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Fennel Seeds Health Benefits, Side Effects & How To Enjoy Them

Lauren Manaker, MS, RDN
July 27, 2023
Lauren Manaker, MS, RDN
Registered dietitian
By Lauren Manaker, MS, RDN
Registered dietitian
Lauren Manaker is an award-winning registered dietitian, freelance writer, and three-time book author who has been in the field for over 20 years. She is a frequent contributor to many media outlets, a national speaker, and a content creator for @LaurenLovesNutrition, with a special focus on women's health.

Fennel seeds are one versatile ingredient: They can be used in recipes, taken as supplements, and even chewed on their own. They're also a good source of antioxidants and powerhouse polyphenols. Keep reading to learn all about these popular seeds—and their potential health benefits.

Fennel seed nutrition

Scientifically known as Foeniculum vulgare, fennel seeds are a popular spice that comes from flowering plants in the carrot family.

They are renowned for their distinct licorice-like flavor and aroma, often used to enhance the taste and fragrance of a variety of dishes around the globe.

Here is the nutritional contents of 1 tablespoon of whole fennel seeds, according to the USDA FoodData Central1

  • Calories: 20 calories
  • Fat: 0.8 g
  • Saturated fat: 0.03 g
  • Cholesterol: 0 mg
  • Sodium: 5 mg
  • Potassium: 98 mg
  • Carbohydrates: 3 g
  • Dietary fiber: 2 g
  • Sugar: 0 g
  • Protein: 0.9 g

"Fennel seed is a highly nutritious herb rich in nutrients like calcium, vitamin C, potassium, manganese, and magnesium," Jen Scheinman, M.S., RDN, registered dietitian, explains. She adds that "they are loaded with potent antioxidants and healthy plant compounds called polyphenols that can lower the risk of chronic health conditions such as heart disease, some types of cancer, and Type 2 diabetes."

Specifically, these seeds contain the plant compounds quercetin and apigenin. Preliminary data suggest that these compounds may offer cognitive health benefits2 and have anti-cancer properties3

Health benefits

When you sprinkle fennel seeds onto your dishes, you're getting more than a bold flavor boost. The nutrients and compounds naturally found in fennel seeds may support your overall health in the following ways. Note, however, that research on fennel seeds is still pretty limited, so don't expect these tiny seeds to move the needle on health in any major ways.


They may support intestinal health

Some evidence suggests that fennel seeds may support intestinal health in various ways, although more well-designed clinical trials are needed to confirm this.

A recent study published in PLoS One evaluated the effects of fennel seed extract on certain effects people may experience when they have inflammatory bowel disease (IBD). Results showed that fennel seed extract was linked to improved barrier function4 of the gastrointestinal tract. Additionally, mice treated with fennel seed showed significantly lower ulcer indexes than control mice.

"The problem with substantiating fennel claims [and intestinal health benefits] is that it's usually combined with other nutrients, like curcumin," Michael A. Smith, M.D., director of education at Life Extension, cautions.

He does highlight that one placebo-controlled clinical trial published in the Journal of Gastrointestinal and Liver Disease5 "showed significant improvement in bloating and other digestive discomforts for people taking a combination of fennel seed oil and turmeric."


They may promote weight loss

While there is very little in the medical literature that suggests fennel seed impacts weight loss, according to Scheinman, there is some evidence "showing that drinking fennel seeds can suppress appetite, so that may play a role in weight loss and reducing belly fat." 

One very small study published in Clinical Nutrition Research showed that after people were provided with fennel tea, fenugreek tea, or a tea void of these ingredients and then provided with a food buffet, those who consumed the fennel tea experienced less hunger6 and consumed less food at the mealtime vs. those who did not consume this tea.

"Since there is little risk associated with consuming fennel seeds, sipping on fennel tea before a meal might offer some help for people, but I wouldn't expect major results from this," Scheinman adds. 


They have some hair and skin benefits

Fennel seed benefits for skin may be a result of the antioxidants that these tiny seeds provide, as these compounds may help fight free radical damage and can help maintain healthy skin7. Fennel seed benefits for hair may be linked to the antioxidant content as well. Oxidative stress may impact hair loss8, and antioxidants can help combat the oxidative stress in the body, possibly helping people maintain their hair health over time. 


