Black tea has long been attributed with numerous health benefits. There is now increasing evidence that one of the most widely consumed beverages globally might be able to severely reduce the risk of developing a number of disease conditions across the board. Some of the most prominent include boosting overall antioxidant content, controlling diabetes, reducing weight gain, improving heart health by reducing blood pressure, acting on depression, and boosting the immune system.
The tea comes from the beloved plant, Camellia sinensis. Tea generally comes in many forms including green tea, white, pu-er, English Breakfast, Earl Grey, Yorkshire (actually really strong tea in my book) and so on.
Black tea is one of the strongest types of tea in terms of flavour and is higher in caffeine than other types of tea. It also contains a host of antioxidants amongst myriad other compounds that are not so common in other teas. Currently, about 78% of all tea drunk is black and so it deserves especial attention (Li et al., 2013). Many of the properties of tea including green tea and other tea extracts can be extended to black tea and vice versa but it is worth honing in on this particular black form.
Black tea is a more heavily oxidised product of tea leaf fermentation. Many of the components in tea are ones that often get cited for their specific properties. We have in tea various theaflavins and thearubigins along with catechins. For many US citizens and indeed for many others who drink tea, it is their only sources of compounds like flavan-3-ol and flavonol (Song & Chun, 2008).
A lot of authors have reviewed the benefits of black tea as well as other types of tea but it’s worth checking out the major reviews on research (Sharma & Rao, 2009; Hayat et al., 2015).
Antioxidant Benefits
Antioxidants have many strong claims to be highly beneficial in health. If they are present in the body they will mop up free radicals which in turn reduces the potential for damaging cells which in turn means a real decrease in developing chronic diseases. The types of chronic disease we are discussing are cancers, rheumatoid arthritis, metabolic diseases and so on.
Tea is full of antioxidants and back in 2003 in the Journal of Nutrition, a number of studies were cited showing how tea generally, let alone black tea was important in human clinical studies.
Part of the reason for black tea’s antioxidant benefit is the level of flavonoids which are known to be strong radical scavengers. If you drink any tea there is observed a significant increase in the plasma antioxidant content in humans overall about 1 hour after consuming the beverage. The level of tea drunk which might be between 1 to 6 cups per day is significant and there is a dose dependent effect too.
Back in 2003 it was speculated that an enhanced blood antioxidant potential produced a reduction in the levels of oxidation damage to important biomolecules such as fats and DNA. The reduction in damage was apparently felt almost immediately in the gut but many of the benefits could soon be seen around the body soon after drinking tea (Rietveld & Wiseman, 2003).
Other antioxidant components which should be widely considered include the theaflavins and thearubigins. We also have catechins and epigallocatechin. The flavonoids can also chelate heavy metal ions. The theaflavins are known to activate transcription factors as well as inhibit the activity of proxidation enzymes such as xanthine oxidase and nitric oxide synthase.
Subsequent human studies have established links for many of these antioxidant effects and its worth now considering what these are.
Reducing The Risk Of Diabetes
Type 2 diabetes is a major health condition and risk for many other diseases. If it is left untreated then the risk of heart disease, stroke and other diseases is escalated. The level of diabetes globally is staggering and now runs into hundreds of millions of people globally.
Black tea is generally drunk unsweetened so the absence of sugar means there is no immediate stimulus for insulin to be released to deal with any spike in blood sugar level.
At the Tianjin Key Laboratory in China recently, researchers looked at the polysaccharide levels of green, oolong and black teas. Their interest was in those polysaccharides that might help in diabetes management. We know that fibre which includes starch, pectin, soluble fibres etc. can help suppress or retard the absorption of glucose. In this case, of all the three teas, the polysaccharides in black tea had most of the glucose-inhibiting benefit. As with antioxidants generally, the polysaccharides had a mopping -up activity on free radicals.
At the cellular level there is plenty of evidence to suggest that many of the compounds in black tea can improve resilience to diabetes. One of the key compounds in the diabetes story is epigallocatechin gallate (ECGC) which is found in other plant products and possessing similar benefits.
Heart Benefits
Hypertension
In 2012 there was a six month study published by researchers at the University of Western Australia in conjunction with Unilever and the National Health and Medical Research Council of Australia. The study was published in the Archives of Internal medicine. That study found that people who drank black tea through the day also benefited from a slight reduction in their blood pressure (Hodgeson et al., 2012).
The study looked at 95 Australians between the ages of 35 and 75. They were recruited to drink either three cups of black tea or another beverage of similar taste and caffeine content. There was no tea involved. The drinking tea study lasted six months. Before the study started, the participants’ blood pressure throughout the day was recorded at 121/172 millimeters of mercury (mm Hg). Blood pressure readings less than or equal to 120/180 mm Hg are considered normal. the top number is the systolic blood pressure and the lower number is the diastolic pressure. It seems after the 6 month period that the tea drinker’s blood pressure dropped by just 2 or 3 mm Hg compared to those who did not drink tea. It seems a very small drop to be honest but over a longer term period of tea drinking might well be highly significant as a benefit. There are other studies which suggest that there is a link between components in tea and healthier blood vessels which covers elasticity and ability to cope with sudden increases in blood pressure.
