Onion: Calories, Nutrition and Health Benefits
Nature's flavor powerhouse packed with quercetin, antioxidants, and powerful anti-inflammatory compounds for optimal health.
Quick Nutrition Facts
Per 100g (1 medium onion)
| Nutrient | Amount |
|---|---|
| Calories | 40 kcal |
| Protein | 1.1g |
| Carbohydrates | 9g |
| Fiber | 1.7g |
| Sugars | 4.2g |
| Fat | 0.1g |
| Vitamin C | 7.4mg |
| Folate | 19mcg |
| Potassium | 146mg |
| Quercetin | ~10-25mg |
Macronutrient Breakdown
NUTRITIONIST INSIGHT
Onions are one of the richest dietary sources of quercetin, a powerful antioxidant linked to heart health and anti-inflammatory benefits. Raw onions preserve maximum nutrients, while cooked onions offer enhanced digestibility and prebiotic compounds.
Myth Busters
MYTH #1: Onions Are Just Flavoring with No Nutrition
TRUTH: Onions are nutritional powerhouses containing quercetin, sulfur compounds, vitamin C, and prebiotic fiber. They provide significant anti-inflammatory and cardiovascular benefits beyond just flavor.
MYTH #2: Raw Onions Are Bad for Digestion
TRUTH: While raw onions can cause gas in some people, they contain prebiotic fiber that feeds beneficial gut bacteria. Most people tolerate them well. Start with small amounts if sensitive; cooked onions are easier to digest.
MYTH #3: Onions Spike Blood Sugar
TRUTH: Onions have a very low glycemic index (10-15) and may actually help regulate blood sugar. Studies show quercetin and sulfur compounds improve insulin sensitivity and glucose metabolism.
MYTH #4: Cooked Onions Lose All Nutrients
TRUTH: While vitamin C reduces with cooking, other beneficial compounds become more bioavailable. Cooking increases quercetin absorption and creates new antioxidants. Both raw and cooked onions offer unique health benefits.
MYTH #5: Onions Cause Bad Breath So Avoid Them
TRUTH: The sulfur compounds that cause breath odor are the same ones providing cardiovascular and anti-cancer benefits. Simple solutions: chew parsley, mint, or fennel seeds; drink milk; brush teeth. Don't avoid onions due to temporary breath concerns.
MYTH #6: Red Onions Are Much Healthier Than White
TRUTH: Red onions have more anthocyanins (antioxidants) giving them color, but all onion varieties provide significant quercetin and health benefits. White and yellow onions are excellent choices too.
NutriScore by Health Goals
| Health Goal | NutriScore | Why This Score? |
|---|---|---|
| Weight Loss |  | Only 40 calories per 100g, high water content (89%), 1.7g fiber for satiety. Adds flavor without calories. |
| Muscle Gain |  | Low protein but excellent anti-inflammatory support for recovery. Quercetin reduces exercise-induced inflammation. Best used as flavor base in high-protein meals. |
| Diabetes Management | | Very low GI (10-15), quercetin improves insulin sensitivity, sulfur compounds support glucose metabolism. Unlimited portions allowed. |
| PCOS Management | | Anti-inflammatory quercetin reduces PCOS inflammation, low carbs don't spike insulin. Supports hormonal balance and weight management. |
| Pregnancy Nutrition | | Folate supports neural tube development, vitamin C for immunity, fiber prevents constipation. Cook thoroughly for safety. |
| Viral/Flu Recovery | | Vitamin C and quercetin boost immunity, sulfur compounds have antimicrobial properties. Easy to digest when cooked. Traditional remedy for respiratory health. |
PERSONALIZED NUTRITION
Track your meals with NutriScan for personalized NutriScores based on your specific health goals!
Blood Sugar Response to Onions
Onions have one of the lowest glycemic responses among vegetables, making them exceptional for blood sugar control.
Typical Glucose Response Curve
*This chart shows minimal blood glucose impact from onions. Individual responses may vary. Not medical advice.*
Blood Sugar Benefits of Onions
Research shows onions actively support blood sugar control through multiple mechanisms:
- Quercetin - Improves insulin sensitivity and glucose uptake
- Sulfur compounds - Support pancreatic beta cell function
- Prebiotic fiber - Slows carbohydrate digestion
- Low glycemic load - Minimal impact on blood sugar even in large quantities
Best Practices: Add raw onions to salads; cook onions into dal, sabzi, curries; use as base for soups and stews; consume regularly for cumulative benefits.
Cultural Significance
Onions have been cultivated for over 7,000 years and hold important cultural and medicinal significance worldwide.