They may help improve cognitive health

Cognitive health refers to our ability to think, learn, and remember. Our cognitive health can decline naturally as we age, and it can be affected by many factors, including our diet. 

While more human studies are needed to confirm this link, preliminary data suggests that fennel seed extract may offer unique benefits among rodents with Alzheimer's disease symptoms9

One reason fennel seed may positively impact cognitive health is because it contains a plant compound called quercetin. This compound is linked to improved memory, learning, and cognitive function10. And according to data published in Biomolecules and Therapeutics2, quercetin can impact the brain in various ways that may help treat certain effects of Alzheimer's disease.


They may support heart health

Among the many factors that may negatively impact heart health, consuming too much sodium is one culprit. Excessive sodium consumption has been linked to high blood pressure11, which can increase the risk of heart disease and stroke12

It is recommended that most Americans limit their sodium intake to less than 2,300 mg of the mineral every day13. One serving of fennel seeds contains a nominal 5 mg of sodium, yet it is incredibly flavorful, making it a fantastic addition to recipes instead of table salt (which is a major contributor to our sodium intake). 

Fennel seeds also contain natural nitrites, which may act as a vasodilator in the body. Vasodilators can help support healthy blood flow, which may support heart health as well. Thus, consuming fennel seeds may positively support cardiovascular health, according to a study published in the Journal of Food Science14.


Some people use them to squash bad breath

In certain areas of the world, like India, it is common to chew on fennel seeds after a meal to help combat bad breath. These tiny seeds may help keep halitosis at bay thanks to their antimicrobial properties15.

While we need more robust clinical trials to confirm this link, chewing on fennel seeds comes with little risk, so it may be worth exploring if you don't have any minty gum on hand.


Compounds in fennel seeds may support gut health and promote weight loss, though we need more research to be sure. The quercetin in fennel seeds may also benefit the brain, while the seeds' natural nitrates may support healthy blood pressure. Some people also use fennel seeds for more aesthetic reasons: to freshen breath and fortify the hair and skin.

Allergies and side effects

Like many other seeds and spices, fennel seeds can indeed go rancid if not stored properly. Exposure to heat, light, and moisture can degrade the seeds over time, leading to a loss of flavor and nutritional value. However, when stored in a cool, dark, and dry place, fennel seeds can maintain their quality for up to six months. For longer storage periods, refrigeration or freezing in an airtight container can further preserve the seeds' freshness and potency.

Despite their numerous health benefits, fennel seed side effects need to be recognized. Consumption of fennel seeds may lead to allergic reactions16 in some individuals. These reactions can range from mild to severe, including symptoms such as skin rashes, itching, swelling of the mouth or throat, difficulty breathing, and digestive issues.

In rare cases, a severe allergic reaction known as anaphylaxis may occur, which is a medical emergency. It's important to note that if you have a known allergy to plants in the carrot family, which includes fennel, you may be more likely to be allergic to fennel seeds. Always consult with a health care professional before including fennel seeds in your diet if you have food allergies or sensitivities.

Pregnant people are advised to avoid consumption of fennel seeds, as ingestion may stimulate uterine contractions, potentially increasing the risk of premature labor. Those with bleeding disorders or who are on blood-thinning medications should also be wary, as fennel may slow blood clotting17.

Since the effects of eating fennel seeds are not well studied in the pediatric population, children should avoid consuming large quantities of this seed unless under the guidance of a health care provider. 

Fennel seeds vs. other seeds

OK, so fennel seeds are healthy—but how do they stack up to other popular seeds you'll see on shelves?

Fennel seeds vs. chia seeds

When comparing fennel seeds and chia seeds, it's clear that both possess their unique health benefits. While fennel seeds have digestive, anti-cancer, and cognitive support benefits, chia seeds are a rich source of omega-3 fatty acids, fiber, and essential minerals—features that may support heart health, digestion, and bone health.

It's also important to note that chia seeds do not have the same potential side effects as fennel seeds. They are generally safe for everyone, including pregnant people and children, except in cases of known allergies. However, they should always be consumed in moderation due to their high fiber content. 