So it seems we now have a clear link between drinking black tea and a small drop in blood pressure but what this mechanism is depends on further investigative research.
Black Tea And Benefits In Reducing Cancer Development
Whilst cancer is still one of the major killers and not all can be prevented, it is still feasible to believe that the incidence can be reduced if certain foods were ingested. Much credence has been given to the polyphenols in black tea which may prevent cancers forming but there is still plenty of research to be conducted to really nail this proof (Beltz et al., 2006).
At the molecular level there are several targets that black tea is claimed to influence and they include COX-2, 5-LOX, AP-1, JNK, STAT, EGFR, AKT, Bcl2, NF-κB, Bcl-xL, caspases, p53, FOXO1, TNFα, PARP, and MAPK. It’s worth reading the article by Singh to see how the antioxidant molecules in black tea can affects all these different molecules which are intimately linked with cancer development. How significant each interaction is happens to be part of considerable research (Singh et al., 2017).
It can not be said that black tea or indeed any tea cures cancer but there is a distinct possibility it reduces the formation of cancer cells.
Black Tea And Weight Loss
We’ve discussed at length some of the work on black tea in regards to weight loss but it’s worth looking at some of the other aspects of influence too in obesity management. We are well aware of particular polyphenols that have potential in both preventing and treating obesity. One of the most effective ways to achieve weight loss is to reduce fat adsorption in the body. At the biochemical level any fats (triacylglycerols) which are ingested are turned into micelles in the duodenum of the intestine. They must be converted to fatty acids and 2‐monoacylglycerol using the enzyme pancreatic lipase. These micelles are then absorbed by epithelial cells in the small intestine (Lowe, 1994).
To inhibit pancreatic lipase means that the adsorption of triacylglycerol can be delayed (Gu et al., 2011) which they found when administering cocoa extracts. It seems theaflavins and catechins will inhibit pancreatic lipase so the potential for reducing weight gain or encouraging weight loss is also in tea (Nakai et al., 2005; Kusano et al., 2008).
One other means by which weight gain is prevented is to alter the gut microbiome. This area of research is still in its infancy but there are studies with animals that show the polyphenols from both black and green tea could induce weight loss by changing the gut microbiota. There is also a second means which is to increase hepatic 5′adenosylmonophosphate-activated protein kinase (AMPK) phosphorylation.
The study was published in the European Journal of Nutrition (Henning et al., 2018). The scientists fed four groups of mice different diets: (1) a high-fat, high-sugar diet; (2) a high-fat, high-sugar diet supplemented with green tea extract; (3) a high-fat, high-sugar diet supplemented with black tea extract; (4) and a low-fat, high-sugar diet.
After four weeks, the researchers found that the mice who had the green tea and black tea extracts lost the same amount of weight as those who had the low-fat diet.
The intestines of these mice was examined. The researchers looked at the bacteria and checked the liver for levels of fat deposits. The mice who consumed the black and green teas had less of the bacteria associated with the obesity and more of the bacteria linked with lean body mass. The mice that consumed the black tea had more Pseudobutyrivibrio bacteria and intestinal formation of short-chain fatty acids (SCFA).
That study showed in their press release that “both black and green tea polyphenols induced weight loss in association with alteration of the microbiota and increased hepatic AMPK phosphorylation.”
They also hypothesized that black tea polyphenols “increase pAMPK through increased intestinal short-chain fatty acid production, while green tea polyphenols increased hepatic AMPK through green tea polyphenols present in the liver.”
Black Tea And Mental Health
Whilst black tea is referenced heavily in alleviating many issues associated with poor mental health there is one major investigative article that suggests regular tea consumption of any sort helps reduce depression. The pathways and mechanisms are probably highly interactive but research at the South China Agricultural University in Guangzhou in China has attempted to put all the various mechanisms into context (Rothenberg & Zhang, 2019).
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References
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Hayat, K., Iqbal, H., Malik, U., Bilal, U., Mushtaq, S. (2015) Tea and its consumption: benefits and risks. Crit. Rev. Food Sci. Nutr. 55(7) pp. 939–954. (Article)
Henning, S. M., Aronson, W., Niu, Y., Conde, F., Lee, N. H., Seeram, N. P., … & Hong, J. (2006). Tea polyphenols and theaflavins are present in prostate tissue of humans and mice after green and black tea consumption. The Journal of Nutrition, 136(7), pp. 1839-1843.
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Henning, S.M., Yang, J., Hsu, M. et al. (2018) Decaffeinated green and black tea polyphenols decrease weight gain and alter microbiome populations and function in diet-induced obese mice. Eur. J. Nutr. 57: 2759. (Article)
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