Vegetables in the Allium genus include onions, shallots, leeks and scallions, as well as herbs like garlic and chives. These vegetables and herbs all contain "organosulfur compounds" and have been shown to possess antioxidant properties that make them protective against health conditions such as heart disease and cancer.
Onions, Shallots, Leeks, and Scallions
While Allium vegetables like onions, shallots, leeks, and scallions don't contain significant amounts of vitamins or minerals, they are a good source of allyl sulfides, which are compounds that may help lower blood pressure and hinder tumor growth. They also contain saponins, which may prevent tumors and reduce cholesterol.
A particularly important nutrient in Allium vegetables is quercetin. This anti-inflammatory antioxidant may benefit people with inflammatory conditions such as arthritis. People who have arthritis, especially rheumatoid arthritis, have fluid between their joints that contains a significant amount of tumor necrosis factor (TNF), a highly inflammatory chemical. In studies, quercetin was able to limit the inflammatory effects of TNF, which is why these vegetables are believed to help prevent and treat arthritis. Quercetin has also been shown to reverse some age-related memory loss. If you suffer from migraines you may want to steer clear of onions, which contain an amino acid that triggers migraines in some people.
A chive is an herb, not a vegetable, but like its Allium vegetable relatives — onions, shallots, leeks, and scallions — chives contain quercetin and sulfur compounds. However, because chives contain fewer of these nutrients they taste milder and are likely to have a milder effect on health conditions.
Garlic contains allicin, a naturally occurring antioxidant that may help improve heart health. Compounds in garlic also act as powerful antioxidants. There is some evidence that garlic may lower blood pressure and LDL-cholesterol levels — as well as decrease levels of homocysteine — a by-product of protein breakdown that causes inflammation and damages blood vessels.
Although most of the studies that support the health benefits of garlic are done with garlic supplements, they certainly encourage the continued use of garlic as a delicious flavor enhancer in everyday food. Because garlic can act as a blood thinner, it’s important for you to check with your doctor before adding large amounts of garlic to your diet if you take any blood-thinning medications (such as Warfarin) or aspirin.
If bad breath (also known as halitosis) is a problem for you, cutting down on garlic and onions may help. These Allium vegetables contain smelly compounds that get absorbed into your bloodstream and exhaled from your lungs for hours after you eat them.
People who suffer from IBS should be careful about eating onions and garlic, as they are common IBS trigger foods and may lead to discomfort after eating them. Raw garlic, in particular, can be difficult for some people to tolerate, especially if IBS is an issue; so if you have a sensitive stomach it’s probably best to add garlic only during cooking.
The best Allium vegetables are onions, shallots, leeks, and scallions — and herbs like garlic and chives.