Yellow Onion Calories: Facts & Nutrition Breakdown

A medium yellow onion (approximately 148g) contains 64 calories, with just 40 calories per 100g. This versatile kitchen staple offers valuable nutrition with minimal caloric impact, making it an excellent choice for health-conscious cooking.

Discover exactly what's inside your yellow onions and how this common kitchen ingredient can enhance your meals without derailing your nutrition goals. Whether you're meal prepping, watching your weight, or simply curious about what you're eating, understanding yellow onion calories helps you make informed cooking decisions.

Nutritional Profile of Yellow Onions: Beyond Just Calories

Yellow onions serve as the flavor foundation in countless recipes worldwide, but their nutritional value often gets overlooked. Let's examine what makes these kitchen workhorses worth keeping in your pantry.

According to the USDA FoodData Central database, the complete nutritional breakdown for raw yellow onions per 100g serving reveals why they're considered a nutrient-dense food choice:

Nutrient	Amount per 100g	Daily Value %
Calories	40	2%
Total Carbohydrates	9.3g	3%
Dietary Fiber	1.7g	6%
Sugars	4.2g	-
Protein	1.1g	2%
Vitamin C	7.4mg	8%
Folate (B9)	19μg	5%
Potassium	146mg	3%

This nutritional profile comes from the official USDA FoodData Central database, the most authoritative source for food composition information in the United States. The data reflects raw yellow onions, as cooking methods can slightly alter nutritional content.

Yellow Onion vs. Other Varieties: Calorie Comparison

Not all onions are nutritionally identical. Understanding the differences helps you make informed choices based on your dietary needs and flavor preferences.

Onion Type	Calories per 100g	Carbohydrates	Sweetness Level
Yellow Onion	40	9.3g	Moderate
Red Onion	40	9.3g	Moderate
White Onion	42	9.7g	Mild
Sweet Onion (Vidalia)	41	9.6g	High

The minimal differences in calorie content between onion varieties means you can choose based on flavor profile rather than caloric concerns. Yellow onions contain slightly less sugar than sweet varieties like Vidalias, making them a better option when you want savory depth without excessive sweetness.

Practical Applications: Using Yellow Onions in Calorie-Conscious Cooking

Understanding yellow onion calories is just the beginning. The real value comes from knowing how to incorporate them effectively into your meals:

• Flavor foundation without fat: Sauté yellow onions in a small amount of water or broth instead of oil to build flavor in soups, stews, and sauces with minimal added calories
• Volume enhancer: Add diced yellow onions to ground meat dishes (like burgers or meatloaf) to increase portion size while reducing overall calories per serving
• Raw preparation benefits: Raw yellow onions retain maximum vitamin C content, which diminishes with cooking
• Caramelization science: When caramelizing onions, remember that the natural sugars concentrate as water evaporates, slightly increasing calories per ounce but creating rich flavor that requires less added sugar or fat

Health Benefits Beyond Calorie Counting

Yellow onions offer more than just low-calorie flavor. They contain several beneficial compounds that contribute to overall health:

Research published in the journal Molecules highlights that yellow onions contain higher levels of quercetin—a flavonoid with antioxidant properties—compared to other common onion varieties. This compound may help reduce inflammation and support cardiovascular health.

The fiber content in yellow onions (1.7g per 100g) contributes to digestive health and helps maintain stable blood sugar levels, making them a smart choice for those managing diabetes or insulin sensitivity.

Storage Tips to Preserve Nutritional Value

How you store your yellow onions directly impacts their nutritional quality over time:

• Store whole, unpeeled yellow onions in a cool, dry, dark place with good air circulation
• Avoid refrigeration for whole onions, as moisture accelerates spoilage
• Once cut, store in an airtight container in the refrigerator for up to 7 days
• Nutrient degradation: Vitamin C content decreases by approximately 15-20% after 30 days of proper storage

According to agricultural research from Cornell University, proper storage conditions help maintain the maximum nutritional value of yellow onions throughout their typical shelf life of 2-3 months.

Common Questions About Yellow Onion Nutrition

Let's address some frequently asked questions about yellow onion calories and nutrition:

How many calories are in a medium yellow onion?

A medium yellow onion (approximately 148g) contains 64 calories. This makes yellow onions an excellent low-calorie ingredient for adding flavor to dishes without significantly increasing the calorie count.

Are yellow onions good for weight loss?

Yes, yellow onions can support weight loss efforts. With only 40 calories per 100g and 1.7g of fiber, they add volume and flavor to meals while contributing minimal calories. The fiber content also promotes feelings of fullness, which can help reduce overall calorie intake.

Do cooked yellow onions have more calories than raw?

The calorie content per 100g actually increases slightly when yellow onions are cooked because water evaporates during cooking. However, the total calories in the entire onion remain the same. A cooked yellow onion will have more calories per ounce than raw because it's more concentrated, but the overall calorie count for the whole onion doesn't change.

How do yellow onions compare to sweet onions nutritionally?

Yellow onions and sweet onions have very similar nutritional profiles, with yellow onions containing slightly less sugar (4.2g vs 4.7g per 100g) and calories (40 vs 41). The main difference is flavor profile rather than significant nutritional variation. Both varieties offer comparable fiber, vitamin C, and beneficial compounds like quercetin.

Can I eat yellow onions on a low-carb diet?

Yellow onions contain 9.3g of carbohydrates per 100g, which may be too high for strict ketogenic diets but can fit within more moderate low-carb eating plans. A small serving (about 1/4 cup diced) contains approximately 5g net carbs. Those following very low-carb diets often substitute shallots or green onions, which have slightly lower carbohydrate content.