In this article:
- Fennel is classically used in Italian dishes but is starting to enter the kitchens of many Americans.
- It is a versatile ingredient in cooking because it can be used as an herb, spice, or vegetable.
- As one of the oldest cultivated plants, fennel has many traditional uses in food and medicine. It aids digestion, freshens breath, and helps reduce menstrual cramps.
- Fennel even has uses outside of the kitchen. In medieval times, people believed that fennel could ward off evil spirits, so they hung fennel over doorways.
Fennel is a member of the Umbelliferae (Apiaceae) family, closely related to carrots, parsley, celery, and dill. From the large white bulb, multiple bunches of 4-5 long stems extend up to 6-7 feet above the ground.
Many simple leaves (called fronds) about 2-15 cm in length grow on the stems, giving fennel its characteristic feathery appearance.
You may mistake its leafy green stems for carrot tops! However, unlike carrot tops, bunches of small yellow flowers may begin to grow on the plant. The herb should ideally be harvested before the stems start to flower in late summer.
As one of the oldest cultivated plants, fennel has many traditional uses in food and medicine. This article will review the types, nutritional value, proposed health benefits, cautions, and preparation of fennel.
Types of Fennel
|Sweet||Fresh and dried leaves used in food|
|Purpureum||Bronze leaf for decoration|
|Rubrum||Bronze/red leaf for decoration|
|Rondo||High quality, round bulb, high yield|
|Zefa Fino||Can be harvested in just 65 days|
|Cantino||Slow to grow; can be planted early in the season|
There are two main types of fennel:
- Herb Fennel (Foeniculum vulgare): The long, aromatic stems, leaves, and seeds are usually used as an herb or spice.
- Florence Fennel (Foeniculum vulgare var. dulce): With shorter stems, it is usually grown for the large bulb and eaten as a vegetable. Like other root vegetables, it can be eaten raw or prepared in a dish.
Both types of fennel have distinct anise or licorice flavor. Fennel is often mistakenly sold at supermarkets labeled as anise due to their similar flavor and aroma.
Both plants are members of the Apiaceae family. However, anise (Pimpinella anisum) is a completely different plant.
The only part of the anise plant that is used in foods is the seeds, whereas all parts of the fennel plant are edible.
The nutritional content for 100g of fennel includes: (1)
|Nutrient||Amount per 100 g Fennel bulb||% Daily Value|
|Vitamin C||12 mg||20%|
|Lutein + Zeaxanthin||607 mcg|
The fennel bulb is a good source of fiber, potassium, manganese, and vitamin C. It also contains calcium, iron, folate, and antioxidants lutein and zeaxanthin.
The seeds are typically consumed in small amounts (of up to 1–1 ½ teaspoons per day) in tea or as a spice in prepared food. They also contain potassium, vitamin C, manganese, iron, calcium, and folate.
Additionally, 1 teaspoon of seeds has 33.8 mg of polyunsaturated omega-6 fats and antioxidants kaempferol and quercetin.
Proposed Health Benefits
Traditional uses for fennel range from helping the body pass gas to freshening the breath. This section will discuss a few of the proposed benefits and uses of fennel.
1. May Reduce Menstrual Cramps
Increased uterine contractions cause cramps during a woman’s menstrual cycle. Contractions are stimulated by the hormone oxytocin and prostaglandin.
One study of 50 women found that taking 30 mg of fennel extract four times daily significantly reduced menstrual pain compared to the wheat flour-filled placebo.
Fifty-two percent of the women taking fennel extract reported that the treatment was excellent compared to only 8% in the placebo group.
Mefenamic acid is an NSAID drug that is commonly used to treat menstrual pain. A study that included 60 women found that fennel oil was equally as effective in decreasing menstrual pain as 250 mg mefenamic acid. (6)
Research demonstrates that fennel may be a safe and natural method to reduce menstrual pain.
