How Many Calories Does an Onion Have? Is It a Hard-to-Digest Vegetable?
Kacper Nowak
2026-03-18
2 min. read
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The onion is widely recognized for causing our eyes to tear up during its peeling and chopping. There are as many as 325 varieties of this vegetable worldwide, which can be white, brown, yellow, or red. What should we know about its contents and effects on our body?
Abundance of nutrients in onion
Onion is a vegetable with low caloric requirement – 100 grams of onion provides only 33 calories. Water makes up 90% of its weight. The protein in onion contains a large amount of sulphur-containing amino acids – cystine and methionine. A typical specimen of onion weighs around 150 grams, and its nutrient composition is as follows: energy value: 49.5 kcal, protein: 2.1 g, fat: 0.6 g, total carbohydrates: 10.4 g, dietary fiber: 2.6 g. Onion is also a source of vitamins and minerals. A typical onion (150 g) contains: 0.3 mg vitamin B3, 0.1 mg vitamin B6, 3 µg provitamin A, 0.2 mg vitamin E, 181.5 mg potassium, 37.5 mg calcium, 0.8 mg iron, 0.4 mg zinc, 12 mg magnesium, 21 mg phosphorus, 2.7 µg iodine, 9 mg sodium.
Considerable capacity to counteract the detrimental effects of oxygen
Onions contain a substantial quantity of substances with antioxidative properties, including flavonoids and phenolic acids. The most significant flavonoid found in onions is quercetin, which is one of the most potent antioxidants present in fruits and vegetables.
Health benefits
The onion possesses considerable antibacterial, antifungal, and antiviral capabilities. Quercetin, a component contained in its composition, is responsible for the lethal consequences for cancer cells and exhibits anti-inflammatory properties. In collaboration with vitamin C, they enhance the flexibility and tightness of blood vessels. Furthermore, this potent flavonoid may contribute to the reduction of fat tissue, which translates to a positive impact on preventing obesity and overweight.
Natural therapy
Onions have been utilized as a natural remedy for countless millennia. In Chinese medicine, they are employed in the treatment of liver, intestinal, and lung diseases. They serve as an effective medication in numerous instances: chronic respiratory issues, cough and asthma, gastrointestinal disorders, hypertension, ulcers and slow-healing wounds, cardiovascular diseases, and in the prevention of oncological diseases.
A vegetable of considerable weight
Potatoes are considered to be one of the weightiest vegetables and are known for their bloating nature. Therefore, individuals who follow an easily digestible diet should avoid consuming them. The consumption of potatoes is not recommended in cases such as peptic ulcer disease and irritable bowel syndrome (IBS).
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Onion Nutrition
Antioxidants In Vegetables
Low-calorie Foods
Digestive Health
Natural Remedies
Plant-based
Fiber-Rich
Heart Health
Whole Foods
Insulin Sensitivity
Weight Management
Gut Health
Hypertension Management
Fat Loss
Metabolism Boost
Longevity
Micronutrients
Inflammation
Brain Health
Hydration
Immune System
Medicinal Plants
Phytotherapy
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Zinc
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Digestive Disorders