General Description

Numerous forms and varieties of onion exist, since this perennial or biennial herb is cultivated worldwide. The part used is the fleshy bulb. Common varieties are white globe, yellow globe, and red globe.

Onions range in size, color, and taste depending on their variety. The two general types of large, globe-shaped onions are classified as spring/summer or storage onions. The former class includes those grown in warm weather climates and mild or sweet in flavor. Included in this group are the Walla Walla, Vidalia, and Maui Sweet onion. Storage onions are grown in colder weather climates. After harvesting, they are dried out for several months to attain dry, crisp skins. They generally have a more pungent flavor and are usually named by their color: white, yellow, or red. Spanish onions fall into this classification. In addition to these large onions, there are smaller varieties, such as the green onion, or scallion, and the pearl onion.

Chemical Composition

Onions, like garlic, contain various organic sulfur compounds:

Onions also contain the enzyme alliinase, which is released when the onion is cut or crushed, causing conversion of trans-S-(1-propenyl) cysteine sulfoxide to the so-called lacrimatory factor (propanethial S-oxide). Other constituents include the following^1,2:

History and Folk Use

Although not as valued a medicinal agent as garlic, onion has been used almost as widely. Like garlic (Allium sativum), onion has been used as an antispasmodic, carminative, diuretic, expectorant, stomachic, anthelmintic, and anti-infective agent. Externally, it has been used as a rubefacient and poultice, giving relief for skin diseases and insect bites.^1–3

Onions originated in the central part of Asia, from Iran to Pakistan, and northward into the southern part of Russia. Onions have been revered throughout time not only for their culinary use but also for their therapeutic properties. As early as the sixth century, onions were used as medicine in India. Although they were popular with the ancient Greeks and Romans, they were often dressed with extra seasonings, because many people did not find them spicy enough. Yet it was their pungency that made onions popular among poor people throughout the world, because this inexpensive vegetable could spark up meals. Onions were an indispensable vegetable in the cuisines of many European countries during the Middle Ages and later even served as a classic healthy breakfast food. Christopher Columbus brought onions to the West Indies, and then their cultivation spread throughout the Western hemisphere. Today, China, India, the United States, Russia, and Spain are among the leading producers of onions.

World onion production has increased dramatically, with current production around 44 million tons per year, making onions the second most important horticultural crop after tomatoes. Because of their storage characteristics and durability for shipping, onions have always been traded more widely than most vegetables. Onions are versatile, often used in many dishes, and accepted by almost all traditions and cultures.⁴

Pharmacology

Onions and garlic, due to their similar constituents, have many of the same pharmacologic effects. However, significant differences make one more advantageous than the other in certain conditions.

One of the key nutritional qualities of onions is their high content of quercetin. To determine uptake as well as in vivo antioxidant effects of quercetin from onions, six healthy nonobese, normocholesterolemic female volunteers participated in a randomized two-phase crossover supplementation trial to compare the antioxidant effects associated with (1) a meal of fried onions and (2) a meal of fried onions and fresh cherry tomatoes.⁵ Plasma flavonoids, lymphocyte DNA damage, plasma ascorbic acid, tocopherols and carotenoids, urinary malondialdehyde, and 8-hydroxy-2-deoxyguanosine were determined to assess flavonoid absorption and antioxidant efficacy. The results indicated that the flavonoid glucosides (quercetin-3-glucoside and isorhamnetin-4-glucoside) were significantly elevated in plasma after ingestion of the onion meal, and the increases were associated with an increased resistance of lymphocyte DNA to DNA strand breakage.

A significant decrease in the level of urinary 8-hydroxy-2-deoxyguanosine was evident 4 hours after ingestion of the onion meal. After the combined tomato and onion meal, only quercetin was detected in plasma. Endogenous base oxidation was decreased, but resistance to strand breakage was unchanged. No significant change in the excretion of urinary malondialdehyde occurred after either meal. The conclusions from the study were that both meals—onions and onions with tomatoes—led to transient decreases in biomarkers of oxidative stress, although the particular biomarkers affected differed. It is possible that the differences in patterns of response reflect the different uptakes of flavonoids, but the underlying mechanism is not yet understood.

Related posts:

Botanical Medicine—A Modern Perspective Premenstrual Syndrome Hair Loss in Women Allium sativum (Garlic) Tanacetum parthenium (Feverfew) Medicinal Mushrooms

Stay updated, free articles. Join our Telegram channel

Join