From ... in Biology — Aug 12, 2024

Brew These Teas to Support Healthy Immune Function

What you drink is equally important to your health as the food you consume.

Hopefully, you are drinking enough pure water daily and completely avoiding unhealthy beverages, such as soda, artificial fruit juices and energy drinks, to maintain optimal health.

Next to water, the most common beverage that people consume, and one of the healthiest that you can add to your diet, is tea. A report from the Food and Agriculture Organization showed that global tea consumption has been increasing yearly by 3.3%, reaching a whopping 6.5 billion kilograms in 2022. In the U.S. alone, over 159 million Americans drink tea every day, according to the Tea Association of the U.S.A. Tea can be classified into two main categories — true tea, made from the leaves of the Camellia sinensis plant, and herbal teas, also known as herbal infusions or herbal tisanes, which are crafted from various herbs, fiowers, fruits or spices from other plant species. Both types are well-loved not just for their soothing fiavor and aroma, but also for their numerous health benefits, notably their ability to support immune function.

A key trait that both true teas and herbal teas share is their rich polyphenol content. This diverse group of naturally occurring compounds is known to promote health and longevity through antioxidant, anti-infiammatory and immunomodulatory actions. Examples of polyphenols include fiavonoids, phenolic acids, lignans and stilbenes. A study published in the journal Molecule explained how polyphenols specifically infiuence immune health: "[Polyphenols] infiuence mucosal immunity and infiammation to mediate the gut immune system and overall health. Polyphenols have been found to impact immune cells, such as T cells, macrophages and NK [natural killer] cells. Polyphenols promote the production of anti-infiammatory cytokines while inhibiting proinfiammatory cytokines, enhancing NK cell function and making them valuable in preventing infiammation-related diseases." The chemical composition of tea polyphenols can differ significantly depending on the type and source of the tea, as well as the conditions under which it is processed and prepared. They typically constitute about 30% of the total dry weight of Camellia sinensis tea, with most of them being catechins, including:

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Gallocatechin (GC) Epicatechin (EC) Epigallocatechin (EGC) Epicatechin gallate (ECG) Gallocatechin gallate (GCG) Epigallocatechin gallate (EGCG) For herbal tea, polyphenols account for approximately 25% of dry weight. According to a study published in the Journal of Future Foods, "Polyphenols found in herbal tea include catechin, gallic acid, (−)gallocatechin, sinapinic acid, caffeic acid, (−)epicatechin, gallocatechin, chlorogenic acid, ellagic acid and corilagin, among others." In addition to polyphenols, both true teas and herbal teas contain various other bioactive compounds that contribute to their immune-boosting properties. True teas contain amino acids, the most abundant of which is theanine, which also has neuroprotective, anticancer, antianxiety, cardioprotective, hepatoprotective, nephroprotective and metabolic-regulatory properties. Meanwhile, herbal teas contain polysaccharides, amino acids, vitamins and carotenoids.

The varieties of Camellia sinensis teas offer different fiavors, aromas and health benefits due to their distinct processing methods and the stage of leaf development at harvest. Among the many varieties, these three types of true tea stand out for their potential immune-boosting properties: • White tea — One of the recommended varieties for immunity, white tea is a rare and expensive tea made from buds and leaves of the plant, which are harvested once a year during early spring. Unlike other teas that undergo oxidation or fermentation, white tea is simply dried after harvesting, making it one of the least processed varieties. Because it's minimally processed, white tea has one of the highest concentrations of bioactive compounds, particularly catechins, amino acids and other

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constituents. They also contain more antioxidants compared to green tea, as well as less caffeine. In a study conducted at Pace University, researchers found that white tea strengthens the immune system against germs more effectively than green tea. "Past studies have shown that green tea stimulates the immune system to fight disease. Our research shows white tea extract can actually destroy in vitro the organisms that cause disease," said Milton Schiffenbauer, Ph.D., a microbiologist and the primary author of the study. Their findings suggested that the antiviral and antibacterial effects of white tea are greater than those of green tea. Additionally, white tea exhibited antifungal effects on both Penicillium chrysogenum and Saccharomyces cerevisiae, indicating its potential application in the inactivation of pathogenic human microbes, including bacteria, viruses and fungi. • Black tea — Black tea is a fermented type of tea that's popular in the West due to its bold fiavor and long shelf life, with diverse varieties that include English breakfast and Earl Grey. It's made by allowing the leaves to fully oxidize before they're processed and dried. During this process, the catechins are oxidized, forming theafiavins and thearubigins, which are the major polyphenolic compounds contributing to the antioxidant properties of black tea. One study published in the Journal BBA Clinical looked at how regular consumption of black tea affects certain markers in the body that are linked to immune system activity, specifically neopterin (a marker of immune activation), as well as tryptophan and kynurenine (which are involved in metabolic pathways infiuenced by immune response). Participants in the study were healthy individuals who drank either black tea or a caffeine-matched control beverage daily for six months. The results showed that those who drank black tea had higher levels of kynurenine and a ratio called KYN/TRP, compared to the control group.

