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Onion nutrition, glycemic index, calories, net carbs & more

Onions, raw
*all the values are displayed for the amount of 100 grams
Article author photo Victoria Mazmanyan by Victoria Mazmanyan | Last updated on April 03, 2022
Education: General Medicine at YSMU


While onions are not particularly high in most macronutrients, they can be an excellent source of phytochemicals that provide an array of beneficial effects on human health.

Most of the macronutrient content of onions is composed of carbohydrates and a smaller amount of protein. Onions can also be a good source of vitamin B6 and vitamin C.


Onions are one of the most commonly used vegetables around the world. They are famous for their flavorful taste, pungent smell, and eye-irritating qualities. However, the nutrition of onions is often left out of the conversation. In this article, we will be discussing every detail of the nutritional content of onions.


The nutritional information below is presented as the average number for raw onions. We will also separately compare the nutrition of specific types of onions.

One average serving of onions per person is one tablespoon of chopped onions, equal to 10g.

Onions are not very dense in nutrients overall, consisting of 89% water and only 11% nutrients.

Macronutrients chart

2% 10% 90%
Daily Value: 2%
1.1 g of 50 g
Daily Value: 0%
0.1 g of 65 g
Daily Value: 3%
9.34 g of 300 g
Daily Value: 4%
89.11 g of 2,000 g
0.35 g


A 100g serving of raw onions provides 40 calories. Consequently, one average serving size of onions contains 4 calories.


Onions are not exceptionally high in proteins, containing only 1.1g of protein in a 100g serving.

Proteins found in onions include low levels of all essential amino acids, except for methionine which is absent in this vegetable.

Protein quality breakdown

Tryptophan Threonine Isoleucine Leucine Lysine Methionine Phenylalanine Valine Histidine 15% 6% 3% 3% 6% 1% 5% 4% 6%
Tryptophan: 14 mg of 280 mg 5%
Threonine: 21 mg of 1,050 mg 2%
Isoleucine: 14 mg of 1,400 mg 1%
Leucine: 25 mg of 2,730 mg 1%
Lysine: 39 mg of 2,100 mg 2%
Methionine: 2 mg of 1,050 mg 0%
Phenylalanine: 25 mg of 1,750 mg 1%
Valine: 21 mg of 1,820 mg 1%
Histidine: 14 mg of 700 mg 2%


Among macronutrient content, carbohydrates are found in the highest amounts in onions.

A hundred gram serving of onions provides 9.34g of carbohydrates.

Carbohydrate type breakdown

0.99% 1.97% 1.29%
Starch: 0 g
Sucrose: 0.99 g
Glucose: 1.97 g
Fructose: 1.29 g
Lactose: 0 g
Maltose: 0 g
Galactose: 0 g

Net Carbs

Most of the onion’s carbohydrates consist of net carbs. A hundred grams of raw onions provide 7.64g of net carbs, which makes up 82% of the total carb content.

However, not all of the net carbohydrates are composed of sugars. Of the net carb content, 55% are sugars, and 45% are other carbohydrates.

The sugar content consists predominantly of glucose and fructose while also containing some sucrose.

In a comparison between different varieties of onions, one study found white onions from the US to contain over 3 times more sugar compared to red onions from Egypt (1).

Dietary Fiber

The other 18% of the carbohydrate content is made up of dietary fiber. In a 100g serving, onions contain 1.7g of fiber.

Of this fiber content, 37% consists of soluble and 63% of insoluble fiber (2).

Fiber content ratio for Onion

4.24% 1.7% 3.4%
Sugar: 4.24 g
Fiber: 1.7 g
Other: 3.4 g

Below, you can find a carbohydrate content comparison between four onion varieties (3, 4, 5, 6).



Net carbs


Dietary fiber

Red onion





White onion





Yellow onion





Green onion






Onions contain a negligible amount of fats - around 0.1g per every 100g serving.

Fat type information

0.042% 0.013% 0.017%
Saturated Fat: 0.042 g
Monounsaturated Fat: 0.013 g
Polyunsaturated fat: 0.017 g


Onions are a good source of vitamin C, falling in the top 27% of foods as a source of vitamin C. However, a 100g serving covers only 8% of the daily needed amount of vitamin C.

The same serving size of onions can also cover 9% of the daily needed vitamin B6 content.

Onions are relatively high in vitamin B9, also known as folate.

