Fennel vs. Onion

Nutrition comparison of Fennel and Onion


Ever wonder how your favorite foods stack up against each other in terms of nutrition?

We compared the nutritional contents of fennel versus onion (100g each) below using 2020 USDA and NIH data[1].

For a quick recap of significant nutrients and differences in fennel and onion:

  • Fennel is a great source of calcium.
  • Fennel is an excellent source of dietary fiber and potassium.
  • Onion has more thiamin and Vitamin B6, however, fennel contains more niacin and pantothenic acid.
Detailed nutritional comparison of fennel and onion is analyzed below. You can also visualize the nutritional comparison for a custom portion or serving size and see how the nutrition compares.

USDA sources for nutritional information: Fennel (Fennel, bulb, raw) and Onion (Onions, raw) . Have a correction or suggestions? Shoot us an email.


Image of Fennel src
Image of Onion src

Calories and Carbs

calories

Fennel and onion contain similar amounts of calories - fennel has 31 calories per 100 grams and onion has 40 calories.

For macronutrient ratios, fennel is lighter in carbs, heavier in fat and similar to onion for protein. Fennel has a macronutrient ratio of 14:81:6 and for onion, 11:88:2 for protein, carbohydrates and fat from calories.

Macro Ratios from Calories:

Fennel Onion
Protein 14% 11%
Carbohydrates 81% 88%
Fat 6% 2%
Alcohol ~ ~

carbohydrates

Fennel and onion contain similar amounts of carbs - fennel has 7.3g of total carbs per 100 grams and onion has 9.3g of carbohydrates.

dietary fiber

Fennel is an excellent source of dietary fiber and it has 82% more dietary fiber than onion - fennel has 3.1g of dietary fiber per 100 grams and onion has 1.7g of dietary fiber.

sugar

Fennel and onion contain similar amounts of sugar - fennel has 3.9g of sugar per 100 grams and onion has 4.2g of sugar.

Protein

protein

Fennel and onion contain similar amounts of protein - fennel has 1.2g of protein per 100 grams and onion has 1.1g of protein.

Fat

saturated fat

Both fennel and onion are low in saturated fat - fennel has 0.09g of saturated fat per 100 grams and onion has 0.04g of saturated fat.

Vitamins

Vitamin C

Fennel has 62% more Vitamin C than onion - fennel has 12mg of Vitamin C per 100 grams and onion has 7.4mg of Vitamin C.

Vitamin A

Fennel has more Vitamin A than onion - fennel has 48ug of Vitamin A per 100 grams and onion does not contain significant amounts.

Vitamin E

Fennel and onion contain similar amounts of Vitamin E - fennel has 0.58mg of Vitamin E per 100 grams and onion has 0.02mg of Vitamin E.

Vitamin K

Fennel has 156 times more Vitamin K than onion - fennel has 62.8ug of Vitamin K per 100 grams and onion has 0.4ug of Vitamin K.

The B Vitamins

Onion has more thiamin and Vitamin B6, however, fennel contains more niacin and pantothenic acid. Both fennel and onion contain significant amounts of riboflavin and folate.

Fennel Onion
Thiamin 0.01 MG 0.046 MG
Riboflavin 0.032 MG 0.027 MG
Niacin 0.64 MG 0.116 MG
Pantothenic acid 0.232 MG 0.123 MG
Vitamin B6 0.047 MG 0.12 MG
Folate 27 UG 19 UG

Minerals

calcium

Fennel is a great source of calcium and it has 113% more calcium than onion - fennel has 49mg of calcium per 100 grams and onion has 23mg of calcium.

iron

Fennel has 248% more iron than onion - fennel has 0.73mg of iron per 100 grams and onion has 0.21mg of iron.

potassium

Fennel is an excellent source of potassium and it has 184% more potassium than onion - fennel has 414mg of potassium per 100 grams and onion has 146mg of potassium.

