Firstly, although this notes that the herb has a "very low toxicity" profile (elsewhere: "the seeds are characterized by a very low degree of toxicity") which is true in the acute sense (see below) when you crunch the numbers for chronic toxicities, it is surprising how little powder the safe doses found in the studies below equivalence to in dry powder dosages.
A good rule of thumb seems to be (warning: please check the calculations for yourself before relying on them) that:
1 level teaspoon of black seed powder = ~50mg of pure thymoquinone (TQO), (the active constituent and the primary toxicity concern).
However, glucosides are also toxic and their effect also needs to be taken into account (the constituent is present in n.sattiva as the flavenoid comferol diglucoside.
Note that even at this small amount it is probable to either level with or exceed the extrapolated NOAEL for humans.
At 80kg bodyweight (NOAEL = 0.6mg TQO/kg/day), that works out at only 48g TQO/day, slightly under one level teaspoon powdered..
Toxicity Studies
Hepatoxicity - monitor with LFTs.
Nephrotoxicity - montior with serum creatinine.
Leukopenia - monitor with white cell count.
Thrombocytopoenia - monitor with platelet count.
Conversions
Powder - oil conversion factor: To convert from dried powder to fixed oil (assuming no degradation during the grinding and storage process, of course, which is unlikely; different to essential oil, below) factor in an oil percentage of 36-38% (reference; source in footnotes).
Thymoquinone (TQO) from dry weight: (Source) The essential oil is generally 0.4 - 0.45 % of the dry weight and thymoquinone makes up 27.8 - 57% of the essential oil. Using 0.45% and 57% this means the TQO = 0.026% of the dry powder weight. Therefore, 1 level teaspoon (2g dry n. sattiva) = 52mg TQO
Dried weights: 1 level teaspoon = ~2g. 1 heaped teaspoon = ~3g.
A good rule of thumb seems to be (warning: please check the calculations for yourself before relying on them) that:
1 level teaspoon of black seed powder = ~50mg of pure thymoquinone (TQO), (the active constituent and the primary toxicity concern).
However, glucosides are also toxic and their effect also needs to be taken into account (the constituent is present in n.sattiva as the flavenoid comferol diglucoside.
Note that even at this small amount it is probable to either level with or exceed the extrapolated NOAEL for humans.
At 80kg bodyweight (NOAEL = 0.6mg TQO/kg/day), that works out at only 48g TQO/day, slightly under one level teaspoon powdered..
Toxicity Studies
- Humans: (link) Estimated No Observed Adverse Effect Level (NOAEL) for humans extrapolated from the below animal studies to be: 0.6mg/kg/day for purified thymoquinone taken orally (active constituent) but only gives the whole seed NOAEL level based on the extract.
- Humans (link) In study testing N.Sattiva as an adjunct to therapy for H.Pylori, 3 g a day for 4 weeks was considered safe "in light of the chronic toxicity studies."
- Mice/rats (fixed oil; 2ml/kg bw/day): Regarding oil extract use: Link: "Chronic toxicity was studied in rats treated daily with an oral dose of 2 ml/kg body wt. for 12 weeks. Changes in key hepatic enzymes levels ... and histopathological modifications (heart, liver, kidneys and pancreas) were not observed after 12 weeks of treatment (good)." however: "The serum cholesterol, triglyceride and glucose levels and the count of leukocytes and platelets decreased significantly, compared to control values, while hematocrit and hemoglobin levels increased significantly." (I presume the underlined effects would be problematic).
- Rats (oil; 15-25ml/kg bw/day): (Link) Nephrotoxicity and hepatotoxicity reported after continuing this dosage for one month.
- Rats (powder, up to 1g / kg bw / day) (Link) No nephro-toxicity (histology and biochemistry) at this dosage for 5 weeks.
- Mice (purified TQO; 90mg/kg bw/day): (Link) No toxicity (histological exam and biochemistries) at 09mg/kg bw/day of pure TQO for 90 days.
- Mice (various preparations up to 21g/kg bw/day): (link) No mortality even at the highest dose for a week. However, aqeous extracts at these doses did show degenerative hepatic change (need full access for details).
- Rats (powder; 1g/kg bw/day): link No hepatoxicity observed at high dose level (1g/kg/day).
- Rats (purified TQO) (link) Acute toxicity with oral dosing was reached at 250mg/kg bw. Directly equivalencing this to humans, for an 80kg person, this would equal 20g of pure TQO, which would require the ingestion of 769g of seed (385 teaspoon-fuls).
- This is an older toxicity study which used the powdered form (more applicable to what I'll be doing) but the abstract doesn't list the dosage used (impact on variables studies was favourable anyway).
- Link: Anecdotal claim: "black Seed has been reported to be toxic in the amount of 25 grams or more" (~12 level tea-spoons). Further: "The maximum dosage for any cure is 3 teaspoons per day." Another anecdotal report: "nigella sativa is toxic in high doses".
Hepatoxicity - monitor with LFTs.
Nephrotoxicity - montior with serum creatinine.
Leukopenia - monitor with white cell count.
Thrombocytopoenia - monitor with platelet count.
Conversions
Powder - oil conversion factor: To convert from dried powder to fixed oil (assuming no degradation during the grinding and storage process, of course, which is unlikely; different to essential oil, below) factor in an oil percentage of 36-38% (reference; source in footnotes).
Thymoquinone (TQO) from dry weight: (Source) The essential oil is generally 0.4 - 0.45 % of the dry weight and thymoquinone makes up 27.8 - 57% of the essential oil. Using 0.45% and 57% this means the TQO = 0.026% of the dry powder weight. Therefore, 1 level teaspoon (2g dry n. sattiva) = 52mg TQO
Dried weights: 1 level teaspoon = ~2g. 1 heaped teaspoon = ~3g.
