Beeturia is passing of red or pink urine and feces after eating beets. It affects 10-14% of the population. While some believe it to be an autosomal recessive trait, it has shown that individuals differ over time in having beeturia.
The red color seen in beeturia is caused by the presence of betalain pigments passed through the body. One article believes that when beets cause your urine to turn red it is because you may have an iron deficiency.