Further investigation is needed to determine its long-term effects and safety of use. If treatment is ineffective, further medical management may still be warranted.
2. May Help In Weight Management
The fiber and water in fennel, like other vegetables, promote satiety by filling up the stomach without providing many calories.
Some researchers believe that anethole, a compound found in the oils of fennel seeds, may also contribute to appetite control.
Anethole has a similar structure to amphetamine, a hormone in the body that helps control appetite.
A study in 2015 examined the effect of fennel seeds on food intake and appetite. Nine women were given either a fennel seed-infused tea or a placebo prior to eating a lunch buffet. One week later, they received the opposite treatment prior to the same buffet. (2)
The researchers found that although food intake did not differ between the 2 days, the women reported decreased hunger and increased feelings of fullness on the day they drank the fennel tea. (2)
Conclusions from this study are limited due to the small sample size. Only nine women were evaluated.
Additionally, the strength of appetite suppression from the fennel tea was not strong enough to reduce food intake.
Another study of 53 overweight women found that consuming 3, 100 mg capsules of fennel per day did not effect weight or fat loss. (3)
Fennel has been advertised as a “fat buster” or “metabolism booster.” Although fennel is a nutritious and low-fat vegetable, there is no research to support that fennel will accelerate fat loss.
Fennel can be included in a healthy diet that contributes to weight control, but it is not a cure for obesity.
3. May Improve Blood Flow
Nitrites and nitrates are chemicals that are converted to nitric oxide (NO) in the body. NO is a vasodilator, which means it relaxes blood vessels and enhances blood flow. These actions could help improve physical performance in endurance exercise.
Fennel seeds contain nitrites and nitrates. Some researchers hypothesize that the nitrites and nitrates in fennel could help promote vascular function and improve physical performance. (9)
There is not enough research to support this hypothesis. More research is needed to investigate the effects of fennel on blood flow.
4. May Help Relieve Constipation
Fennel is traditionally used as a laxative in various cultures. Constipation is characterized by decreased water excretion in the colon, causing tough stools that are difficult to pass.
Scientists find that the mucosa, the fluid-excreting cells of the colon, are reduced in patients with severe constipation.
One study showed that fennel restored the mucosa layer in the colons of constipated rats. (10) Constipation symptoms were also dramatically improved.
A randomized controlled trial studied the effect of a traditional Brazilian laxative containing fennel on relieving constipation. (11)
Within 2 days of starting to consume the herbal tea, patients perceived improved bowel function and had a greater average number of stools per day.
Based on the study results, it is difficult to conclude the true effect of fennel as a laxative because there were other herbs included in the tea preparation.
More rigorous scientific studies are needed to validate the use of fennel as a laxative.
5. Acts as a Carminative
A carminative helps the body to expel gas, relieving stomach cramps, and gastrointestinal discomfort. Fennel is traditionally used as a carminative due to anethole in the oils, which reduces muscle cramping.
These effects have the potential to relieve the symptoms of patients with irritable bowel syndrome (IBS).
A study that included 121 patients with IBS showed that treatment, including a combination of curcumin and fennel oils for 30 days, reduced IBS symptoms compared to a placebo. (12) Patients who received the treatment also reported improved quality of life.
More research is needed to determine fennel’s exact mechanism, safety, and dosage for IBS symptom relief.
6. May Eliminate the Symptoms of Colic
Infantile colic is a common complaint among new parents. Colic is defined by the “3, 3, 3 rule:” at least 3 hours of crying per day, 3 days a week, continued for at least 3 weeks.
Colic is often caused by food intolerances or allergies that lead to intestinal discomfort. Mothers of colicky infants are recommended to first remove allergens from their diet. If symptoms persist, a lactose-free or dairy-free formula may be warranted.
The only medicinal treatment for colic is dicyclomine hydrochloride. However, parents may be hesitant to try this medication due to its potentially harmful side effects, including death.