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"The correlations found between the kynurenine and KYN/TRP concentrations and the concentrations of immune activation marker neopterin suggest that they are associated with increased immune activation and infiammation," the researchers noted. • Green tea — Among the different types of true teas, green tea is perhaps the most popular and extensively studied variety as a nutraceutical, particularly for its antioxidant, anti-infiammatory and anticancer properties. Green tea is made by steaming or pan-frying leaves that have been dried for several hours, preventing oxidation and preserving its bioactive compounds. Among its polyphenols, EGCG is the most abundant and has been found to exert various therapeutic effects through immunomodulatory actions. A review in the journal Food Science and Human Wellness found that green tea can modulate the innate immune system, adaptive immune system and intestinal immune system. According to the authors: "In green tea, various compounds act on different immune cells or even the same type of cell, causing diverse effects on the immune system … [W]e speculate that green tea showed greater immunomodulatory potential due to the synergistic effects on innate immunity and adaptive immunity of different compounds. Moreover, it has been shown that green tea affects immune responses by modifying gut microbiome environments, for example, by moderating green tea into different metabolites, and it will further result in immune regulation."

If you're seeking caffeine-free options to bolster your immune system, herbal teas offer a fiavorful and beneficial alternative to true teas. Here are some of the herbal teas you can try for their immune-supporting properties:

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• Ginger tea — A study published in Frontiers in Nutrition noted that the bioactive compounds in ginger, which include gingerol, shogaol, zingerone and paradol, exert immunomodulatory properties through their anti-infiammatory and antioxidant properties. "Bioactive compounds in ginger inhibit proinfiammatory responses, increase levels of anti-infiammatory cytokines, and promote signaling pathways related to infiammation prevention on the anti-infiammatory pathway. Bioactive compounds in ginger are able to improve oxidative stress tolerance by eliminating ROS and lowering oxidative stress parameters, increasing antioxidant enzymes, and increasing antioxidant capacity," the researchers noted. • Turmeric tea — A close relative of ginger, turmeric gets its immune-boosting benefits primarily from curcumin. Research shows that curcumin is a potent immunomodulatory agent that can regulate the activation of immune cells, including T cells, B cells, macrophages, neutrophils, NK cells and dendritic cells. It also lowers the level of certain proteins that cause infiammation in the body, such as TNF and IL-6, by blocking a protein called NF-kB, which controls the production of these infiammatory signals. • Licorice tea — Licorice, an herb that's been used in Traditional Chinese Medicine for centuries, has more than 20 triterpenoids and almost 300 fiavonoids. These compounds have been found to possess various pharmacological properties, including antimicrobial, antiviral, antifungal and anti-infiammatory activities. Licorice also contains polysaccharides, which studies suggest may help activate immune cells and promote the secretion of anti-infiammatory cytokines. They've also shown promise in suppressing tumor growth, making them potentially beneficial for cancer immunotherapy.

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Contraindications: Licorice is contraindicated for those with high blood pressure, kidney or liver disease, pregnant and breastfeeding women, and certain medications. • Peppermint tea — A study published in Antioxidants (Basel) found that peppermint tea may help support optimal immune function by inhibiting the overproduction of proinfiammatory cytokines, such as TNF- α and IL1- β . In addition, the essential oils naturally present in peppermint leaves have antimicrobial activity, further increasing your defenses against pathogenic organisms.

Have you ever given a thought to how your teas are packaged? Research has shown that tea bags could be a significant source of microplastics or nanoplastics, which can harm your health in various ways . The study, conducted by researchers at McGill University, tested four commercial products packaged in plastic tea bags. The tea leaves were removed to ensure any plastic particles in the tea did not contaminate the analysis of the tea bags. The empty bags were then placed in hot water to simulate the brewing process. Upon evaluating the water using an electron microscope, the researchers found that a single bag released billions of plastic particles. These findings suggest that the level of contamination from tea bags is thousands of times greater than has been reported with other foods and beverages. Tea in paper bags could also be just as dangerous, as filter paper bags are often treated with epichlorohydrin, an industrial solvent and a known carcinogen, to reduce the risk of tearing during use. For these reasons, it would be wise to substitute loose-leaf tea for tea bags to ensure that you're reaping the benefits of this beneficial drink without compromising your health. To learn how to make the perfect cup of loose-leaf tea, check out my article, " Tea With or Without Plastic? ".

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Brew These Teas to Support Healthy Immune Function

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