Global tea consumption is estimated to be around 6.7 billion kilograms per year, with around 3 billion people drinking tea. Tea from Camellia sinensis is the world's second most consumed beverage after water.
Various types of tea are categorized based on the degree of fermentation during processing. Each of the four types has a different chemical composition and health benefits: nonfermented (green) tea, partially fermented (oolong) tea, fully fermented (black) tea, and post-fermented (Puer) tea.
Tea contains over 4,000 phytochemicals, many of which have health benefits. Unlike green tea, fermented teas contain catechins that convert into oxidized compounds such as thearubigins and theaflavins.
A recent study examined how different types of coffee and tea affect blood sugar and fat levels after eating. Eighteen healthy young adults participated. After fasting overnight, they drank water, freeze-dried coffee, spray-dried coffee, green tea, black tea, or oolong tea with a breakfast of an egg and fried dough sticks. Blood samples were taken over three hours (1).
Results showed that green tea significantly lowered triglyceride levels compared to black and oolong tea. Green and oolong tea also reduced total cholesterol more than black tea. Oolong tea lowered both good (HDL) and bad (LDL) cholesterol compared to black tea. The study showed that drinking tea may help control triglyceride and cholesterol levels after high-fat meals, highlighting its potential benefits for heart health (1).
One study examined the effects of green tea extract combined with brisk walking on cholesterol levels and liver function in overweight and obese men. Twenty-four participants were randomly assigned to either the green tea extract group or a placebo group for 12 weeks, with a 4-week follow-up. They completed four 60-minute walking sessions per week and took two daily tablets (150 mg green tea extract or placebo) (2).
After 12 weeks, the green tea extract group showed a significant reduction in LDL (bad) cholesterol and total cholesterol (p < 0.01) compared to the placebo group. They also had a significant decrease in aspartate aminotransferase (a liver enzyme) (p < 0.01), while the placebo group showed no changes. The study showed that green tea extract combined with brisk walking improved cholesterol levels and liver function, with greater benefits than walking alone (2).
The walking program that was included in the study was four 60-minute sessions per week, with a 5-minute warm-up and cool-down. Since all participants were inactive, overweight, or obese men, the program started with a lower intensity (50%- 65% of maximum heart rate) for the first three weeks. The intensity was then gradually increased to 65%- 80%. The maximum heart rate (HRmax) was calculated using the formula HRmax = 220—age (2).
Each participant wore a heart rate monitor and a pedometer to track their heart rate and step count during exercise. During the study, they took two tablets daily (either green tea extract or a placebo)—one after breakfast and one after dinner—with a cup of water (2).
A randomized, double-blind, placebo-controlled trial examined the impact of green tea extract on minerals, body weight, cholesterol, blood sugar, and antioxidant levels in 46 obese patients who took either 379 mg of green tea extract or a placebo daily for three months. Measurements were taken at the start and end of the study, including body weight, blood pressure, antioxidant levels, and blood levels of lipids, glucose, and minerals (3).
After three months, the green tea group showed reduced BMI, waist circumference, total cholesterol (from 5.22 ± 0.97 to 4.86 ± 0.94 mmol/L), LDL (bad) cholesterol (from 3.44 ± 1.03 to 3.02 ± 0.96 mmol/L), and triglycerides (from 1.46 ± 0.49 to 1.23 ± 0.41 mmol/L). They also had increased antioxidant levels and higher zinc levels. Blood sugar and iron levels were lower in the green tea group compared to the placebo, while HDL (good) cholesterol and magnesium were higher. These findings suggest that green tea extract improves mineral balance and supports weight management, cholesterol levels, and antioxidant status in obese individuals (3).
While studies have shown that green tea may help improve heart health by lowering blood fat levels, most studies have been small and short-term. One study tested the effects of green tea extract with high epigallocatechin gallate (EGCG) on blood lipids in healthy postmenopausal women for a longer term (4).
Researchers conducted a double-blind, randomized, placebo-controlled 12-month trial with 1,075 women, who took either green tea extract (1315 mg catechins, 843 mg EGCG) or a placebo daily. Blood lipid levels (total cholesterol, HDL, LDL, and triglycerides) were measured at the start, 6 months, and 12 months (4).
