What causes urine to change color to reddish-pink after consuming beets?

The change in urine color to reddish-pink after consuming beets is primarily due to a pigment called betalain. Betalains are natural pigments found in beets and some other plants, and they can be excreted in urine. When digested, these pigments can result in a noticeable change in urine color, a phenomenon known as beeturia. This occurrence is generally harmless and results from the body's breakdown of these pigments, which can vary in intensity depending on the individual's metabolism and the amount of beets consumed.

This is distinct from the other factors listed, which do not directly contribute to this specific change in urine color. Excessive hydration tends to dilute urine, often making it clearer or lighter in color. Irritation of the bladder could potentially cause discoloration due to blood or other byproducts, but this is not related to beet consumption. A vitamin deficiency may affect overall health and bodily functions but does not specifically cause the urine to turn reddish-pink after eating beets.