Asparagus

Well known for its bright emerald green and crisp stalks, locally grown asparagus is nutrient powerhouse delivering fibre,vitamins,minerals and anti-inflammatory phytonutrients. This month I'm saluting one of my favourite green vegetables - asparagus!

Asparagus

Nutrition Notes

Asparagus has a unique combination of nutrients an phytochemcials which makes it an exceptionally healthy vegegable to include in your diet.

Like most green vegetables, asparagus is low in calories and virtually fat free; six spears of asparagus have just 20 calories and 0.2 grams of fat.  For so few calories, it also delivers vitamins A, C and K and folate along with potassium, a mineral that helps maintain healthy blood pressure.

Asparagus is a leading source of folate, a B vitamin that keeps the DNA of our cells in good repair.  One serving of asparagus (1/2 cup or 6 spears) delivers one-third of a day's worth of folate (adults need 400 micrograms daily). 

Research suggests asparagus is an anti-inflammatory food, thanks to its unique combination of phytochemicals, including saponins, quercetin, rutin and kaempferol.  Chronic inflammation, the body's ongoing release of harmful chemicals, is considered a risk factor for many chronic diseases including type 2 diabetes, heart disease and Alzheimer's disease.  Foods such as asparagus help lessen inflammation in the body by promoting the production of anti-inflammatory immune compounds.

Asparagus also contains an impressive amount of antioxidants, including glutathione, one of the most powerful antioxidants studied.  Gram for gram, asparagus contains just as many antioxidants as many other vegetables including broccoli and cabbage.

Asparagus helps support digestive health, thanks to its inulin content.  Inulin is a type of carbohydrate, also known as a "prebiotic", that gets broken down in the large intestine and helps support the growth of healthy "probioic" bacteria, including Bifidobacteria and Lactobacilli.

Nutrient information per 6 medium spears (or 1/2 cup) of asparagus:

Calories 20 kcal
Fat  0.2 g
Carbohydrate 3.7 g
Fibre 2 g
Folate  134 mcg
Vitamin K 45 ug
Vitamin C 5 mg
Potassium  202 mg

Source: Canadian Nutrient File, 2007b

Varieties

The green varieties of asparagus we're most familiar with in Canada include the Viking and Centennial varieties.

White asparagus, available at farmer markets and specialty food stores, is not actually a different variety of asparagus.  It is the result of a cultivation technique in which the stalks are protected from light by being buried under soil during their growing period.  Less bitter than its green counterpart, white asparagus is extremely popular in Western Europe.

Purple asparagus was originally developed in Italy and is grown on a small scale in some countries, including the U.S.  Purple asparagus differs from green and white asparagus in that it has a higher sugar content and less fibre.

Buying

When buying fresh asparagus, look for stalks that are crisp, straight and bright green. They should have compact, closed and relatively dry tips that are deep green or purplish in colour.  Avoid asparagus with tips that are partially open, wilted, mushy or with flowers starting to form - these indicate that asparagus is past its prime, and will likely have dry, tough and stringy stalks.

Asparagus loses about half its weight once it's been trimmed and cooked.  When purchasing fresh asparagus, aim for about one pound (450 g) of fresh asparagus to serve four people as a side dish.

Storing

If not stored properly, asparagus can rapidly decrease in quality and perish quickly.  There are two ways to store asparagus. 1) Wrap the stems in damp paper towels and cover the entire bunch with plastic wrap or a plastic bag; 2)  trim ¼-inch off the bottom of the stems and then stand them upright in a jug of water in the fridge.

Stored properly, fresh asparagus will last for three days in the fridge.

Preparing

To prepare asparagus, first wash it under cool running water. If the tips have any sand on them, dunk them in and out of the water, then rinse thoroughly.

To trim asparagus, cut off the tough bottom inch using a knife.  Alternatively bend the asparagus toward the bottom of the stalk; you'll notice asparagus spears tend to naturally snap and break at the point where the stalks become tough and fibrous.  You can reserve the woody, fibrous stalks for use in homemade vegetable or chicken stock.

Asparagus requires a very short cooking in time.  It's a common mistake to overcook asparagus to the point that it is limp, mushy and discoloured.  Overcooked asparagus loses some of its nutrients and health benefits.

Steaming: Asparagus can be steamed upright or flat in a saucepan. To steam upright: fasten the stalks with kitchen string. Stand the stalks upright in a double boiler or a tall, lidded pot with the tips extending an inch or more above the boiling, salted water. There are also special asparagus cookers designed for upright cooking. Bring to a rapid boil, then cover.

For extra flavor you can add a clove of garlic, a slice of onion or a lemon wedge to the water. Cook until tender, about 5 to 8 minutes.

Alternately, put the asparagus spears in a collapsible vegetable steamer and place in a large skillet. Fill the skillet with enough water to reach just below the bottom of the steamer. Bring water to a boil and cook, uncovered, until crisp-tender, 3 to 5 minutes.

Stir-frying: Cut spears diagonally in 1/2-inch pieces, leaving the tips whole. Stir-fry in a skillet or wok with a couple of teaspoons of canola oil at medium high heat. Stir constantly until tender-crisp, about 3 to 5 minutes.

Microwaving: Place in a microwavable dish. If cooking whole spears arrange with the tips pointing toward the center. Add ¼ cup (50 ml) water and cover. Rotate the dish halfway through the cooking time. Microwave at full power for 4 to 7 minutes for spears, 3 to 5 minutes for cuts and tips.

Roasting: Trim the stalks, then place in a baking dish and lightly drizzle with a small amount of olive oil. Roast uncovered at 400°F (200°C) for approximately 3 to 7 minutes (thinner stalks will cook more quickly than thicker ones).

Grilling: To grill asparagus, trim stalk and brush with a small amount of olive oil.  Place on grill, directly over medium heat, for 3 to 7 minutes, turning once halfway through cooking.

Eating

Though traditionally served with melted butter, hollandaise sauce or poached eggs, there are plenty of other (lower fat) ways to serve fresh asparagus.  Add asparagus to soups, salads, omelets, frittatas, stir-fries or enjoy them on their own.

Healthy ways to enjoy

Breakfast

  • Add asparagus tips to omelets or frittatas.
  • Serve steamed asparagus with poached or scrambled eggs.

Lunch

  • Add leftover grilled asparagus to a spinach or green salad.
  • Make a veggie sandiwch with leftover roasted or grilled asparagus, red pepper, red onion and portobello mushroom.
  • Toss cooked asparagus with pasta, shredded chicken breast, fresh chopped basil and drizzle with olive oil and lemon juice for a hearty mid-day meal.

Dinner

  • Add asparagus spears to a stir-fry; add them in the last few minutes of cooking to ensure they don't overcook.
  • Whip up a pot of asparagus soup. Click here for a recipe.
  • Toss asparagus spears on the barbecue when grilling meat for nutritious side dish.

Did you know?

  • Some people produce strong smelling urine after eating asparagus. It's harmless and not everyone experiences it.  It's thought some people are genetically inclined to metabolize asparagus in such a way that generates odor-producing substances.  Scientists suspect the likely culprit is methylmercaptan, a sulfur-containing derivative of an amino acid in asparagus called methionine.

More Information

Foodland Ontario

Ontario Asparagus Growers' Marketing Board

World's Healthiest Foods

Wikipedia