In India:
- Essential base for most Indian curries and gravies
- Ayurveda recognizes onion's warming properties and digestive benefits
- Used in traditional remedies for colds, coughs, and fever
- Regional varieties: Nashik red onions (famous for pungency), Bengaluru rose onions (milder)
- Considered tamasic in strict sattvic diets but widely consumed
Global Impact:
- Fourth most produced vegetable globally (100+ million tons annually)
- Ancient Egyptians worshipped onions as symbol of eternal life
- Traditional medicine across cultures for respiratory health, infections, and circulation
- Modern research validates traditional uses through quercetin and sulfur compounds
Compare & Substitute
Onion vs Similar Vegetables (Per 100g)
| Nutrient | 🧅 Onion | 🧄 Garlic | 🧅 Shallots | 🧅 Leeks |
|---|---|---|---|---|
| Calories | 40 kcal | 149 kcal | 72 kcal | 61 kcal |
| Carbs | 9g | 33g | 17g | 14g |
| Fiber | 1.7g | 2.1g | 3.2g | 1.8g |
| Protein | 1.1g | 6.4g | 2.5g | 1.5g |
| Fat | 0.1g | 0.5g | 0.1g | 0.3g |
| Vitamin C | 7.4mg | 31.2mg | 8mg | 12mg |
| Quercetin | High | Moderate | Very High | Moderate |
| Best For | Base | Immune | Flavor | Mild base |
Frequently Asked Questions
Are onions good for weight loss?
Yes, onions are excellent for weight loss. With only 40 calories per 100g, high water content (89%), and 1.7g fiber, onions add volume and flavor to meals without adding significant calories.
Best practices: Add raw onions to salads; use as base for soups and stews; sauté in minimal oil; eat before meals to promote fullness; replace high-calorie ingredients with onions for volume.
Can diabetics eat onions?
Yes, onions are highly beneficial for diabetics. They have a very low glycemic index (10-15) and contain quercetin and sulfur compounds that improve insulin sensitivity and glucose metabolism.
Tips for diabetics:
- Unlimited portions - Onions won't spike blood sugar
- Raw or cooked - Both forms provide benefits
- Regular consumption - Daily intake supports long-term blood sugar control
- Combine with meals - Use as base for curries, add to salads
Research shows regular onion consumption can significantly improve HbA1c levels in diabetics.
Is raw onion better than cooked onion?
Both raw and cooked onions offer unique benefits. Choose based on your needs and digestive tolerance.
Raw Onions:
- Higher vitamin C content (retained fully)
- Maximum quercetin concentration
- Stronger antimicrobial properties
- More pungent flavor
Cooked Onions:
- Easier to digest, less gas formation
- Increased quercetin bioavailability (better absorption)
- Enhanced prebiotic fiber activity
- Sweeter, milder flavor
Recommendation: Combine both in your diet - raw in salads, cooked in main dishes.
What are the main health benefits of onions?
Key Benefits:
- Heart Health: Quercetin and sulfur compounds reduce blood pressure, cholesterol, and inflammation
- Anti-inflammatory: Powerful antioxidants reduce systemic inflammation
- Blood Sugar Control: Very low GI, improves insulin sensitivity
- Gut Health: Prebiotic fiber feeds beneficial bacteria
- Immune Support: Vitamin C, quercetin, antimicrobial sulfur compounds
- Cancer Prevention: Antioxidants may reduce cancer risk (studies ongoing)
Are onions safe during pregnancy?
Yes, onions are safe and beneficial during pregnancy. They provide folate for fetal neural tube development, vitamin C for immunity, and fiber for digestive health.
Pregnancy Benefits:
- Folate (19mcg) supports fetal development
- Fiber prevents pregnancy constipation
- Antimicrobial properties protect against infections
- Low calories support healthy weight gain
Food Safety: Cook onions thoroughly in curries and gravies. Raw onions in salads are safe if properly washed. Avoid if they cause severe heartburn or gas.
Do onions help with immunity and fighting infections?
Yes, onions are powerful immune boosters with traditional and scientific backing.
Immune Benefits:
- Vitamin C (7.4mg) supports white blood cell function
- Quercetin enhances immune response and reduces inflammation
- Sulfur compounds have antibacterial and antiviral properties
- Prebiotic fiber supports gut health (70% of immune system in gut)
Traditional Use: Onion juice with honey for coughs; raw onion for preventing colds; onion poultice for chest congestion. Modern research validates antimicrobial effects.
How much onion should I eat per day?
General Guidelines:
- 50-100g daily (1/2 to 1 medium onion) - Most people for health benefits
- Unlimited - Weight loss, diabetes management (no restrictions)
- Small amounts (25-50g) - If prone to gas or digestive sensitivity
Forms: Mix raw and cooked throughout the day. Raw in salads, raita; cooked in curries, dal, soups.
Track your meals with NutriScan app to see how onions fit your personal nutrition goals.
Can I eat raw onions every day?
Generally safe and beneficial for most people. Raw onions provide maximum quercetin and vitamin C.
Best practices:
- Start small - Begin with 25-50g and increase gradually
- Pair with meals - Add to salads, raita, chutneys
- Manage breath - Chew parsley, mint, or fennel seeds after
- Choose variety - Red onions have more antioxidants; white/yellow are milder
May want to reduce if you have:
- Acid reflux/GERD - Can trigger symptoms in some
- IBS - May cause gas and bloating
- Blood thinning medication - Consult doctor (onions have mild blood-thinning effects)
Most people benefit from daily raw onion consumption. Start gradually and listen to your body.
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