Yunnan is the native region of tea trees, serving as the origin for various teas worldwide, with most tracing back to Pu-erh tea-producing areas in Yunnan. As one of Yunnan's iconic products, Pu-erh tea has long been highly sought after in the market. Meanwhile, as research on Pu-erh tea deepens, people are gaining new insights into these leaves steeped in tea bowls for centuries. Recently, discussions about Pu-erh tea have quietly gained momentum. A reporter interviewed Sheng Jun, a professor at Yunnan Agricultural University and Vice Chairman of the Chinese Society for Microbiology, on related topics.

~~How do we define Pu-erh tea?

Sheng Jun: The national standard defines Pu-erh tea as tea made from sun-dried green tea leaves of Yunnan large-leaf species within the protected geographical indication area, processed using specific techniques to achieve unique quality characteristics. Based on processing methods and quality features, Pu-erh tea is categorized into raw Pu-erh tea and ripe Pu-erh tea.

~~Why did you choose to study Pu-erh tea?

Sheng Jun: Yunnan has two special sets of data related to health and longevity. First, Yunnan is one of China's five longevity zones, with the longevity areas coinciding with regions where Dai ethnic groups, who consume Pu-erh tea, are concentrated—such as Dehong Luxi and Xishuangbanna's Jinghong and Menghai. Second, Yunnan ranks last in mortality rates for four types of cancer (liver, stomach, colorectal, and leukemia) in China's three retrospective surveys on cancer mortality. These millennia-old statistical data provide scientists with critical clues and evidence for researching human longevity and identifying cancer-preventive foods and patterns.

~~As people's understanding of Pu-erh tea grows, it is no longer just a beverage. Based on your research, what lesser-known benefits does Pu-erh tea offer?

Sheng Jun: Due to the involvement of multiple beneficial microorganisms in tea fermentation, ripe Pu-erh tea develops many unique compounds, forming its characteristic functional qualities. Theabrownin, a key active component, is a signature bioactive factor in ripe Pu-erh tea. Theabrownin is a macromolecule formed through the polymerization of tea polyphenols, proteins, and polysaccharides under specific temperature, humidity, and microbial conditions, facilitated by microbial enzymes and tea polyphenol oxidase. Retaining functional groups of tea polyphenols, theabrownin preserves many of their benefits—such as antioxidant, anti-tumor, and antimicrobial properties—while adding new functions. For example, theabrownin in Pu-erh tea strongly binds fats, inhibiting absorption and significantly reducing LDL cholesterol. It also complexes with caffeine, minimizing sleep disruption for most people.

Additionally, recent research by Luo Ying et al. shows that Pu-erh tea effectively prevents formaldehyde-induced cell death in wild-type mouse embryonic fibroblasts, suggesting its potential in mitigating formaldehyde-related biological hazards.

~~Many claim Pu-erh tea should not be consumed excessively, as it may leach calcium from the body. Does Pu-erh tea really cause calcium loss?

Sheng Jun: Latest research from Australia, published in the American Journal of Clinical Nutrition, indicates that tea consumption reduces bone loss and osteoporosis. The study found that regular tea drinkers, especially elderly women, have higher bone density and mineral content with less bone density loss compared to non-drinkers. Taiwanese researchers discovered that drinking two cups of tea daily—whether black, green, oolong, or Tieguanyin—for at least six years strengthens bones. Studies suggest tea polyphenols may mimic estrogen, counteracting bone loss. Professor Shao Wanfang of Yunnan Agricultural University observed no changes in blood calcium levels in rats fed Pu-erh tea over three months.

Professor Chen Liying's team at Jilin Academy of Traditional Chinese Medicine studied tea's effects on bone density and estrogen in ovariectomized rats. Results showed that rats fed black or Pu-erh tea maintained estrogen levels and prevented bone density loss due to estrogen reduction. This animal study explains global observational findings on tea's role in preventing osteoporosis.