Personal Health: Urine has a uniquely valuable role in medicine: It holds clues not just to what people eat and drink, but also to how well their bodies are functioning.
I happen to love asparagus and eat it often. But an acquaintance once told me she carefully avoids this wholesome vegetable simply because it makes her urine smell bad.
I was tempted to ask her who is likely to know or care, except perhaps a stranger in a public restroom. Surely there are worse offenses.
As one of the four routes by which substances normally exit the body (the others being feces, breath and sweat), urine has a uniquely valuable role in medicine: It holds clues not just to what people eat and drink, but also to how well their bodies are functioning. The search for these telltale signs is why doctors routinely request urine samples from patients, whether they seem healthy or are obviously sick.
The color, clarity and other physical characteristics of urine, as well as substances dissolved in it, can provide clues to a wide range of problems, including infections, inherited metabolic disorders, kidney disease, bladder cancer, diabetes, substance abuse, exposure to toxins, inadequate or excessive fluid intake and, as many competing athletes know all too well, the use of performance-enhancing drugs.
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Recently, in an eight-year European study, the sodium content of 24-hour urine samples from 3,681 adults was used to estimate the effect of daily sodium intake on the development of high blood pressure and illness and death from heart disease. The authors’ conclusion that too little dietary sodium was riskier than too much has been widely challenged, and until further notice most Americans would be wise to reduce significantly how much salt and other dietary sources of sodium they regularly consume.
COLOR AND ODOR
Urine can acquire off-odors from consumption of a few foods like asparagus (a genetic factor in some people is most likely responsible) and beverages like coffee, or as a consequence of health problems like a urinary tract infection or diabetes (a sweet smell from excess sugar). But the characteristic of urine most likely to be noted by a lay person is color.
If you are well hydrated, normal urine is clear and pale yellow, a color imparted by the pigment urochrome. Dehydration — which can be the consequence of drinking too little, sweating too much or suffering from repeated bouts of vomiting or diarrhea — results in dark urine with a smell of ammonia; it should be treated as a warning to drink more water or other plain fluids.
But consistently dark-colored urine can be a sign of hepatitis, a liver disease that requires prompt medical attention.
Less seriously, many foods and certain medications can impart an unusual and, to the unsuspecting, sometimes alarming color. For example, beets, which contain a betalain pigment that turns hands and cooking water red, can turn urine a color that may resemble blood. Likewise, blackberries and rhubarb can result in red or pink urine.
Tea-colored urine can follow the consumption of fava beans and sometimes rhubarb. The beta carotene in carrots, carrot juice and high doses of vitamin C can cause orange-colored urine, and B vitamins and asparagus may turn urine a greenish color.
Among medications that can affect urine color are the laxative senna, which can bring a red or reddish brown tinge; chlorpromazine (Thorazine) and thioridazine (Mellaril), which may add redness; indomethacin (Indocin), cimetidine (Tagamet) and promethazine (Phenergan), which can color urine blue or green; warfarin (Coumadin), phenazopyridine (Pyridium) and rifampin, which can add orange; and chloroquine (Aralen), metronidazole (Flagyl), nitrofurantoin (Furadantin) and primaquine, which can make urine brown. Of course, sometimes blood does appear in urine — for example, as a result of a urinary tract infection, a kidney or bladder stone, an enlarged prostate, or a jarring accident that injures the bladder or urethra. Or blood-tinged urine may follow strenuous exercise like a long run or triathlon.
If there is no obvious explanation for blood in the urine or if it persists, a visit to the doctor is mandatory to check for kidney disease or cancer. If no other explanation for red-tinged urine is uncovered, a test for toxic levels of lead and mercury should be done.
If urine is excreted very rapidly, it may appear foamy. But consistently foamy urine can be a sign that protein is being lost, a symptom of kidney disease, and that a medical exam is needed.
Cloudy urine is typically a result of a bladder or urinary tract infection, which is typically accompanied by a frequent urge to urinate and a burning sensation or pain when urinating.
OTHER IMPORTANT FACTORS
The volume of urine produced can be an important indicator of hydration. Normally, a healthy person produces about 100 milliliters (about 3.4 ounces) of urine an hour, or about one cup in 2 ½ hours. If the hourly output exceeds 300 milliliters, it could be a sign of excessive fluid intake; if the volume drops below 30 milliliters, it is probably a sign of dehydration.
Consuming lots of salty foods or carbohydrates can temporarily reduce urine output, because salt, sugar and starch hold more water in the body than, say, protein. And consuming foods or beverages that are diuretics — including caffeine-containing drinks (like coffee, tea and many soft drinks), alcoholic drinks (especially beer), and foods with a high water content, like watermelon or asparagus — can temporarily result in higher-than-average urine output.
The urine of two-legged and four-legged athletes is now commonly tested for signs that performance-enhancing drugs were responsible for an unfair competitive advantage. Sometimes athletes who take medication for legitimate medical problems get caught in the net.
When you provide a urine sample as part of a routine medical checkup, it is likely to be tested for the presence of sugar (an indicator of diabetes) and protein (a sign of kidney disease), and perhaps for bile acids (an indicator of liver disease) or white blood cells (the result of an infection).
If symptoms of a urinary tract infection are present, the culprit organism — often the bacterium E. coli, a common resident of the lower digestive tract — can be isolated from urine and, if necessary, tested for antibiotic sensitivity.