According to popular Chinese legend, the discovery of the tea attributed to the Chinese emperor Shen Nung occurred by chance when the leaves of a certain plant were deposited on a glass of boiling water. Tea is a traditional infusion made from the leaves of the Camellia sinensis plant, however, black tea is obtained by the fermentation of the leaves of the same plant.
As a consequence of the fermentation process, black tea presents a darker color together with a different flavor and appearance. From the nutritional point of view, black tea contains a higher content of caffeine and is richer in minerals such as zinc, calcium, chromium, magnesium, manganese, iron, potassium, phosphorus, fluoride and aluminum with respect to green tea (1 ).
The presence of flavonoids and polyphenols in its composition, suggests that it may have beneficial effects on health. However, regardless of whether these beneficial effects can be demonstrated, globally, black tea is the most consumed, and this will remain as consumers drink black tea for its peculiar aroma and flavor.
Identify the main benefits associated with a consumption maintained over time of black tea and, on the other hand, check based on other research if these effects have been demonstrated in humans.
MATERIAL AND METHODS
A bibliographical search was carried out in Pubmed, using the keywords "black tea"
The main effects of tea are due to its antioxidant properties. It is thought that the major polyphenols in black tea are theaflavins and catechins that are also the most active components. These compounds act by inhibiting and eliminating free radicals and acting as chelating agents for metal ions. In addition, black tea theaflavins may influence the activation of transcription factors such as NF-kB (nuclear factor enhancer of the kappa light chains of activated B cells). Finally, tea theaflavins can act as inhibitors of oxidative enzymes such as xanthine oxidase or the enzyme nitric oxide synthase (2, 3).
Human studies have been conducted to evaluate the consumption of black tea on cardiovascular risk factors, although these have been limited to a few months (4).
The conclusions of this study have not been positive or conclusive since no significant statistical effects were found in the evaluated biomarkers (lipids, hemoglobin, inflammatory markers and oxidability of lipoproteins).
Human studies are currently underway to evaluate the properties of black tea in reducing body weight. This study has enormous potential because obesity is one of the most prevalent diseases worldwide and continues to increase over the years. The effect on obesity would be in the polyphenols of black tea, since they would inhibit the digestion and absorption of lipids and saccharides, while in green tea its anti-obesity properties would be due to an effect on the gut microbiota (5).
Most of the studies that have been carried out to date to evaluate the biological potential of the polyphenolic compounds present in black tea have been carried out in vitro or in very limited human trials. Therefore, long-term studies are required to establish a safe dose of black tea before giving a conclusive recommendation to the population.
Sang S, Lambert JD, Ho CT, Yang CS. The chemistry and biotransformation of tea constituents. Pharmacol Res. 2011; 64 (2): 87-99.
Łuczaj W, Skrzydlewska E. Antioxidative properties of black tea. Prev Med.2005; 40 (6): 910-8.
Frei B, Higdon JV. Antioxidant activity of tea polyphenols in vivo: evidence from animal studies. J Nutr. 2003; 133 (10): 3275S-84S.
Mukamal KJ, MacDermott K, Vinson JA, Oyama N, Manning WJ, Mittleman MA. 6-month randomized pilot study of black tea and cardiovascular risk factors. Am Heart J. 2007; 154 (4): 724.e1-6. 3.
Pan H, Gao Y, Tu Y. Mechanisms of Body Weight Reduction by Black Tea Polyphenols. Molecules. 2016; 21 (12).