Amazing Asparagus

TON - JUNE 2012 VOL 5, NO 5 published on June 29, 2012 in Supportive Care
Karen Connelly, RD, CSO

The mighty green spear of the asparagus is a welcome sign of spring. This nutrient-packed vegetable has been harvested for more than 2500 years and has been highly regarded as a promoter of health and wellness.1 Asparagus has been a staple for many different people of different cultures around the world for its taste as well as its proposed medicinal properties. The ancient Greeks and Romans heralded asparagus as the ultimate delicacy.1 The variety of vitamins, minerals, and phytochemicals contained in asparagus make it a vegetable not to be ignored. Take advantage of this superb vegetable while it is at its peak this season.

Thanks to the many different species of asparagus, its use and function can vary widely. Asparagus belongs to the lily family (Liliaceae) and as such is related to onions, leeks, and garlic.2 Two main species of asparagus have been researched extensively: the wild asparagus type, Asparagus racemosus, which has been cultivated and used in India and the Himalayas as a medicinal food, and Asparagus officinalis, the most commonly consumed type of asparagus in the United States. One particular study examined the antimicrobial impact of medicinal plants, including Asparagus racemosus, on secondary infections that occurred in treated immunocompromised oral cancer patients.3

The investigators determined that the secondary infections these oral cancer patients developed were due to bacterial and fungal species. They then isolated these microbial species from the oral cancer patients and assessed the in vitro antimicrobial activity of medicinal plants against them. The results of the study demonstrated that the medicinal plants, including Asparagus racemosus, did show antimicrobial activity against the clinical isolates from the oral cancer cases. These findings help validate the long history of using plants for medicinal purposes. This study also renews interest in testing the safety and efficacy of medicinal plants used against resistant strains of bacterial and fungal infections in cancer patients, which may be of significant therapeutic benefit to their overall clinical outcome.

While the study of medicinal plants is an exciting and promising area of research, those studied are not usually the edible type. The good news is that researchers are also studying active components of the common fruits and vegetables we eat on a daily basis. Both Asparagus officinalis and Asparagus racemosus, in addition to various types of vegetables, beans, and herbs, have been found to contain a powerful phytonutrient called saponins. Saponins are naturally occurring steroid or triterpene glycosides found in plants, and have the ability to foam when shaken in water.

The saponins found in the asparagus typically consumed in the United States are asparanin A, sarsasapogenin, protodioscin, and a small amount of the saponin diosgenin. A 2009 research study isolated asparanin A, a steroidal saponin found in Asparagus officinalis, and found that it has an active cytotoxic component.4 Although the exact mechanism of its cytotoxic activity is unknown at this time, asparanin A has been shown to induce cell cycle arrest and trigger apoptosis in human hepatocelluar carcinoma cells.4 Further research may look into how this saponin might be used in the prevention of hepatocellular carcinoma or perhaps as a treatment against this type of cancer.

Asparagus contains a wide variety of vitamins, minerals, and phytochemicals. Due to this impressive nutrient content, asparagus has anti-inflammatory and antioxidant properties. For example, asparagus is an excellent source of folic acid; a 5.3-ounce serving of asparagus provides 60% of the recommended daily allowance for folic acid.2 The benefits of folic acid are numerous: it is a water-soluble B vitamin that helps in reducing the level of a chemical called homocysteine in the blood, which when present in high levels has been linked to heart disease; folic acid also participates in protein metabolism, red blood cell and DNA production, and prevention of neural tube defects in pregnancy.5 Asparagus also contains a very potent antioxidant called glutathione (GSH). The role of GSH as an anticarcinogenic and antioxidant compound is significant to our overall health status.

GSH is present in many cells of the body and helps support the immune system. GSH also detoxifies carcinogenic compounds and neutralizes free radicals that occur due to environmental exposure or as the natural byproduct of certain metabolic processes. Asparagus is also a good source of thiamine, vitamin B6, and potassium and is naturally free of fat and cholesterol and very low in sodium.2 Not only is asparagus a great choice for a low-fat diet, but it also fits very nicely into a calorie-controlled diet, with each spear contributing less than 4 calories. Encourage patients to incorporate asparagus into their daily diet to reap all of these exceptional nutritional benefits.

In addition to the numerous nutritional benefits of asparagus mentioned above, it also boasts yet another well-known component by the name of fiber. Asparagus contains approximately 3 grams of fiber per cup, with about 2 grams of insoluble fiber and 1 gram of soluble fiber. Fiber in the diet is important for a variety of reasons. Insoluble and soluble fiber help promote bowel regularity, regulate blood sugar, maintain healthy cholesterol levels, and reduce the risk of certain types of cancer. In addition to soluble and insoluble fiber, asparagus also contains inulin. The National Cancer Institute defines inulin as “a naturally occurring, indigestible and nonabsorbable oligosaccharide produced by certain plants with prebiotic and potential anticancer activity. Inulin stimulates the growth of beneficial bacteria in the colon, including Bifidobacteria and Lactobacilli, thereby modulating the composition of microflora. This creates an environment that protects against pathogens, toxins, and carcinogens, which can cause inflammation and cancer.

