Living longer with Tea ?

3 juin

For many years now, tea has been praised for its many benefits. Now, with a Chinese study released in January 2020, tea is hitting back even harder: tea is said to help you live longer! In the articles published on my blog Sciences Thé, the finding is often closer to nuance than to panacea. What does this study really show, and why is it interesting?

Antioxidant, anti “bad” cholesterol, tea has invited itself into all our bodies for better ... and for better! But never before has it been claimed that we can live “longer” by drinking tea.

But what do we mean by “live longer?”

Beyond these catchy terms relayed by the press, we need to talk about prevention, reducing the risk of disease occurrence. In this case, a Chinese study published in early 2020 focuses on the prevention of atherosclerosis, a cardiovascular disease. Research into cardiovascular disease is more necessary than ever, as it is responsible for 30% of global mortality and is the second leading cause of death in France. Atherosclerosis is a little-known name, yet it is the main cause of myocardial infarction, stroke and angina pectoris.

Atherosclerosis is a thickening of the lining of blood vessels, which can eventually become clogged or form blood clots. We are all at risk of contracting the disease, especially as we age and our blood vessel walls become stiffer. The main risk lies in the type of artery blocked: a clot in a leg artery will not have the same consequences as in the heart's aorta.

Atherosclerosis: a forced marriage between cholesterol and the immune system

The onset of the disease is highly dependent on each individual's lifestyle: sedentary lifestyle, smoking, chronic hypertension, diet, hypercholesterolemia. One of the keystones of atherosclerosis is cholesterol. Cholesterol is a lipid that is essential for the membrane of our body's cells. In the blood, cholesterol is carried by two types of protein: HDL (“good cholesterol”) and LDL (“bad cholesterol”). LDL, which carries cholesterol in the blood, can bind it to cells in the blood vessel wall. The problem is not the presence of LDL, but its quantity.

When there is an excess of cholesterol in the bloodstream, LDL particles can lead to the formation of fatty deposits in the blood vessels, known as fatty streaks. In cases where lifestyle or genetic factors promote disease, these deposits gradually thicken the vessel walls. While cholesterol buildup is a precursor to disease, it is not the only cause. Excess fat accumulation in the blood vessels damages the vascular cells. This triggers the production of reactive oxygen species (ROS), molecules that oxidize cholesterol. Once oxidized, cholesterol becomes toxic to cells and must be removed.

Oxidized cholesterol is detected by immune cells present in the blood or already located near the blood vessels. These immune cells, called macrophages, absorb the oxidized cholesterol to isolate it. They may also release inflammatory molecules to recruit more macrophages to the site of the fatty streaks.

When the accumulation of oxidized cholesterol becomes chronic, macrophages can no longer keep up. They begin to die, releasing both oxidized cholesterol and inflammatory molecules, leading to chronic inflammation. In an effort to contain the damage, vascular cells elongate and encapsulate the cholesterol-macrophage mixture. These fatty streaks then develop into large masses known as atherosclerotic plaques.

Over time, the vessel wall cells die, and immune activity becomes poorly regulated. Atheromas may rupture, tearing the vessel walls and triggering blood clots. This can block blood flow, causing a heart attack or stroke depending on the affected area.

From Study Design to Data Compilation

The most recent study on atherosclerosis, published last January, combined data from no fewer than four cohorts spanning from 1998 to 2015. A cohort refers to a group of individuals monitored under similar conditions. In this case, participants consumed tea regularly—or not—over a specific period.

The data from 113,848 individuals were gathered and analyzed. Over the course of long-term studies, participants may be excluded if they no longer meet the criteria: stopping tea consumption, death, development of unrelated diseases, or the discovery of family history with cardiovascular risks. Ultimately, the results of 100,902 individuals were included—making this the largest study ever conducted on tea consumption.

Participants were divided into two groups:

Those who drank tea at least 3 times per week
Those who drank tea fewer than 3 times per week

Men and women were analyzed separately. Other parameters were also considered. For example, 49% of regular tea drinkers consumed green tea, and the heaviest tea drinkers were men, particularly those who smoked or drank alcohol.

Results That Speak for Themselves

To assess the effects of tea on cardiovascular risk, blood pressure was measured three times per medical visit, and blood samples were taken to evaluate lipid levels—particularly LDL. Lifestyle (diet, smoking, physical activity) and tea type (49% green, 9% black, 43% flavored/other) were taken into account. However, it’s regrettable that the researchers did not create subgroups. Doing so might have revealed whether tea combined with exercise is more protective than either alone, or which type of tea offers the greatest benefit.

Although the study did not show changes in LDL blood levels, tea drinkers were about 20% less likely to develop atherosclerosis-related cardiovascular disease. One common challenge in scientific research is reproducibility—results can vary across studies. Repeating cohort studies with larger populations strengthens reliability. Observing consistent trends across different time periods is highly encouraging and supports a potential protective cardiovascular effect.

In the most recent cohort (2012–2015), additional data revealed even greater protection for those who had always consumed tea compared to those who started later or had stopped: a 39% reduction in cardiovascular disease and stroke incidence. Beyond regular tea drinking, long-term effects may be at play. While the frequency of weekly tea consumption was recorded, the researchers did not specify the quantities consumed. This raises questions about whether tea's effects depend on dosage, consistency, or cultural drinking habits (which differ in China and Western countries).

A Delayed Onset of Disease?

The researchers also found that people who drank tea more than three times per week could delay the onset of disease by nearly 1.5 years at age 50—and gain an additional 1 year and 2 months of life expectancy at that age. However, such data should be interpreted cautiously. According to the authors’ charts, the gain in cardiovascular disease–free years decreases with age: at 75, only about 1 year is gained. Similarly, the “1 year and 2 months” of additional life expectancy at 50 drops to under 1 year at age 75.

These estimates are derived from statistical models, and results may vary depending on the method used.

Toward Cardiovascular Disease Prevention — How?

To understand how tea might prevent cardiovascular disease, the authors proposed several hypotheses. While they focused on the role of polyphenols, other mechanisms are also known. At Sciences Thé, we’ve highlighted that tea may influence inflammation and blood lipid levels—two major contributors to atherosclerosis.

By compiling all this information, future cohort studies could become increasingly precise and useful in developing tea consumption guidelines as part of disease prevention strategies.