With obesity affecting over a third of adults in the United States, identifying new weight loss strategies is a key priority for researchers. Tea, one of the most beloved drinks across the world, delivers a variety of health benefits beyond helping you stay hydrated. Black tea and green tea, two of the most popular types of tea, have been at the center of a long-standing debate regarding their health benefits, particularly in relation to weight loss. Both originate from the same plant, Camellia sinensis, but the way they are processed creates distinct differences in their appearance, taste, and nutritional value. This article delves into the nuances of black tea and green tea, exploring their unique properties, potential benefits for weight loss, and overall impact on health.
Origins and Processing
Both black and green tea originate from the same tea plant, Camellia sinensis, but they differ in how they are processed. Black tea is fully oxidized, or fermented, giving it a dark hue and bold flavor. Black tea leaves are first rolled and then oxidized (exposed to air), whereas green tea is unoxidized. This reaction causes black tea leaves to turn dark brown while green tea leaves remain green. Green tea leaves are quickly dried or steamed after harvesting to prevent oxidation, preserving their green color and delicate flavors. The different methods of processing impact the appearance, taste, and nutritional value of the tea as well.
Nutritional Profiles
Tea is brewed, which means that tea leaves are steeped in boiling water and then removed before drinking. So essentially, tea is flavored water, which means that like water, it contains no calories, sugar, fat, or protein on its own-though this will change if you add anything to the tea, such as milk, sugar, or honey. One thing that brewed black and green tea do deliver is caffeine. According to the Mayo Clinic, an 8-ounce cup of black tea contains 47 milligrams (mg) of caffeine, while an 8-ounce cup of green tea contains 29 mg. For comparison, an 8-ounce cup of coffee can deliver up to 96 mg of caffeine. Besides caffeine content, black tea and green tea also differ in how they are made. This allows for the existence of different nutrients and beneficial plant compounds in each type of tea.
Health Benefits of Black Tea
While green tea’s health benefits tend to get all the attention, black tea offers its own powerful advantages. Black tea may promote weight loss and other health benefits by changing bacteria in the gut. Black tea contains polyphenols and antioxidants that support heart and gut health. The most powerful of these are theaflavins, which develop during oxidation and therefore are not present in any other types of tea. According to research in Trends in Food Science & Technology, theaflavins work to protect cells from damage and injury, can block inflammation, and even fight viruses (hence the advice to sip tea when you’re sick). Black tea also contains flavonoids, another type of antioxidant that has been shown to support healthy blood pressure and cognitive function.
Black Tea and Weight Loss Mechanisms
Black tea polyphenols are the major components in black tea which reduce body weight. Black tea polyphenols are more effective than green tea polyphenols. Black tea polyphenols exert a positive effect on inhibiting obesity involving in two major mechanisms: (i) inhibiting lipid and saccharide digestion, absorption and intake, thus reducing calorie intake; and (ii) promoting lipid metabolism by activating AMP-activated protein kinase to attenuate lipogenesis and enhance lipolysis, and decreasing lipid accumulation by inhibiting the differentiation and proliferation of preadipocytes; (iii) blocking the pathological processes of obesity and comorbidities of obesity by reducing oxidative stress.
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Inhibiting Lipid and Saccharide Digestion and Absorption
Fat digestion is an interfacial process which depends on the adsorption of lipase on the surface of lipid droplets. The formation of emulsion droplets provides a surface for lipase adsorption which influences the anchoring of lipases, and plays an important role in the rate of lipid digestion. In a model system simulating small intestinal conditions, it was observed that black tea extract inhibited the emulsion of droplets and reduced the surface area. Black tea extract was more effective in changing the emulsion properties than green tea extract due to the thearubigins and theaflavins in black tea. It was also found that theaflavins inhibited the incorporation of 14C-labeled cholesterol into simulative dietary mixed micelles and increased their particle size. Adsorption of lipase on the surface of emulsified fat droplets causes a conformational rearrangement, and the enzymatic hydrolysis of triglycerides (TGs) by specific lipases occurs. Black tea polyphenols dose-dependently inhibited the activity of pancreatic lipase in vitro. Theaflavins with galloyl moieties inhibited the activity of pancreatic lipase in vitro. As the activity of lipase is inhibited by black tea polyphenols, much fewer hydrolysis products of fat will be absorbed into the plasma. Black tea polyphenols significantly alleviated the increase in serum glucose, total lipid, TG and phospholipid levels in rat models. The black tea polyphenols could increase the fecal fatty acid content, thereby preventing high-fat diet-induced obesity. Total lipid excretion increased after black tea extract intake in comparison with the control which indicated that black tea extract increased lipid excretion.
