The Hindu Business Line : Zinc: More than a micronutrient

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Zinc deficiency…A wake-up call for India.

The just concluded global meet on Zinc “Zinc Crops 2007”, between May 24 and 27 in Istanbul, Turkey, under the joint auspices of the International Zinc Association, Brussels, Belgium; the International Fertiliser Industry Association, Paris; the Harvest Plus, US, and Sabanci University, Turkey, saw top agronomists, soil scientists, physiologists, plant and human nutritionists and medical experts from over 50 countries debate the crucial role Zinc (Zn) plays in human nutrition vis-À-vis agriculture.

The focus was primarily the developing world, hence Turkey, the bridge between Asia and Europe, as the venue for the meet. The “Zinc Alarm” is ticking for the world and on the “High Alert List” is India that has among the most Zn deficient soils in the world, (91 million hectares).

This is the fallout of the so-called Green Revolution, whose approach of extensive use of major fertilisers, pesticides and also excessive use of irrigation water, while producing large quantities of grains, completely depleted the soils of the crucial micronutrient Zn.

Widespread Problem

The first human symptom of Zn deficiency was observed in Egypt where an odd couple — a full-grown husband and a dwar wife — was observed and the physical abnormality traced to acute Zn deficiency in the body. Excessive consumption of cereal-based foods such as wheat, growing in highly Zn deficient soils, was found to be the cause of stunted growth of children and pregnant mothers. More than 840 million people around the world — more than 220 million in India — do not have adequate food to meet their basic daily energy needs. A lot more, an estimated three billion, suffer the insidious effects of micronutrient deficiencies, Zn being the most common, because they lack the money to buy enough meat, poultry, fish, fruits, legumes and vegetables. Poor women and children in India are particularly vulnerable to Zn deficiency. Whole of India is Zn deficient, only the scale varies from State to State. Zn deficiency is spreading and the country is unprepared to face this challenge.

Current efforts to combat Zn deficiency focus on fortifying foods with this micronutrient through post-harvest processing. This approach has accomplished much elsewhere but not in India.

In regions with adequate infrastructure and well-established markets for delivering processed foods such as salt, sugar and cereal flours, food fortification can greatly enhance the Zn intake of vulnerable populations. But there are limits to commercial fortification and supplementation. Fortified foods may not reach a large number of people most in need because of weak market infrastructure.

Supplementation, likewise, depends on a highly functional health infrastructure, a condition that is often absent in developing countries such as India. Thus, new approaches are needed to complement existing interventions.

Biofortifying Food Crops

Biofortified plant foods — varieties bred for increased mineral and vitamin content — will complement existing nutrition interventions and provide sustainable and low-cost ways of reaching people with poor access to formal markets or health-care systems. Once the investment is made in developing nutritionally improved varieties at central research facilities, seeds can be adapted to growing conditions in many countries.

Biofortified varieties of food crops such as wheat have the potential to provide sustained benefits throughout the developing world at a lower recurring cost than either supplementation or post-production fortification.

Why Zinc?

Zn is absolutely essential for the normal healthy growth and reproduction of all higher plants, animals, and humans and is therefore, no more to be considered as a “micronutrient” (required in small quantities, and hence, the term “micro” nutrient), but must be considered as an “essential micronutrient”. Zn is required in small, but critical concentrations, to allow several physiological pathways to function normally. These pathways have important roles in photosynthesis and sugar formation, protein synthesis, fertility, seed production, growth regulation and defence against disease. Zn deficiency has very serious consequences for human health, such as, impairment of the immune system, as a result of which increased prevalence of childhood infections, such as diarrohea and pneumonia occur. Children and adolescents can end up with impaired growth.

In developing countries, Zn deficiency in the fifth major risk factor. The World Health Organisation (WHO) has developed a system, CHOICE (CHOosing Interventions that are Cost-Effective), for identifying and reporting cost-effective health interventions consistently across the world. CHOICE options are contained in a new statistical database, one of the largest projects undertaken by the WHO.

Zinc fertiliser

There are many scientific methods to estimate soil Zn for compensatory fertiliser application. Experience, however, has shown that even the widely used DTPA (Diethylene Triamine Penta Acetic Acid) extraction method fails to provide precise results in many situations in the developing world. On the other hand, “the Nutrient Buffer Power Concept”, tested over varied soils across Europe, Africa and Asia over the last quarter century, has provided remarkably precise results.

Before making an appropriate Zn fertiliser recommendation for a soil, the soil’s Zn “buffer power” is determined and for this the author has developed precise laboratory analytical techniques for calibration. Over- or under-use must be avoided. Classical “text book knowledge” will only lead to unsatisfactory results and lead the farmer to needless pecuniary difficulties, besides leading to Zn pollution of soil.

Zinc supplementation and fortification have been shown to be cost-effective public health interventions all over the world. Today Zn has turned out to be the most ubiquitous of all micronutrients involved in human metabolism.

Zn participates in all major biochemical pathways and plays multiple roles in the perpetuation of genetic material, including transcription of DNA, translation of RNA, and ultimately cell division. More than 300 enzymes require Zn for their catalytic function.

And for millions of poor and impoverished people around the world, like the vast number in India, a few milligrams of Zn each day can make the difference between illness and a healthy and productive life. Is it not high time that India woke up to this urgent wake-up call?

Public health programmes

Several options are available to fight Zn deficiency in populations at risk. These are Zn supplements, fortification of common foods with Zn, and modifying dietary habits.

Supplemental Zn is recommended, for example, as an adjunct therapy during treatment of diarrohea in children, where a high daily dosage is administered for some weeks.

Common Zn salts, such as, Zn sulphate, Zn acetate or Zn gluconate should be used as supplements. Chewable Zn tablets have also been given to school-going children.

Another approach is to use single-dose sachets of dry micronutrients that are sprinkles, or crushable tablets that are added to food at the time of serving.

The optimal form of the supplement depends on the age of the target group, the cultural preferences, and the need to include additional nutrients in the supplement.

(The author is Programme Director and Head of Services Innovation and Research Centre.)