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Consumers should be wary of teas advertised as "detoxifying" or "weight-loss" that have unclear ingredients. Photo: Pexels . |
Tea is a familiar beverage consumed daily by many. However, not all types of tea should be drunk regularly. In particular, the risk doesn't necessarily lie in the tea leaves themselves, but may stem from the quality of the raw materials, the processing methods, storage, and the amount of tea used.
Some teas are even advertised as "health-promoting tea" or "detox tea," but contain concentrated ingredients or herbs of unknown origin. Therefore, tea drinkers should pay attention to the following five groups, according to Tencent News.
The tea became moldy due to being stored in a humid environment.
When tea is damp, under conditions of high temperature and humidity, mold can grow rapidly. Aflatoxin B1 is a Group 1 carcinogen, primarily causing liver damage. Regularly consuming small amounts of this substance over a long period can be more concerning than occasional exposure. Aflatoxin cannot be broken down by normal heating, so rinsing tea once with boiling water will not remove the toxin.
Some surveys in China have detected aflatoxin B1 in Pu-erh tea samples stored in humid environments. However, this does not mean Pu-erh tea is inherently toxic. The main risk is related to the raw materials and storage conditions. Tea stored in humid environments to create an aged appearance, cheap loose tea, or improperly sealed storage during the rainy season can all increase the risk of mold growth.
Tea that shows white or green mold, clumps together, has a musty or rancid smell, or has an unusually cloudy color should not be used. Do not attempt to wash, sun-dry, or rinse with boiling water to save the tea, as these methods do not guarantee the removal of mold toxins.
The roasted tea leaves are burnt.
Some types of tea are roasted or toasted to create their distinctive aroma. However, if the temperature is too high, the tea leaves burn, or they are exposed directly to fire and smoke, this process can produce undesirable substances.
Of particular note are polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (B[a]P). These are potentially carcinogenic and can cause cell damage, and the liver is one of the organs involved in metabolizing and eliminating these compounds. Therefore, regularly consuming foods or beverages containing high levels of PAHs is not beneficial for long-term liver health.
When buying roasted tea, observe the dry tea leaves. If there are many burnt leaves, charcoal spots, or a strong burnt smell, do not choose it for regular consumption. In particular, if the tea has a harsh, burnt taste that irritates the mouth or throat, discard it.
Tea left overnight
What really needs attention is the storage environment. In the summer , if tea is left at room temperature, uncovered, or has added sugar or milk, bacteria and mold can grow more rapidly. If the tea tastes sour, develops a film on the surface, becomes cloudy, or has mold spots, it should be discarded immediately.
It's best to brew and drink tea on the same day. If left at room temperature, it shouldn't be kept for more than 8-12 hours, and even shorter in hot weather. Any leftover tea should be covered and refrigerated. Before drinking it the next day, check its smell and color to determine if it's suitable for consumption.
With tea that's brewed too strong and left overnight, caffeine and theophylline levels can remain high. People who are prone to insomnia or have stomach problems should avoid drinking this type of tea.
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Tea left at room temperature for too long can deteriorate in quality, especially in hot weather. Photo: Shutterstock. |
The tea is too strong.
The problem with overly strong tea isn't that the tea itself is toxic, but primarily due to its high caffeine and theophylline content. It's estimated that every 100 ml of strong tea can contain around 60-80 mg of caffeine, almost the same as a cup of coffee. If total daily caffeine intake exceeds 400 mg, some people may experience symptoms such as rapid heartbeat, insomnia, or stomach irritation.
Caffeine is primarily metabolized in the liver via the enzyme CYP1A2. Metabolism varies from person to person; some people metabolize caffeine more slowly, which can lead to nervousness, rapid heartbeat, or difficulty sleeping even with small amounts.
In particular, high tannin content can bind to iron and protein, so regularly drinking strong green or black tea on an empty stomach can increase acid reflux, stomach pain, and affect iron absorption, especially in people at risk of iron deficiency.
According to the common recommendation of Popular Chinese Science , for diluted tea, adults can consume about 3-6 grams of dried tea per day, divided into 3-5 servings; it is advisable to avoid drinking very strong tea 4-6 hours before bedtime.
Weight loss tea, detox tea containing concentrated extracts.
Weight-loss teas, detox teas, and liver-cleansing teas containing senna leaves or other herbs of unknown origin may cause more significant drug-induced liver damage compared to regular teas that are brewed too strongly.
Long-term use of high doses of green tea extract or EGCG-containing supplements has also been shown to be associated with a risk of liver toxicity. Additionally, some herbal remedies of unknown composition may contain pyrrolizidine alkaloids, compounds that can potentially damage the small veins in the liver.