Asparagus: nutrition facts and health benefits

Asparagus

Asparagus is a plant consisting of an underground stem, the claw. It produces buds, which are called turions. They stretch underground in search of light. On the end of the bud, turions change color in open air and light. It turns from pink to purple before being green.

Asparagus had always grown in the wild around the edge of the Mediterranean basin and also in minor Asia. In Ancient history, Romans invented its culture (Apicius cooked mashed egg with it). Egyptians immortalized this vegetable because the asparagus had a reputation of being an aphrodisiac food. Greeks also consumed asparagus and used it as a medicinal plant. Centuries later, king of France Louis XIV was passionate about this to the point of wanting it on his table in all season. He preferred eating it in an egg shell. His gardener invented a way in order to grow it all year round in a greenhouse.

History of asparagus

Asparagus is a plant whose claw produces each year buds that stretch in fleshy stems called turions. It takes its name from the latin word asparagus which itself is borrowed from the Greek asparagos, which comes from Persian.

It is believed that asparagus comes from the East of the Mediterranean basin and minor Asia. The Romans have domesticated asparagus 200 years before our era. The Greeks preferred to pick them in the wild, convinced that it was a much better remedy. Indeed, it had a great reputation as a medicinal plant. It was supposed to cure everything, from bee stings to heart problems as well as dropsy and toothache. It was also considered an aphrodisiac and it’s for this reason people didn’t hesitate to drink the water in which it was cooked. Moreover, its diuretic properties are undeniable.

A vegetable leaving odoriferous traces

Asparagus has a particular smell giving a strong scent to urine. This is due to the presence of 6 sulfur compounds coming from the degradation of some amino acids in the plant. But it seems that some people do not detect that particular smell.

Asparagus is part of exotic plants. In the 16th century, Italian Princess Catherine de Medici brought it when she crossed the Alps to marry the future King of France, Henri II. A century later Louis XIV gave a title to its first gardener and a plot of land to thank him for having found a way to grow this valuable vegetable year-round. At this time, French gardeners developed the know-how for obtaining a white colored turion. The method is to cover their land base as they grow to deprive them of having sun thus preventing them from producing chlorophyll. This know-how was then passed to Germany and to other European countries. Meanwhile it was never fully adopted in North America because people mostly preferred the green asparagus rather than the white variety.

Asparagus is appreciated all over the world. It has been incorporated into both Western Oriental cuisines. However, it’s relatively expensive, because it must be harvested by hand, unlike many other vegetables.

Asparagus health profile

Asparagus is eaten in all parts of the world. They can be white, green or purple. This vegetable is an excellent source of folate, an essential vitamin for pregnant women who are breast-feeding. It contains antioxidants helping your body to prevent many diseases.

The benefits of asparagus

Benefits of asparagus on human health were assessed by few studies. However, several epidemiological and prospective studies have shown that a high consumption of fruit and vegetables can reduce the risk of cancers, cardiovascular diseases, and other chronic diseases. The presence of antioxidant compounds in fruits and vegetables could play a role in this protection.

What contains asparagus?

Phenolic compounds

Asparagus contains several phenolic compounds, including flavonoids (mainly rutin) and phenolic acids (including acid hydroxycinnamique). These compounds have antioxidant properties, which mean that they reduce the damage caused by free radicals in the body. Free radicals are highly reactive molecules that are thought to be involved in cardiovascular disease, some cancers and other diseases related to aging.

Purple and green asparagus contain more phenolic content than white asparagus. When it is fresh, peeling the asparagus does not seem to affect its content in phenolic compounds. However it does reduce its phenolic content when it’s peeled before being stored.

Asparagus would possesses the best qualitative antioxidants as compared to several vegetables commonly consumed in the United States and Europe. Their antioxidants have better quality than those from garlic, broccoli, sweet pepper, yellow onion and red onion. But its consumption is relatively small. From a health point of view, an increase in the consumption of asparagus would be welcome.

