Colorful varieties, such as yellow or red ones, pack more antioxidants than white ones. Onions are rich in plant compounds and antioxidants, especially quercetin and sulfur-containing compounds. In fact, yellow onions may contain almost 11 times more antioxidants than white onions ( 25).Ĭooking can significantly reduce levels of some antioxidants ( 26). Red and yellow onions are richer in antioxidants than other types. These sulfur-containing compounds may inhibit the growth of harmful microorganisms and prevent the formation of blood clots ( 24). These are mainly sulfides and polysulfides, which may protect against cancer ( 21, 22, 23). An antioxidant flavonoid, quercetin may lower blood pressure and improve heart health ( 19, 20). Only found in red or purple onions, anthocyanins are powerful antioxidants and pigments that give these onions their reddish color. The most abundant plant compounds in onions are: In many countries, onions are also among the main dietary sources of flavonoids, specifically a compound called quercetin ( 16, 17, 18). The health benefits of onions are attributed to their antioxidants and sulfur-containing compounds ( 3). Their main fibers, fructans, can feed the friendly bacteria in your gut, though they may cause digestive problems in some people. Onions consist mostly of water, carbs, and fiber. However, fructans are considered FODMAPs, which may cause unpleasant digestive symptoms in sensitive individuals, such as those with irritable bowel syndrome (IBS) ( 7, 8, 9). This leads to the formation of short-chain fatty acids (SCFAs), such as butyrate, which may improve colon health, reduce inflammation, and cut your risk of colon cancer ( 4, 5, 6). In fact, onions are among the main dietary sources of fructans ( 2, 3).įructans are so-called prebiotic fibers, which feed the beneficial bacteria in your gut. They are very rich in healthy soluble fibers called fructans. Onions are a decent source of fiber, which accounts for 0.9–2.6% of the fresh weight, depending on the type of onion. They consist mostly of simple sugars, such as glucose, fructose, and sucrose, as well as fiber.Ī 3.5-ounce (100-gram) portion contains 9.3 grams of carbs and 1.7 grams of fiber, so the total digestible carb content is 7.6 grams.

The main nutrients in 3.5 ounces (100 grams) of raw onions are ( 1):Ĭarbohydrates make up about 9–10% of both raw and cooked onions.

Raw onions are very low in calories, with only 40 calories per 3.5 ounces (100 grams).īy fresh weight, they are 89% water, 9% carbs, and 1.7% fiber, with tiny amounts of protein and fat.

Benefits of eating raw purple onions