This vegetable contains moderate-to-low levels of vitamin A, vitamin K, vitamin E, and vitamins B1, B2, B3, and B5.

Onions are entirely absent in vitamin D and vitamin B12.

Vitamin coverage chart

Vitamin A Vitamin E Vitamin D Vitamin C Vitamin B1 Vitamin B2 Vitamin B3 Vitamin B5 Vitamin B6 Folate Vitamin B12 Vitamin K 1% 1% 0% 25% 12% 7% 3% 8% 28% 15% 0% 1%
Vitamin A: 2 IU of 5,000 IU 0%
Vitamin E : 0.02 mg of 15 mg 0%
Vitamin D: 0 µg of 10 µg 0%
Vitamin C: 7.4 mg of 90 mg 8%
Vitamin B1: 0.046 mg of 1 mg 4%
Vitamin B2: 0.027 mg of 1 mg 2%
Vitamin B3: 0.116 mg of 16 mg 1%
Vitamin B5: 0.123 mg of 5 mg 2%
Vitamin B6: 0.12 mg of 1 mg 9%
Folate: 19 µg of 400 µg 5%
Vitamin B12: 0 µg of 2 µg 0%
Vitamin K: 0.4 µg of 120 µg 0%


Onions provide some levels of most essential minerals. They are relatively rich in calcium, manganese, and potassium.

These vegetables contain low amounts of magnesium, phosphorus, copper, zinc, iron, selenium, and choline.


Onions without added salt contain only 4mg of sodium per 100g serving.

Mineral coverage chart

Calcium Iron Magnesium Phosphorus Potassium Sodium Zinc Copper Manganese Selenium Choline 7% 8% 8% 13% 13% 1% 5% 14% 17% 3% 4%
Calcium: 23 mg of 1,000 mg 2%
Iron: 0.21 mg of 8 mg 3%
Magnesium: 10 mg of 420 mg 2%
Phosphorus: 29 mg of 700 mg 4%
Potassium: 146 mg of 3,400 mg 4%
Sodium: 4 mg of 2,300 mg 0%
Zinc: 0.17 mg of 11 mg 2%
Copper: 0.039 mg of 1 mg 4%
Manganese: 0.129 mg of 2 mg 6%
Selenium: 0.5 µg of 55 µg 1%
Choline: 6.1 mg of 550 mg 1%


As plants, onions are abundant in health-beneficial phytonutrients which do not fall under the previously mentioned categories.

The onion species is known to contain many secondary metabolites, such as flavonoids, phytosterols, saponins, and anthocyanins (7, 1).

Potentially the largest importance of phytochemical compounds is their antioxidant capability, which reduces cell damage in the body by inhibiting lipid oxidation.

Due to these and other compounds, onions have expressed anticancer, antidiabetic, antioxidant, antiplatelet, antihypertensive, antidepressant, neuroprotective, anti-inflammatory, antiparasitic effects, and more (8).


Isoalliin is a major sulfur-containing component of onions, which gives this vegetable its specific taste and eye-irritating quality (9). This compound is named after the scientific name of onions - Allium cepa.


Flavonoids are potent antioxidants from the polyphenol family of phytochemicals. Onions are considered an incredible source of flavonoids. In particular, onions are rich in quercetin, kaempferol, and isorhamnetin (9).


Anthocyanins are also antioxidants from the phenolic group. These compounds are pigments responsible for the red, blue, and purple colorings of fruits and vegetables. Therefore, red onions are considerably richer in anthocyanins compared to white onions (1).


Saponins are bitter-tasting compounds found in many fruits and vegetables, including onions. This phytochemical has been proven to reduce cholesterol absorption from the intestines. Saponins have also been studied to have antifungal and antitumor qualities (10).

Different Types of Onions

In this section, we will look at how the nutritional contents differ based on the variety of onions. The information is presented for 100g servings of raw red, white, yellow onions, and young green onion tops (3, 4, 5, 6).

Variety (raw)





Red onion





White onion





Yellow onion





Green onion





Glycemic Index

An exact number for the glycemic index value of onions has not been calculated, but it is assumed to be low.

Raw onion has been researched to lead to reduced blood glucose concentration and body weight gain (11).

Freeze-dried onion powder has been studied to be protective against hyperglycemia and dyslipidemia arising from diabetes in animal studies (12).

