According to a recent worldwide cancer report by the World Health Organisation (WHO) specialised agency on cancer research (IARC) and Cancer Research UK, liver cancer is the sixth most common cancer, the third leading cause of cancer deaths and the cancer with the second highest number of healthy life years lost as a result of premature death or disability.
The first is the fact that developing countries, particularly sub-Saharan Africa and the Asia Pacific regions, bear the greatest burden of liver cancer, with estimated 84 per cent of all cases and mortality occurring there. The World Cancer Research Fund International ranks Ghana 11th in the top 20 countries with the highest incidence of liver cancer. The list includes 10 additional sub-Saharan African countries.
The most plausible explanation in the geographic distribution of liver cancer has often been Hepatitis B viral infection and dietary exposure to aflatoxins, which are two of the major causative agents of primary liver cancer.
Hepatitis B is a viral infection of the liver with both chronic (long-term) and acute (short-term) forms. Highly endemic regions include sub-Saharan Africa with estimated prevalence of eight - 20 per cent, from the global cancer database (GLOBOCAN).
The WHO estimates that about 25 per cent of chronic hepatitis B patients die from Hepatitis B-related liver cancer. Chronic Hepatitis B is known to be the most common (60-80 per cent) cause of liver cancer, and there are reported 40-50 per cent chances of death in men compared to 15 per cent in their women counterparts.
Aflatoxins are a group of mycotoxins produced by Aspergillus sp (mould). They are present in both human food and animal feed, and are of great importance in food safety and public health, due to their potency as immunosuppressants (weaken immune system), mutagens (cause mutation in cells), carcinogens (cancer-causing agents) and teratogens (produce birth defects). Some food commodities that may contain aflatoxins include maize, groundnut, rice, wheat, sorghum, millet, cocoa beans, etc. Animal products such as milk, eggs and meat may also have aflatoxins because of the animal consumption of aflatoxin-contaminated feed. A report by the International Food Policy Research Institute (IFPRI) on mycotoxin food safety risk highlights the presence of aflatoxins in human breast milk and umbilical cord blood samples from Ghana and other tropical developing countries; this thus points to the chronic dietary aflatoxin exposure in Ghana.
Available information depicts that aflatoxin contamination often occur in the field prior to harvest. Post-harvest contamination may also occur if crop drying is delayed and if moisture is allowed to exceed critical limits for the growth of the mould during storage. Insect infestation and rodent invasion are also known to facilitate the growth of the mould in stored commodities.
According to some researchers, temperature and moisture are the two major factors that regulate the production of aflatoxins. This puts tropical countries at elevated risk to aflatoxin exposure because the climate, characterised by high temperatures and humidity, favour the proliferation of the mould.
According to the World Bank, European Union regulation of aflatoxins cost African countries US$ 670 million in annual export losses. By implication, the best quality foods would always get exported and the poor quality ones would be left for local consumers, especially the poor who could only afford limited food variations and may easily compromise on the safety of food.
Direct correlation between consumption of aflatoxin-contaminated food and the incidence of primary liver cancer has been found in many studies in several geographic regions, with the strongest association reported in sub-Saharan Africa. It is documented that between five-28 per cent of liver cancer cases globally are attributable to dietary aflatoxin exposure. The classification of aflatoxins, notably aflatoxin B1 (the commonest and the most potent of aflatoxins) by the IARC as group one human liver carcinogen, dates back in 1988.
The Synergy Hepatitis B and Aflatoxins
Hepatitis B and aflatoxins are independent causative agents of primary liver cancer, and both have similar geographic distributions. The Co-existence of Hepatitis B and aflatoxin produces a synergistic effect that increases liver cancer risk by 12-fold than in someone infected with hepatitis B alone which already causes five-fold increase in the risk of liver cancer, according to WHO expert group on aflatoxins and health. It is suggested that the immunosuppressive effects of aflatoxins increases susceptibility to chronic Hepatitis B infection and viral replication.
The high endemicity of Hepatitis B with the concomitant heavy dietary exposure to aflatoxins in tropical developing countries may be the reason for the striking geographic discrepancy in the burden of liver cancer.
The way forward
According to the WHO, Hepatitis B vaccine has been available since 1982 and there is 95 per cent efficacy. Lets remove stigma and demystify Hepatitis B because the Hepatitis B patient could live a full productive life with early diagnosis and close monitoring.
On aflatoxins, practical measures within reach at individual and household levels to reduce exposure involve dietary diversity. Dietary diversity is the number of individual food items or food groups consumed over a given period of time. It has been validated to reflect access to variety of foods and nutrient adequacy. This tool is recommended by the FAO, IFPRI and WFP for measuring food consumption and food security.
Promoting good agricultural practices like timed harvesting may also go a long way in reducing aflatoxin contamination of food commodities.
Strengthened systems for food inspection and monitoring at all levels for aflatoxins is also emphasised, and to this end, engagement of policy-makers may be crucial as far as food safety and the health of the public are concerned.
The writer is a Regulatory Officer with the Food and Drugs Authority
Source: Daily Graphic
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