The results showed that green tea extract significantly reduced total cholesterol (-2.1% vs. +0.7%), LDL cholesterol (-4.1% vs. +0.9%), and non-HDL cholesterol (-3.1% vs. +0.4%). HDL cholesterol stayed the same. The cholesterol-lowering effect was strongest in women with high initial cholesterol (≥200 mg/dL). Triglycerides increased by 3.6% in the green tea extract group but dropped by 2.5% in the placebo group. Triglyceride increases were mainly seen in obese women and those taking statins. The study concluded that green tea extract helped lower total and LDL cholesterol, especially in women with high cholesterol, but slightly increased triglycerides (4).
One study compared the health benefits of catechin-enriched green tea (CEGT) and catechin-enriched oolong tea (CEOT) in individuals with mild high cholesterol. Sixty participants with cholesterol levels between 180 and 220 mg/dL were divided into three study groups: CEGT, CEOT, or a placebo. The participants were instructed to drink 2 × 300 mL of CEGT (780.6 mg of catechin), CEOT (640.4 mg of catechin), or placebo beverage daily for 12 weeks (5).
Drinking CEGT and CEOT significantly decreased (p < 0.05) the body weight, fat, BMI, lipid peroxidation as well as lipid profile (TC, LDL-c, HDL-c, and TG). Also, intervention with CEGT and CEOT significantly improved (p < 0.05) the oxidative indices (TEAC and GSH) and antioxidant enzymes (SOD, CAT, GPx, and GR). Moreover, ultrasound examination endorsed the hepatoprotective activity of CEGT and CEOT by reverting mild fatty liver to the normal hepatic condition because of antioxidant and hypolipidemic activities (5).
Overall, both teas provided similar antioxidant and liver-protective benefits. However, CEOT was more effective at lowering cholesterol than CEGT or the placebo, making it a promising option for improving health in individuals with mild hypercholesterolemia (5).
One study determined the anti-obesity effects of oolong tea on diet-induced overweight or obesity. Overweight or obese subjects (n=102) ingested 8 g of oolong tea daily for 6 weeks (6).
70% of the severely obese subjects showed a decrease of more than 1 kg in body weight, including 22% who lost more than 3 kg. Similarly, 64% of the obese subjects and 66% of the overweight subjects lost more than 1 kg during the experiment, and the subcutaneous fat content decreased in 12% of the subjects. Moreover, the plasma levels of triglyceride and total cholesterol of the subjects with hyperlipidemia were remarkably decreased after ingesting oolong tea for 6 weeks (6).
The authors concluded that Oolong tea could decrease body fat content and reduce body weight by improving lipid metabolism. Chronic consumption of oolong tea may prevent obesity (6).
A blinded randomized crossover study examined how black tea affects cholesterol in adults with mildly high cholesterol. Participants (7 men and 8 women) followed a controlled diet while drinking either tea or a placebo (3 weeks/treatment) that matched tea in color and taste. In a third period, caffeine was added to the placebo in an amount equal to that in the tea (7).
Drinking five cups of tea daily lowered total cholesterol by 6.5% and LDL (bad) cholesterol by 11.1% compared to a caffeine-added placebo. Tea reduced total cholesterol by 3.8% and LDL cholesterol by 7.5% compared to a caffeine-free placebo, while other cholesterol-related measures remained unchanged. Tea did not affect antioxidant levels. This study showed that adding tea to a low-fat diet could significantly lower cholesterol and may help reduce the risk of heart disease, but it did not impact antioxidant status (7).
The authors discussed that most studies have found that drinking black tea does not improve antioxidant levels in the blood, though some research suggests it may temporarily boost antioxidant activity. Long-term tea consumption has been linked to reduced LDL oxidation. However, some prior trials found no effect on cholesterol levels. The authors speculated that since those previous studies did not control for diet, they might have missed small changes in antioxidants and blood lipids as what they found in this study (7).
One study examined how daily Puer tea extract affects body weight, fat composition, and lipid levels in a non-Asian population without dietary restrictions. In a 20-week randomized trial, 59 overweight or mildly obese participants with high cholesterol (≥220 mg/dL) took either Puer tea extract (3 g/day) or a placebo. Researchers measured body composition, blood lipids, fasting glucose, and appetite at regular intervals (8).
