It sure is a colorful life. I recall vividly a scary episode almost forty-five years ago when my wife came running to me brandishing our infant daughter's diaper in her hands. It looked pretty scary, filled with bright red stuff. There were a few moments of panic until we took a closer look and realized that earlier in the day the young lady had been introduced to the delights of red licorice! The red dye was making a triumphant exit.
This of course was not a unique experience. The scientific literature records the case of a young boy who succeeded in terrifying his mother with a bright red-orange output after dining on some colorful "Nerds" cereal. Even more unusual is a case of "Hydrox fecalis," aptly named after an American brand of chocolate sandwich cookies. The coloring in these cookies is cocoa powder which can turn the stool black approximately 18-24 hours after ingestion. You do, however, have to eat a lot of cookies. Like, half a pound. This is enough to cause abdominal pain, which coupled with the black colour can certainly throw a good scare into someone.
Black stools are a real cause for concern because they can be a sign of gastrointestinal tract bleeding. But they can also be caused by iron supplements, black licorice, blueberries or medications which contain bismuth compounds (such as Pepto-Bismol)! Ignorance of the blueberry effect has resulted in many an unnecessary trip to the emergency room.
The brown color of normal feces is mostly due to remnants of bile secreted by the liver into the small intestine. The brownish hue is due to bilirubin, a major breakdown product of red blood cells. Its precursor is actually a green compound known as biliverdin which sometimes shows up in the feces making them green. This happens when transit time through the digestive tract is rapid (often due to a viral infection) and there is less of an opportunity for biliverdin to be converted to bilirubin. Babies will often have quick transit times and produce bright green stools. Unusually light or "clay colored" feces on the other hand can be a sign that there is a blockage in the bile duct. This is very uncommon, more likely the patient has consumed a large amount of white Maalox or other antacid!
Some bilirubin is absorbed into the bloodstream and is eventually excreted in the urine, giving it its yellowish glow. When the kidneys secrete considerable water, the urine is pale. But when the body needs to conserve liquids, the urine is more concentrated and darker. This may occur after heavy exercise and sweating. Very dark yellow urine can be a sign of dehydration. If too many bile pigments end up in the urine due to impaired liver function, the urine takes on a greenish appearance. But this can also be due having consumed asparagus. A genetic trait possessed by some will lead to green urine after eating this vegetable. Similarly, about 15% of people will produce red urine after eating beets.
This latter is a particularly interesting scenario. Beet roots have both red (betacyanins) and yellow pigments (betaxanthins) known collectively as betalains. The betacyanins of course far exceed the betaxanthins. Dried beet powder is even available commercially and has been used to color candies, yogurts, ice creams, salad dressings, drinks and gelatin desserts. Most people do not have to deal with the after-effects of beet consumption because hydrochloric acid in the stomach and bacteria in their colon break down the pigments before they can be absorbed into the bloodstream. But not everyone has the same mix of bacteria in their colon and apparently people who note the colorful aftermaths of beets are missing the bacteria that degrade the betalains.
Under certain conditions, even people who have not previously been subjected to these technicolor effects may note redness in the feces or urine after eating beets. It depends on what else they ate along with the beets. Oxalic acid, which is found in a variety of foods, actually protects betalains from being broken down by bacteria. Oysters, spinach and rhubarb eaten together with beets (admittedly an unusual combo) can have a disturbing consequence for anyone not familiar with this bit of obscure chemistry.
Red urine of course is very frightening because the discoloration may stem from the presence of blood and can be a sign of kidney or bladder problems. It must be investigated. In some cases it can have an innocent cause. For example, drummers can have red urine because the repeated tapping of the fingers and hands can cause red blood cells to burst, releasing their hemoglobin into the urine. In some parts of Africa, the contention is that if a drummer doesn't pee red he is not playing well!
Purple urine may be a sign of a disease known as porphyria. In one variant of this disease an inherited enzyme deficiency causes the metabolic pathway for the making of hemoglobin to be interrupted. Porphyrins, which are molecules that would normally be used by the body to make hemoglobin, are now excreted and appear in the urine. Porphyria can cause various symptoms, including mental impairment. King George III, the British monarch during the American War of Independence, is believed to have suffered from porphyria, perhaps explaining his bizarre handling of the colonial situation.
It is no wonder that historically doctors, or in the Middle Ages specialists known as "piss prophets," have taken pains to examine the color of urine, looking for signs of disease. But one wonders how many people were subjected to various nonsensical treatments as a consequence of having eaten beets or asparagus!
There is one final colorful story. According to an old wives tale, if you want to know whether a baby will be a boy or a girl, take a sample of urine produced during the sixth month of pregnancy and mix it with an equal volume of liquid Drano. If the mixture turns green it's a boy; if yellow, it's a girl. The test is correct about 50% of the time.