Promoting Lipid Metabolism
After being absorbed through the intestines, lipids are transported to liver cells, muscle cells or adipocytes through the lymph system. Lipids are mainly sent to liver cells, muscle cells and adipocytes. The lipids sent to liver cells are esterified to triglycerides, converted into very-low-density lipoprotein (VLDL), and released into the blood to transport endogenous-derived lipids. Lipids sent to muscle cells can be oxidized in the mitochondria for energy. Fat accumulation is controlled by the balance between lipogenesis and lipolysis. Lipogenesis is a metabolic process that converts simple sugars to fatty acids and synthesizes triglycerides through the reaction of fatty acids with glycerol. Lipolysis is the process in which triglycerides are hydrolyzed to generate glycerol and free fatty acids. Theaflavins are identified as novel mimics of insulin/IGF-1, acting on the phosphorylation of mammalian forkhead transcription factor family O1a (FOXO1a) and subsequently on the inactivation of the promoter of the phosphoenolpyruvate carboxykinase (PEPCK) gene. PEPCK is an important enzyme in hepatic gluconeogenesis. Fatty acid synthase (FAS) regulates the rate-limiting step in fatty acid synthesis. Theaflavins inhibit the activity and expression of FAS. AMP-activated protein kinase (AMPK) is an important therapeutic target for obesity treatment and a major target of theaflavins for their anti-obesity effect. Lin et al. proved that theaflavins significantly decreased lipid accumulation, reduced fatty acid synthesis, and promoted fatty acid oxidation in vitro and in vivo. Black tea suppresses adiposity via phosphorylation of AMPK and increases UCP-1 expression as a marker for the conversion of white to brown adipose tissue. Black tea polyphenols act on the nuclear receptors, in addition to their activation of AMPK, to influence glucose and fatty acid metabolism. Theaflavins have been reported to suppress the adipogenic differentiation of stem cells, the differentiation of preadipocytes to adipocytes and the proliferation of preadipocytes.
Potential Downsides of Black Tea
All that said, there are a few potential downsides to drinking black tea. Han notes that it contains the most caffeine of all types of tea, so if you’re sensitive to caffeine you may need to be mindful of how much you consume. Black tea can stain your teeth over time. Black tea may also reduce iron absorption in the body, especially iron from plant-based foods-but waiting an hour between drinking the tea and eating can diminish this effect, per Japanese research.
Health Benefits of Green Tea
If black tea boasts too strong of a flavor, green tea may be more your speed. And fortunately, this light, grassy tea delivers some health perks of its own. Green tea may play a role in certain types of cancer prevention, support healthy weight management, and promote heart and brain health. Research backs her up: The Frontiers in Nutrition study mentioned above also found that the more green tea you drink, the lower your risk of developing coronary artery disease, while a review in the British Journal of Nutrition found that drinking green tea regularly can lead to weight loss. It may promote slight increases in fat oxidation when consumed consistently. That perk comes from the EGCG, which has been found to turn white fat (the not-so-great kind) into brown fat (the metabolically active kind). Green tea catechins, the most powerful antioxidants in the brew, have been shown to impact the survival, growth, and proliferation of cancer cells. And the amino acid L-theanine can provide a brainpower and mood boost. L-theanine may support focus and promote calm alertness. Green tea is an excellent source of the potent antioxidant epigallocatechin-3-gallate (EGCG), which is responsible for many health benefits.
