Tainted spinach

Spinach (Spinacia oleracea) is a leafy green vegetable that originated in Persia. It belongs to the amaranth family and is related to beets and quinoa.

Popeye, a pugnacious, wisecracking cartoon sailor popularised the beneficial effects of spinach by showing superhuman strength after ingesting an always-handy can of spinach.

And it’s true, spinach is considered very healthy, as it’s loaded with nutrients and antioxidants and is also high in insoluble fibre. Eating spinach, as part of a generally healthy diet, may benefit eye health, reduce oxidative stress, help prevent cancer, and reduce blood pressure levels.

There is a small caveat about the fairly high levels of nitrate in spinach. But nothing to worry too much about as we have previously explained.

So all good?

Well, that is until December 2022 when about 200 Australians were reported as being poisoned with symptoms typically occurring within one hour after eating fresh baby spinach leaves. They were reported to show quite serious symptoms including nausea, blurred vision, delirium, confusion, hallucinations, rapid heartbeat, flushed face and dried mouth and skin. Quite a list!

While there were several hospitalisations, most people affected were experiencing symptoms for a short time and recovered fairly quickly. After some considerable detective work the baby spinach was found to be contaminated with the leaves of the noxious weed thornapple, a poisonous invasive species that is found across Australia and in several other countries. 

Thornapple, also known as Jimson weed, devil’s snare and devil’s trumpet, with the scientific name Datura stramonium, belongs to the Solanaceae family of plants. This family includes both healthy kitchen staples like tomatoes and potatoes but also highly poisonous plants such as thornapple, mandrake (Mandragora officinarum) and belladonna (Atropa belladonna) that all contain a group of toxins called tropane alkaloids. This group comprises more than 200 different compounds with limited data on their occurrence in food and feed and their toxicity.

As usual it is the dose that makes the poison. As a matter of fact, small amounts of plant extracts containing tropane alkaloids have been used for centuries in human medicine and are still used, like atropine, hyoscyamine and scopolamine. These uses include for example the treatment of wounds, gout and sleeplessness, and pre-anaesthesia. Extracts from belladonna were used to dilate pupils for cosmetic reasons and to facilitate ophthalmological examination. In India, the root and leaves of thornapple were burned and the smoke inhaled to treat asthma. Some of these poisonous plants have also been used as recreational drugs, although under such less controlled circumstances ingestion could be deadly.

The thornapple culprit!

Thornapple is cultivated worldwide for its chemical and ornamental properties. The plant is one of the 50 fundamental herbs used in traditional Chinese medicine, where it is called yáng jīn huā. It prefers warm-temperate and sub-tropical regions, and as an invasive weed is often found on river flats, roadsides and agricultural lands where it competes with summer crops. It spreads by seed, with each plant producing up to 30,000 seeds and living for up to 40 years in the soil.

The active constituents in thornapple include scopolamine, atropine and other tropane alkaloids acting on the nervous system. Combined they cause stimulation of the nervous system in low doses and depression of the system at higher doses. Ingestion of plant parts may lead to generalised confusion, delirium and powerful hallucinations that often leave the person in a state of panic and severe anxiety.

All parts of the plant contain the highly poisonous tropane alkaloids. They are toxic also in tiny quantities with symptoms like flushed skin, headaches, hallucinations, and possibly convulsions or even coma. Eating a single leaf can lead to severe side effects as was noted in the Australian outbreak.

How did it get into spinach?

The baby spinach producer confirmed that when checking they found thornapple leaves in its baby spinach fields. It is likely that the high amount of rainfall during 2022 in Australia had contributed to the spread of the weed. A few young leaves that would have been looking like baby spinach leaves at that stage of growing were picked up during spinach harvest.

This is not a unique occurrence as seeds of tropane alkaloid-producing plants have been found as impurities in other important agricultural crops such as linseed, soybean, millet, sunflower and buckwheat. The consumption of a few berries from henbane (Hyoscyamus niger) or from belladonna has previously caused severe intoxication, including deaths in young children.

What can we learn?

From this incident we can learn that vigilance is important to avoid contamination of toxic weeds in agricultural crops.

It is also important to have an efficient reporting and tracing system of food related toxic events to capture outbreaks early.

However, fortunately it’s all clear for the baby spinach itself.

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