Black Cumin and Its Oil: Effects on Blood Sugar, Blood Pressure and Cholesterol
Laura Chrobok 19.10.2026
A plant and the oil extracted from it — used for centuries and now even the subject of clinical diabetes research: black cumin oil has properties that go beyond its value as an ordinary cooking oil. Today, specific studies allow us to assess just how much health potential lies within these small black seeds.
Some findings deserve particular attention — not least because they show that modern research into this traditional medicinal plant is far from complete.
Black Cumin: Constituents and Distinctive Properties
Black cumin (Nigella sativa) belongs to the buttercup family (Ranunculaceae). Despite its name, it is not closely related to either caraway or cumin. The plant originally comes from regions of Western Asia and the Mediterranean. Its small black seeds have been used as a spice for centuries and are also used to produce vegetable oil.
Black cumin oil consists predominantly of unsaturated fatty acids. It also contains various secondary plant compounds whose biological properties are increasingly being investigated.
Particularly noteworthy are:
o Linoleic acid is an essential omega-6 fatty acid that makes up a large proportion of the oil.
o Oleic acid is a monounsaturated fatty acid that is also found in olive oil, for example.
o Thymoquinone is a bioactive compound whose influence on inflammatory processes, cellular protection and metabolism is being investigated.
Thymoquinone is attracting particular attention because experimental studies have shown that this plant compound can influence signalling pathways associated with inflammatory reactions and the regulation of glucose metabolism, among other things (Shaukat et al., 2023).
The Effects of Black Cumin Oil on Metabolism
Thymoquinone belongs to the quinones, a group of organic compounds that can participate in so-called redox reactions, meaning they can accept and release electrons — fundamental processes in numerous biological functions. Thymoquinone is of particular interest in metabolic research because it influences various mechanisms involved in diabetes and insulin resistance in cell and animal models.
Among other things, effects have been documented on:
o Insulin signalling pathways: Processes through which the hormone insulin regulates the uptake and utilisation of glucose.
o AMPK: An enzyme that plays an important role in regulating cellular energy metabolism.
o Oxidative stress: Processes in which reactive oxygen compounds overwhelm the cells’ protective mechanisms.
o Inflammatory reactions: Particularly signalling pathways involved in the development and maintenance of chronic inflammatory processes.
These experimental findings provide possible explanations for the effects of black cumin. However, studies in which black cumin oil has been administered to humans are particularly informative. We will now take a closer look at these.
The Effects of Black Cumin Oil in Diabetes
A randomised, double-blind, placebo-controlled study investigated the effects of black cumin oil in 72 people with type 2 diabetes. Participants received either 3 g of black cumin oil or a placebo in capsule form daily for 12 weeks.
At the end of the study, significant improvements were observed compared with the placebo group in several metabolic parameters:
o fasting blood sugar
o HbA1c levels
o LDL cholesterol
o triglycerides
(Heshmati et al., 2015).
HbA1c is particularly interesting because it plays a central role in assessing diabetes. Further studies have also confirmed these findings.
A systematic review and meta-analysis published in 2025 included 16 clinical studies involving people with type 2 diabetes.
Compared with the respective control groups, the results showed average reductions of:
o 21.43 mg/dl in fasting blood sugar
o 0.44 percentage points in HbA1c
o 18.80 mg/dl in total cholesterol
o 19.53 mg/dl in LDL cholesterol
All differences were statistically significant.
The studies investigated used both black cumin oil and other preparations made from the seeds. These average values therefore relate to Nigella sativa as a whole, rather than exclusively to the oil.
There were also indications that factors such as duration of use, dosage and formulation can influence the results. For example, studies involving supplementation for more than eight weeks showed a significant reduction in fasting blood sugar.
The combined clinical findings therefore suggest that black cumin preparations may provide additional benefits in regulating glucose metabolism (Karimi et al., 2025). Further experimental studies on thymoquinone have also described improved insulin signalling and reduced glucose production in the liver (Shaukat et al., 2023).
However, the long-term effects on diabetes-related complications still need to be investigated.
The Effects of Black Cumin on Cholesterol and Blood Pressure
Alongside blood sugar, cholesterol and blood pressure are among the most frequently investigated metabolic and cardiovascular parameters.
Elevated LDL cholesterol levels and persistently high blood pressure, in particular, contribute to the development of cardiovascular disease.
A meta-analysis investigated the effects of various Nigella sativa preparations on blood pressure.
The pooled results showed statistically significant differences compared with the control groups:
o an average reduction of 3.06 mmHg in systolic blood pressure
o an average reduction of 2.69 mmHg in diastolic blood pressure
(Kavyani et al., 2023).
In 2025, a further meta-analysis examined 82 randomised trials involving a total of 5,026 participants.
Significant changes were identified in various metabolic and cardiovascular risk markers, including:
o total cholesterol and LDL cholesterol
o HDL cholesterol and triglycerides
o systolic and diastolic blood pressure
o fasting blood sugar and HbA1c
o inflammatory markers such as C-reactive protein
The treatment periods investigated ranged from 1 to 48 weeks.
