Lemon is acidic before it enters the human body, with a pH value of less than 7.

After entering the human body, citric acid (a weak acid) can be completely metabolized in the body to produce carbon dioxide and water, which can be excreted with respiration. It is rich in potassium, calcium and other strong alkaline metal ions, which combine with the acid ions in the body to raise the pH value of the body.

Therefore, lemon is classified as an alkaline food.

The acidity or alkalinity of a food has nothing to do with its pH value (a food that tastes acidic is not necessarily acidic), but is mainly defined by whether the food is acidic or alkaline in the human body after digestion, absorption, and metabolism.

Acid-producing substances are called acidic foods, such as animal organs, muscles, plant seeds (grains). Those that produce alkaline substances are called alkaline foods, such as vegetables, melons and beans, and teas.