Green tea is one of the world’s most popular beverages, associated with various health benefits. A common question concerns its physical effects, specifically whether the bright green liquid causes urine color to change to green. While green tea may slightly alter urine color due to its diuretic properties, it typically does not make urine green. Occasional green or bright yellow urine is almost always the result of other factors, such as vitamins or certain foods, rather than the tea itself.
What Determines Normal Urine Color?
The characteristic yellow hue of urine is due to urobilin, a metabolic byproduct. Urobilin is a pigment originating from the continuous breakdown of old red blood cells. Hemoglobin from these cells is processed into bilirubin by the liver, then converted into urobilinogen in the intestines.
A small fraction of this urobilinogen is reabsorbed and excreted by the kidneys as urobilin, which colors the urine yellow. The intensity of this color relates directly to the pigment’s concentration. When a person is well-hydrated, the urobilin is diluted, resulting in a pale yellow color. Conversely, low fluid intake concentrates the urine, making it appear darker yellow or deep amber.
How the Body Processes Green Tea Compounds
Green tea contains two main types of compounds that might concern a person about urine color: the green pigment chlorophyll and polyphenols, particularly catechins. Chlorophyll is the molecule that gives the tea leaves their vibrant green color, yet it has a minimal impact on the color of urine. The digestive system poorly absorbs chlorophyll, and consequently, most of it passes through the gastrointestinal tract and is excreted in the feces.
The active compounds, catechins like epigallocatechin gallate (EGCG), are absorbed and extensively metabolized by the liver and the gut microbiome. These metabolic processes transform the catechins into various colorless or faintly colored breakdown products, such as glucuronides, sulfates, and ring-fission metabolites. These metabolites are then excreted in the urine, but their chemical structure does not possess a pigment strong enough to impart a noticeable green or unusually bright color.
Dietary and Supplement Causes of Bright Yellow Urine
The perception of bright or neon-colored urine after consuming a beverage is often due to the consumption of supplements. The most common cause of a harmless, fluorescent bright yellow or greenish-yellow urine is the presence of excess Riboflavin, also known as Vitamin B2. This water-soluble vitamin is naturally yellow and is a common ingredient in multivitamins and B-complex supplements.
When a person consumes more Riboflavin than the body can immediately use, the excess is simply filtered out by the kidneys and excreted. The distinct fluorescent hue of Riboflavin is strong enough to visibly color the urine, which can be alarming but is not a sign of a health problem. Other dietary items, such as certain medications or foods like asparagus or beets, can also temporarily alter urine color.