The Nutritional Benefits of Onions: An In-Depth Guide

For individuals looking to maintain wellness or begin their wellness journey like increasing antioxidants, protection against cancer, immune system support and other health benefits, can adding onions be a nutritious way to improve overall health?

Onions

Onions are nutritious vegetables like garlic, chives, leeks, and shallots. The most common types are red, white, yellow, and Spanish onions. They have antifungal, antibacterial, anti-inflammatory, and other healthful properties.

• Whichever way they are prepared they do lose some of their nutritional value when cooked.
• They contain flavonoids, glutathione, selenium compounds, vitamin E, and vitamin C.
• When selecting onions, look for those without blemishes or discoloration, that are firm, and have dry, papery skins.

Benefits

They contain phytochemicals – compounds plants produce to fight off harmful bacteria, viruses, and fungi. These phytochemicals provide health benefits when consumed and provide the following properties: (Xin-Xin Zhao, et al., 2021)

• Anti-obesity
• Antioxidants
• Antidiabetic
• Anti-inflammatory
• Antimicrobial
• Anticancer
• Protect the cardiovascular, digestive, respiratory, reproductive, and neurological systems.
• Protect against liver disease.
• Support a healthy immune system.

Types and Varieties

They belong to the Allium plant genus which includes plants like garlic, leeks, and chives. (Oregon State University. 2022)

• They vary in flavor and can be sweet, tangy, and sour.
• Different varieties combined with farming practices contribute to the flavor profile of onions.
• There are many varieties of onions.
• The most common and widely available are red, white, yellow, and Spanish.
• Other types include cipollini, pearl, and Vidalia.

Raw or Cooked

They are beneficial whether eaten raw or cooked, cooking them reduces the number of thiosulfinates – compounds that provide antimicrobial, antifungal, and antibiotic properties.

• Research shows that onions that are crushed before cooking retain their health benefits. (Holly L. Nicastro, et al., 2015)
• Boiling and frying onions has been shown to cause the most significant loss in nutritious value.
• Other preparation methods that decrease health benefits include sautéing, steaming, and microwaving.
• Baking onions is shown to increase flavonoid levels.
• Consuming dried, powdered onions can also provide nutritious value to foods, especially if the powder is freeze-dried. (Damini Kothari, et al., 2020)

Nutrition Facts

Onions can contribute to a healthy diet. The flavonoids, glutathione, selenium compounds, vitamin E, and vitamin C, contribute to the antioxidant properties of the vegetable. (Holly L. Nicastro, et al., 2015) The nutrition information for one medium onion: (U.S. Department of Agriculture. N.D.)

• Total calories: 44
• Total fat: 0 grams
• Cholesterol: 0 milligrams
• Carbohydrates: 10 grams
• Dietary fiber: 2 grams
• Total sugars: 5 grams
• Protein: 1 grams
• Calcium: 2 milligrams
• Sodium: 4 milligrams
• Iron: 1 milligrams
• Vitamin D: 0 micrograms

When Selecting

Onions can contain pesticide residue, heavy metals, microbial contamination, and nitrate accumulation. Knowing where the onions come from can help ensure there was no incorrect use of pesticides or that the soil they were grown in was not enriched with heavy metals. When possible, purchase from reputable sources with transparent farming practices, like the farmers markets. (Xin-Xin Zhao, et al., 2021)

• Onions found in environments that have not been effectively sterilized have an increased risk of growing harmful bacteria.
• To avoid contamination of Escherichia. coli or E. coli, salmonella, and mold, it’s safest to purchase whole onions and cut them at home rather than purchasing pre-chopped onions. (Xin-Xin Zhao, et al., 2021)
• Select those that feel firm, have little to no bruises or discolored spots, and have dry papery skin.
• Avoid those that show evidence of mold, like white or black spots on the surface or inside the layers, and those with green shoots, which means the onion is still edible but won’t last that long.

Hypertension Diet

References

Zhao, X. X., Lin, F. J., Li, H., Li, H. B., Wu, D. T., Geng, F., Ma, W., Wang, Y., Miao, B. H., & Gan, R. Y. (2021). Recent Advances in Bioactive Compounds, Health Functions, and Safety Concerns of Onion (Allium cepa L.). Frontiers in nutrition, 8, 669805. https://doi.org/10.3389/fnut.2021.669805

Oregon State University. Types of onions and varieties.

Nicastro, H. L., Ross, S. A., & Milner, J. A. (2015). Garlic and onions: their cancer prevention properties. Cancer prevention research (Philadelphia, Pa.), 8(3), 181–189. https://doi.org/10.1158/1940-6207.CAPR-14-0172

Kothari, D., Lee, W. D., & Kim, S. K. (2020). Allium Flavonols: Health Benefits, Molecular Targets, and Bioavailability. Antioxidants (Basel, Switzerland), 9(9), 888. https://doi.org/10.3390/antiox9090888

U.S. Department of Agriculture. Onions.