The stomach is a sturdy, bag-like organ located in the upper abdomen below the lungs. The wall of this bag, called the gastric wall, consists of three layers of tissue: the inner mucosal layer, the middle muscular layer, and the outer serosal layer. The mucosal layer contains gastric glands responsible for secreting mucus, gastric acid, and pepsin. Gastric acid is highly acidic, and when food enters the stomach, the acid is secreted in large quantities, lowering the pH to below 2. Pepsin digests and breaks down proteins. Mucus acts as a lubricant and barrier, protecting the mucosa from corrosion by gastric acid and digestion by pepsin.

First, drinking tea replenishes water in the body. When the body is well-hydrated, the mucosa can secrete sufficient mucus, providing better protection for the epithelial cells.

Second, the pH of tea is typically between 5.5 and 7, making it weakly acidic. Compared to the strong acidity of gastric acid, this is negligible and will not irritate the gastric mucosa or neutralize stomach acid.

Third, tea contains caffeine, which briefly stimulates the central nervous system, promoting the secretion of gastric juice and gastrointestinal motility, thereby aiding digestion—hence the saying "tea aids digestion." However, if the stomach is empty, excessive gastric acid may irritate the gastric mucosa, causing a burning or stinging discomfort. Therefore, it is advisable to avoid drinking tea on an empty stomach.

The claim that "green tea harms the stomach, while black tea nourishes it" lacks scientific basis.

Although black tea is warming, it cannot simply be equated with nourishing the stomach. While the polyphenols in tea are beneficial, they can also irritate the stomach, especially when consumed on an empty stomach. Although black tea undergoes fermentation and roasting, reducing the polyphenol content compared to green tea and thus being less irritating, this does not mean it is universally suitable.

Therefore, even though black tea is warming and aligns with the stomach’s preference for warmth, it is not suitable for everyone. Those with stomach issues should still be cautious with black tea, especially if it is overly strong, as the high caffeine content can still irritate the stomach. Thus, while black tea may warm the stomach, it is not the same as nourishing it.

Tea can be categorized as cooling or warming, and human constitutions also vary in terms of heat or cold. Whether tea nourishes or harms the stomach depends on the season and individual constitution. Drinking green tea over the long term may not be ideal for the stomach, so moderation is key. If you have a heat-prone constitution, drinking more green tea can help expel internal heat and detoxify. Conversely, if your stomach tends to be cold, drinking more warming teas will make it happier and more efficient.

Therefore, regardless of individual differences, it is not recommended to drink only one type of tea for extended periods. Instead, a balanced approach across the six major tea types is advised—drinking them according to fermentation levels (unfermented, lightly fermented, semi-fermented, fully fermented), seasonal changes, and even time of day (morning, noon, evening).

Additionally, factors like a regular lifestyle, adequate sleep, emotional stability, and balanced stress levels are crucial for stomach health. If drinking tea helps regulate emotions and relieve stress, it can become a valuable ally in promoting stomach health rather than harming it.