found in the jasmine plant, induces the death of cervical cancer cells.
And, if you happen to enjoy drinking jasmine tea simply because you love the way it smells, there's actually a good reason for that. Research that was published in the European Journal of Applied Physiology explained that the smell of jasmine tea is soothing, able to calm nerves, and able to help regulate mood.
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3. Rooibos tea
Another type of tea with antioxidant properties is rooibos, or "redbush tea," which is prepared from the Aspalathus linearis plant native to South Africa.
Rooibos tea may protect liver health.
Research has suggested that the antioxidant effects of rooibos are similar to, if not quite as strong as, those of green tea.
A recent study on the rat model has suggested that the antioxidants in rooibos tea may protect the liver from oxidative stress, helping to render this organ more resilient to induced damage.
The researchers who conducted the study noted that their findings suggest that rooibos tea or rooibos-derived dietary supplements may offer a useful health boost.
"Results from this study suggest that the daily intake of unfermented rooibos herbal tea or a derived commercial rooibos supplement may benefit human health by providing the liver with an enhanced antioxidant capacity to reduce damage induced by toxicants."
Moreover, rooibos has also been cited as helpful in lowering blood pressure and relaxing tense muscles, suggesting that the active ingredient in this instance might be one of the flavonoids (pigments) that it contains: chrysoeriol.
Unlike green or black tea, rooibos does not contain any caffeine, so it won't have the same stimulating effects. This makes it safe to drink well into the evening.
4. Hibiscus tea
Those of you who enjoy the refreshing taste of a more sour brew may also be familiar with herbal infusions of hibiscus, a plant whose flowers can be used not just to make invigorating beverages, but also to give a subtle "punch" to salads, or as an elegant garnish for sophisticated dishes.
Hibiscus tea is an antioxidant and may bring cardiovascular benefits.
The most commonly used variety is Hibiscus sabdariffa, also known as the "roselle."
For the tea — or, more correctly "tisane" (herbal tea) — its calyces are typically used, although other parts of the plant, such as the leaves, seeds, and roots, are safe for consumption.
Studies have suggested that extracts from the hibiscus calyx and hibiscus leaves have antioxidant and antitumoral effects.
Therefore, they may protect against the aging action of free radicals at a cellular level, as well as fight certain types of leukemia cells.
Though not so commonly used to brew tea, hibiscus leaves have also been linked repeatedly to a wide array of health benefits. Thus, the polyphenols in hibiscus leaves may help to induce tumor cell death in skin cancer, according to a 2015 study.
5. Lemon verbena tea
Another herbal tea whose medicinal properties are getting increasingly recognized is that made out of lemon verbena, scientifically dubbed Aloysia citrodora.
Infusions with lemon verbena are said to help with weight management.
It is the citrus-flavored cousin of a better-known plant that has been used in herbal infusions for years: verbena, or vervain (Verbena officinalis).
Infusions made with lemon verbena are great for those who, like me, prefer a subtler citrusy aroma in their hot drinks, rather than the strong, lemony flavor of commonly commercialized citrus tea blends.
The first time that I came upon this plant sold as a tisane herb was in a local organic shop that was selling it as "weight loss tea."
In fact, studies have shown that the polyphenols in this plant can decrease the formation of fatty acids, marking its potential use in the treatment of obesity-related health issues.
"Results demonstrate that supplementation with lemon verbena extracts may affect the cytokine [inflammation markers] profile depending on the clinical subtype," the study authors conclude.
Having a cup of your tea — or tisane — of choice may be a pleasant way to carve out some self-indulgence time and stimulate your bodily and mental well-being in a subtle way.
But always keep in mind that, as the saying goes, "one swallow does not a summer make," and the most potent health benefits are best reaped by leading a healthful, wholesome lifestyle.