Green Tea and Weight Loss Mechanisms
Drinking green tea can help you lose weight thanks to its high catechins content. Catechins are another kind of antioxidants - particularly epigallocatechin gallate or EGCG. Research shows that EGCG can inhibit the breakdown of norepinephrine, a fat-burning hormone. The more norepinephrine in the body, the more your body can break down fat. EGCG is also suggested to have a synergistic effect with caffeine, which is also found in green tea. The EGCG catechins in green tea are also linked to better fat burning during exercise and rest. Other studies have linked EGCG to higher metabolic rates - the rate at which your body burns calories.
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Potential Downsides of Green Tea
Green tea carries the same potential downsides as black tea as far as the presence of caffeine and the ability to interfere with iron absorption. However, it does contain less caffeine and block iron absorption to a lesser degree than its oxidized cousin.
Black Tea vs. Green Tea: A Comparative Study
In a new study, scientists reveal how drinking black tea could be one such strategy. Researchers say that black tea may be just as effective as green tea for weight loss. But the new study indicates that black tea should not be disregarded; it may be just as effective as green tea for losing the pounds - it just works in a different way. Both black tea and green tea contain polyphenols. These are antioxidants that protect cellular structures - such as DNA and cell membranes - against damage from free radicals. Polyphenols from green tea are small enough to be absorbed into the bloodstream and body tissues, and studies have shown that they can alter the liver’s energy metabolism in a way that promotes weight loss. As Henning explains, “Our new findings suggest that black tea, through a specific mechanism through the gut microbiome, may also contribute to good health and weight loss in humans.”The team came to its findings by studying four groups of mice. Each group followed a different diet for a period of 4 weeks: a high-fat, high-sugar diet; a high-fat, high-sugar diet supplemented with green tea extract; a high-fat, high-sugar diet supplemented with black tea extract; and a low-fat, high-sugar diet. The researchers collected liver tissue samples from the rodents in order to measure fat deposits, and they also collected samples from the large intestine, which enabled them to assess bacterial diversity. At the end of the 4-week dietary intervention, the researchers found that both the green tea and black tea groups lost weight, and their weights became comparable with the low-fat, high-sugar diet group. The study also revealed that both tea groups experienced increases in gut bacteria related to lean body mass and decreases in gut bacteria associated with obesity. On further investigation, the researchers noticed that black tea and green tea affected the liver metabolism of rodents in different ways. Henning explains that the smaller green tea molecules are absorbed more easily, meaning they can reach the liver directly to affect energy metabolism. However, black tea molecules are too large to be absorbed in this way. Instead, they remain in the intestine, where they boost the growth of “friendly” gut bacteria and form metabolites that help to control liver energy metabolism. It was also found that the black tea group had higher levels of a bacteria called Pseudobutyrivibrio, which they suggest could play a role in the differing effects of green and black tea on energy metabolism. Overall, they believe that their findings indicate that black tea may be just as beneficial for health as the widely acclaimed green tea. For black tea lovers, there may be a new reason to keep drinking it.
Impact on Gut Microbiome
UCLA researchers have demonstrated for the first time that black tea may promote weight loss and other health benefits by changing bacteria in the gut. Previous studies indicated that chemicals in green tea called polyphenols are absorbed and alter the energy metabolism in the liver. The researchers also collected samples from the mice’s large intestines (to measure bacteria content) and liver tissues (to measure fat deposits). The new study also concluded that both green tea and black tea have different effects on liver metabolism. According to Henning, the molecules in green tea are smaller and can more readily be absorbed into the body and reach the liver directly, while black tea molecules are larger and stay in the intestine rather than being absorbed.
Which is Better for Weight Loss?
Both black tea and green tea are smart sips to incorporate into your diet if weight loss is your goal. Green tea may have a slight edge in supporting fat breakdown, particularly when consumed several times per day, while black tea can aid weight management by replacing high-calorie coffee drinks if taken plain and by helping reduce hunger levels due to its higher caffeine content.
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