Black seed or its extracted oil (black seed oil) has been used for thousands of years as a food additive and herbal health preparation in the Middle East, Far East and Asia.
Due to their special aroma and flavor, black cumin seeds are used for spice, flavoring, and antiseptic purposes, added to a variety of foods such as yogurt, pickles, seasonings, baked goods, cheeses, and salads.
In addition to this, in Islamic literature, black cumin is considered one of the greatest healing medicines. The use of black seeds has been mentioned in the medical literature to treat diseases such as asthma, cough, bronchitis, headache, rheumatism, fever, influenza, eczema, scorpion stings, and snakebites
In empirical medicine, what are the benefits of black seeds? Are there any side effects of black seeds? See the article for details
What is black seed/nigella seed?
Black seed/Nigella sativa, also known as black cumin, is an annual herbaceous flowering plant belonging to the ranunculaceae family, found worldwide, but mainly in Eastern Europe, the Middle East and Western Asia.
Nigella is about 20–30 cm tall, with linear leaves, and the flowers are usually light blue and white with five to ten petals. The fruit is a large, inflated capsule consisting of three to seven joint sacs, each containing seeds.
Nigella seeds are similar in size to sesame seeds (about 1 to 5 mm) and are often referred to as black seeds, or black cumin (Kalonji)
Nigella seeds contain a variety of active ingredients, such as thymoquinone, alkaloids, saponins, flavonoids, proteins, fatty acids, etc., of which thymoquinone is considered the most beneficial active ingredient.
What are the benefits of black cumin seeds?
1. Nigella seeds to assist COVID-19 treatment
The global pandemic of coronavirus disease (COVID-2) caused by severe acute respiratory syndrome (SARS-CoV-19) has spread rapidly around the world, infecting more than 2021 million people on five continents as of December 12.
SARS-CoV-2 is 96% identical to the entire genome of the coronavirus found in bats, so domestication or consumption of these wild animals was initially pointed to as one of the possible sources of the outbreak.
A randomized, controlled, open-label clinical trial (10-day trial of 173 patients with young adult COVID-19) noted that treatment with nigella seed oil supplementation (500 mg twice daily) resulted in faster recovery compared with standard care. Note 1
*Conclusion: For mild COVID-19, early application of nigella seed oil may bring positive help, but limited by small sample sizes, more studies are needed for further validation
2. Nigella seeds are beneficial for non-alcoholic fatty liver disease
Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is thought to be caused by the accumulation of fat in liver cells (prevalence estimated at 20% to 30%, increasing worldwide).
Factors are associated with obesity, type 2 diabetes, and hyperlipidaemia, but age, sex, and ethnicity may influence the prevalence.
Given the three stages of NAFLD’s development, non-alcoholic fatty liver (NAFL), non-alcoholic steatohepatitis (NASH), and cirrhosis, the healthcare costs and metabolic comorbidities of NAFLD place a significant burden on global health systems.
A systematic literature review and meta-analysis (6 randomized controlled trials with 358 participants in nonalcoholic fatty liver disease) noted that supplementation with nigella seed or nigella seed oil improved alanine aminotransferase (ALT), aspartate aminotransferase (AST), fasting blood glucose (FBS), high-density lipoprotein cholesterol (HDL), high-sensitivity C-reactive protein (hs-CRP) levels, and fatty liver fractionation compared with placebo. Note 1
*Conclusion: For patients with non-alcoholic fatty liver, nigella seeds may have positive help in improving liver function, but limited by the small sample size, more large-scale high-quality studies are still needed for further verification
3. Nigella seeds are good for asthma
Asthma is a chronic inflammatory disease of the respiratory tract associated with airway hyperresponsiveness (an exaggerated narrowing of the airways that targets specific triggers such as viruses, allergens, and exercise), resulting in recurrent asthma, dyspnea, chest tightness, and coughing, which vary with time and intensity.
It is estimated that about 10% of the population suffers from the disease. It is also the most common chronic disease in children, with the highest prevalence in adolescents (> 12%).
A meta-analysis (4 randomized controlled trials with 187 participants diagnosed with asthma) noted that, overall, supplementation with nigella extract or nigella seed oil improved asthma control test scores and forced expiratory volume at one second, compared with controls. However, there was no significant effect on peak expiratory flow, interleukin-4 γ, and interferon gamma. Note 1
*Conclusion: For asthmatic patients, supplementation with nigella related preparations may have a positive effect on disease control, but limited by the small sample size, more long-term studies are still needed to support it
4. Black cumin seeds are beneficial for male infertility
Infertility is a condition with psychological, economic and medical implications that can cause trauma and stress, especially in a procreational social environment that affects 8% to 12% of couples worldwide.
