Red onions, also known as purple onions, are distinct from other types of onions such as Vidalias due to their deep, dark color. Unlike other types of onion, red onions are often consumed raw, with slices of raw onion a popular topping for sandwiches or hamburgers. Red onions may also be grilled or sauteed for use in a broad range of recipes. Red onions can be a good choice for dieting, as they provide bold flavor with few calories.
Red onions are low in calories, which can make them suitable for a wide range of diet plans. Each medium red onion -- weighing 148g -- contains 60 calories. That amount comprises just 3 percent of the daily recommended intake of 2,000 calories. If you're active, you can burn the calories in red onions relatively quickly; a six-minute jog or five minutes of jumping rope would burn about 60 calories.
As with many other vegetables, carbohydrates are the main source of calories in red onions. Each 148g red onion contains 16g of carbohydrates, so an entire onion would not be ideal for a low-carbohydrate diet, but using smaller portions could be appropriate. Carbohydrates are your body's primary energy source, so high-carbohydrate diets are beneficial for athletes.
Red onions are rich in fiber; each 148g red onion provides 3g. Consuming dietary fiber is essential for proper health, as the nutrient promotes feelings of fullness, helps protect your digestive system from hemorrhoids and other conditions and can help stabilize blood sugar levels.
Red onions contain very little protein. A 148g onion contains only 1g of protein, or 1/8 of what a cup of milk provides. Red onions are often served with protein-rich foods, such as a topping for meaty sandwiches or caramelized on top of steak. Your body needs protein to maintain and build tissues.
Red onions don't provide any dietary fat. While this nutrient is high in calories, you shouldn't avoid eating it, even when dieting. Dietary fats help provide energy, aid in vitamin absorption and ensure proper growth and brain function.
Vitamins and Minerals
Red onions aren't rich in vitamins and minerals. A 148g raw onion provides just 5 percent of the daily suggested intake of vitamin C, but it isn't a significant source of other vitamins and minerals.