The Latest News About Onions
Summary
What would a kitchen be without the distinctively pungent smell and taste of onions filling out the flavors of almost every type of cuisine imaginable? Fortunately, yellow storage onions are available throughout the year although sweet varieties have a much more limited growing season and are available only a few months out of the year.
While onions may bring a tear to your eye and a pungency to your breath they will also certainly bring delight to your taste buds. The onion, known scientifically as Allium cepa, is, on the surface, a humble brown, white or red, paper-thin skinned bulb; yet, despite its plain looks, it has an intense flavor and is a beloved part of the cuisine of almost every region of the world.
What's New and Beneficial About Onions
The flavonoids in onion tend to be more concentrated in the outer layers of the flesh. To maximize your health benefits, peel off as little of the fleshy, edible portion as possible when removing the onion's outermost paper layer. Even a small amount of "overpeeling" can result in unwanted loss of flavonoids. For example, a red onion can lose about 20% of its quercetin and almost 75% of its anthocyanins if it is "overpeeled."
The total polyphenol content of onions is much higher than many people expect. (Polyphenols are one of the largest categories of phytonutrients in food. This category includes all flavonoids as well as tannins.) The total polyphenol content of onion is not only higher than its fellow allium vegetables, garlic and leeks, but also higher than tomatoes, carrots, and red bell pepper. In the French diet, only six vegetables (artichoke heart, parsley, Brussels sprouts, shallot, broccoli, and celery) have a higher polyphenol content than onion. Since the French diet has been of special interest to researchers in terms of disease prevention, onion's strong polyphenol contribution will very likely lead to follow-up studies that pay closer attention to this unique allium vegetable.
Within the polyphenol category, onions are also surprisingly high in flavonoids. For example, on an ounce-for-ounce basis, onions rank in the top 10 of commonly eaten vegetables in their quercetin content. The flavonoid content of onions can vary widely, depending on the exact variety and growing conditions. Although the average onion is likely to contain less than 100 milligrams of quercetin per 3-1/2 ounces, some onions do provide this amount. And while 100 milligrams may not sound like a lot, in the United States, moderate vegetable eaters average only twice this amount for all flavonoids (not just quercetin) from all vegetables per day.
When onions are simmered to make soup, their quercetin does not get degraded. It simply gets transferred into the water part of the soup. By using a low-heat method for preparing onion soup, you can preserve the health benefits of onion that are associated with this key flavonoid.
When we get quercetin by eating an onion-rather than consuming the quercetin in purified, supplement form-we may end up getting better protection from oxidative stress. That's exactly what happened in an animal study where some animals had yellow onion added to their diet in a way that would provide the same amount of quercetin provided to other animals in the form of purified quercetin extracts. The best protection came from the onion version of this flavonoid, rather than the supplement form.
Several servings of onion each week are sufficient to statistically lower your risk of some types of cancer. For colorectal, laryngeal, and ovarian cancer, between 1-7 servings of onion has been shown to provide risk reduction. But for decreased risk of oral and esophageal cancer, you'll need to consume one onion serving per day (approximately 1/2 cup).
WHFoods Recommendations
With their unique combination of flavonoids and sulfur-containing nutrients, the allium vegetables - such as onions - belong in your diet on a regular basis. There's research evidence for including at least one serving of an allium vegetable - such as onions - in your meal plan every day. When onion is your allium vegetable of choice, try to consume at least one-half of a medium onion on that day, and use this guideline to adjust your recipes accordingly. For example, if you are following a recipe that yields 4 servings, include at least 2 medium onions in the recipe so that each of your 4 servings will contain at least one half medium onion.
To bring out the sweet flavor of onions we recommend using our Healthy Saute method of cooking onions for just 7 minutes. Cut onions into slices of equal 1/4-inch thickness to help them cook more evenly. The thinner you slice the onions the more quickly they will cook. Let them sit for at least 5 minutes before cooking to enhance their health-promoting properties. For more details see the Healthiest Way of Cooking Onions in the How to Enjoy section on our website.
Health Benefits
Onions provide numerous health benefits including:
Heart health support
Promotes bone and connective tissue health
Anti-inflammatory benefits
Potentially blood sugar regulation effects
Anti-cancer properties
For more details on onions' health benefits, see this section of our onions write-up.
Nutritional Profile
The outstanding polyphenol content of onions (including their rich concentration of flavonoid polyphenols) is probably the most overlooked nutrient content of these allium vegetable. Among the flavonoids, onions also provide a particularly large amount of quercetin. A wide variety of allyl sulfides are found in onion, including the four major diallyl sulfides: DMS (diallyl monosulfide), DDS (diallyl disulfide), DTS (diallyl trisulfide), and DTTS (diallyl tetrasulfide). Also present are a wide variety of sulfoxides, including (+) S-methyl-L-cysteine sulfoxide (MCSO), (+)-S-(1-propenyl)-L-cysteine sulfoxide (PRENCSO), S-methyl-l-cysteine sulfoxide, S-propyl-l-cysteine sulfoxide, and S-propenyl-l-cysteine sulfoxide.
Onions are a very good source of biotin. They are also a good source of manganese, vitamin B6, copper, vitamin C, dietary fiber, phosphorus, potassium, folate, and vitamin B1.
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