Asparagus Nutrition Facts and Health Benefits

Asparagus annotated

Verywell / Alexandra Shytsman  

Asparagus spears are both delicious and nutritious. Asparagus (scientific name Asparagus officinalis) is a perennial flowering plant that has been used as a food and medicine since as far back as 3,000 B.C. Many early cultures imbued it with aphrodisiac properties. Today, asparagus is recognized as an excellent source of vitamins, minerals, and fiber, with few calories or sodium.

Asparagus Nutrition Facts

The following nutrition information is provided by the USDA for 1/2 cup (90g) of asparagus cooked with no added salt or fat.

  • Calories: 20
  • Fat: 0.2g
  • Sodium: 13mg
  • Carbohydrates: 3.7g
  • Fiber: 1.8g
  • Sugars: 1.2g
  • Protein: 2.2g

Carbs

Asparagus is an excellent addition to any low-carb or ketogenic diet. Only a small portion of the carb content is from simple carbs (namely sugar), so it has little impact on blood sugar and a glycemic index (GI) of less than 15.

Asparagus also offers a healthy dose of dietary fiber, the indigestible carbs that help regulate digestion, blood sugar, and fat absorption in the body. Most of the fiber in asparagus is insoluble, meaning that it draws water from the intestines to soften stools and ease them from the digestive tract.

Fat

Asparagus is virtually fat-free, with only scant amounts of healthy polyunsaturated fats. These essential fatty acids are important for brain function and cell growth.

Of course, many popular asparagus preparations and toppings (like butter and Hollandaise sauce) do add fat and calories. As an alternative, drizzle spears with a teaspoon of extra virgin olive oil for flavor and more healthy fats.

Protein

At 2.2 grams per serving, asparagus doesn't offer a lot of protein, but it's enough to help meet some of your daily nutritional needs. On average, adults should eat around 0.8 grams of protein per kilogram of body weight (or 0.36 grams per pound) per day. This amounts to 56 grams per day for the average sedentary man and 46 grams per day for the average sedentary woman.

Vitamins and Minerals

Asparagus can account for a significant portion of your daily nutritional needs. Based on a 2,000-calorie diet, the amount of each vitamin offered in a serving of asparagus as a percentage of reference daily intakes (RDI) break down as follows:

Asparagus also provides some vitamin A, vitamin C, iron, potassium, and phosphorus.

Health Benefits

Certain nutrients and compounds in asparagus are believed to offer significant health benefits. These include the reduction of high blood pressure, the promotion of a healthy pregnancy, and the avoidance of certain diseases.

Lowers Blood Pressure

Asparagus is a source of potassium. Increased intake of potassium-rich foods is associated with lower blood pressure because it relaxes the walls of the arteries (thereby improving circulation) and increases the excretion of sodium from the kidneys.

Vitamins A and C are also powerful antioxidants that help eliminate free radicals circulating in the blood. Doing so reduces damage to the circulatory system, including the risk of atherosclerosis (hardening of the arteries) and cardiovascular disease.

Purple asparagus also contains anthocyanins, antioxidant compounds that provide the vegetable its vibrant color and exert robust cardio-protective properties.

Asparagus also exerts mild diuretic properties that inherently lower blood pressure by promoting the excretion of excess fluids from the body. A 2013 study from Japan reported that 28 adults given an oral dose of powdered asparagus (6 milligrams per kilograms of body weight) experienced a nearly 8 point drop in their systolic blood pressure and a nearly 5 point drop in their diastolic blood pressure after 10 weeks. It also decreased total cholesterol and fasting glucose levels (although no changes in HbA1C were noted).

Supports a Healthy Pregnancy

Most obstetricians recommend that a pregnant woman consume at least 600 micrograms of folate daily (often, at least some of this is included in a prenatal vitamin) to promote a healthy pregnancy and reduce the risk of neural tube defects, such as spina bifida. A half-cup serving of asparagus provides 134 micrograms of folate.

