The study was conducted by a team of researchers from the University of Tunis EL Manar and the University of Carthage in Tunisia and Université Paris Diderot in Paris. The research team sought to determine the effects of long-term consumption of green tea and black tea on the lipid digestion of rats fed with a high-fat diet. The rats in the experiment were given green tea decoctions, black tea decoctions, or a placebo for 10 weeks. They measured the fat excreted in feces, liver fat content, the weight of abdominal fat tissues, food intake, and body weight gain.
The major polyphenolic compounds of a 15-minute decoction of green tea were epigallocatechin gallate (EGCG), epigallocatechin (EGC), catechin, EGC-3-methyl gallate, epicatechin gallate ECG, vanillic acid ester, kaempferol 3-glycoside, and caffeine. On the other hand, theaflavins, caffeine, gentissic acid esters, gallic acid esters, catechin, EGCG, kaempferols, and quercetin were the major polyphenolic compounds found in the black tea decoction.
Results revealed that the 10-week consumption of green tea and black tea decreased lipid digestion by increasing fecal lipids and triglycerides excretion. Adipose tissue gains were also reduced, which is in line with the reduction of circulating leptin levels. In addition, the consumption of teas decreased body weight gain of rats fed with high-fat diet. However, black tea was found to be more efficient compared to green tea.
"Therefore, these beverages containing high amounts of TPC and caffeine could constitute a natural alternative in the prevention of obesity," the research team wrote.
Green tea versus black tea
Both green tea and black tea are made from the same plant called Camellia sinensis. However, they undergo different processes. Green tea leaves undergo minimal processing, while black tea undergoes an oxidation process known as fermentation. Both drinks provide many health benefits, although there may be slight differences.
When it comes to anti-cancer properties, green tea offers more than black tea. Green tea contains higher amounts of catechins, such as EGCG. EGCG regulates gene activity in cancer cells and might combat cancer growth.
Both black and green tea support cardiovascular health. According to a study published in the Journal of Biological Chemistry, the abundance of EGCG in green tea interacts with the cells lining the blood vessels and promotes autophagy, which is a physiological process that protects the cells from stress. It also helps regulate blood cholesterol levels. Meanwhile, black tea enhances blood vessel function in people with coronary heart disease, according to the Linus Pauling Institute. (Related: Green tea confirmed as a weight loss nutrient and heart health antioxidant.)
The caffeine levels of green and black tea differ. Black tea contains higher caffeine content with 42 to 72 mg per cup, while green tea contains between nine and 50 mg per cup. Caffeine temporarily boosts mental alertness, promote productivity, and help in weight loss. However, it can also keep a person up at night, which is why caffeine consumption should be limited.
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