2 min read
Onion – health benefits, vitamins, calories, and culinary applications
Kacper Nowak
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Diets Premium Expert • 23.10.2026
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Scientifically reviewed by a clinical dietitian:
This article has been peer-reviewed for adherence to IŻŻ, WHO, and PTGiP clinical nutritional standards.
| Diets Premium Expert Kacper Nowak | min read 2 min | Scientifically reviewed by a clinical dietitian 23.10.2026 |
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Key Takeaways
The common onion (Allium cepa) is one of the oldest and most versatile cultivated vegetables. Belonging to the allium family, it is renowned for its high concentration of organosulfur compounds, quercetin, and vitamin C. Common culinary varieties include yellow, red, white onions, shallots, and scallions. Discover why onions function as a potent natural antimicrobial, how they support immune defense and cardiovascular health, and how to harness their culinary and medicinal value.
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Nutritional Properties of Onions – Vitamins, Minerals, and Sulfur Compounds
Onions possess a wide spectrum of health benefits owing to their bioactive composition. They exert potent antibacterial, antiviral, and anti-inflammatory actions. Rich in polyphenols, particularly the powerful antioxidant quercetin and kaempferol, onions neutralize free radicals, prevent LDL cholesterol oxidation, and support endothelial function. For individuals with diabetes, organosulfur compounds such as allyl propyl disulfide promote glycemic regulation by assisting insulin action. Furthermore, onions supply bioavailable vitamin C, potassium, calcium, magnesium, and dietary fiber.
Caloric Value – How Many Calories Are in an Onion?
100 grams of raw onion provides only approximately 35–40 calories, containing 1.4 g of protein, 0.2 g of fat, and roughly 8–9 g of carbohydrates (including 1.7 g of dietary fiber, notably prebiotic inulin). With an exceptionally low glycemic index (GI = 15) and minimal caloric density, onions are an ideal food for weight loss, enhancing meal satiety and gut microbiome health without surplus energy.
Culinary and Phytotherapeutic Uses of Onions
Onions are an indispensable culinary base in worldwide gastronomy, consumed raw, caramelized, roasted, or gently braised. Raw sliced onions enhance fresh salads (like Greek salad), pickled herring, and sandwiches. Cooked onions form the aromatic foundation (mirepoix, soffritto) for soups, stews, sauces, and roasts. In traditional medicine, homemade onion syrup with honey or lemon is a celebrated home remedy for coughs and upper respiratory infections, while cut raw onion provides soothing relief for insect stings.
Kacper Nowak
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