Is your milk safe? Understanding aflatoxin risks

Milk consumption is common in most households, with a cup of milk tea being a staple in homes and offices every morning. However, the safety of that milk is a concern. Globally, an estimated 600 million people (almost 1 in 10) fall ill annually from consuming contaminated food. A significant contributor to this is the prevalence of dangerous mycotoxins, particularly aflatoxin, in food and dairy products.

How are farmers managing their feeds and milk to ensure safety? Rose Muthoni Muchiri, a dairy farmer in Ruiru, explains that they buy their feeds from trusted suppliers who provide certificates confirming their products have been tested. The raw materials used to formulate dairy meals include maize gem, maize bran, polland, rice polish, and sunflower.

“If it’s a new supplier, we take a sample of their product to a private lab to test aflatoxin levels before offloading,” she says.

For silage, Muthoni ensures they harvest maize stalks at maturity, compact well when storing in silos, and seal silos properly to prevent air entry. Once a silo is opened, samples are taken for mycotoxin testing before consumption.

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Mycotoxins are naturally occurring toxins produced by certain molds (fungi) and can be found in food.

“We conduct organoleptic checks (appearance, taste, smell), an alcohol test (mastitis check), lactometer test (density check), clot on boiling test (quality check), resazurin test (hygiene check), and microbial strip test (check for animal drugs in milk),” she says.

Dr Maurice Karani Murungi, a veterinarian and epidemiologist, explains that aflatoxins are toxic substances produced by molds, primarily Aspergillus flavus and Aspergillus parasiticus, which grow on agricultural commodities like maize, peanuts, and other grains. Dairy meal feed is mainly made from such grains, which can lead to contamination.

“When cows consume contaminated feed, aflatoxins can pass into their milk, though usually in much lower concentrations,” Dr Karani says.

Dr Victor Yamo, Executive Director of Global One Health Advocacy, adds that aflatoxins are abundant in warm and humid regions, particularly among agricultural crops like maize, wheat, sorghum, rice, and peanuts, due to fungal contamination pre- and post-harvest.

“Aspergillus can grow under various environmental conditions, making aflatoxins a problem during food and grain storage, processing, and transportation. The absence of visible fungal growth does not always mean aflatoxins are absent,” Dr Yamo explains.

Aflatoxin contamination of milk occurs when animals consume contaminated feeds. During digestion, aflatoxins are absorbed into the animal’s bloodstream, metabolized in the liver, and excreted in milk.

Aflatoxins are potent carcinogens posing serious health risks to both animals and humans.

“In humans, long-term exposure to high levels of aflatoxins is associated with increased risks of liver cancer, suppressed immune function, and potentially stunted growth in children. In animals, it can cause liver damage, reduced productivity, and sometimes death,” says Dr. Karani.

Dr Yamo adds that aflatoxins cause a wide range of adverse health effects, including cancer, liver damage, embryo malformation, genetic mutations, immune suppression, stunted growth, and reproductive disorders.

Aflatoxin toxicity in humans can lead to general malaise, nausea, vomiting, abdominal pain, fluid accumulation in body cavities, jaundice, disorientation, confusion, and convulsions due to acute liver injury. Long-term exposure may cause growth retardation, severe liver damage, difficulty in blood clotting, fluid buildup in the lungs and brain, cancers, and ultimately death.

“In farm animals and pets, aflatoxin-contaminated feeds increase susceptibility to infections, cause weight loss, reduced productivity, and reproductive issues, leading to death,” Dr. Yamo says.

Some pets may suffer liver damage without early signs and may die suddenly if they continue eating contaminated food.

Reducing aflatoxin levels in milk

Can boiling milk reduce aflatoxin levels? Dr Karani explains that boiling milk does not reduce aflatoxin levels. Aflatoxins are stable compounds resistant to high temperatures and many processing methods. The best approach is to prevent contamination at the source, namely in the feed given to dairy cattle.

Dr. Yamo adds that most mycotoxins, including aflatoxins, are thermally stable and not destroyed during normal cooking processes like boiling. However, temperatures above 150°C have been shown to significantly reduce aflatoxin levels in foods.

In January 2024, Bio Foods launched the “Safe Milk Kenya” project, co-funded by a USAid grant. During the launch, US Ambassador to Kenya, Meg Whitman, announced a $240,000 (Sh30,900,000) commitment from the United States to this partnership, complementing Bio Foods’ investment of nearly $300,000 (Sh38,625,000). Kenya has the highest per capita milk consumption in sub-Saharan Africa.

The Ministry of Health, as the legal entity responsible for food safety, has developed the Food and Feed Safety Control Coordination Bill 2023 to reform food safety in Kenya. The bill aims to safeguard consumer health and safety by ensuring food is safe and nutritious, and it establishes the office of the food safety controller to address weaknesses in the existing regulatory and control systems.