What is the Nutritional Value of Onions?

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Whole and halved onions on a cutting board.
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Whether you enjoy onions for the taste or the crunch, do not underestimate the nutritional value of the onion. In addition to healthful fiber, onions serve up vitamins and minerals useful for meeting your nutritional goals. Pay no attention to that onion breath you may get from eating them; your significant other may not thank you, but your body will.

Basic Nutrition

A 1-cup serving of chopped onions contains 51 calories and 0.13 g of fat. If you follow a 2,000-calorie diet, this accounts for 2.5 percent of the calories and very little of the 44 to 78 g of fat you may consume daily. Each cup of onions also provides 11.6 g of carbohydrates, a nutrient used for fuel in your body. While protein is also used for energy, it is a secondary source. One serving of onions has 1.3 g of protein.


Onions are a healthy choice for getting more fiber into your diet. Each serving of this vegetable serves up 2.1 g of fiber, which contributes toward your soluble fiber intake. The type of fiber in onions may lower your chances of developing cardiovascular disease, such as high blood pressure, stroke, heart failure and heart attacks. It may also help reduce your cholesterol. Consume 25 to 38 g of fiber per day.


One serving of onions provides 11.5 percent of the vitamin B-6 you need each day. This makes onions a smart choice for cognitive and nerve function as vitamin B-6 helps your body manufacture serotonin and make myelin, the layer of fats and proteins that cover your nerves. Many Americans suffer from a mild vitamin B-6 deficiency, which can impact the nerves in your legs and arms. You also get 5.9 percent of the daily recommended intake of folate as well as 3.9 percent of the vitamin C your body requires each day.


While onions may not be the first thing you reach for to increase your calcium intake, one serving of this vegetable provides 3.5 percent of the calcium you need daily. The calcium in onions lends critical strength and density to your bones and teeth. Each serving of onion provides a small amount of manganese as well. In addition, eating onions may help your body more effectively get some minerals from the grains you eat. Research published in the July 2010 issue of the "Journal of Agricultural and Food Chemistry" notes that consuming up to 3 g of onion per 10 g of grains increased the amount of available zinc and iron up to 73 percent, making grains more nutritious.

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