Fennel is commonly included in “gripe water” preparations that are rumored to relieve colic. Ingredients depend on the brand; however, gripe water usually contains sodium bicarbonate and other herbs such as ginger, clove, dill, peppermint, cinnamon, and cloves.
Although traditional gripe water contained alcohol, it is now known that this ingredient is inappropriate for infants.
Fennel is known to improve colic symptoms in infants. A study that included 125 infants found colic was eliminated in 65% of infants treated with fennel seed oil compared to 23.7% in the control group. (13)
Additionally, no significant side effects were reported among the treatment group.
7. Freshens Breath
Mukhwas is a traditional Indian snack usually eaten after meals to freshen breath. Mukhwas is a mix of seeds, herbs, and spices, including fennel as well as anise, ginger, dill, coconut, coriander, or sesame.
You may encounter mukhwas at your favorite Indian restaurant, served as a sugar-coated candy after the meal.
Cautions To Keep In Mind
Nontherapeutic doses of fennel used as a spice in food are usually benign. However, larger doses in tea or capsules may have harmful side effects. Please consider the following cautions:
Skin sensitivity: Fennel may increase skin sensitivity and the risk of sunburn. Avoid tanning beds and reduce exposure to direct sunlight.
Use a sunscreen, hats, umbrellas, or extra clothing to protect your skin from the sun. The most common side effects of using fennel are abnormal skin reactions, including rashes and itching.
Birth control pills: Fennel contains phytoestrogens and may reduce the effectiveness of some forms of birth control. Discuss birth control with your doctor before taking high doses of fennel.
Allergies: Do not take fennel if you have an allergy. People with an allergy to other members of the Apiaceae family, such as celery, carrots, parsley, dill, and anise, can also have reactions to fennel. Symptoms of allergies include difficulty breathing, rashes, hives, and swelling.
Abnormal breast development: There has been one report of a one-year-old girl developing breasts related to consuming 2-3 teaspoons of fennel in tea daily to prevent restlessness. After discontinuing the tea, her breasts gradually reduced to normal size within one year. (15)
Breastmilk: Two cases of fennel toxicity have been reported in breastfeeding infants. Mothers drinking 2 liters of tea infused with anise, fennel, and goat’s rue per day reported weakness and pain in their infants. (8) These symptoms subsided when the mothers stopped drinking the tea. Moderate intake of fennel has not been associated with these risks.
Fennel has also caused allergic reactions in some infants. Mothers of infants with an allergy to other plants of the Apiaceae family, such as carrots or celery, should avoid fennel.
Drug interactions: Fennel interacts with seizure medications and may decrease their effectiveness, increasing the risk for seizures.
Always consult with your doctor before taking supplements. You may need to avoid fennel if you are on any seizure medications, including:
- Phenytoin (Dilantin)
- Oxcarbazepine (Trileptal)
- Gabapentin (Neurontin)
Fennel is known for being an easy-to-grow herb. However, as a short-lived perennial, it will last for only a few years.
As it originates from the Mediterranean region, it grows best in a mildly warm climate. It can survive a light frost and grow again the next year.
Consider these tips for successfully adding fennel to your garden:
- It is best to plant in early spring, a few weeks before the last frost of the season.
- Place the plant where it will receive full sunlight with moist soil.
- Plant the seeds 12 inches apart.
- If you cut off the stems without removing the bulbs when harvesting, the stems will regrow.
Processing and Storage of Fennel
Fennel Herb: The stems of the plant can be trimmed about 3 inches from the bulb, wrapped in a plastic bag, and stored in the fridge. Alternatively, place them upright in a vase of water. Consume promptly after harvest for the strongest flavor.
Stalks can also be dried for increased shelf life. Follow these steps:
- Preheat the oven to 200°F.
- Place the stalks in a single layer on a baking sheet.
- Bake for 3 hours.
- Turn off the oven.
- Leave the stems in the oven overnight.
The feathery leaves (called fronds) are best used as a fresh herb in salads and soups or as a garnish.
