Black seed has anti-inflammatory and antioxidant effects and immune-modulating properties. Currently, the most well-studied benefits of black seed are for cardiovascular health and metabolic health.[reference|url=https://pubmed.ncbi.nlm.nih.gov/37036558|title=The effect of Nigella sativa (black seed) on biomarkers of inflammation and oxidative stress: an updated systematic review and meta-analysis of randomized controlled trials.|published=2023-Jun|authors=Kavyani Z, Musazadeh V, Golpour-Hamedani S, Moridpour AH, Vajdi M, Askari G|journal=Inflammopharmacology|]
Black seed may improve glycemic control by lowering fasting glucose and hemoglobin A1c (HbA1c) by a clinically significant degree. This effect is the greatest in people with type 2 diabetes, but benefits are still observed in other relevant conditions like metabolic syndrome and nonalcoholic fatty liver disease (NAFLD).[reference|url=https://pubmed.ncbi.nlm.nih.gov/38265398|title=Effect of Nigella sativa Consumption on Lipid Profile and Glycemic Index in Patients with Metabolic Syndrome: A Systematic Review and Meta-analysis of Randomized Controlled Trials.|published=2024-Jan-23|authors=Shabani M, Ghavidel F, Rajabian A, Homayouni-Tabrizi M, Jamialahmadi T, Hosseini H, Sahebkar A|journal=Curr Med Chem|][reference|url=https://pubmed.ncbi.nlm.nih.gov/36034891|title=supplementation improves cardiometabolic indicators in population with prediabetes and type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials.|published=2022|authors=Saadati S, Naseri K, Asbaghi O, Abhari K, Zhang P, Li HB, Gan RY|journal=Front Nutr|][reference|url=https://pubmed.ncbi.nlm.nih.gov/32394508|title=Effects of Nigella sativa on glycemic control, lipid profiles, and biomarkers of inflammatory and oxidative stress: A systematic review and meta-analysis of randomized controlled clinical trials|published=2020 Oct|authors=Jamal Hallajzadeh, Alireza Milajerdi, Moein Mobini, Elaheh Amirani, Susan Azizi, Elhameh Nikkhah, Babak Bahadori, Razieh Sheikhsoleimani, Seyyed Mehdi Mirhashemi|journal=Phytother Res|][reference|url=https://pubmed.ncbi.nlm.nih.gov/30873688|title=Effect of Nigella sativa (black seed) supplementation on glycemic control: A systematic review and meta-analysis of clinical trials.|published=2019-May|authors=Askari G, Rouhani MH, Ghaedi E, Ghavami A, Nouri M, Mohammadi H|journal=Phytother Res|]
Black seed may also improve lipid profiles, including reduced triglycerides, low-density lipoprotein (LDL) cholesterol, and total cholesterol, and increased high-density lipoprotein (HDL) cholesterol.[reference|url=https://pubmed.ncbi.nlm.nih.gov/32394508|title=Effects of Nigella sativa on glycemic control, lipid profiles, and biomarkers of inflammatory and oxidative stress: A systematic review and meta-analysis of randomized controlled clinical trials|published=2020 Oct|authors=Jamal Hallajzadeh, Alireza Milajerdi, Moein Mobini, Elaheh Amirani, Susan Azizi, Elhameh Nikkhah, Babak Bahadori, Razieh Sheikhsoleimani, Seyyed Mehdi Mirhashemi|journal=Phytother Res|][reference|url=https://pubmed.ncbi.nlm.nih.gov/36034891|title=supplementation improves cardiometabolic indicators in population with prediabetes and type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials.|published=2022|authors=Saadati S, Naseri K, Asbaghi O, Abhari K, Zhang P, Li HB, Gan RY|journal=Front Nutr|][reference|url=https://pubmed.ncbi.nlm.nih.gov/38265398|title=Effect of Nigella sativa Consumption on Lipid Profile and Glycemic Index in Patients with Metabolic Syndrome: A Systematic Review and Meta-analysis of Randomized Controlled Trials.|published=2024-Jan-23|authors=Shabani M, Ghavidel F, Rajabian A, Homayouni-Tabrizi M, Jamialahmadi T, Hosseini H, Sahebkar A|journal=Curr Med Chem|] This lipid-modulating effect has not been found in people with NAFLD despite other observed benefits in this population (reduced levels of liver enzymes, C-reactive protein, and liver fat).[reference|url=https://pubmed.ncbi.nlm.nih.gov/33728708|title=Effect of Nigella sativa in the treatment of nonalcoholic fatty liver disease: A systematic review and meta-analysis of randomized controlled trials|published=2021 Mar 16|authors=Gang Tang, Linyu Zhang, Jie Tao, Zhengqiang Wei|journal=Phytother Res|]
Lastly, black seed may reduce blood pressure, and in people with overweight or obesity, it may cause slight reductions in weight and body mass index (BMI).[reference|url=https://pubmed.ncbi.nlm.nih.gov/37341696|title=Antihypertensive effects of Nigella sativa supplementation: An updated systematic review and meta-analysis of randomized controlled trials.|published=2023-Aug|authors=Kavyani Z, Musazadeh V, Safaei E, Mohammadi Asmaroud M, Khashakichafi F, Ahrabi SS, Dehghan P|journal=Phytother Res|][reference|url=https://pubmed.ncbi.nlm.nih.gov/29857879|title=Effect of Nigella sativa supplementation on obesity indices: A systematic review and meta-analysis of randomized controlled trials.|published=2018-Jun|authors=Mousavi SM, Sheikhi A, Varkaneh HK, Zarezadeh M, Rahmani J, Milajerdi A|journal=Complement Ther Med|]
Most of these effects have been observed in short-term studies (≤12 weeks), meaning the long-term effectiveness of black seed supplementation still needs to be determined. An exception to this is the effect of black seed on glycemic control, with benefits being maintained in some studies spanning 6 to 12 months.[reference|url=https://pubmed.ncbi.nlm.nih.gov/32394508|title=Effects of Nigella sativa on glycemic control, lipid profiles, and biomarkers of inflammatory and oxidative stress: A systematic review and meta-analysis of randomized controlled clinical trials|published=2020 Oct|authors=Jamal Hallajzadeh, Alireza Milajerdi, Moein Mobini, Elaheh Amirani, Susan Azizi, Elhameh Nikkhah, Babak Bahadori, Razieh Sheikhsoleimani, Seyyed Mehdi Mirhashemi|journal=Phytother Res|]