Onion powder has also been demonstrated to decrease the glycemic index of the pasta it was supplemented with (13).


The acidity of onions has been calculated to fall in the range of 6.2 (Baby variety) to 6.4 (Leek variety). Yellow, green, and red onions have a pH value of about 6.3 (14). This shows that onions are slightly acidic.

However, the potential renal acid load or PRAL value of onions is -2, proving onions to be alkaline-forming inside the body.

Comparison to Similar Foods

In this section, we will compare onions with similar vegetables, namely chives, garlic, and leek.

Compared to chives, onions are richer in calories and net carbs, while chives are richer in dietary fiber and 3 times higher in protein. Chives also contain appreciably larger amounts of most minerals and vitamins.

Between garlic and onion, garlic is significantly higher in calories, protein, and carbohydrates, including both net carbs and dietary fiber. Garlic is also richer in most vitamins, except for folate. However, it is important to note that the average serving size of garlic is about 4 times smaller than onions.

Compared to garlic, leeks are also slightly higher in calories, protein, carbohydrates, and vitamins.


Article author photo Victoria Mazmanyan
Education: General Medicine at YSMU
Last updated: April 03, 2022

Important nutritional characteristics for Onion

Glycemic index ⓘ Gi values are taken from various scientific sources. GI values less than 55 are considered as low. Values above 70 are considered as high.
15 (low)
Insulin index ⓘ
Net Carbs ⓘ Net Carbs = Total Carbohydrates – Fiber – Sugar Alcohols
7.64 grams
Serving Size ⓘ Serving sizes are taken from FDA's Reference Amounts Customarily Consumed (RACCs)
1 tbsp chopped (10 grams)
Acidity (Based on PRAL) ⓘ PRAL (Potential renal acid load) is calculated using a formula. On the PRAL scale the higher the positive value, the more is the acidifying effect on the body. The lower the negative value, the higher the alkalinity of the food. 0 is neutral.
-2 (alkaline)
73% Vitamin C
60% Fiber
56% Folate, food
51% Folate
50% Sugar
Explanation: The given food contains more Vitamin C than 73% of foods. Note that this food itself is richer in Vitamin C than it is in any other nutrient. Similarly, it is relatively rich in Fiber, Folate, food, Folate, and Sugar.

Onion Glycemic index (GI)

Gi values are taken from various scientific sources. GI values less than 55 are considered as low. Values above 70 are considered as high.

Mineral chart - relative view

23 mg
TOP 50%
0.129 mg
TOP 58%
146 mg
TOP 71%
10 mg
TOP 84%
29 mg
TOP 84%
0.039 mg
TOP 85%
0.17 mg
TOP 87%
0.21 mg
TOP 88%
0.5 µg
TOP 89%
6.1 mg
TOP 90%
4 mg
TOP 92%

Vitamin chart - relative view

Vitamin C
7.4 mg
TOP 27%
19 µg
TOP 49%
Vitamin B6
0.12 mg
TOP 60%
Vitamin A
2 IU
TOP 73%
Vitamin B1
0.046 mg
TOP 74%
Vitamin K
0.4 µg
TOP 82%
Vitamin B5
0.123 mg
TOP 87%
Vitamin B2
0.027 mg
TOP 88%
Vitamin B3
0.116 mg
TOP 91%
Vitamin E
0.02 mg
TOP 93%
Vitamin B12
0 µg
TOP 100%
Vitamin D
0 µg
TOP 100%

