Eating asparagus benefits your body in several ways. This vegetable is low in calories and rich in B vitamins, antioxidants and vital minerals, according to the USDA.
But a trip to the bathroom after eating a few stalks may reveal minor side effects, such as gas and smelly urine.
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Asparagus Side Effects
1. Stinky Urine
Ever noticed a pungent odor from your urine after you eat asparagus? This vegetable contains a chemical compound called asparagusic acid that, when digested, breaks down into the sulfur-containing compounds responsible for the strong, unpleasant odor of your urine, according to a January 2014 review in Phytochemistry.
But as strange as it may sound, not everyone smells the stinky pee, and scientists are not exactly sure why. Two possible explanations for this: Not all people excrete smelly compounds in their urine after eating asparagus, or not all people can smell the compounds. Scientists speculate that genetics may be involved in this phenomenon.
Researchers have studied whether there are inherited factors associated with smelling asparagusic metabolites in urine. About 58 to 61 percent of people studied couldn't distinguish the strong smell in a December 2016 study in the BMJ. Researchers believe that genetic variations of olfactory receptors are associated with the ability to detect the smell.
Whether you can smell it or not, there are no harmful effects of producing or smelling the odorous results of eating asparagus.
2. Gas and Bloating
Sometimes, asparagus causes gas and bloating.
"While asparagus is a very nutrient-dense food, it may cause gas for some people due to its chemical makeup," says dietitian Sarah Schlichter, MPH, RDN. "Asparagus contains natural sugars and oligosaccharides, such as raffinose and fructose. These may cause gas in the lower intestine because they are fermented by gas-producing bacteria."
To reduce gas and bloating from eating asparagus, make sure it's fully cooked. It's not a particularly hard-to-digest vegetable, Schlichter says, but raw vegetables are more likely to cause these symptoms than cooked, softened ones.
"When eaten raw or in excess, it may lead to more temporary bloating and gas," she says.
People who have difficulty digesting the natural sugars in asparagus may experience diarrhea. This isn't the case for everyone, though.
In some cases, though, eating asparagus can help reduce diarrhea. When you have diarrhea, eating the tips of asparagus, specifically, may help, according to the National Library of Medicine.
Schlichter recommends reducing the chances of getting diarrhea from asparagus by drinking plenty of water and eating enough fiber.
If eating a few stalks gives you stomach pain, you may have an intolerance to fructan, a carbohydrate in asparagus. Because the symptoms are similar to those of gluten sensitivity, intolerance to fructan is often misdiagnosed, according to Ohio State University.
Fructan intolerance is common. Up to one-third of people with suspected irritable bowel syndrome (IBS) actually have fructan malabsorption and dietary fructan intolerance, according to January 2014 research in Current Gastroenterology Reports.
Although wheat and onions are the most common sources of fructan, some vegetables, including asparagus, contain this compound too. If you have trouble digesting fructans, you may experience symptoms like:
Symptoms can range from mild to severe enough to necessitate missing work or school, according to Ohio State University.
It's also possible for some people to be sensitive to asparagus because of a food allergy to the Alliaceae family of vegetables, which includes garlic, onions, chives and leeks in addition to asparagus. Each member of the family has the potential of cross-reactivity with each other and may trigger allergic reactions.
At least six Immunoglobulin E (IgE) compounds have been detected in raw asparagus. IgE is an antibody produced by your immune system in response to overreacting to an allergen. This compound releases chemicals in your cells, causing an allergic reaction that may induce symptoms affecting your skin, throat, nose or lungs, according to the American Academy of Allergy, Asthma and Immunology.
While most of the negative side effects of asparagus are non-threatening, severe allergic reactions may cause life-threatening anaphylaxis, which requires immediate medical attention.
- MyFoodData: "Nutrition Facts for Asparagus (Cooked)"
- USDA: "2020-2025 Dietary Guidelines for Americans"
- Mayo Clinic: "Dietary Fiber: Essential for a Healthy Diet"
- The BMJ: "Sniffing Out Significant “Pee Values”: Genome Wide Association Study of Asparagus Anosmia"
- Ohio State University: "Should You Avoid Eating Fructans?"
- Current Gastroenterology Reports: "Dietary Fructose Intolerance, Fructan Intolerance and FODMAPs"
- Nutrients: "Lutein and Zeaxanthin—Food Sources, Bioavailability and Dietary Variety in Age-Related Macular Degeneration Protection"
- Phytochemistry: "Asparagusic Acid"
- Harvard Health Publishing: "Is something in your diet causing diarrhea?"
- National Library of Medicine: "When you have diarrhea"
- American Academy of Allergy, Asthma & Immunology: "Immunoglobulin E (IgE) Defined"