Nigella: Benefits, Dosage, Contraindications

Antiallergic

Antihistamine effects have been demonstrated in human and animal studies. A decrease in the synthesis of pro-inflammatory leukotrienes via inhibitory action on the arachidonic pathway has been described. Immunomodulatory effects have also been reported. Taking nigella (black seeds) improves the capabilities of immune cells, polymorphonuclear leukocytes, to engulf and destroy pathogens in patients undergoing immunotherapy for allergies.

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Anticancer

It has been shown that thymoquinone, the main active constituent of the black seed, possesses a number of anticancer properties mediated by different mechanisms. In vitro and in vivo studies have identified antiproliferative actions, induction of apoptosis, cell cycle arrest, generation of reactive oxygen species, and antimetastatic/antiangiogenic effects. Thymoquinone interacts with several key molecular elements (p53, p73, PTEN, STAT3, PPAR-g, and caspase activation), which contribute to inhibiting the growth of various types of cancer cells. These include several cancers such as neuroblastoma, pancreatic, breast, ovarian, colorectal, bone, lung, and some forms of leukemia. Moreover, laboratory models have shown that a combination of thymoquinone and chemotherapy agents, like doxorubicin or cisplatin, has a more significant effect than chemotherapy alone. Encapsulating thymoquinone in nanoparticles could enhance the antiproliferative, anti-inflammatory, and chemosensitizing effects of thymoquinone, according to study results. While thymoquinone appears to be the most promising anticancer constituent of nigella, other constituents such as α-hederin and derivatives of these compounds have also been identified as having therapeutic potential.

Anti-inflammatory

The anti-inflammatory effects of certain constituents of nigella likely play a role in its potential clinical effects. It has been shown that dithymoquinone, thymohydroquinone, thymol, carvacrol, and thymoquinone induce anti-inflammatory effects by inhibiting cyclooxygenase-1 (COX-1) and/or cyclooxygenase-2 (COX-2) in laboratory research. Some evidence also suggests they reduce the production of certain inflammatory cytokines. Moreover, clinical research shows that taking black seeds reduces levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, or C-reactive protein (CRP). In a meta-analysis, CRP was reduced compared to placebo in patients suffering from conditions associated with a state of chronic, mild inflammation, such as obesity, non-alcoholic fatty liver disease (NAFLD), metabolic syndrome, and rheumatoid arthritis.

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Respiratory effect

Nigella has traditionally been used for respiratory disorders. Laboratory research suggests that nigella may relax the smooth muscle of the trachea. Nigella's essential oil acts on various receptors in the body. It opposes the action of a receptor linked to muscle contraction (muscarinic), reduces the activity of a receptor related to allergic reactions (histamine H1), and influences calcium channels. Additionally, it activates receptors that help relax smooth muscles. Thymoquinone, a component of the oil, might contribute to these anti-inflammatory effects.

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Neurological

Black seed oil is an inhibitor of acetylcholinesterase, reduces tumor necrosis factor-03b1 (TNf-b1) and increases brain-derived neurotrophic factor. In a study, thymohydroquinone was identified as a compound having the strongest AChE inhibitory effect. By increasing acetylcholine, AChE inhibitors have shown to be useful in treating apathy, autism, dementia, Alzheimer's disease, schizophrenia, and Parkinson's disease. Alzheimer's disease is a slowly progressing neurodegenerative disorder of the central nervous system, characterized by profound impairment of cognitive and memory functions. Pathologically, it is characterized by progressive atrophy of the brain, accumulation of cortical senile plaques, and neurofibrillary tangles. A fibrillary amyloid substance deposits in senile plaques, formed by the aggregation of beta-amyloid peptide (Ab2). A study on rats suggests that thymoquinone has a potential neuroprotective effect against Ab2 in hippocampal and cortical neurons of rats and thus could be a promising candidate for Alzheimer's disease treatment. In other animal models, it was found that the oil or seed extract improved learning and memory and could protect against cell loss and neurodegeneration.