Puer tea extract led to significant weight loss compared to the placebo (~2% fat percentage reduction, p < 0.05). Fat reduction was observed in the arms, legs, and belly area, though differences between groups were not significant. Puer tea extract also improved lipid levels, reducing cholesterol (~10 mg/dL reduction), triglycerides (~30 mg/dL reduction), and very small-density lipoproteins, with levels normalizing by week 8 (p < 0.08). There were no significant effects on fasting glucose or inflammation markers. A slight, temporary appetite reduction was noted in the Puer tea extract group (p < 0.1). The results showed that daily Puer tea extract consumption was linked to weight loss, lower BMI, and better lipid profiles (8).
These studies illuminated the remarkable potential of various types of tea for lowering cholesterol levels and enhancing heart health. Hope that such convincing evidence may remind us of the immense benefits that nature offers in our wellness pursuits. Drinking tea as a powerful ally in our journey toward better cholesterol management and cardiovascular health.
References:
1. Zhang C, Zhang J, Li D, Hu X. Effects of coffee and tea on postprandial cardiometabolic risk factors in healthy individuals: a randomized crossover trial. Asia Pac J Clin Nutr. 2024 Mar;33(1):102-110. doi: 10.6133/apjcn.202403_33(1).0011. PMID: 38494692; PMCID: PMC11170016.
2. Zhang T, Li N, Chen SI, Hou Z, Saito A. Effects of green tea extract combined with brisk walking on lipid profiles and the liver function in overweight and obese men: A randomized, double-blinded, placebo-control trial. An Acad Bras Cienc. 2020 Nov 16;92(4):e20191594. doi: 10.1590/0001-3765202020191594. PMID: 33206794.
3. Suliburska J, Bogdanski P, Szulinska M, Stepien M, Pupek-Musialik D, Jablecka A. Effects of green tea supplementation on elements, total antioxidants, lipids, and glucose values in the serum of obese patients. Biol Trace Elem Res. 2012 Dec;149(3):315-22. doi: 10.1007/s12011-012-9448-z. Epub 2012 May 15. PMID: 22581111; PMCID: PMC3501173.
4. Samavat H, Newman AR, Wang R, Yuan JM, Wu AH, Kurzer MS. Effects of green tea catechin extract on serum lipids in postmenopausal women: a randomized, placebo-controlled clinical trial. Am J Clin Nutr. 2016 Dec;104(6):1671-1682. doi: 10.3945/ajcn.116.137075. Epub 2016 Nov 2. PMID: 27806972; PMCID: PMC5118731.
5. Venkatakrishnan K , Chiu HF , Cheng JC , Chang YH , Lu YY , Han YC , Shen YC , Tsai KS , Wang CK . Comparative studies on the hypolipidemic, antioxidant and hepatoprotective activities of catechin-enriched green and oolong tea in a double-blind clinical trial. Food Funct. 2018 Feb 21;9(2):1205-1213. doi: 10.1039/c7fo01449j. PMID: 29384173.
6. He RR, Chen L, Lin BH, Matsui Y, Yao XS, Kurihara H. Beneficial effects of oolong tea consumption on diet-induced overweight and obese subjects. Chin J Integr Med. 2009 Feb;15(1):34-41. doi: 10.1007/s11655-009-0034-8. Epub 2009 Mar 7. PMID: 19271168.
7. Davies MJ, Judd JT, Baer DJ, Clevidence BA, Paul DR, Edwards AJ, Wiseman SA, Muesing RA, Chen SC. Black tea consumption reduces total and LDL cholesterol in mildly hypercholesterolemic adults. J Nutr. 2003 Oct;133(10):3298S-3302S. doi: 10.1093/jn/133.10.3298S. PMID: 14519829.
8. Jensen GS, Beaman JL, He Y, Guo Z, Sun H. Reduction of body fat and improved lipid profile associated with daily consumption of a Puer tea extract in a hyperlipidemic population: a randomized placebo-controlled trial. Clin Interv Aging. 2016 Mar 24;11:367-76. doi: 10.2147/CIA.S94881. PMID: 27069360; PMCID: PMC4818050.
Photo by 五玄土 ORIENTO on Unsplash
Comentarios