Fennel Bulb: The bulb should be separated from the stems before storage. It can be stored on the countertop in a brown paper bag for 2-3 days, in the fridge for 7-12 days, or in the freezer for 8 months.
Fennel Seeds: The yellow flowers of the fennel plant produce small, comma-shaped, brown seeds. After they are collected from the plant, they should be stored in a cool, dry, dark area of the kitchen.
The seeds are often ground into a powder and used as a spice in cooking. Freshly ground seeds should be stored in the refrigerator.
After grinding, use the spice as soon as possible as the flavor diminishes with time.
If you do not have fennel in your garden or it is not the growing season, fennel seeds are always available in the spice section of grocery stores. They are available as whole seeds or powder.
Fennel seeds should not be mistaken for cumin seeds. Fennel seeds have a slight green color, whereas cumin seeds are larger and brown. Both plants are in the Apiaceae family; however, they have distinctly different tastes.
Fennel is sweet and licoricey, whereas cumin is bitter and slightly spicy. Cumin is often used in curry and Mexican dishes.
Fennel Oil: Fennel oil is created by distilling crushed fennel seeds. The aroma and flavor are powerful in the concentrated oils. A small amount can be used to flavor tea, soups, or dressings. Usually, just a drop or two is needed.
The oils are also used in cosmetics and fragrances. The scent is touted for its rejuvenating and energizing effects.
Of note, these oils should not be ingested as they also contain other ingredients that may not be edible.
How to Use Fennel In Recipes
As all parts of the plant can be used in foods, fennel has many culinary applications. These are just a few ways that fennel is enjoyed in cultures worldwide:
- The bulb can be sliced and eaten raw in salads or on a sandwich.
- Bulbs pair well with onions, drizzled with oil and roasted, baked or sautéed.
- Fennel can be paired with yogurt, honey, and mint leaves to bring out its sweet side.
- Dried fennel adds a licorice tone to egg, fish, risotto, and other dishes.
- Fennel is a key ingredient of sweet Italian sausage.
- Fennel is baked into European bread.
- Ground fennel is included in spice mixes such as Chinese five-spice and curry powders.
- The popular French alcoholic drink absinthe contains fennel herbs.
- The fronds can be used as a garnish or fresh herb in salads or soups.
- Sliced fennel stems can replace celery in your favorite stuffing or salad recipe.
Roasted Fennel with Parmesan
- 4 fennel plants
- Olive oil
- Salt and pepper to taste
- Parmesan cheese to taste
- Preheat the oven to 375°F.
- Remove the stems from the fennel bulb and slice the bulb in half.
- Laying the flat side of the bulb on the counter, cut horizontally in slices about 1/3 inch thick.
- Lightly oil the bottom of a 9 x 13 x 2-inch glass baking dish.
- Arrange the sliced bulb in the pan.
- Sprinkle with fennel fronds, salt, pepper, and parmesan cheese.
- Drizzle with a little more oil.
- Bake until the fennel can be easily pierced with a fork and is golden brown on top (about 45 minutes).
- Sprinkle with additional fresh fronds and serve.
Fennel, Orange, and Avocado Salad
- 2 large oranges, sliced into rounds
- 1 avocado, sliced
- 1 fennel bulb, thinly sliced
- 2 cups mixed greens
- 2 tbsp olive oil
- 2 tbsp lemon juice
- 2 tbsp orange juice
- Salt and pepper to taste
- Fennel fronds
- Slice the oranges, avocado, and fennel bulb.
- Mix the salad ingredients in a bowl.
- Mix the dressing ingredients well in a separate bowl.
- Pour the dressing over the salad and toss to combine.
- Serve and enjoy!
Fennel is a versatile ingredient that adds a unique flavor to many dishes. Cultures around the world use fennel in their most iconic dishes and to treat various health ailments.
