Aflatoxins: Occurrence and health risks

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Updated 07 November 2012
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Aflatoxins: Occurrence and health risks

Aflatoxins are toxic substances produced by certain microorganisms in/on foods and feeds. Aflatoxins have been associated with various diseases, such as aflatoxicosis, in livestock, domestic animals and humans throughout the world. The occurrence of aflatoxins is influenced by certain environmental factors; hence the extent of contamination will vary with geographic location, agricultural and agronomic practices, and the susceptibility of commodities to fungal invasion during pre-harvest, storage, and/or processing periods. Aflatoxins have received greater attention than any other toxins because of their demonstrated potent carcinogenic effect in susceptible animals and their acute toxicological effects in humans. As it is realized that absolute safety is never achieved, many countries have attempted to limit exposure to aflatoxins by imposing regulatory limits on commodities intended for use as food and feed.
In the 1960 more than 100,000 young turkeys on poultry farms in England died in the course of a few months from an apparently new disease that was termed ‘Turkey X disease’. It was soon found that the difficulty was not limited to turkeys. Ducklings and young pheasants were also affected and heavy mortality was experienced. An intensive investigation revealed that there are four major aflatoxins: B1, B2, G1, G2 plus two additional metabolic products, M1 and M2 that are of significance as direct contaminants of foods and feeds.
Aflatoxins often occur in crops in the field prior to harvest. Postharvest contamination can occur if crop drying is delayed and during storage of the crop if water is allowed to exceed critical values for the mold growth. Insect or rodent infestations facilitate mold invasion of some stored commodities. Aflatoxins are detected occasionally in milk, cheese, corn, peanuts, cottonseed, nuts, almonds, figs, spices, and a variety of other foods and feeds. Milk, eggs, and meat products are sometimes contaminated because of the animal consumption of aflatoxin-contaminated feed. However, the commodities with the highest risk of aflatoxin contamination are corn, peanuts, and cottonseed.
Corn is probably the commodity of greatest worldwide concern, because it is grown in climates that are likely to have perennial contamination with aflatoxins, and corn is the staple food of many countries. Nevertheless, procedures used in the processing of corn help to reduce contamination of the resulting food product. This is because although aflatoxins are stable to moderately stable in most food processes, they are unstable in processes such as those used in making tortillas that employ alkaline conditions or oxidizing steps. Aflatoxin-contaminated corn and cottonseed meal in dairy rations have resulted in aflatoxin M1 contaminated milk and milk products, including non-fat dry milk, cheese, and yogurt. 
Fungal growth and aflatoxin contamination are the consequence of interactions among the fungus, the host and the environment. The appropriate combinations of these factors determine the infestation and the amount of aflatoxin produced. However, a suitable substrate is required for fungal growth and subsequent toxin production, although the precise factor(s) that initiates toxin formation is not well understood. Water stress, high-temperature stress, and insect damage of the host plant are major determining factors in mold infestation and toxin production. Similarly, specific crop growth stages, poor fertility, high crop densities, and weed competition have been associated with increased mold growth and toxin production. Aflatoxin formation is also affected by associated growth of other molds or microbes. For example, preharvest aflatoxin contamination of peanuts and corn is favored by high temperatures, prolonged drought conditions, and high insect activity; while postharvest production of aflatoxins on corn and peanuts is favored by warm temperatures and high humidity. 
Humans are exposed to aflatoxins by consuming foods contaminated with products of fungal growth. Such exposure is difficult to avoid because fungal growth in foods is not easy to prevent. Even though heavily contaminated food supplies are not permitted in the market place in developed countries, concern still remains for the possible adverse effects resulting from long-term exposure to low levels of aflatoxins in the food supply. Evidence of acute aflatoxicosis in humans has been reported from many parts of the world, namely the Third World Countries, like Taiwan, Uganda, India, and many others. The syndrome is characterized by vomiting, abdominal pain, pulmonary edema, convulsions, coma, and death with cerebral edema and fatty involvement of the liver, kidneys, and heart.
Conditions increasing the likelihood of acute aflatoxicosis in humans include limited availability of food, environmental conditions that favor fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control. Because aflatoxins, especially aflatoxin B1, are potent carcinogens in some animals, there is interest in the effects of long-term exposure to low levels of these important toxins on humans. In 1988, the International Agency for Research on Cancer (IARC) placed aflatoxin B1 on the list of human carcinogens. This is supported by a number of epidemiological studies done in Asia and Africa that have demonstrated a positive association between dietary aflatoxins and Liver Cell Cancer (LCC). 
Additionally, the expression of aflatoxin-related diseases in humans may be influenced by factors such as age, sex, nutritional status, and/or concurrent exposure to other causative agents such as viral hepatitis or parasite infestation. In the Kingdom of Saudi Arabia, strict standards have been set by the Saudi Arabian Standard Organization (SASO) for the presence of Aflatoxins in edible commodities (0.05 micrograms per gram). 
The economic impact of aflatoxins derive directly from crop and livestock losses as well as indirectly from the cost of regulatory programs designed to reduce risks to animal and human health. The Food & Agriculture Organization (FAO) estimates that 25 percent of the world’s food crops are affected by aflatoxins. Aflatoxin losses to livestock and poultry producers from aflatoxin-contaminated feeds include death and the more subtle effects of immune system suppression, reduced growth rates, and losses in feed efficiency. Other adverse economic effects of aflatoxins include lower yields for food and fiber crops.
In addition, the ability of aflatoxins to cause cancer and related diseases in humans given their seemingly unavoidable occurrence in foods and feeds make the prevention and detoxification of these toxic substances one of the most challenging toxicology issues of present time. 

