Uganda’s maize poses cancer risk – experts

Ugandan maize, sorghum and groundnuts contain 10 times or higher concentration of aflatoxin than the safety threshold recommended by the World Health Organisation (WHO), scientists at the National Agricultural Research Organisation (Naro), have said.

Dr Godfrey Asea, the director for research at the National Crops Resources Research Institute (NaCRRI), said grains they examined in different parts of the country contained 100 to 1,000 per billion (ppb) parts higher than the recommended, presenting cancer risk to consumers.

READ: The real threat of aflatoxins in your food

Dr Asea made the revelations on Tuesday while giving a guided tour to Agriculture Minister Frank Tumwebaze and his Finance counterpart Matia Kasaija, who visited the crop and animal research institutes at Nakyessa on Gayaza-Zirobwe Road to acclimatise themselves with their operations and innovative outputs.

What it means
News about higher concentration of potentially cancer-causing contaminants in indigenous foods is a health concern because maize meals, for instance, are a mainstay for millions of Ugandan families and more dominant diet at schools.

The government scientists, in conjunction with the International Institute of Tropical Agriculture, conducted the research to ascertain the aflatoxin content in the cereals from 2007 to 2023. The study involved examining both the soil and grains.

“We got both good and bad fungi. When you have high concentration of good fungus, it displaces the bad one in a process known as competitive exclusion and this is the principle we used to develop aflasafe,” Dr Asea said in reference to a biological product used to reduce aflatoxins.

“Uganda produces about five million metric tonnes of grain per year and from the research, samples of these grains contain up to 100 parts per billion of aflatoxins, which is higher than that recommended by WHO (10 parts per billion),” Dr Asea explained in a subsequent interview.

Prof Archileo Kaaya, the head of the department of food technology and nutrition at Makerere University, said this type of fungi, if present, can grow onto the food, feed on it then produce waste products so when you eat the food, you may suffer food intoxication.

“Aflatoxins are, therefore, a type of toxins that are produced by molds. They are a highly toxic and carcinogenic compounds produced by the fungi Aspergillus flavus,” he said.

Not even cooking or roasting of the plant produce can kill the toxins. 
This is because the roasting usually happens at 150 degrees Celsius yet aflatoxins can only be destroyed at 400 degrees Celsius.

What this means
Having higher levels of aflatoxin contamination in grains and other agricultural produce has both economic and health impacts to the country.  

Many countries that we export to can reject our agricultural produce like what happened to our maize export to Kenya in 2021.

“It is hard to completely eliminate aflatoxins given the high temperature and humidity as in Uganda and the surrounding countries but there is a standardised limit, which is 10 parts per billion (ppb) amount of produce for East Africa and that of Europe (4ppb),” Prof Kaaya said.

The agriculture products from Uganda, however, are usually between 100 and 700ppb.
Prof Kaaya said over 600,000 metric tonnes of maize exports to Kenya were rejected in 2021 over similar concerns.

When the produce is rejected at the export market, it is supposed to be destroyed because it is not safe for consumption but people do not want to make losses, so they sell it the local population.

Mr Amanda Tumwebaze, a nutritionist at Human Mechanic Physiotherapy Ltd, said if one consumes food that has very high levels of aflatoxins, they can suffer acute toxicity.

ALSO READ: Aflatoxins hurt farmers’ earnings

In 2004, 125 people in Kenya died and others were hospitalised after they reportedly consumed maize contaminated with Aspergillus flavus.

In June 2016, 20 people in central Tanzania died of acute toxicity after eating molded maize and 48 people were hospitalised.

The cases of toxicity present with jaundice, abdominal pain, vomiting, diarrhoea and ascites (the accumulation of fluid in the peritoneal cavity, causing abdominal swelling).

Consuming foods containing aflatoxins exposes an individual to chronic toxicity, which is likely to cause cancer, especially of the liver, the commonest caused by aflatoxin.

The toxins can cause stunting in infants. In Uganda, about 29 percent of children below five years are reported to have stunted growth as a result of eating foods containing aflatoxins. However, this percentage rises to 51 in Buhweju District.

Aflatoxins also deny the body essential nutrients such as zinc, iron, proteins and some vitamins, thereby lowering its immunity and causing kwashiorkor in children.

“The toxins can also cross the placental barrier in expectant mothers to affect the unborn child. By the time the child is born, it is contaminated with aflatoxins and if the mother keeps eating the same food, her milk will also contain the toxins so the baby’s first 1,000 days are all contaminated,” Prof Kaaya said.

“Unfortunately, aflatoxins cannot be seen by our eyes, unless one has tested the grains,” Dr Asea said, adding,

“So it may be hard to identify them when the produce is on the market.  Procurement officers in schools and bakeries should ensure the grains they are procuring suit the Uganda National Bureau of Standards (UNBS) standards.  They should be stored in well-aerated stores.”

Depending on the diet and the health conditions such as hepatitis, repeated intake of aflatoxins can cause accumulation and, therefore, cause cancer over a short period of time.

How aflatoxins emerge
Dr Godfrey Asea, the director for research at the National Crops Resources Research Institute (NaCRRI), said the fungus naturally lives in the soil and when the conditions are moist, it sprouts in the air. However, it is aggravated by handling, where some farmers dry their produce on the bare ground, increasing the risk of molds developing in the produce.

READ: About aflatoxins

Drought conditions also stress the plants, forcing them to dry before they actually mature, thereby creating favourable conditions for the growth of molds.

“Some farmers leave the produce, especially maize, to dry in the garden but since there is heat during day and dew in the night, molds grow on the maize to produce aflatoxins,” Dr Asea explains.

Sometimes the foods are not dried to the right moisture content and poor storage creates an environment for the growth of molds.

Also, store houses that are not well-aerated and moist expose the food to molds.
Livestock and poultry become contaminated because they are fed with feeds whose raw materials are contaminated. 

“Farmers get shrank and spent grains and use them as ingredients for animal feeds like maize bran,” he says.
Rabbits, dogs and cows are very sensitive to aflatoxins and can die once they consume them in high quantities.

Most affected foods

●   Foods that are dried at home can be contaminated by aflatoxins. These include maize, cassava, sorghum, groundnuts, soybeans, millet, rice (cereals and legumes).
●   Milk (including milk from lactating mothers), meat, eggs and poultry.
●   Animal feeds can contain aflatoxins because they are usually made from contaminated ingredients like maize, silver fish.
●   Dried fish, especially silver fish (mukene), may grow aflatoxic molds if not well dried.
●   Dried spices like chili
●   Beer made from sorghum and barley and local brew. The fermentation process does not eliminate aflatoxins.

How to reduce aflatoxins in your grains

Prof Archileo Kaaya, the head of the department of food technology and nutrition at Makerere University, cautions farmers not to dry their agricultural products on the bare ground but put them on a clean surface such as a tarpaulin. Also, they should ensure effective drying of all farm produce to the required moisture content.

“Also, farmers can use the salt method to ensure their foods are dried to the right moisture content,” he says.

“Stores should be arranged properly and produce kept in clean sacks. Farmers should use stones or wood to prevent the food from being in direct contact with the ground because dried plant produce usually have high ability to pull water from the surrounding environment,” he further explains.

He also recommends good agricultural practices by farmers starting with land preparation, selecting healthy seeds, weeding, applying the right fertilisers at the right time and irrigating would help produce crops that are healthy and can resist mold attacks.

Farmers should ensure they sort and grade seeds to remove diseased, broken or shrunk grains that are likely to be contaminated from the healthy ones. Those that seem to be contaminated should be thrown away.