The findings show that black cumin preparations can influence various risk factors. According to experimental studies, thymol contained in black cumin can inhibit calcium entry into the muscle cells of blood vessels, allowing them to relax and dilate. Antioxidant and blood-pressure-lowering effects have also been observed for thymoquinone in experimental studies (Maideen et al., 2021). Whether these changes also lead to fewer cardiovascular diseases in the long term is the subject of further research.
The Quality of Black Cumin Oil Is a Crucial Factor
The quality of black cumin oil is of great importance, particularly for medicinal use. There are many different oils, and they cannot all be considered equivalent.
An investigation of 13 oils extracted in the laboratory from black cumin seeds of different origins revealed the following: while the fatty acid composition was similar, the concentrations of other constituents sometimes varied considerably. This was particularly true of certain volatile plant compounds, as well as tocopherols and tocotrienols.
Commercial black cumin oils are often advertised as cold-pressed. However, this production method alone does not guarantee a particular thymoquinone content.
Nor does a particularly high concentration of this plant compound automatically mean a stronger health effect. Appropriate comparative clinical studies would be needed to establish this.
Tolerability of Black Cumin Oil
Black cumin seeds have long been used as food. In clinical studies, corresponding oil and seed preparations have also generally been well tolerated.
Nevertheless, possible side effects include:
· abdominal discomfort and flatulence
· diarrhoea
· changes in taste
· headaches
· allergic reactions
(LiverTox, 2023).
Severe contact allergies have also occasionally been reported following topical application of black cumin oil (Assier et al., 2023).
Potential interactions with medicines deserve particular attention. Memorial Sloan Kettering Cancer Center points out that constituents of Nigella sativa can influence certain enzymes involved in the breakdown of medicines in laboratory studies. The clinical significance of these interactions has not yet been sufficiently investigated.
Anyone who regularly takes medicines, particularly for diabetes or high blood pressure, should therefore seek medical or pharmaceutical advice before additionally taking concentrated black cumin preparations (Memorial Sloan Kettering Cancer Center, 2023).
Black Cumin: Naturopathic Tradition Combined with Scientific Findings
The results of clinical studies show that there is more behind its traditional use than mere historical practice.
In particular, its metabolism-regulating properties make Nigella sativa a remarkable plant whose health potential is increasingly being explored through scientific research.
FAQ — Frequently Asked Questions About Black Cumin (Oil)
1. How much black cumin oil can I consume daily?
There is currently no generally accepted therapeutic daily dose. Different amounts have been used in clinical studies.
2. How long does it take for black cumin oil to produce the effects described?
In clinical studies, changes in various metabolic parameters have been investigated and observed after as little as 8 or 12 weeks. However, no universally applicable timeframe for its effects can be derived from this. The results depend, among other things, on the preparation used, the individual’s initial condition and the metabolic parameter investigated.
3. Can black cumin oil be taken during pregnancy and breastfeeding?
There is insufficient clinical safety data on the regular use of concentrated black cumin preparations during pregnancy and breastfeeding. Taking concentrated preparations independently during pregnancy and breastfeeding is therefore not advisable.
This should be distinguished from using normal culinary amounts as a spice.
4. Is black cumin essential oil the same as ordinary black cumin oil?
No. Ordinary black cumin oil is a fatty seed oil consisting predominantly of fatty acids.
Black cumin essential oil, by contrast, contains a more concentrated mixture of volatile plant compounds. The two differ considerably in their composition and must not be treated as equivalent in terms of use or dosage.
Black cumin essential oil is not automatically suitable for oral consumption.
Further information on black cumin — and also on many other topics — can be found on our blog, in our “Medizinskandale” book series and in the “Codex Humanus”, the fifth volume of which was recently published. We look forward to welcoming you to our online shop.
Sources:
· Shaukat, A. et al. (2023): “Mechanism of the antidiabetic action of Nigella sativa and Thymoquinone: a review,” Frontiers in Nutrition.
· Heshmati, J. et al. (2015): “Nigella sativa oil affects glucose metabolism and lipid concentrations in patients with type 2 diabetes: A randomized, double-blind, placebo-controlled trial,” Food Research International.
· Karimi, M. et al. (2025): “Effects of black seed (Nigella sativa L.) on cardiometabolic indices in type 2 diabetic patients: A systematic review and meta-analysis of RCTs,” Complementary Therapies in Medicine.
· Kavyani, Z. et al. (2023): “Antihypertensive effects of Nigella sativa supplementation: An updated systematic review and meta-analysis of randomized controlled trials,” Phytotherapy Research.
· Maideen, N. M. P. et al. (2021): “Nigella Sativa (Black Seeds), A Potential Herb for the Pharmacotherapeutic Management of Hypertension – A Review,” Current Cardiology Reviews.
· LiverTox (2023): “Black Cumin Seed,” LiverTox: Clinical and Research Information on Drug-Induced Liver Injury.
· Assier, H. et al. (2023): “Severe allergic contact connubial dermatitis to Nigella Sativa Seed Oil due to repeated contacts to beard cosmetics,” Contact Dermatitis.
· Memorial Sloan Kettering Cancer Center (2023): “Nigella sativa,” About Herbs.
Header images are AI-generated illustrative images.