Sliced Onions: Calories, Nutrition and Health Benefits
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Perplexity Nature's anti-inflammatory powerhouse packed with quercetin, prebiotic fiber, and sulfur compounds for robust health across every life stage.
Quick Nutrition Facts
Per 1 Cup Sliced Onions (160g)
| Nutrient | Amount |
|---|---|
| Calories | 64 kcal |
| Protein | 1.7g |
| Carbohydrates | 15g |
| Fiber | 2.7g |
| Sugars | 7g |
| Fat | 0.2g |
| Vitamin C | 8.9mg |
| Folate | 30mcg |
| Manganese | 0.2mg |
| Potassium | 234mg |
Macronutrient Breakdown
NUTRITIONIST INSIGHT
Onions contain quercetin, a potent flavonoid with documented anti-inflammatory and antioxidant properties. Raw onions retain higher vitamin C; cooking increases quercetin bioavailability. The inulin prebiotic fiber feeds beneficial gut bacteria, supporting digestive and immune health.
Myth Busters
MYTH #1: Onions Cause Bad Breath and That Means They're Toxic
TRUTH: The sulfur compounds (thiosulfates, disulfides) that create onion breath are the same compounds that fight inflammation and oxidative stress. Bad breath is a sign of bioactive compounds at work, not toxicity. Rinse or chew parsley after eating.
MYTH #2: Cooking Destroys Onion Nutrients Completely
TRUTH: Cooking reduces vitamin C (~25% loss) but increases quercetin availability for absorption. Studies show cooked onions deliver more antioxidant benefits than raw because heat breaks cell walls. Use both raw and cooked.
MYTH #3: Onions Are High in Carbs and Bad for Diabetics
TRUTH: Onions have a glycemic index of ~10 and studies show onion consumption improves insulin sensitivity and blood sugar control. One cup provides only 15g carbs with 2.7g fiber, making net carbs just 12g—safe for diabetics.
MYTH #4: All Onion Varieties Have the Same Nutrition
TRUTH: Red onions contain 25% more quercetin than yellow, while white onions have the most sulfur compounds. The phytonutrient profile varies by variety and growing conditions. Red and purple onions pack the strongest anti-inflammatory punch.
MYTH #5: Sliced Onions Go Bad Quickly and Lose Nutrients
TRUTH: Sliced onions retain nutrients for 3-7 days when refrigerated in an airtight container. Some studies suggest light cutting slightly increases quercetin availability due to enzyme activation. Store properly and use within a week.
NutriScore by Health Goals
| Health Goal | NutriScore | Why This Score? |
|---|---|---|
| Weight Loss |  | Only 40 calories per medium onion, 2.7g fiber promotes fullness, inulin supports satiety. Eat freely; use as base for curries and salads. |
| Muscle Gain |  | Low calorie with prebiotic fiber supports nutrient absorption and gut health for better protein digestion. Add to all meals for micronutrient boost. |
| Diabetes Management | | GI ~10, low glycemic load, allyl compounds improve insulin sensitivity. Use 1/2-1 cup daily; no portion restrictions needed. |
| PCOS Management | | Anti-inflammatory quercetin targets PCOS-related inflammation; inulin fiber aids hormonal balance. Include daily in meals. |
| Pregnancy Nutrition | | Rich in folate (30mcg supports fetal development), vitamin C aids iron absorption; quercetin anti-inflammatory benefits prevent gestational complications. |
| Viral/Flu Recovery | | Vitamin C boosts immunity; sulfur compounds support mucus clearance; raw onions provide enzymes; gentle on compromised digestion. |
PERSONALIZED NUTRITION
Track your meals with NutriScan for personalized NutriScores based on your specific health goals!
Blood Sugar Response to Sliced Onions
Onions have minimal blood glucose impact due to their extremely low glycemic index and high fiber content.