Fennel seeds vs. flaxseeds

Flaxseeds, like chia seeds, are a rich source of omega-3 fatty acids, which are essential for heart health. They also provide an impressive amount of dietary fiber, which aids digestion and can help manage weight. Additionally, flaxseeds are rich in lignans, compounds that have been shown to have antioxidant properties and may help manage some perimenopausal symptoms (like hot flashes)18

Fennel seeds vs. hemp seeds

Hemp seeds, also known as hemp hearts, are the seeds of the hemp plant, Cannabis sativa. Renowned for their nutritional profile, hemp seeds are packed with essential fatty acids like omega-3 and omega-6, fiber, and plant-based protein. They also contain vitamins and minerals such as vitamin E, potassium, magnesium, calcium, iron, and zinc. 

Both fennel seeds and hemp seeds may offer some similar health benefits. But because hemp seeds contain more healthy fats than fennel seeds, they may be a better choice for those who are focused on their heart health. 

Ways to enjoy fennel seeds

Fennel seeds are a relatively low-cost addition to your diet, selling for around $6 per 3.5-ounce bag.

"Fennel seed can have a mild licorice-like flavor, but its distinctive taste makes it perfect for marinades, dressings, and rubs," Scheinman shares, adding that "many Indian and Middle Eastern dishes use fennel seed as one of their key spices, and it tastes amazing in curries and sauces."

Here are a few ideas to get you started working with fennel seeds in your kitchen:

  1. Toast them and add them to grain dishes, use them in salad dressings, or add them to smoothies
  2. Consume them raw, sprinkled on salads or soups.
  3. Take a note from Ella Davar, R.D., CDN, and use them to prepare herbal teas or spirits.
  4. Follow Amy Shapiro, M.S., RDN's lead, and add them to water to create a sippable beverage. When soaked, fennel seeds can release antioxidants into the water, creating a potent health drink.

Certain supplement brands offer fennel seed extract in supplemental form as well. 

Buying and storage tips

When purchasing and storing fennel seeds, it is important to keep the following tips in mind:

  1. Check the packaging date on the label to ensure your seeds are not expired.
  2. If possible, smell the seeds and opt for those with a stronger aroma. Your seeds should have a licorice scent. 
  3. The color of the seeds can also be a good indicator of quality; they should be greenish-yellow and not too dark. 
  4. Choose raw fennel seeds over their processed counterparts when possible. Processed fennel seeds might have gone through processes that diminish their nutritional value. 
  5. Store your fennel seeds in an airtight container in a cool, dark place to preserve their flavor and medicinal properties. 


How much fennel seed should I eat every day?

Fennel seeds can safely be consumed every day. While there is no official dose that people should aim to eat daily, Scheinman shares that "about 1 tablespoon of fennel seeds will provide you with about 2 grams of fiber, 5% of your daily calcium and magnesium needs, 6% of your iron needs, and 17% of your daily manganese needs."

Can fennel seeds reduce belly fat?

While certain features of fennel seeds may help support belly fat reduction, like the fiber content that may support satiety, there is no high-quality data suggesting that consuming this seed every day will guarantee a flat belly. 

Who should not eat fennel seeds?

Despite the health benefits of fennel seeds, they may not be suitable for everyone. Pregnant women, in particular, should avoid consuming fennel seeds in large amounts as they may have uterine-stimulating effects. Individuals with a history of hormone-sensitive conditions, such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids, should also exercise caution, as fennel seeds may mimic estrogen in the body. Fennel seeds may interact with anticoagulants and antiplatelet drugs, potentially increasing the risk of bleeding. Furthermore, people who are allergic to carrots or celery, both of which belong to the same plant family as fennel, may also have an allergic reaction to fennel seeds. As always, when in doubt, it's best to consult a health care provider.

The takeaway

Fennel seeds can add a unique flavor profile to dishes and drinks. And while these seeds provide some nutrients and antioxidants without being high in calories, unhealthy fats, or sodium, the data surrounding the health benefits associated with consuming fennel seeds is not incredibly strong.

But since including these seeds in your diet comes with little risk, as long as consuming them is OK with your health care provider, adding them to your recipes, using them as a tea ingredient, or simply chewing on them post-meal may offer some benefit for certain individuals. 

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