— Dr. Muhammad Waqar Ashraf is a professor of Environmental Chemistry at Prince Mohammad Bin Fahd University.

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Take a healthy approach to the issue of nutritional supplements

Updated 21 April 2018
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Take a healthy approach to the issue of nutritional supplements

JEDDAH: There is a growing need for dietary supplements in Saudi Arabia, given the increasing popularity of junk food and the effective role supplements can play in treating diseases caused by mineral and vitamin deficiencies.

A recent study found that 22 percent of Saudi people take nutritional supplements. It is no surprise, then, that many Saudi businesses have forged partnerships with international dietary-supplement companies.

Dr. Rowaidah Idriss, a Saudi dietitian with a Ph.D. in nutrition, said dietary supplements can be defined as substances that provide the human body with a nutrient missing from a person’s regular diet. However, she stressed that they are not intended to replace healthy eating.

She also warned against taking them without first talking to a doctor or dietitian, as some products can have side effects, especially if taken before surgery or with other medicines. 

“They can also cause problems if someone has a history of certain health issues,” she added.

A blood test can determine which nutrients we are not getting enough of in our diet, and therefore which supplements might be beneficial. Nutritional supplements are also used to help treat certain health conditions. 

“Vitamin C, for example, is often used to reduce cold symptoms,” said Idriss. “Fish oil is taken to lower elevated blood triglycerides.”

She suggested four daily essentials that can bridge nutritional gaps in our diet: a multivitamin, vitamin D, calcium and omega-3 fatty acids. 

“I routinely recommend a daily multivitamin and mineral supplement to my clients after consulting with their doctors,” she said. 

“For menstruating women, who require 18 milligrams of iron each day, a daily supplement helps boost iron intake.”

She said people over the age of 50 are advised to take a multivitamin to ensure they are getting enough B12, which plays a key role in the functioning of the nervous system and the development of red blood cells. 

“Older adults are more vulnerable to B12 deficiency because they are more likely to have decreased production of stomach acid, which is needed to release B12 from the proteins in food.” said Idriss. 

“It is also a good idea to take a daily multivitamin if one is following a low-calorie diet.”

She also pointed out that a high intake of DHA and EPA, the two omega-3 fatty acids found in fish oil, are linked with a lower risk of heart disease and Type 2 diabetes. A deficiency of DHA might also increase the risk of Alzheimer’s. 

“A daily intake of 1,000 milligrams of both DHA and EPA is equivalent to eating 12 ounces of salmon a week,” said Idriss.

The dietitian believes that the Saudis who take food supplements often do so more to benefit their appearance than their health. 

“Saudi women consume more dietary supplements than other people in Saudi Arabia,” she said. 

“They do so either to lose weight or to care for their hair and nails. Bodybuilders also take large amounts of supplements.”

However, both groups, according to Idriss, tend to take supplements on the recommendation of friends and trainers, not doctors. 

She warned that commercials and social-media rumors can persuade people to buy supplements online that may not be approved as safe by the Saudi Food and Drug Authority, and advised people to get as much of their daily nutrient needs as possible from healthy eating.

Dr. Rowaidah Idriss

“Along with vitamins and minerals, a healthy diet provides fiber and hundreds of protective phytochemicals, something a supplement cannot do,” she said, adding that the body absorbs natural food more effectively than supplements.

In addition, combining supplements with medications can have dangerous, even life-threatening, effects. 

“Drugs for heart disease and depression, treatments for organ transplants, and birth-control pills are less effective when taken with herbal supplements,” she said.

“Taking an anticoagulant, aspirin, and a vitamin E supplement together may increase the potential for internal bleeding or even stroke.”

 

Natural sources

With the spread of fast-food restaurants and their alluring ads, the long-term health of the Saudi people is in danger, as children and young people snub natural sources of nutrients, such as fruit and vegetables. 

“This can lead to many deficiency diseases. Moreover, vegetarians can develop similar illnesses due to the absence of meat in their diet,” she said.
Dr. Ashraf Ameer, a family-medicine consultant, said the importance of nutritional supplements lies in treating mineral and vitamin deficiency, especially for pregnant women, growing children, diabetics, people with chronic diseases, and the elderly. 

“However, these products should come from reliable companies and meet Saudi food and drug requirements,”he added.

Mohammed Yaseen, who has a food supplements business, said his company works with a leading British health-care company to provide the Saudi market with high quality products.

“With this we hope we can contribute to the national transformation program by raising private-sector spending in health care from 25 percent to 35 percent, which in turn would lead to the sector’s financial sustainability and boost economic and social development in the Kingdom,” Yaseen said.

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Vitamin Terms

DHA stands for docosahexaenoic acid. EPA stands for eicosapentaenoic acid.  Phytochemical is a biologically active compound found in plants.