Not all traditional medicinal uses of fennel have been proven by research; however, many people swear by its health benefits. Fennel is a healthy vegetable that provides vitamins, fiber, and phytochemicals that contribute to overall health.
Expert Answers (Q&A)
Answered by Evelyn Fuller, CDN (Registered Dietitian)
Information on the web is that fennel seeds aid in weight loss by curbing hunger and reducing cravings. However, the research to support this claim is not enough.
No current studies are available to support that fennel seeds are beneficial for weight loss.
A balanced diet that includes different fruits and vegetables is good for reducing hunger and cravings. As fruits and vegetables are low in calories and high in fiber, vitamins, and minerals, they help maintain a healthy weight.
It appears safe for healthy adults to eat fennel seeds regularly when consuming them in food form (vs. oil).
Fennel seeds are likely safe when used in appropriate doses over a short duration of time. However, there is no evidence for their long-term medicinal use.
Pregnant and lactating women should avoid the use of fennel seeds as there is not enough evidence that supports their safety during these times. There were documented incidences, in an old study, of two breastfeeding infants who experienced damage to their nervous systems after their mothers drank an herbal tea that contained fennel. (15)
Side effects are rare, but gastrointestinal upset and seizures are related to ingesting fennel essential oil by mouth.
Those who have allergies to celery, carrots, and mugwort are more likely to be allergic also to fennel. If you are using fennel seeds as a supplement, apply sunblock on sunny days. Fennel is known to increase skin sensitivity. (16)
While fennel has estrogen-like activity, research has not been able to determine that it increases estrogen levels.
Fennel oil was found to have significantly reduced the frequency of uterine contractions by inhibiting the effect of prostaglandin E2, which induces contractions. It was also reported that fennel oil can promote menstruation, alleviate the symptoms of female climacteric, and increase libido. (17)
Fennel has also been studied for its claim to increase lactation in breastfeeding mothers and infant weight gain. However, many of the studies conducted were not randomized or blinded. Thus, there is no significant evidence that fennel does indeed increase lactation or promote weight gain in breastfeeding infants. (18)
Fennel seeds should not be used as a treatment for asthma. Those who have asthma should regularly follow up with their physician and consult them when beginning a new dietary supplement.
One study found that fennel seeds may provide bronchodilator effects. Although the result was promising, the subjects were animals, and, thus, evidence from this particular study cannot be applied or generalized to humans. (19)
It is suggested that fennel seeds have anti-inflammatory properties. According to a 2004 study, the anti-inflammatory activity of the methanol extract of fennel seeds significantly reduced the inflammation symptoms in acute inflammatory disease. However, the study was conducted on animals, hence, the results are subject to interpretation. (20)
While fennel seeds may be considered thermogenic, food that increases metabolism and calories burned, it is unlikely that these seeds actually increase your internal body temperature.
Thermogenesis is a process that takes place after digestion when your body burns the calories from your last meal. The calories are then converted to heat. About 10% of the total calories burned are via diet-induced thermogenesis.
The fennel plant, including its seeds and oil, has been used for a wide array of conditions for a very long period of time. No adverse effects have been reported or documented to indicate any harm to the kidneys.
Roasted fennel seeds are not less beneficial for health. Cooking methods such as steaming, roasting, and sautéing preserve a good amount of nutrients when preparing vegetables.
Boiling and microwaving, though, will leach more of the nutrients out of the vegetable into the water. However, the water can then be preserved by freezing and used at a later date in soups and sauces for an added nutrient boost.
About Evelyn Fuller, RD, CDN: Evelyn is from upstate New York and started working at Clifton Springs Hospital in January of 2019.
She completed her first degree in psychology at SUNY Brockport and received her baccalaureate degree in nutrition and dietetics at the University of North Florida. Evelyn finished her dietetic internship with the Wellness Workdays distance program out of Hingham, MA.
She recently moved into the outpatient and inpatient setting at Clifton Springs. She has a passion for working together with patients to improve their overall health and wellness at any life stage.