Carotenoids

Asparagus contains carotenoids pigments, mainly zeaxanthin, lutein, beta-carotene, and capsanthin. During the asparagus ripening, beta carotene and lutein concentrations tend to decrease, while the quantities of capsanthin and zeaxanthin increase. Carotenoids are compounds with antioxidant properties and consumption of foods with many carotenoid would be linked to a lower risk of some cancers and cardiovascular disease.

Excellent source of folate (vitamin B9)

Asparagus have a high folate content, which puts it in the 5th place for foods with the most folate, after beef liver and certain types of legumes. Five cooked asparagus provide about 25% of the daily needs in folate for the general population and 15% to 20% for pregnant or breastfeeding women. Canned asparagus contain almost as much folate than fresh asparagus.

Thiols

Asparagus would ranks first among fifteen vegetables with respect to its content in two types of thiols, glutathione, and the acetylcysteine. These compounds have different antioxidant properties. Among other things, glutathione may improve the elimination of oxidized cholesterol, which is very damaging for the arteries. Food consumption rich in glutathione may also decrease the risk of having cancer from the top of the digestive tract. As these results are not related to specific ingestion of asparagus, more studies will be needed to determine the effect of consuming thiols from this vegetable.

Saponins

Asparagus contain saponin, mainly protodioscin. In addition to the antioxidant activity of asparagus, this saponin is also known for its toxic effects in vitro on cancerous human cells. This effect was not assessed on the consumption of asparagus, but researchers have observed that the lower part of this vegetable contains up to 100 times more protodioscin than the upper part. The basis of the asparagus is usually cut before consuming it, therefore the beneficial effects of this compound would be more often lost.

Phytoestrogens

Asparagus contains small amounts of isoflavones and lignans, two types of phytoestrogens. These compounds, whose structure is similar to estrogen, could reduce the risk of some cancers. It should be noted that asparagus isoflavone content is substantially lower than soy products (about 200 times less of isoflavones than tofu and 90 times less than soy milk). On the other hand, the amount of lignans present in asparagus is usually equal to or higher than soy products. Cooking asparagus wouldn’t have a major impact on their concentration in phytoestrogens. Asparagus could therefore help increase phytoestrogens intake from food.

Fructo-oligosaccharids

Fructo-oligosaccharids or oligofructoses are a natural type of carbohydrates present in some fruit and vegetables such as asparagus, artichoke, onions, garlic, banana and chicory. Fructo-oligosaccharids are known for their health benefits, especially for their prebiotic effect, their favorable effect on mineral absorption, as well as the decrease of cholesterol, triacylglycerols and phospholipids blood.

Sulphide compounds

In some vegetables, including the asparagus, a sulfide compound named dimer has been detected. This molecule has recently been demonstrated to have antioxidant properties and has been found in human plasma and urine. These results are promising and more research should be conducted to better understand the effect of this compound among humans.

More minerals in the tips

The tip of green asparagus and white asparagus has more concentrated in certain minerals than the base of asparagus (1.5 to 2.5 times more). This is good news, given the tip of the asparagus is especially popular among consumers.

Precautions

Vitamin K and blood thinners

Asparagus contains high amounts of vitamin K. This vitamin, necessary among other things to blood clotting, can be produced by the body in addition of being found in certain foods. People taking anticoagulant drugs (Coumadin, Warfilone, Sintrom, etc.) must adopt a diet whose content in vitamin K is relatively stable from one day to the other. Asparagus is part of a list of foods that should be consumed at least 1 time per day. The recommended serving is 250 ml (1 cup) each time. It is strongly recommended to people taking anticoagulation medicine to consult a dietitian, nutritionist or doctor to know which food is a source of vitamin K and to ensure the most stable daily intake.

Asparagus and botulism

Food botulism is caused by consumption of food contaminated with botulinum toxin. Improper home canning is involved in several reported cases of botulism food especially from low-acid foods such as asparagus.