Typical Glucose Response Curve
*This chart shows typical blood glucose response for general healthy individuals. Individual responses may vary. Not medical advice.*
Why Onions Keep Blood Sugar Stable
The low glycemic index (~10) and high insoluble fiber suppress glucose absorption. Even better, pairing onions with protein amplifies satiety:
- 🍗 With chicken or fish - Slows carb absorption, extends fullness
- 🧈 With butter or oil - Increases fat-soluble nutrient absorption (quercetin)
- 🥛 With yogurt or curd - Adds probiotics; proteins reduce glycemic response
- 🌾 With whole grains - Fiber synergy improves digestion
Cultural Significance
Onions have been cultivated for over 5,000 years, originating in Central Asia and spreading globally as a dietary staple.
In India:
- Fundamental base (tadka) for nearly all curries and home cooking
- Used medicinally in Ayurveda for respiratory health and digestion
- Red onions (लाल प्याज़) preferred for pickles and raw salads
- Wedding ceremonies traditionally avoid onions during fasting periods
- Everyday vegetable in Indian diet (onions, ginger, garlic trio)
Global Impact:
- Fourth most produced vegetable globally (100 million tons annually)
- Stored long-term without refrigeration, making them a food security crop
- Different varieties thrive in diverse climates (tropical to temperate)
- Every part utilized: bulb, greens (spring onions), and stalks
Compare & Substitute
Sliced Onions vs Similar Vegetables (Per 100g)
| Nutrient | 🧅 Sliced Onions | 🧄 Garlic | 🌱 Leeks | 🧅 Red Onions |
|---|---|---|---|---|
| Calories | 40 kcal | 149 kcal | 61 kcal | 43 kcal |
| Carbs | 9g | 33g | 14g | 10g |
| Fiber | 1.7g | 2.1g | 2.4g | 1.7g |
| Protein | 1.1g | 6.4g | 1.5g | 1.1g |
| Fat | 0.1g | 0.5g | 0.3g | 0.1g |
| Quercetin | Moderate (4-7mg) | Low (0.2mg) | Low (0.3mg) | High (12-13mg) |
| Vitamin C | 8.9mg | 31mg | 12mg | 8.8mg |
| Best For | Anti-inflammatory base, salads | Intense flavor, immune boost | Mild flavor, soups, leek-based | Maximum quercetin, pickles |
Frequently Asked Questions
Are onions good for weight loss?
Yes, onions are an excellent weight loss food. One cup has only 64 calories, 2.7g fiber for fullness, and inulin that feeds satiating bacteria. The quercetin supports metabolic health. Eat onions freely in all meals; they're calorie-free relative to their volume and benefit.
Can diabetics eat onions?
Absolutely. Onions have a glycemic index around 10 and contain allyl compounds that enhance insulin sensitivity. Aim for 1/2 to 1 cup daily; portion control isn't critical given the low carb load.
What makes onions anti-inflammatory?
The compound quercetin, a flavonoid with proven anti-inflammatory properties; sulfur-based thiosulfates and disulfides; and organosulfur compounds all target multiple inflammation pathways. Together they reduce cytokine production and oxidative stress throughout the body.
Are red onions better than white or yellow?
Red and purple onions contain 25% more quercetin and 60% more anthocyanins (additional antioxidants) than yellow or white varieties. For maximum anti-inflammatory benefit, choose red; for everyday cooking, any variety works.
How should I store sliced onions?
Refrigerate in an airtight container for 3-7 days. Raw sliced onions retain nutrients better than pre-chopped; if buying pre-sliced, use within 2-3 days. Freeze for 2-3 months if not using fresh; thaw only for cooked dishes.
Can raw onions cause digestive issues?
Raw onions contain fermentable oligosaccharides (FODMAPs) that trigger bloating or gas in sensitive individuals (IBS, small intestinal bacterial overgrowth). Cooking reduces FODMAP content by ~50%. If sensitive, steam or sauté onions lightly.
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