Zinc is a mineral nutrient critical for human health and responsible for physical growth, immunity, prevention and treatment of common cold and diarrhoea. Zinc comes from two groups of food sources—plant based foods and animal source foods.
A cereal/rice-based predominantly plant food system is the major source of zinc. The other important but smaller source of zinc is food from the animal sources-- fishes, eggs, beef, chicken and liver.
In a plant based food source for zinc, despite accounting for the largest share, very little zinc gets absorbed into the human body. The reason is an organic chemical known as phytate, which overwhelmingly comes from cereal food and pulses. Phytate imparts an unfavorable anti-nutritional effect, it binds to the essential minerals, such as zinc, iron, and calcium during digestion of the foods in the intestines and flushes them off the body.
Therefore, if the diet is predominantly plant-based, zinc, one of the most critical nutrients for health, fails to get absorbed in the body in optimum amount. On the other hand, the advantage of the zinc intake from the animal source foods is that these do not contain phytate; and as a result, the essential minerals in the food including zinc can be absorbed with ease. Hence, animal source foods are superior sources of zinc.
State of the low zinc nutrition in Bangladesh and how it happened
The traditional dietary habit of the Bangladeshi population, including children, is generally plant-based with little share of animal source foods. The customary food plates of Bangladesh contain mostly rice, some vegetables, pulses and a little amount of animal source foods. Rice, leafy vegetables and pulses are rich in phytate.
Considering the volume of intake, these plant-based foods are much greater in content of zinc than that contained in the paltry amount of animal foods in our diet. But due to the presence of phytate, the abundant amount of zinc from plant based foods largely remains unabsorbed into the body and lost along with phytates. The result is obvious.
The deficiency of zinc in our population is very high at a level consistent with public health concern. A nationally representative survey on micronutrients (2011-12) reported that nearly half of all under-5 children were deficient in zinc status and more than half of the women were suffering from the condition. There is a standard requirement for every nutrient which is known as the recommended dietary allowance (RDA).
The in-depth analysis of data showed that only 11-44% of our under-5 children can fulfill the required zinc intake. The intake in women is worse; 1-6% of women can fulfill the required intake of zinc. Hence, a high zinc deficiency in our population is understandable. Zinc deficiency is often regarded as a proxy indicator of childhood growth faltering and the prevalence of children who are short-for-age is still high.
Additional analysis of Bangladeshi data showed that the purchasing capacity of the families, higher socio-economic status and consumption of animal source zinc are associated with higher zinc nutrition status. On the contrary, intake of plant-origin zinc is associated with lower status of zinc.
On this background dynamics of zinc nutrition, the country has been on an impressive run to improve its aqua-culture, poultry and livestock crops over the last decade that led to a favorable outcome on the zinc intake across the population. Unfortunately, the pandemic Covid-19 has inflicted a blow to this progress. The pandemic has given rise to a grave non-clinical adversary--through loss of employment, income, dwindling food security and price hikes of essential food items.
Rising poverty compromises people's purchasing capacity for nutritious food, especially the animal source foods not only among the disadvantaged people but the urban new poor and the lower middle class are harmed as well. A recent study projecting the potential fallout of the micronutrient status in the Bangladeshi population due to the Covid-19 pandemic reports that the projected risk of the decline of zinc status is high, likely to regress to a decade back level.
Does a solution exist?
When the cloud of the problem is dark, there is a silver lining around with the rays of hope sprawling.
Over the decades, the effort is ongoing to introduce zinc-fortified rice in the country. Bangladesh Rice Research Institute (BRRI) is endeavoring to introduce zinc biofortified rice. Though the development continues over several varieties, recently the BRRI-100 genre has come out which is high in zinc content (25.7 mg of zinc per 1 kilogram of rice), fine grains and non-sticky, the preferred attributes for rice among the consumers.
Similarly, BRRI -84, another fine variety of rice has 27.6 mg of zinc per 1 kilogram of rice, and BRRI-74, a coarse variety, has 24.2mg of zinc per kilogram of milled rice. The BRRI-74, has a very high yield, from 7.1 to 8.3 ton per hectare, making it lucrative for the farmers. But being a coarse variety, it may not command an attractive market price, and a large portion of the harvest is consumed by the farming households and the local communities.
However, this is a prospective variety for the government's various food transfer and food security programs, and for other institutional buyers who procure in bulk, due to its cheaper price and high nutrition value, not only in zinc content but also in protein (8.3%) and high resistance to pests and diseases as well.
There are few other zinc fortified rice variants developed by the BRRI. All these varieties are agronomically bio-fortified, and no elemental zinc is mixed from outside. On the other hand, the World Food Program adopting a slightly different fortification technology has been in partnership with the Government's Vulnerable Group Development (VGD) Program in implementing the rice fortified with a mix of micronutrients containing zinc.
Bio-fortified zinc rice could be a cost-effective solution to address nutrition deficiency amongst the poorer section of Bangladeshi population, but the issue of absorption into the body remains a challenge.
Dr. Sabuktagin Rahman, MBBS (Dhaka Medical College), MFSN (Ghent University, Belgium), Ph.D. Fellow, Griffith University, Australia. He was also the Principal Investigator to the first National Micronutrient Survey 2011-12. Email: [email protected]
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