Is mustard oil dangerous for human consumption?

Question

I see warnings of the erucic acid contained in mustard oil, e.g.

15 amazing facts and uses of mustard oil (Times of India):

According to celebrity nutritionist Sandhya Gugnani, "There was a myth attached to mustard oil...unfortunately it was considered unfit for consumption by countries like USA, Canada and Europe as it contained erucic acid which had an adverse effect on rats. But now it has been proved that it has no adverse impact on humans.
Mustard oil is considered one of the healthiest oils as compared to other oils as it has optimum ratio of omega 3 and omega 6 fatty acids and is low in saturated fats and high in MUFA (mono unsaturated fatty acids)."

'Mustard oil has health risks' (Times of India):

Mustard oil is banned for edible consumption in the EU, USA and Canada, principally due to its erucic acid content. The USFDA requires all mustard oil to be labelled "For External Use Only". Erucic acid is known to cause the following health risks: Accumulation of triglycerides in the heart; development of fibriotic lesions of the heart; increase in risk of lung cancer; and anaemia.

6 Extremely Dangerous Side Effects Of Mustard Oil:

However, this oil contains moderate amounts of erucic acid. Consuming erucic acid rich oils like mustard oil can unleash a host of health problems which includes anemia, fibrocystic heart lesions and even lung cancer.

Answer 1

In summary, there is no direct evidence of harm from consumption of mustard oil in humans. However, there is some evidence from observational studies about the association (not necessary a cause-effect relation) between high consumption of erucic acid (otherwise found in mustard oil) and higher incidence of congestive heart failure.

Erucic acid is a common name for a monounsaturated omega-9 fatty acid with a chemical name cis‐13‐docosenoic acid, abbreviated as 22:1 n‐9 or 22:1 ω‐9.

According to Scientific Opinion: Erucic acid in feed and food (European Food Safety Authority, 2016):

The heart is the principal target organ for toxic effects following short‐term or long‐term exposure of rats, pigs, monkeys, rabbits and gerbils to diets with oils containing erucic acid. The most common and sensitive effect observed in all species is myocardial lipidosis, i.e. an accumulation of triacylglycerols in myocardium that appear as neutral lipid droplets. Lipidosis is reversible and transient during prolonged exposure.

...myocardial lipidosis has never been reported in humans exposed to erucic acid and an extrapolation from effects on the rat or pig heart to the human heart is complicated by differences in physiology.

They have observed some association between high intake of erucic acid (not specifically from mustard oil, though) and higher incidence of congestive heart failure and low platelet levels, but lower incidence of coronary heart disease:

A higher level of 22:1 in plasma phospholipids has been associated with higher incidence of congestive heart failure in two independent cohorts whereas higher circulating levels of erucic acid in erythrocytes have been associated with lower incidence of coronary heart disease.

The therapeutic use of erucic acid results in haematological effects, most notably thrombocytopenia and morphological alterations of thrombocytes, at doses of about 0.1 g/kg bw per day.

In the European Union, mustard oil can be sold if it does not contain more than 5% of erucic acid. Anyway, some mustard oils tested in Germany and Austria contained up to 50% of erucic acid (Food Chemistry, 2014).

The US Food and Drug Administration has an Import Alert from 2016:

Expressed mustard oil is not permitted for use as a vegetable oil. It may contain 20 to 40% erucic acid, which has been shown to cause nutritional deficiencies and cardiac lesions in test animals.

Answer 2

There are essentially two kinds of mustard oil. The Expressed Mustard Oil, most commonly used as a cooking oil in India, is not approved for food use in the United States. It is covered under the FDA Import Alert 26-04, dated 11/18/2016. Their comments about both types of Mustard Oil are below, in quotation marks. "Reason for Alert:" "Expressed mustard oil is not permitted for use as a vegetable oil. It may contain 20 to 40% erucic acid, which has been shown to cause nutritional deficiencies and cardiac lesions in test animals. Expressed mustard oil is reportedly used by some cultures as a cooking oil. NYK-DO has documented entries of this product for cooking or other general use. It is important to note that there is another product referred to as mustard oil that is GRAS (Generally Recognized As Safe) and does have an approved food use. This oil is Essential oil of mustard or volatile mustard oil and is a flavoring produced by steam distillation of black mustard flour or mustard cake. Although commonly referred to as mustard oil, this product has very little triglyceride component, and therefore, probably very little viscosity. This essential oil has an approved use as a flavoring per CFR 182.20"