The poisons and heavy metals in our food - part II

Mouldy bread from Shutterstock
Mouldy bread from Shutterstock

Last week in the first article on “Hazardous substances in food”, we considered “classic murder mystery poisons”, like arsenic and cyanide that could cause havoc if they entered our food supply.

Heavy metals like mercury and lead are also relatively well-known, but most people are unaware of other normally occurring compounds in food which are toxic, like mycotoxins (e.g. patulin in apple juice) and aflatoxins.

Toxins in baby food might affect hormones

Mycotoxins and aflatoxins

Mycotoxins are toxins that are produced by moulds or fungi that grow on food in warm, humid conditions. For example, patulin “is a mycotoxin that is produced by certain species of Penicillium, Aspergillus and Byssochylamys moulds that may occur on a variety of foods including fruit, grains and cheese.”

Patulin is problematic because it can contaminate processed products such as apple juice. Many populations drink large quantities of pure apple juice and apple juice concentrate is diluted and added to most other commercial fruit juices made from less prolific or more expensive fruit, such as granadilla, berries, etc.

Read: Recalled yogurt tied to fungus infections 

The name aflatoxins refers to four different carcinogenic mycotoxins produced by the Aspergillus species of fungi, namely aflatoxin B1, B2, G1, and G2. The most potent carcinogen is B1 which has been linked to liver cancer in humans and many animal species. 

Hazards caused by mycotoxins

Besides being unsightly, moulds growing on food may also have the following highly toxic properties as defined by a MRC Policy Brief published by Rheeder and colleagues in South Africa in 2009:

Mycotoxins have the potential to be:

  • Genotoxic – causing genetic damage
  • Carcinogenic – causing various type of cancer
  • Teratogenic – interfering with the growth of the embryo or foetus
  • Oestrogenic – duplicating female hormones
  • Immunotoxic – damaging the immune system
  • Nephro- and hepatotoxic – damaging the kidneys and liver, respectively
Susceptible food

The following foods are susceptible to moulds:

  • Peanuts
  • Tree nuts
  • Maize
  • Rice
  • Figs and dried fruits
  • Spices
  • Crude vegetable oils
  • Cacao beans

The logical preventive measure is of course to store or to process these foods in such a way that they do not provide a growth medium for the moulds which produce the toxins, and if we should find any mouldy foods, to discard them.

Read: Fungus-tainted corn spreading HIV?

This is easy for people who have refrigeration, sophisticated food processing and a rapid turnover of produce. But for millions of people living in Africa, Asia, Middle and South America, and the Far East, where grains like maize and rice, fruit, peanuts and other nuts are harvested and stored in hot, humid conditions, moulds flourish and vital food supplies can become contaminated with mycotoxins and aflatoxins.

Such populations are not able to discard contaminated crops and expose themselves and their domestic animals to these toxins. Over time, the toxins can affect unborn children, causing birth defects or lead to the development of various cancers in adults.

Risks in South Africa

South Africa can be very hot during the summer months when many of our crops are grown and harvested. Large areas of our country are also very humid, which creates ideal conditions for the growth of moulds on foods such as peanuts, maize, apples and other fruit.

The MRC (Medical Research Council), an organisation that has done extensive research into the incidence of mycotoxins in this country and the effect they have on health, warns that because of current national food handling and processing trends, there are loopholes in our anti-mycotoxin vigilance to keep our food supply safe:

  • Cases have been reported where food products from South Africa intended for export, were rejected due to unacceptable mycotoxin levels (for example, the EU (2014) have a Maximum [Aflatoxin] Level Commission Regulation (EC) No 1881/2006 which prohibits the imports and sale of foods which contain levels of aflatoxins exceeding their maximum specified safety levels).
  • Imports of low cost foods into our local markets which do not consider the risk to our consumers –  instances of price overriding safety and an inability of governmental agencies to enforce our regulations governing permitted mycotoxin content of foodstuffs and feeds
  • Manufacture of foodstuffs at the lowest possible cost without taking the safety and long-term health of the population and our domestic animals into account (e.g. the reoccurring animal feed scandals)
  • Lack of training of small-scale and emerging farmers who process their home grown crops but are unaware of the hazards posed by moulds growing on such crops  

South African legislation

The South African national regulations (Act No. 54 of 1972, as amended by Government Notice No. R. 1145 of 8 October 2004), specify levels for only two mycotoxins:

  • Aflatoxins in all foodstuffs, but specifically peanuts and dairy milk (milk can be contaminated when dairy cattle eat contaminated feed). The aflatoxin B1 content may not exceed a maximum of 5 µg/kg or 5 parts per billion (ppb) and the total aflatoxin content may not exceed 10 µg/kg or 10 ppb.
  • Milk may not contain more than 0.05 µg/litre or 0.05 ppb of aflatoxin M1.
  • Patulin in apple juice and all foods and beverages that contain apple juice may not contain more than 50 µg/litre or 50 ppb.

While such legislation is praiseworthy, its application may not be as efficient as desired which would account for some of the problems listed above under the heading of "Risks in South Africa".

Read: Curb candida infection naturally

In addition Rheeder and this MRC coauthors, point out that in keeping with international practice South Africa should also include other mycotoxins in their regulations, namely deoxynivalenol which is found in maize and wheat (our two staple foods), ochratoxin A which can contaminate cereals, coffee, dried fruit, wine and many other foodstuffs, and fumonisins, which are also maize-based mycotoxins. If we consider that one of our most important staple foods is maize, then it is indeed cause for concern that these three additional hazardous mycotoxins are all know to contaminate maize, thus putting our population at risk.

Government vigilance to prevent dumping of mould-contaminated foodstuffs in South Africa by developed countries, tightening up of legislation and investment in monitoring of our food and feed supplies for these hidden poisons, are probably the only solutions to prevent our population from being exposed to mycotoxins and aflatoxins – a threat that does entail much more than just discarding the odd bit of mouldy fruit!

Read more:

The poisons and heavy metals in our food – part I

What are heavy metals?
Arsenic poisoning


- EFSA (2014). Aflatoxins in food. aflatoxins. htm
- FDA (2001). Patulin in apple juice, apple juice concentrates and apple juice products. Sept 2001.
- Rheeder JP et al (2009) MRC Policy Brief. October 2009. Guidelines on mycotoxin control in South African foodstuffs.  PROMEC Unit, Medical Research Council, Tygerberg.

Image: Mouldy bread from Shutterstock

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