Poisoning symptoms occur within 6 to 36 hours after eating the offending food. They consist of a difficulty with speech and absorption, a dry mouth and fatigue and double or blurred vision. Food botulism is rare, but it can be deadly. Special precautions must be taken to avoid it, especially when home canning.

Selection and conservation

Choose

Purple asparagus

Contrary to popular belief, thin asparagus is less tender than large ones, because they have proportionately more wood fibers. Choose asparagus whose tips are well closed and compact. You can find purple asparagus on the market. However, cooking makes them lose their color.

Keep

The longer you keep asparagus at room temperature before consuming for a long time, the more fibrous they will be. Their sugars quickly turn into starch and the development of woody tissue is accelerated.

Refrigerator. First surround the boot base of damp paper towel and put everything in a plastic bag. You can also place them vertically in a jar containing 5 cm of water. They may be kept for 1 or 2 weeks. Alternatively, keeping them submerged in cold water until you prepare them for dinner, keeps them tender.

Freezer. Once whitened for 3 minutes in boiling water, asparagus can be kept about 8 months. Cook without defrosting them.

Organic gardening

Asparagus can be planted in every ground as long as they are well-drained. Meanwhile they prefer sandy land and it’s better to avoid having them in the water which is the main cause of claw’s decay. Ground pH should be 6.5 to 7.5. Avoid planting it where it’s less than 6.
You can multiply the asparagus from seed or clutches of 1 year. In the first case, the seedlings are grown inside 10 or 12 weeks before the last frost. Seedlings or claws will be put in the ground when the ground temperature reaches 10 °C. You must install them in the North or West side of the vegetable garden, because the plant can easily goes up to 2 meters, and provide a lot of shadow.

Not too deep

It was thought for a long time that asparagus should be planted deep (30 cm and more), but researchers have recently discovered that more claws are deep, the less plants are productive. The ideal depth is 10 to 15 cm.

Dig a furrow of 10 to 15 cm deep, add a manure or compost layer, drop the claw or the young plant and cover with land. Space them 45 cm in the row and 1.5 m between rows. Spears will emerge a few weeks later. Don’t harvest them the 1st year. Harvest them during 3 weeks the second year, in order to allow the plant to make reserves of nutrients. Its longevity reaches 15 years. The productivity depends on the respect of this rule. For the same reasons, from the 3rd year, you will reap the spears during 6 to 8 weeks each spring, and you will cut the foliage late in the fall or early spring.

Irrigation

The first 2 years, it must be watered if the weather is dry. Subsequently, cut them 1 or 2 times during the period of the harvest and a few times during the summer, upon the foliage formation. Finally, a bit of watering in the fall will increase production of the following year and protect plants from damage that could cause freezing in the winter.

Harvesting and care

It’s preferable to harvest stalks in the morning, when they are 15 to 25 cm long and their tip is still closed. You can either cut them a few centimeters below ground level with a knife, or break them by hand. Pick up all the shoots during the period of harvest regardless their quality. This avoids the early formation of the foliage and delays the arrival of the cereal leaf beetle, an insect feeding itself from the plant and weakens it. Harvest stops normally when the diameter of three-quarters of the shoots is no longer 1 cm or less. At this point, collect all the shoots one last time, add a good layer of compost and mulch to avoid the lifting of weeds. Each spring; add a layer of compost or decayed manure. In autumn, add 10-12 cm of mulch that you will withdraw the following spring.

A mature plant will produce 15 to 20 spears per year. You will need 12 to 18 plants to feed a family of 4 persons with fresh asparagus needs.

Diseases and insects

In the family garden, pests and diseases are rare. You can avoid majority of problems making sure to respect the spacing recommended between the plants and the ranks, well draining soil, good air circulation between plants and water well and fertilize plants. If rust are on the plants, treat them with sulfur. To avoid wilting fusarien, against which there is no treatment, make sure that the seeds or the original plants are not contaminated. To this end, you can ask advice from the seed merchant or a nurseryman. New “Jersey” varieties, which give only male plants, will be more resistant than traditional varieties.

 

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