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March 4, 2012 at 6:49 PMComments: 2 Faves: 2

Food-Body Oddities: Why Asparagus, Carrots and Beets Do Those Things They Do

By Jeffrey VanWingen M.D. More Blogs by This Author

I have been paying more attention to what I eat lately, reminding myself that, “You are what you eat.” Over the years I have found this to be particularly true both personally and as a doctor. Indeed, food not only nourishes our body allowing it to run efficiently, there are some particular foods that have some interesting effects! Occasionally patients will come to me worried about these and I smile, provide reassurance and walk away continually amazed at how our bodies metabolize food in such unusual ways.

This blog will explore three unique things that food can do to our bodies and provide the science behind it.

Asparagus Pee Smell:

"Doctor, every time I eat asparagus, my urine has a particular odor.  Is there a problem with my kidneys? Am I allergic to asparagus?"

Does the bad smell mean it's bad for me? NOPE! For centuries the effects of asparagus on the urine has been noted. It is hard to imagine that such a nutritious and tasty vegetable could be harmful, but its pungent byproduct could leave anyone wondering. Well, keep eating your green stalks of asparagus without fear!

What causes the smell? The peculiar urine smell is simply a byproduct of sulfur-containing metabolites that are put out of the body in the urine. When we eat food, it is broken down into simple chemical compounds that are absorbed into the blood by the small intestine. Some of what is absorbed is used as nutrients and some is filtered out by the kidneys and cast into the urine. Asparagus simply has a lot of those smelly compounds to pass into our urine.

Some people don't get it! It has been debated whether only some people have smelly urine after eating asparagus or if some people just can’t smell the byproduct compounds. After a few research studies to advance science (or just satisfy curiosity), it was determined that there is a genetic-based absence in some people that prohibits the olfactory (smell) detection of the asparagus metabolites in the urine. Is this an advantage? Who knows? 

Carrots and Skin Color:

"My baby is orange! Does he have jaundice?"

Is orange skin harmful? Occasionally a mother will bring such an orange baby to see me, usually between 9 and 18 months of age.  The skin is indeed orange in color. Invariably, this child has a healthy appetite for his veggies, carrots in particular.  This condition is called carotenosis and it is harmless.

Why do carrots make your skin orange? Many vegetables and fruits contain carotenoids, beta-carotene being the most prevalent. Carrots are an excellent source of carotenoids and this is precisely what gives them that orange color. These carotenoids are absorbed in the intestines and some is turned into vitamin A. Excess carotenoids are processed through the body in the sweat and urine but some can get trapped in the skin tissues. Pureed foods (like baby food) make the carotenoids more readily absorbed. As such, this is more common in babies but it can occur in anyone who eats enough carotenoids.The condition can also occur in people who do not metabolize carotenoids properly and this has been seen in diabetes and low thyroid conditions.

How is jaundice different? Carotenosis is distinguished from jaundice in that jaundice is more of a yellow color and is readily noted in the whites of the eyes.  Carotenosis does not affect the eyes.  It takes about 4-7 weeks to accumulate the orange pigment in the skin and it takes just as long for it to return to normal. 

Beets and Red Pee:

"My urine is red! I must have blood in my urine."

Should I be worried about red in my pee? Usually red urine is due to blood. Blood in the urine could mean an infection, a kidney stone or possibly cancer. Occasionally, however, I’ll look under the microscope and see no red blood cells at all. This will prompt the question, “Have you been eating beets?”

Why do beets cause red urine? Beeturia is the condition of red-tinged urine following the consumption of beets.  Not everybody who eats beets gets red urine, however - only about 14%. Sometimes the tendency for beeturia comes and goes in a person. The condition of beeturia is harmless. These people have a higher amount of a chemical called oxalic acid in the intestine which preserves the red beet pigment from getting broken down.  Thus, more is absorbed and then filtered through the kidneys as waste.

Foods come in all colors of the rainbow with various tastes and aromas.  Sometimes they cast their shades, smells and tints on us.  These conditions are completely harmless, but interesting nonetheless!

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  • Thanks for posting, Dr. V. I've heard of the asparagus and the carrot "side effects" before, but I've never heard of red urine being attributed to eating too many beets. Very interesting!

  • I want really want to test the carrot coloring my skin! I wonder how many carrots you have to eat....?

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