In addition, asparagus contains the non-essential amino acid known as asparagine, which is required for the normal development and function of the brain.

Protects Against Some Chronic Diseases

Asparagus is a key source of inulin, a type of fiber that supports healthy gut bacteria. It does so in part by inhibiting powerful bacterial endotoxins known as polysaccharides

With roughly 2 to 3 grams of inulin per serving, asparagus could potentially aid in the control of certain diseases attributed to excessive polysaccharides. These include ulcerative colitis, Crohn's disease, Helicobacter pylori (H. pylori) infection, and, to a lesser degree, cystic fibrosis, atherosclerosis, and certain autoimmune diseases like rheumatoid arthritis.

Allergies

Asparagus is rarely implicated in allergy. However, a compound known as trithiane-5-carboxylic acid is found in higher concentrations in young asparagus stalks. People who pick or eat these slender, early-season stalks may experience contact dermatitis, mainly on the hands or fingers, or contact urticaria, causing swollen and itchy lips.

Allergy symptoms tend to be mild or last for only a few minutes. Call your doctor if the symptoms persist or worsen.

Adverse Effects

Because asparagus has a mild diuretic effect, you may need to avoid eating it while taking the drug lithium. Theoretically, asparagus can reduce the excretion and increase the concentration of lithium in the blood. Doing so may amplify the side effects of the drug.

Asparagus is also high in vitamin K. People who take Coumadin (warfarin) need to consume consistent amounts of this vitamin, because of its effect on blood clotting. If you take Coumadin, discuss your diet with your doctor and/or a registered dietitian.

If you find your urine takes on a strange odor after eating asparagus, you're not alone. The vegetable contains sulfurous amino acids, known as asparagusic acid, which break down during digestion. This produces pungent chemical compounds that are excreted soon after eating asparagus and up to a day later. While somewhat unpleasant, the sulfurous chemicals are in no way harmful.

Varieties

You can find asparagus in green, white, or even purple varietals. In the United States, the green variety is most common, while white asparagus is prevalent throughout Europe.

Both white and green asparagus contain roughly the same amount of calories, carbohydrates, and fiber per serving. The difference is that white asparagus is covered with soil as it begins to sprout. Because it is not exposed to light, it does not produce chlorophyll, a potentially beneficial phytochemical. White asparagus contains marginally less vitamin C as well.

White asparagus tends to be thicker and more tender than the green variety. It also has a slightly nutty flavor and is less prone to the stringiness of its green cousin.

Asparagus can also be purchased frozen and canned. Frozen vegetables retain all the same nutrients as fresh varieties. Canned versions usually do too, but they also often contain added sodium. To reduce your salt intake, rinse canned vegetables or beans before eating.

When It's Best

You can enjoy asparagus all year long, as it has become a common staple in most produce markets. Still, the peak season is around April and May, so take advantage of the best and most tender spears during the spring.

When selecting fresh asparagus, choose stalks that have a tightly closed bud. The stalks should be rich in color, stand firm, and appear plump and straight. Avoid asparagus that is limp, mushy, blemished, or dull in color.

Storage and Food Safety

Fresh asparagus can dry out quickly, so it's important to store it properly to maintain freshness. To extend its shelf life and prevent food waste:

  1. Keep your asparagus bundle in a rubber band. The stalks should not be washed until just before cooking.
  2. Trim an inch off the bottoms of the stalks.
  3. Wrap the ends in a moist paper towel.
  4. Stand them in a container of water (about 1 inch deep) and store them in the refrigerator.

How to Prepare

Asparagus can be steamed, boiled, stir-fried, grilled, or sliced thinly and eaten raw in salads. Thicker, late-season stalks may be needed to be peeled before cooking. Snap off the woody end of the stem before eating or cooking.

Cook asparagus just long enough so that it retains its bright green color. Once it begins to turn a pea soup green, it will likely be overcooked and limp. Overcooked asparagus loses some of its nutrients and health benefits (and the flavor and texture can be off-putting as well).

Recipes

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