All nutrients for Onion per 100g

Nutrient DV% In TOP % of foods Value Comparison
Net carbs N/A 50% 7.64g 7.1 times less than Chocolate Chocolate
Protein 3% 84% 1.1g 2.6 times less than Broccoli Broccoli
Fats 0% 93% 0.1g 333.1 times less than Cheese Cheese
Carbs 3% 50% 9.34g 3 times less than Rice Rice
Calories 2% 91% 40kcal 1.2 times less than Orange Orange
Starch 0% 100% 0g N/A Potato
Fructose 2% 85% 1.29g 4.6 times less than Apple Apple
Sugar N/A 50% 4.24g 2.1 times less than Coca-Cola Coca-Cola
Fiber 7% 40% 1.7g 1.4 times less than Orange Orange
Calcium 2% 50% 23mg 5.4 times less than Milk Milk
Iron 3% 88% 0.21mg 12.4 times less than Beef Beef
Magnesium 2% 84% 10mg 14 times less than Almond Almond
Phosphorus 4% 84% 29mg 6.3 times less than Chicken meat Chicken meat
Potassium 4% 71% 146mg Equal to Cucumber Cucumber
Sodium 0% 92% 4mg 122.5 times less than White Bread White Bread
Zinc 2% 87% 0.17mg 37.1 times less than Beef Beef
Copper 4% 85% 0.04mg 3.6 times less than Shiitake Shiitake
Vitamin A 0% 73% 2IU 8353 times less than Carrot Carrot
Vitamin E 0% 93% 0.02mg 73 times less than Kiwifruit Kiwifruit
Vitamin D 0% 100% 0µg N/A Egg
Vitamin C 8% 27% 7.4mg 7.2 times less than Lemon Lemon
Vitamin B1 4% 74% 0.05mg 5.8 times less than Pea Pea
Vitamin B2 2% 88% 0.03mg 4.8 times less than Avocado Avocado
Vitamin B3 1% 91% 0.12mg 82.5 times less than Turkey meat Turkey meat
Vitamin B5 2% 87% 0.12mg 9.2 times less than Sunflower seed Sunflower seed
Vitamin B6 9% 60% 0.12mg Equal to Oat Oat
Folate 5% 49% 19µg 3.2 times less than Brussels sprout Brussels sprout
Vitamin B12 0% 100% 0µg N/A Pork
Vitamin K 0% 82% 0.4µg 254 times less than Broccoli Broccoli
Tryptophan 0% 94% 0.01mg 21.8 times less than Chicken meat Chicken meat
Threonine 0% 97% 0.02mg 34.3 times less than Beef Beef
Isoleucine 0% 97% 0.01mg 65.3 times less than Salmon Salmon
Leucine 0% 97% 0.03mg 97.2 times less than Tuna Tuna
Lysine 0% 96% 0.04mg 11.6 times less than Tofu Tofu
Methionine 0% 98% 0mg 48 times less than Quinoa Quinoa
Phenylalanine 0% 96% 0.03mg 26.7 times less than Egg Egg
Valine 0% 97% 0.02mg 96.6 times less than Soybean Soybean
Histidine 0% 96% 0.01mg 53.5 times less than Turkey meat Turkey meat
Cholesterol 0% 100% 0mg N/A Egg
Trans Fat N/A 100% 0g N/A Margarine
Saturated Fat 0% 87% 0.04g 140.4 times less than Beef Beef
Monounsaturated Fat N/A 91% 0.01g 753.8 times less than Avocado Avocado
Polyunsaturated fat N/A 94% 0.02g 2774.9 times less than Walnut Walnut

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Nutrition Facts
___servings per container
Serving Size ______________
Amount Per 100g
Calories 40
% Daily Value*
Total Fat 0g
Saturated Fat 0g
Trans Fat g
Cholesterol 0mg
Sodium 4mg
Total Carbohydrate 9g
Dietary Fiber 2g
Total Sugars g
Includes ? g Added Sugars
Protein 1g
Vitamin D 0mcg 0%

Calcium 23mg 2%

Iron 0mg 0%

Potassium 146mg 4%

The % Daily Value (DV) tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

Health checks

Low in Cholesterol
 ⓘ Dietary cholesterol is not associated with an increased risk of coronary heart disease in healthy individuals. However, dietary cholesterol is common in foods that are high in harmful saturated fats.
No Trans Fats
 ⓘ Trans fat consumption increases the risk of cardiovascular disease and mortality by negatively affecting blood lipid levels.
Low in Saturated Fats
 ⓘ Saturated fat intake can raise total cholesterol and LDL (low-density lipoprotein) levels, leading to an increased risk of atherosclerosis. Dietary guidelines recommend limiting saturated fats to under 10% of calories a day.
Low in Sodium
 ⓘ Increased sodium consumption leads to elevated blood pressure.
Low in Sugars
 ⓘ While the consumption of moderate amounts of added sugars is not detrimental to health, an excessive intake can increase the risk of obesity, and therefore, diabetes.

Onion nutrition infographic

Onion nutrition infographic
Infographic link


The source of all the nutrient values on the page (excluding the main article and glycemic index text the sources for which are presented separately if present) is the USDA's FoodCentral. The exact link to the food presented on this page can be found below.


Data provided by should be considered and used as information only. Please consult your physician before beginning any diet.