Nigella sativa (N. sativa) is a small flowering plant that grows in Southwest Asia, the Middle East, Southern Europe, and Northern Africa (1).
This shrub also produces fruit with tiny black seeds. Commonly referred to as simply black seed, N. sativa seeds go by many other names, including black cumin, black caraway, nigella, fennel flower, and Roman coriander (2, 3).
Black seed oil is extracted from N. sativa seeds and has been used in traditional medicine for over 2,000 years due to its many therapeutic benefits.
Studies suggest it may have numerous applications for health, including the treatment of asthma and aiding weight loss. Itâ€™s also applied topically to benefit skin and hair (1, 2, 4, 5).
This article reviews the potential health benefits of black seed oil, as well as any possible side effects and dosing information.
Potential health benefits of black seed oil
In traditional medicine, black seed oil has been used to treat a variety of health conditions. As a result, it has sometimes been referred to as â€œpanaceaâ€ â€” or universal healer (4, 6).
While not all of its proposed medicinal uses have been proven to be effective, black seed oil and its plant compounds have been linked to several benefits for health.
High in antioxidants
Black seed oil is high in antioxidants â€” plant compounds that help protect cells against damage caused by unstable molecules called free radicals (7, 8, 9, 10).
Antioxidants are important for health, as research has shown that they can reduce inflammation and protect against conditions like heart disease, Alzheimerâ€™s disease, and cancer (11).
In particular, black seed oil is rich in thymoquinone, which has potent antioxidant and anti-inflammatory effects. As a result, studies suggest this compound may protect brain health and aid in treating several types of cancer (7, 12, 13, 14).
May help in treating asthma
Asthma is a chronic condition in which the lining of your airways swell and the muscles around them constrict, making it difficult for you to breathe (15).
Research has shown that black seed oil, and specifically thymoquinone in the oil, may help in treating asthma by reducing inflammation and relaxing muscles in the airway (4, 16, 17).
One study in 80 adults with asthma found that taking 500 mg of black seed oil capsules twice a day for 4 weeks significantly improved asthma control (16).
While promising, larger and longer studies are needed to assess the long-term safety and effectiveness of black seed oil supplements in the treatment of asthma.
May aid weight loss efforts
While the exact mechanism isnâ€™t fully understood, research shows that black seed oil may help reduce body mass index (BMI) in individuals with obesity, metabolic syndrome, or type 2 diabetes (18, 19, 20).
In one 8-week study, 90 women ages 25â€“50 with obesity were given a low calorie diet and either a placebo or 1 gram of black seed oil per meal for a total of 3 grams per day (21).
At the end of the study, those taking the black seed oil had lost significantly more weight and waist circumference than the placebo group. The oil group also experienced significant improvements in triglyceride and LDL (bad) cholesterol levels (21).
Despite these promising results, more research is needed on the long-term safety and efficacy of taking black seed oil for weight loss.
May lower blood sugar levels
For individuals with diabetes, consistently high blood sugar levels have been shown to increase the risk of future complications, including kidney disease, eye disease, and stroke (22).
Several studies in individuals with type 2 diabetes indicate that a dose of 2 grams per day of crushed whole black seeds may significantly reduce fasting blood sugar levels and hemoglobin A1c (HbA1c) levels, a measure of average blood sugar levels over 2â€“3 months (23, 24, 25).
While most studies use black seed powder in capsules, black seed oil has also been shown to help lower blood sugar levels (25).
One study in 99 adults with type 2 diabetes found that both 1/3 teaspoon (1.5 mL) and 3/5 teaspoon (3 mL) per day of black seed oil for 20 days significantly reduced HbA1c levels, compared with a placebo (26).
May help lower blood pressure and cholesterol levels
Black seed oil has also been studied for its potential effectiveness in reducing blood pressure and cholesterol levels.
High blood pressure and high total and LDL (bad) cholesterol levels are important risk factors for heart disease (27).
Two studies, one in 90 women with obesity and the other in 72 adults with type 2 diabetes, found that taking 2â€“3 grams of black seed oil capsules per day for 8â€“ 12 weeks significantly reduced LDL (bad) and total cholesterol levels (21, 28).
Another study in 90 people with high cholesterol levels observed that consuming 2 teaspoons (10 grams) of black seed oil after eating breakfast for 6 weeks significantly reduced LDL (bad) cholesterol levels (29).
The oil may also help lower blood pressure.
One study in 70 healthy adults noted that 1/2 teaspoon (2.5 mL) of black seed oil twice a day for 8 weeks significantly reduced blood pressure levels, compared with a placebo (30).
While promising, the overall research on black seed oil in reducing blood pressure and cholesterol levels is limited. More research is needed to confirm the optimal dose.
May protect brain health
Neuroinflammation is inflammation of brain tissue. Itâ€™s thought to play an important role in the development of diseases like Alzheimerâ€™s and Parkinsonâ€™s (13, 31).
Early test-tube and animal research suggests that thymoquinone in black seed oil may reduce neuroinflammation. Therefore, it may help protect against brain disorders like Alzheimerâ€™s or Parkinsonâ€™s disease (13, 32, 33, 34).