Antioxidants and Phytonutrients

flavonoids

Naturally occuring in fruits and vegetables, flavonoids are associated with many health benefits and used in a variety of medicinal and pharmaceutical applications. [2][3]

For specific flavonoid compounds,

Fennel Onion
Quercetin 0.23 mg 20.3 mg
apigenin ~ 0.01 mg
luteolin ~ 0.02 mg
isorhamnetin ~ 5.01 mg
kaempferol ~ 0.65 mg
myricetin ~ 0.03 mg

carotenoids

Carotenoids are micronutrients commonly found in plants and some animal products. An example is beta-carotene, the notable carotenoid which is a popular source of Vitamin A.[4][5]

For specific types of carotenoids,

Fennel Onion
beta-carotene 578 UG 1 UG
lutein + zeaxanthin 607 UG 4 UG

Omega-3 and Omega-6

omega 6s

Comparing omega-6 fatty acids, fennel has more linoleic acid than onion per 100 grams.

Fennel Onion
linoleic acid 0.169 G 0.013 G
Total 0.169 G 0.013 G



Customize your serving size


The comparison below is by common portions, e.g. cups, packages. You can also see a more concrete comparison by weight at equal weight (by grams) comparison.

Note: The specific food items compared are: Fennel (Fennel, bulb, raw) and Onion (Onions, raw) .

Fennel 87g

( cup, sliced )
Daily Values (%)

Onion 115g

( cup, sliced )
27KCAL 1%
calories 70%
46KCAL 2%
6.4G 3%
carbohydrates 72%
11G 4%
2.7G 11%
35% dietary fiber
2G 8%
3.4G sugar 44% 4.9G
0.17G 0.3%
42% total fat
0.12G 0.2%
0.08G 0.4%
60% saturated fat
0.05G 0.3%
0.06G 495% monounsaturated fat 0.01G
0.15G 647% polyunsaturated fat 0.02G
45MG 3%
878% sodium
4.6MG 0.3%
Vitamins and Minerals
42UG 6%
>999% Vitamin A
10MG 14%
18% Vitamin C
8.5MG 11%
43MG 4%
65% calcium
26MG 3%
0.64MG 4%
167% iron
0.24MG 1%
15MG 5%
25% magnesium
12MG 4%
360MG 16%
114% potassium
168MG 7%
0.01MG 1%
thiamin (Vit B1) 396%
0.05MG 5%
0.03MG 3%
riboflavin (Vit B2)
0.03MG 3%
0.56MG 4%
331% niacin (Vit B3)
0.13MG 1%
0.04MG 3%
Vitamin B6 249%
0.14MG 11%
0.2MG 4%
43% pantothenic acid (Vit B5)
0.14MG 3%
23UG 6%
5% folate (Vit B9)
22UG 6%
0.5MG 3%
>999% Vitamin E
0.02MG 0.2%
55UG 61%
>999% Vitamin K
0.46UG 1%
1.1G 2%
protein 18%
1.3G 3%
11MG 3%
57% choline
7MG 2%
0.06MG 5%
50% copper
0.04MG 4%
fluoride >999%
0.17MG 9%
13% manganese
0.15MG 8%
44MG 6%
33% phosphorus
33MG 5%
0.61UG 1%
7% selenium
0.57UG 1%
0.17MG 2%
zinc 18%
0.2MG 2%
78G Water 31% 102G


NO SIGNIFICANT AMOUNTS (either food): Starch, Alcohol, chlorine, chromium, iodine, molybdenum, Vitamin D, biotin (Vit B7), Vitamin B12, cholesterol, trans fat.

FAQ

Does fennel or onion contain more calories in 100 grams?
Fennel and onion contain similar amounts of calories - fennel has 31 calories in 100g and onion has 40 calories.

Does fennel or onion have more carbohydrates?
By weight, fennel and onion contain similar amounts of carbs - fennel has 7.3g of carbs for 100g and onion has 9.3g of carbohydrates.

Does fennel or onion contain more potassium?
Fennel is a rich source of potassium and it has 180% more potassium than onion - fennel has 414mg of potassium in 100 grams and onion has 146mg of potassium.

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