About 40 to 50 percent of all cases of infertility are due to “male factors” and up to 2 percent have poor sperm parameters. It may be a form with low sperm concentration, poor sperm motility, or malformation.
A randomized, double-blind, placebo-controlled trial (2-month trial of 68 men with abnormal semen parameters) showed that oral nigella seed oil (5 mL per day) improved sperm count, motility, morphology, semen volume, pH, and round cells compared with placebo. Note 1
*Conclusion: For male infertility patients with abnormal semen parameters, oral administration of nigella seed oil may be of positive help to improve sperm quality
5. Nigella seeds reduce inflammation indicators (C-reactive protein)
C-reactive protein is a serum biomarker of systemic inflammation, which is a better indicator of inflammation than erythrocyte sedimentation rate, more sensitive to changes in clinical conditions, and more responsive to changes in clinical conditions.
Because it responds quickly to the inflammatory process, inflammatory conditions such as infections, autoimmune diseases, or tissue necrosis rise rapidly.
There are many factors that can alter baseline levels of C-reactive protein, including age, sex, smoking status, body weight, lipid levels, and blood pressure, with an average CRP of about 0.8 mg/L in healthy individuals.
A systematic literature review and meta-analysis (5 randomized controlled trials, 439 participants) showed that intake of nigella seed or nigella seed oil (follow-up of 6 to 12 weeks, daily dose of 1 g to 3 g) significantly reduced serum C-reactive protein levels. Note 1
In addition, subgroup analysis further found that the effect of relevant C-lowering reactive protein was most significant in subjects with a BMI ≥ 30 kg/m2.
*Conclusion: Oral administration of nigella seeds and related products may have a positive effect on reducing inflammation indexes (C-reactive protein), but limited by the small sample size and heterogeneity, more studies are needed to support it
6. Nigella seeds improve dyslipidemia
Dyslipidemia, which refers to abnormally high levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and low-density lipoprotein cholesterol (HDL-C), is one of the strongest and most modifiable risk factors for cardiovascular disease.
In fact, dyslipidemia is not a single major phenomenon, but rather a broad term that refers to inappropriate diet and lifestyle, as well as some genetic predispositions.
A systematic literature review and meta-analysis (17 randomized controlled trials, 1185 participants) showed that nigella supplementation reduced serum total cholesterol (WMD: -15.65 mg/dL), LDL cholesterol (WMD: -14.10 mg/dL), and triglycerides (WMD: -20.64 mg/dL). Note 1
In the analysis, it was found that the related blood lipid improvement effect was more obvious with the use of black cumin seed oil, while black cumin seed powder was more helpful in increasing the level of high-density lipoprotein cholesterol (HDL-C).
*Conclusion: Nigella supplementation may help improve blood lipid markers (total cholesterol, LDL-C, triglycerides), but due to the heterogeneity of the included studies, more studies are needed to confirm the optimal dose and duration
7. Nigella seeds are beneficial for blood sugar control
Type 2 diabetes is diabetes and the most common form caused by insulin resistance and defects in insulin secretion.
Strict control of glycated hemoglobin A1c (HbA1c) of less than 7% (53 mmol/mol) can prevent or slow the progression of nephropathy, retinopathy and peripheral nerve diseases.
A systematic literature review and meta-analysis (including 17 randomized controlled trials) pointed out that oral nigella seed supplements reduced fasting blood glucose, postprandial blood glucose and glycated hemoglobin by 9.93 mg/dl, 0.57% and 14.79 mg/dl respectively compared with the control or intervention groups. Note 2
In addition, subgroup analysis found that black cumin seed oil improved fasting blood glucose better than black cumin seed powder.
*Conclusion: Oral nigella seed preparations have a positive effect on glycaemic control, but more studies are needed to support this due to the heterogeneity of the included studies
8. Nigella seeds assist in weight loss
Weight and its composition are the result of genetics, metabolism, environment, behavior, and culture. To date, 35 percent of adults in the United States meet the criteria for obesity (BMI ≥ 30 kg/m2), and another 35 percent are overweight (BMI between 25 and 29.9 kg/m2).
