Onions are excellent dietary sources of fiber. Red onion is the richest variety in fiber, while white onions have the lowest fiber content. An onion contains up to 3.1 g of fiber, or 11% DV.
How much fiber should we consume a day?
A high-fiber diet has been associated with a lower risk of developing heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases. Also, it may lower high blood pressure and serum cholesterol levels, enhance immune function, and improve insulin sensitivity.[1]
We should consume at least 28 g of fiber per 2,000 calories. People who consume more calories should consume more fiber as well.
Most people fail to meet their daily needs in fiber. Actually, 90% of Americans don’t consume enough fiber.
What’s the fiber content of onions?
Onions are excellent dietary sources of fiber, while they’re low in sugar. They contain between 1.2 g and 2.2 g of fiber per 100g, depending on the variety.
White onions have the lowest fiber content. They contain only 1.2 g of fiber per 100g. A medium onion contains about 1.7 g of fiber, or 6% of the recommended daily intake.[1]
Yellow onions have a medium fiber content. They contain 1.9 g of fiber per 100g. Hence, they contain almost 60% more fiber than white onions! Just a medium yellow onion contains 2.7 g of fiber, which is almost 10% DV (Daily Value).
Red onion is the richest variety in fiber. Red onions contain 2.2 g of fiber per 100g. So, they have almost twice the fiber content as compared to white onions! A medium red onion contains about 3.1 g of fiber, or 11% DV.
Onion rings are high in fiber as well. They contain about 2.2 g of fiber per 100g.
Onion greens are also excellent dietary sources of fiber. They contain 2.6 g of fiber per 100g!
What types of fiber are in onions?
Onions contain both soluble and insoluble fiber.
The main types of fiber in onion are cellulose and pectic polysaccharides. Storage of onions increases their insoluble fiber content.[2,3]
Soluble fiber dissolves in water, turning to a gel. It slows down digestion and has satiating effects. Insoluble fiber doesn’t dissolve in water. It absorbs water, making the stool softer, helping defecation.
Common foods high in fiber
Only vegetables, fruits, legumes, beans, mushrooms, whole-grains, seeds, and nuts are good dietary sources of fiber.
Beans have the highest fiber content. For instance, a serving of lentils or chickpeas provides about 45-55% of the recommended daily intake!
Also, vegetables help meet our daily fiber needs. For instance, lettuce, spinach, cabbage, kale, and broccoli are particularly high in fiber.
Favorite foods, like whole-grain bread, pasta, potatoes, and sweet potatoes are great dietary sources of fiber as well. Following a diet high in fiber is easy!
On the other hand, animal-based and refined plant-based foods contain no or negligible amounts of fiber.
Why should we eat onions regularly?
Onions have many health benefits, as they have a superior antioxidant content. For instance, they’re particularly high in flavonoids, quercetin, and phenolic compounds.[4,5]
The outer layers of the onion have the highest antioxidant content, though. Don’t discard them.[6]
Onions have potent antioxidant, anti-inflammatory properties, anticancer, anti-diabetic, and antihypertensive properties. In fact, onions, as part of a well-balanced diet, may help lose weight, reduce elevated LDL-cholesterol, boost the immune system and protect the heart.[7,8,9]
Last, but not least, onions (and garlic) help absorb nutrients of other foods! For instance, onion consumption enhances the bioavailability of minerals, like iron and zinc. Onions are particularly high in sulfur-containing amino acids, which seem to promote mineral absorption.[10]
Also, onions contain small amounts of many minerals, such as iron, potassium, zinc and manganese.
