Heavy metals in your hibiscus: Infusion refusal

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  • Published: May 15, 2013
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Heavy metals in your hibiscus: Infusion refusal

Floral and leafy extracts

Dried hibiscus petals courtesy of Malik. Inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectroscopy (FAAS) have been used to determine concentrations of metals in digests and infusions of Hibiscus sabdariffa (petals), Rosa canina (receptacles), Ginkgo biloba (leaves), Cymbopogon citratus (leaves), Aloe vera (leaves) and Panax ginseng (roots).

Inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectroscopy (FAAS) have been used to determine concentrations of metals in digests and infusions of Hibiscus sabdariffa (petals), Rosa canina (receptacles), Ginkgo biloba (leaves), Cymbopogon citratus (leaves), Aloe vera (leaves) and Panax ginseng (roots).

Herbal infusions, commonly known as teas, have been with us for millennia. Humans have selected botanical ingredients, leaves, stems, flower parts and roots of countless plants, crushed and boiled them with water. They provide a way to add flavour to often tasteless or bad-tasting water and as a side-effect the boiling process and addition of natural products to the water may have the effect of sterilising it as well as acting to preserve it to some degree.

Infusion confusion

There are also many claimed, and sometimes spurious, health benefits, to certain infusions. The growing popularity of such tonics, which might include the likes of ginseng, Gingko biloba and even hibiscus are often seen as a viable alternative to pursuing a healthy diet, lifestyle of taking prescription pharmaceuticals despite there often being little scientific evidence of benefits and sometimes research to show that certain products may be detrimental to health if taken in excess.

One popular infusion, is that of hibiscus, which is prepared from the crimson sepals of the flower and imbibed hot or cold. The "tea", which often goes by the name "Jamaica" in the USA, or "roselle infusion", is a refreshing albeit tart beverage. It is well known in Turkey and Arab countries. It contains vitamin C and various minerals as well as up to a third organic acids - citric, malic and tartaric. The infusions also contain acidic polysaccharides and flavonoid glycosides, including cyanidin and delphinidin, which are deep red. Hibiscus infusions lack caffeine, which is often found in tea, coffee and other infusions.

However, Jan Malik, Adela Frankova, Ondrej Drabek, Jirina Szakova, Christopher Ash, Ladislav Kokoska of the Czech University of Life Sciences Prague, will report in the August issue of the journal Food Chemistry how various heavy metals can also be present in this and other infusions. Their analysis reveals that aluminium, boron, copper, iron, manganese, nickel, phosphorus, zinc, calcium, potassium and magnesium are present.

Aluminium safety alert

Based on their analysis of hibiscus infusions, they found that aluminium levels were high enough for them to recommend that no sensitive person drink more than a litre a day of hibiscus infusion. They suggest that children, pregnant women and anyone with chronic kidney problems should avoid this infusion entirely. Aluminium is a non-essential element and is a neurotoxin the negative effects of which are particularly well known from patients with chronic renal failure on early kidney dialysis machines. The researchers add that hibiscus infusions might also represent a significant source of boron from food for some people, up to approximately 5.5 milligrams per litre as well as manganese. A large amount of available manganese (up to about 17.4 mg/l) can have adverse health effects.

The team points out that in contrast to earlier studies of tea (C sinensis), their analysis of raw materials from hibiscus (petals), rosehip (receptacles), ginkgo (leaves), lemongrass (leaves), aloe (leaves) and ginseng (roots) were demonstrated not to be accumulators of the elements tested. An accumulator is defined as a plant that assimilates aluminium to levels of 1 mg/kg. However, the leachates tested did show high levels of the various elements to different degrees in each plant material used, with hibiscus being particularly worrisome.

Related Links

Food Chem, 2013, 139, 728-734 : "Aluminium and other elements in selected herbal tea plant species and their infusions"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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