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Antioxidant

Antioxidant effects have been reported in several in vitro and animal studies, mainly attributed to the constituent thymoquinone. It has been shown that Nigella seed oil extracted by cold pressing appears to give higher levels of thymoquinone than oil extracted by other techniques. A preliminary clinical study involving 30 menopausal women reported that Nigella oil, at a rate of 3 g/day for 12 weeks, increased levels of superoxide dismutase and glutathione peroxidase enzymes. It was suggested in another study that the majority of the beneficial effects of thymoquinone are primarily related to the modulation of the Nrf2 signaling pathway. Thymoquinone stimulates its activity, encouraging the production of the Nrf2 gene and promoting its movement to the cell nucleus. This process plays an important role in protecting cells against stress and damage. Nuclear factor erythroid 2-related factor 2 (NRF2), is a transcription factor that, in humans, is encoded by the NFE2L2 gene. According to preliminary research, NRF2 may regulate the expression of antioxidant proteins that protect against oxidative damage triggered by injury and inflammation. Several drugs that stimulate the NFE2L2 pathway are being studied for the treatment of diseases caused by oxidative stress.

Antimicrobial

Antibacterial actions have been observed in vitro against Staphylococcus aureus, Helicobacter pylori, and Streptococcus spp. Antiparasitic effects have been identified in animal and human studies against Schistosoma mansoni, which may be due to antioxidant and immunomodulatory effects. Additionally, black seed extract and oil have shown antifungal effects, particularly against Candida and Aspergillus species, likely by inhibiting the germination of dermatophyte arthrospores, supporting traditional use of black seeds for skin fungal infections.

Hypoglycemic

Animal and preliminary human studies on Nigella and its constituent thymoquinone have demonstrated improved glucose tolerance, antioxidant status, kidney function, and reduced blood glucose, serum insulin, and glycosylated hemoglobin levels. Proposed mechanisms of action include reduced hepatic glucose production and inhibition of nitric oxide pathways.

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Hepato-protective

Animal studies indicate that Nigella has protective effects on the liver, acting against various toxic agents. Among its components, thymoquinone plays a key role in reducing hepatic fibrosis, notably by acting on specific cellular pathways (such as Toll-like receptor 4 and phosphatidylinositol 3-kinase). A meta-analysis of clinical research shows that taking Nigella seeds in oil or powder form has beneficial effects on alkaline phosphatase (ALP) and aspartate aminotransferase (AST) levels when used for at least 12 weeks. No effect was observed on alanine aminotransferase (ALT) levels. The potential hepatoprotective effects are likely due to decreased oxidative stress.

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Immunomodulatory

Nigella seed is considered for its beneficial effects on the immune system. Preliminary studies indicate it may help reduce hemoglobin and leukocyte drops often observed after chemotherapy. It also appears to stimulate the production of certain human interleukins and influence macrophage activity. Research on animals has suggested that Nigella essential oil may affect the number and activity of neutrophils and other lymphocytes and could even reduce antibody production.

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Analgesic

Traditionally, black seeds are used orally or topically to treat arthritis, headaches, and other pains. Nigella extracts, oil, and constituents have all shown analgesic effects in animal models. This is likely due to the anti-inflammatory or central nervous system (CNS) depressant constituents of Nigella.

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Gastroprotective

Gastroprotective mechanisms have been observed in an animal study. Thymoquinone may have inhibited proton pump activity and acid secretion while increasing mucin secretion and nitric oxide production. Furthermore, Nigella seeds are used to reduce ulcers. Potential mechanisms of action seem to include the antioxidant or anti-inflammatory effects of black seed constituents like thymoquinone, the antibacterial effects against H. pylori, or protection of the stomach lining against acid.

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Antihypertensive

Some animal and human research suggests that Nigella and its constituents may reduce blood pressure. Potential mechanisms of action include diuresis, regulation of endothelial function, or calcium channel inhibition.

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Antiparasitic

Black seeds have been historically used against parasites. Black seed extract has shown antiparasitic effects against various types of parasites, likely by inhibiting egg laying.