At any given time, more than a quarter of women are trying to lose weight, followed by men, the vast majority of whom lose weight without professional support and a formal weight loss program, so it is often difficult to reach the goal.
A systematic literature review and meta-analysis (13 randomized controlled trials, 875 participants) showed that supplementation with nigella seeds (in oil or capsule form) reduced body mass index by an average of 1.76 kg and -0.85 kg/m2, respectively, but no significant change in waist circumference. Note 3
The mechanisms behind it are associated with reduced lipid absorption, energy intake, pre-adipocytes differentiation/proliferation, and lipogenesis, as well as increased energy expenditure and lipolysis.
*Conclusion: Black cumin seed supplementation has a positive effect on weight loss, but due to the heterogeneity of the included studies, more long-term studies are needed to verify it
9. Black cumin seeds are beneficial for blood pressure regulation
Essential hypertension is the most common type of high blood pressure, affecting 90% to 95% of people with high blood pressure. Factors are associated with sedentary lifestyle, stress, visceral obesity, potassium deficiency (hypokalemia), obesity, salt (sodium) sensitivity, alcohol consumption, and vitamin D deficiency.
Hypertension is a major independent risk factor for coronary heart disease, stroke, and renal failure. In the range of 115/75 to 185/115 mmHg, the risk of fatal coronary events doubles for every 20 mmHg increase in systolic blood pressure and 10 mmHg increase in diastolic blood pressure.
A systematic literature review and meta-analysis (11 randomized controlled trials, 860 individuals with hypertension or normotensive) showed that oral nigella seed extract reduced systolic and diastolic blood pressure (mean reduction of -3.26 mmHg and -2.80 mmHg, respectively) compared with placebo and standard care, and was more effective in powder form. Note 4
*Conclusion: Short-term use of nigella seed meal may be helpful in regulating blood pressure, but limited by the polyphasic nature of the included studies (differences in age, sex, basic health status), more long-term trials are needed to confirm its clinical benefit
10. Nigella seeds help kidney stones dissolve
Kidney stone disease is a crystalline stone that usually forms in the kidneys and is associated with an increased risk of chronic kidney disease, end-stage renal failure, cardiovascular disease, diabetes and high blood pressure.
Initially, stone formation does not cause any symptoms, but as the stone grows, signs may include renal colic, abdominal back pain, hematuria, urinary tract infection, urinary tract obstruction, and hydronephrosis (renal dilation).
One randomized, triple-blind, placebo-controlled, clinical trial (10 weeks, 60 patients with kidney stones greater than 5 mm) used placebo in one group and nigella seed capsules in the other group. Note 5
The results showed that in the nigella seed group, 44.4% of patients completely expelled stones, 51.8% became smaller, and 3.7% remained unchanged in stone size.
In contrast, 15.3% of patients in the placebo group had complete stone clearance, 11.5% had stone reduction, 15.3% had stone enlargement, and 57.6% had no change in stone size.
*Conclusion: Nigella seeds may have a positive effect on preventing kidney stones and reducing early formation of stones, but more studies are needed to support this due to small sample sizes
Are there any side effects of nigella seeds?
For most people, nigella seeds are safe to eat in small amounts as a flavored food.
If the form of ingestion is black seed oil or black seed powder, moderate use in the short term, most studies have not found significant side effects (the safety of long-term use is still unknown), and possible side effects or adverse reactions that have been reported include: stomach upset, vomiting, constipation, abnormal liver test values (ALT, AST, Gamma-GT, ALP), especially in the state of high doses.
Safety precautions (7 contraindications to use)
1. When taken orally or applied to the skin, it may induce allergic reactions, symptoms such as skin rash
2. Pregnant women should consult a doctor before use, because animal studies have found that the use of black seed oil can slow down uterine contractions. Note 7
3. Do not use during lactation (due to unknown safety)
4. Poor coagulation function, take anticoagulants, do not use two weeks before surgery, because black seed oil may have anticoagulant effect
5. Diabetic patients or those taking hypoglycemic drugs should use with caution, or monitor blood sugar regularly (because black cumin seeds may have hypoglycemic effects)
6. Patients with low blood pressure or those taking blood pressure lowering drugs should use with caution, or monitor blood pressure regularly (because black cumin seeds may have blood pressure lowering effects)
7. Do not use in combination with drugs, because it may inhibit Cytochrome P450 enzymes related to drug metabolism, resulting in increased drug efficacy or side effects