Fennel is highly prized for its licorice-like flavor and the myriad of health benefits it provides, and has been used in natural remedies since ancient times. Originally cultivated in the Mediterranean, fennel remains especially prevalent in Greek and Italian cuisine – though its influence has spread globally over the years.
It is easily recognized by its pale bulb and long green stalks, and can be grown almost anywhere. All parts of the fennel plant – including the bulb, stalk, leaves and seeds – are edible and contribute a nice blend of flavor to other foods.
This MNT Knowledge Center feature is part of a collection of articles on the health benefits of popular foods. It provides a nutritional breakdown of fennel and an in-depth look at its possible health benefits, how to incorporate more fennel into your diet and any potential health risks of consuming fennel.
Nutritional breakdown of fennel
One raw fennel bulb contains only 73 calories, 0.5 grams of fat, 0 milligrams of cholesterol, 2.9 grams of protein, 17 grams ofcarbohydrate, and 7 grams of dietary fiber (28% of daily requirements).
That same serving provides 27% of daily potassium needs, 5% of sodium, 6% vitamin A, 11% calcium, 46% vitamin C, 9% iron, 5% vitamin B-6 and 10% of daily magnesium needs.
Fennel also contains phosphorous, zinc, copper, manganese,selenium, niacin, pantothenic acid, folate, choline, beta-carotene, lutein and zeaxanthin (vision), vitamin E and vitamin K.
In addition to all of these nutrients, fennel also contains dietary nitrates and is a natural source of estrogen.
Possible health benefits of consuming fennel
The iron, phosphorous, calcium, magnesium, manganese, zinc and vitamin K content present in fennel all contribute to building and maintaining bone structure and strength.
- Though phosphate and calcium are both important in bone structure, the careful balance of the two minerals is necessary for proper bone mineralization – consumption of too much phosphorus with too little calcium intake can result in bone loss.
- Iron and zinc play crucial roles in the production and maturation of collagen.
- Bone matrix formation requires the mineral manganese, and iron and zinc play important roles in the production and maturation of collagen.
- Low intakes of vitamin K have been associated with a higher risk for bone fracture. Adequate vitamin K consumption is important for good health as it acts as a modifier of bone matrix proteins, improves calcium absorption and may reduce urinary excretion of calcium.
Maintaining a low sodium intake is essential to lowering blood pressure, however increasing potassium intake may be just as important because of its vasodilation effects. According to the National Health and Nutrition Examination Survey, fewer than 2% of US adults meet the daily 4,700 mg recommendation.
In addition, potassium, calcium and magnesium (all present in fennel) have been found to decrease blood pressure naturally.
Dietary nitrates present in certain foods such as fennel have been found to lower blood pressure and protect the heart due to their vasodilatory and vasoprotective properties. One study conducted by the Swedish School of Sport and Health Sciences showed that participants’ blood pressure levels were lower after taking nitrate supplements that contained nitrate amounts equivalent to 150-250 grams of nitrate-rich vegetables than after taking a placebo.
Fennel’s fiber, potassium, folate, vitamin C, vitamin B-6 and phytonutrient content, coupled with its lack of cholesterol, all support heart health.
- Fennel contains significant amounts of fiber, which helps lower the total amount of cholesterol in the blood, thereby decreasing the risk of heart disease.
- In one study, those who consumed 4,069 mg of potassium per day had a 49% lower risk of death from ischemic heart disease compared to those who consumed less potassium (about 1,000 mg per day).4
- Vitamin B-6 and folate prevent the buildup of a compound known as homocysteine. When excessive amounts of homocysteine accumulate in the body, it can damage blood vessels and lead to heart problems.
- Selenium is a mineral that is not present in most fruits and vegetables, but can be found in fennel. It plays a role in liver enzyme function and helps detoxify some cancer-causing compounds in the body. Additionally, selenium prevents inflammation and also decreases tumor growth rates.2
- Fiber intakes from fruits and vegetables like fennel are associated with a lowered risk of colorectal cancer.
- Vitamin C, vitamin A and beta carotene function as powerful antioxidants that help protect cells against free radical damage.
- Fennel also contains folate, which plays a role in DNA synthesis and repair, thus preventing the formation of cancer cells from mutations in the DNA.
The selenium found in fennel has also been found to improve immune response to infection by stimulating production of killer T-cells.
Choline is a very important and versatile nutrient in fennel that helps with sleep, muscle movement, learning and memory. Choline also helps to maintain the structure of cellular membranes, aids in the transmission of nerve impulses, assists in the absorption of fat and reduces chronic inflammation.
Fennel is a source of vitamin B-6, which plays a vital role in energy metabolism by breaking down carbohydrates and proteins into glucose and amino acids. These smaller compounds are more easily utilized for energy within the body.
Digestion and regularity
Because of its fiber content, fennel helps to prevent constipation and promote regularity for a healthy digestive tract.
Weight management and satiety
Dietary fibers are commonly recognized as important factors in weight management and loss by functioning as “bulking agents” in the digestive system. These compounds increase satiety and reduce appetite, making you feel fuller for longer and thereby lowering your overall calorie intake.
Increasing iron absorption
Iron deficiency is one of the most common nutrient deficiencies in developed countries and a leading cause of anemia. Pairing foods like fennel that are high in vitamin C with foods that are iron-rich will maximize the body’s ability to absorb iron.
Estrogen, which is found naturally in fennel, is crucial in regulating the female reproductive cycle and can also affect fertility. The University of Texas Southwestern Medical Center conducted a study on mice, which showed that estrogen also plays an important role in controlling factors that contribute to body weight, such as appetite and energy expenditure.
Fennel is an excellent source of vitamin C. Collagen, the skin’s support system, relies on vitamin C as an essential nutrient that works in our bodies as an antioxidant to help prevent damage caused by the sun, pollution and smoke. Vitamin C also promotes collagen’s ability to smooth wrinkles and improve overall skin texture.
Consuming fruits and vegetables of all kinds has long been associated with a reduced risk of many lifestyle-related health conditions. Many studies have suggested that increasing consumption of plant foods like fennel decreases the risk of obesity and overall mortality, diabetes, heart disease and promotes a healthy complexion and hair, increased energy, overall lower weight.
How to incorporate more fennel into your diet
Fennel has a crunchy texture and mildly sweet flavor, making it a great addition to any dish. All parts of the fennel plant can be eaten, and the seeds are often used as a condiment in many recipes. When purchasing fennel at the market, look for bulbs that are firm and white or pale green and avoid spotted or bruised ones. Look for green stalks and leaves that are straight and bundled together; if the plant has flowering buds, this means that it is overripe.
To prepare fennel, cut the stalks off the bulb at the base where they sprout and then slice the bulb vertically. The fennel leaves, stalks and bulb can be prepared in a variety of ways:
- Use the stalks as a soup base or stock
- Sauté the leaves and stalks with onions for a quick and easy side
- Mix sliced fennel with a variety of your favorite fresh vegetables for a light, crisp salad
- Roasted fennel bulbs make a great addition to any entrée.
Potential health risks of consuming fennel
Some spices, including coriander, fennel and caraway, have recently been shown to cause severe allergic reactions in some individuals when consumed.7 Those who are allergic to these spices should avoid consuming them.
Beta-blockers, a type of medication most commonly prescribed for heart disease, can cause potassium levels to increase in the blood. High potassium foods such as fennel should be consumed in moderation when taking beta-blockers.
High levels of potassium in the body can pose a serious risk to those with kidney damage or kidneys that are not fully functional. Damaged kidneys may be unable to filter excess potassium from the blood, which could be fatal.
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with a variety than to concentrate on individual foods as the key to good health.