In addition, fermentation of inulin leads to an increase in short-chain fatty acids and lactic acid production, thereby reducing colonic pH, which may further control pathogenic bacteria growth and may contribute to inulin’s cancer protective properties.”6 As the definition explains, these attributes make inulin a very useful carbohydrate to include in the diet to help promote digestive health, as well as maintain good glycemic control for patients with diabetes, due to its unique process of metabolism by the body. Adding asparagus to the diet is an easy way for patients to naturally experience the many health benefits of prebiotics and probiotics without having to take a commercial supplement.

During the season, you can find asparagus in a variety of colors—green, purple, and white—at your local grocery store or farmers market. The differences in color have to do, in some part, with the way in which asparagus is harvested. Asparagus is naturally green, but if the developing shoots are covered with dirt and allowed to continue to grow without exposure to the sun, the resulting spears of asparagus are white. This type of asparagus may be found more easily in a gourmet store rather than at your local grocer. Purple asparagus offers an additional health benefit, as it contains anthocyanins, a group of phytochemicals that give the plant its purple color.

Asparagus is not only very nutritious but also very easy and quick to prepare, which may make it a more attractive vegetable choice for the hectic lifestyles many of us lead on a daily basis. Fresh asparagus spears can be steamed in a saucepan or upright in a double boiler in just 5 to 8 minutes. It can also easily be added to a stir-fry, omelets and frittatas, green salads, and whole-grain salads like quinoa. Purchase asparagus spears that are bright in color with firm, thin stalks and closed, compact tips. For best results, first trim the stems and wash in warm water, then wrap the entire spear in a moist towel and refrigerate. Another option for storage is, after washing and trimming the stems, stand them upright in a couple inches of cold water and then place them in the refrigerator. It is best to use fresh asparagus within 1 to 2 days of purchasing.

Asparagus may not always get the attention it deserves compared to other members of the vegetable family, but after listing all of its health benefits, perhaps asparagus will become a staple in many diets. This special vegetable is available from late April through mid to late June, so enjoy its delicate flavor and bountiful health benefits while they last.

References

  1. Michigan Asparagus Advisory Board (MAAB). FAQs: questions about asparagus. MAAB Web site. http://www.asparagus.org/maab/faq.html. Published 2000. Accessed May 7, 2012.
  2. Michigan Asparagus Advisory Board. Nutrition information. MAAB Web site. http://www.asparagus.org/maab/nutrition.html. Published 2000. Accessed May 7, 2012.
  3. Panghal M, Kaushal V, Yadav JP. In vitro antimicrobial activity of ten medicinal plants against clinical isolates of oral cancer cases. Ann Clin Microbiol Antimicrob. 2011;10:21.
  4. Liu W, Huang XF, Qi Q, et al. Asparanin A induces G2/M cell cycle arrest and apoptosis in human hepatocellular carcinoma HepG2 cells. Biochem Biophys Res Commun. 2009;381:700-705.
  5. Murphy M. The Ohio State University Extension fact sheet: folate (folacin, folic acid). OSU Extension Web site. http://ohioline.osu.edu/hyg-fact/5000/pdf/5553.pdf. Updated and revised 2004. Accessed May 7, 2012.
  6. National Cancer Institute, National Institutes of Health. NCI drug dictionary: inulin. NCI Web site. http://www.cancer.gov/drugdictionary?CdrID=486745.

Roasted Beet and Grilled Asparagus Salad With an Orange Tarragon Sour Cream

Ingredients
1 bunch asparagus
1 tablespoon canola oil
1 tablespoon thyme
1 bunch beets
2 oranges, juice and zest
2 oranges, peeled, halved, and sliced
1 tablespoon fresh chopped tarragon
4 tablespoons low-fat sour cream
1 bunch leeks, cut into strips and blanched

  1. Roast beets in a 350-degree oven for 45 minutes. Peel while still warm and let cool. Cut into slices.
  2. Toss asparagus with canola oil and chopped thyme. Grill for 2 to 4 minutes. Let cool.
  3. Combine orange juice, tarragon, and sour cream. Place in a plastic squirt bottle with a wide tip. Set aside.
  4. Use squirt bottle to apply dressing to the plate. In the center of the plate alternate the beets and orange slices in a tight circle.
  5. Tie asparagus in small bundles with leek strips. Place on top of beets and oranges.
  6. Garnish with the orange zest.

Nutritional Information
Yield: 4 servings

180 calories, 6 g total fat, 1.5 g saturated fat,
5 mg cholesterol, 70 mg sodium, 31 g total carbohydrate,
6 g dietary fiber, 17 g sugars, 5 g protein

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Last modified: May 21, 2015