Lemon is the fruit of Rutaceae citrus, which is called "beauty fruit". Fresh lemons contain a lot of water, so the calories are very low. It also contains minerals such as protein, fat, carbohydrate, vitamins A, B 1, B2, C, nicotinic acid, calcium, phosphorus, iron, potassium, etc., and also contains various flavonoids, organic acids, coumarins, sterols and volatile oils. The peel contains hesperidin, naringin, geraniol, neohesperidin, citral, limonin and so on. The seeds contain cortex phellodendri and limonin.

The bitter taste of lemon mainly comes from limonin in peel and seed. If you are afraid of bitterness, you can take a proper amount of brown sugar. Lemon peel contains a considerable amount of citral, which can fight against vitamin A. Therefore, if vitamin A intake in the diet is sufficient, lemon peel can be eaten in large quantities.

Hesperidin and naringin contained in lemon peel have anti-inflammatory effects; In addition to anti-inflammation, hesperidin has the functions of antivirus, cholagogic, anti-ulcer, lowering blood pressure and cholesterol, and relieving or improving atherosclerosis.

Lemon juice has a strong bactericidal effect, which helps digestion and absorption, and can also prevent the formation of black spots and freckles. Lemon juice contains a lot of citrate, which can inhibit the crystallization of calcium salt and prevent the formation of kidney calculi. Citric acid combined with calcium ion to form soluble complex can prevent and treat hypertension and myocardial infarction, but it is not suitable for patients with gastric ulcer and duodenal ulcer.