However, thereâ€™s currently very little research on the effectiveness of black seed oil in humans specifically regarding the brain.
One study in 40 healthy older adults found significant improvements in measures of memory, attention, and cognition after taking 500 mg of N. sativa capsules twice a day for 9 weeks (35).
Still, more research is needed to confirm black seed oilâ€™s protective effects for brain health.
May be good for skin and hair
In addition to medical uses, black seed oil is commonly used topically to help with a variety of skin conditions and to hydrate hair.
Research suggests that due to its antimicrobial and anti-inflammatory effects, black seed oil may help in treating a few skin conditions, including (36, 37, 38):
- general dry skin
Despite claims that the oil can also help hydrate hair and reduce dandruff, no clinical studies support these claims.
Other potential benefits
Black seed oil may have other benefits for health, including:
- Anticancer effects. Test-tube studies have shown thymoquinone in black seed oil to help control the growth and spread of several types of cancer cells (39, 40).
- Reduce symptoms of rheumatoid arthritis. Due to its anti-inflammatory effects, limited research suggests that black seed oil may help reduce joint inflammation in people with rheumatoid arthritis (41, 42, 43).
- Male infertility. Limited research suggests that black seed oil may improve semen quality in men diagnosed with infertility (44, 45).
- Antifungal. Black seed oil has also been shown to have antifungal activities. In particular, it may protect against Candida albicans, which is a yeast that can lead to candidiasis (46, 47).
While early research shows promise in the applications of black seed oil, more studies in humans are needed to confirm these effects and the optimal dosage.
Black seed oil is high in antioxidants and may have several benefits for health. These include the treatment of asthma and various skin conditions, lowering blood sugar and cholesterol levels, aiding in weight loss, and protecting brain health.
Potential side effects and safety concerns
When used in small amounts for cooking, black seed oil is likely safe for most people.
However, thereâ€™s limited research on the long-term safety of consuming larger doses for therapeutic purposes.
In general, short-term use of 3 months or less hasnâ€™t been linked to any serious side effects. However, in one study, taking 1 teaspoon (5 mL) of black seed oil per day for 8 weeks did cause nausea and bloating in some participants (2, 48).
One potential concern is that black seed oil may interact with medications that are processed through the cytochrome P450 pathway. Common medications that could be affected include warfarin (Coumadin) and beta-blockers like metoprolol (Lopressor) (49, 50).
Thereâ€™s also concern that taking too much black seed oil could harm your kidneys. In one reported case, a woman with type 2 diabetes was hospitalized for acute kidney failure after taking 2â€“2.5 grams of black seed capsules daily for 6 days (51).
However, other studies havenâ€™t shown negative effects on kidney health. In fact, some studies have even suggested that black seed oil has a protective effect on kidney function (2, 52, 53).
If you have any current kidney problems, itâ€™s recommended to talk with your medical provider before taking black seed oil.
Finally, due to limited research, women who are pregnant or breastfeeding should avoid using black seed oil, except for in small amounts as a flavoring for food.
Overall, more research is needed on the safety of black seed oil in humans, especially for long-term use.
Culinary use of black seed oil is likely safe in most individuals. Due to a lack of research, long-term safety of using larger doses of black seed oil for medicinal purposes is unknown.
How to use black seed oil
As a supplement, black seed oil can be ingested in pill or liquid form. The oil can also be used topically on skin and hair.
If buying the liquid form of black seed oil, itâ€™s recommended to choose a high quality product that doesnâ€™t have any added ingredients.
Furthermore, as supplements arenâ€™t tested for their safety and effectiveness by the Food and Drug Administration (FDA), itâ€™s important to choose a reputable brand.
It can help to look for products that have been certified by ConsumerLabs, the U.S. Pharmacopeial Convention, or NSF International, all of which test for quality.
Black seed oil has a strong flavor thatâ€™s slightly bitter and spicy. Itâ€™s often compared to cumin or oregano. As a result, if consuming black seed oil as a liquid, you may want to mix it with another strongly flavored ingredient, such as honey or lemon juice.
For topical uses, black seed oil can be massaged onto the skin.
Black seed oil can be consumed in either capsule or liquid form. However, due to its strong flavor, you may want to mix the oil with honey or lemon juice before ingesting.
While black seed oil may have some benefits for health, it doesnâ€™t replace any current medications that you may already be taking.
Additionally, thereâ€™s currently insufficient evidence to establish a recommended dosage. As a result, itâ€™s important to talk with your healthcare provider before using black seed oil.
Depending on the intended use, black seed oil amounts that have been studied vary greatly.
For example, in people with asthma, taking 1 mg of black seed oil capsules daily for 4 months was found to be safe and effective as a supplementary treatment (16).
On the other hand, in weight loss and reducing blood sugar levels, studies have shown higher doses of 2â€“3 grams of black seed oil per day for 8â€“12 weeks to be most effective (19, 21, 23, 24).
As the dosage can vary by use, itâ€™s recommended to first talk with your healthcare provider for personalized dosing recommendations.
Due to insufficient research, thereâ€™s currently no established recommended dose of black seed oil. Itâ€™s important to talk with your healthcare provider for personalized dosing recommendations.
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