Hidden hunger is the micronutrients deficiencies that are very necessary for the normal functioning of body and their deficiency shows no visible symptoms. More than 3 million children die due to undernutrition and micronutrients deficiencies each year. Zinc and Iron deficiencies are the most common of all the nutritional deficiencies. 11% of deaths before 5 years age in the world are due to nutritional deficiencies of Vit A, Zinc, Iron and Iodine. Zinc deficiency is the 5th major health issue in the developing countries in the world and growing rapidly. At present one third population of the world is suffering from zinc deficiency.
Zn is an essential element for the normal metabolism in living organism and due to its importance, it is also termed as “Metal of life”. It is important in anti-depressant medicines because it reduces the depressions. In Alzheimer’s diseases the zinc content in the body is reduced. Zn is also involved in regulating the blood pressure in the blood vessels and. Zinc deficiency in the pregnancy can lead to infertility and rupturing of membranes resulting stillbirth or low birth weight. In later growth stages in children its deficiency leads to loss of weight, stunted growth and enhanced vulnerability to diseases and infections which shows its role in defense of body. It is an important component of the immune system of the body. Zinc plays important role in the cell division, growth and differentiation. Its deficiency leads to skin diseases and poor wound healing mechanism. It is also involved in recovery from pathogenic diseases and eyesight regulation.
To alleviate the problem of micronutrient deficiencies different approaches can be used but most effective, sustainable and practical of them is biofortification. Biofortification is the process by which we develop the varieties of plants which have potential to incorporate more zinc in the produce. Different crop plants can be used for the biofortification but the preference should be given to the staple food of a specific area. The reason for this is the affordability and access to every class of the society.
Maize is the highly consumed crop worldwide. In staple foods it occupies the lion’s share. It is widely accepted and consumed by different nations and has very high production potential. Kernels of the maize are consumed in different ways e.g. parched, boiled, roasted, fermented and grounded. Different beverages are using its kernels. Being the staple food of more than 200 million people, it is providing 15% of daily proteins and 20% calories. The dependence of people on this crop is increasing rapidly so it has a bright future with respect to meet the food requirements of people of the world.
The amount of nutrients present in the maize kernel is affected by different factors like soil quality and nature of fertilizers applied. Normally the 85% of the nutrients are present in the germ of the maize kernels and less than 1% are in the endosperm so germ is very important. The concentration of zinc on average is 25ppm on dry weight basis. While the recommended concentration for maize is 37ppm. There is a need to improve this concentration.
There are different methods that can be used for the biofortification of Zn.
This deals with practices before sowing involved in physical or chemical addition of nutrients such as seed priming, soil application and foliar application with chemicals of zinc.
Agricultural soils are variable in their composition and concentration of different nutrients. Concentration of zinc ranges from 10 to 300 mg/kg. Average in different soils is showing 5 to 55mg/kg. Addition of fertilizer in the soil could increase the bioavailability of zinc and hence increased uptake and retention in the kernel.
The treatment of seeds with nutritional media before sowing is called seed priming. Seeds with this treatment have better germination and tolerance to different stresses. Seed priming is also involved in increasing the biological yield.
The process of enriching the prepared or semi prepared food by adding micronutrients to them is called supplementation for example the food manufacturers prepare a fortified product that has artificial addition of minerals in the diet for example fortified milk.
This is the improvement of genetic make-up of the plants for their zinc uptake and retention in the kernels. It is the most economical and broad-spectrum method for improving the zinc content in the plants. This could be done by the conventional as well as non-conventional methods. Maize is an important cereal for zinc enrichment. There can be two possible ways to increase the zinc content in the maize kernels first being increasing the retention of zinc in the kernels and second being enhancing the bioavailability of the soil. There are different techniques that can be used for the biofortification of the crop for example mutation breeding, marker assisted background selection and quantitative trait loci. Quantitative trait loci could be very efficient approach in identification of the genomic regions which are responsible for zinc uptake. The plants showing highest zinc level could be selected and then crossed and then the genomic regions of hybrid plants can be selected and then used in the breeding programs for future use. According to a report it has been presented that there are nearly 48 candidate genes that can control the Iron and Zinc transportation in Maize.
There are some important factors which should be kept under consideration while breeding for higher micronutrient fortification. First of all, the increase in zinc concentration should not compromise the yield or production of the crop. Secondly the trait selected for fortification should be stable environmentally. The breeding program should increase the zinc concentration to a level that is enough for creating a positive influence on the health. The priorities of the consumer should also be kept under the consideration.
According to literature scientists are working with a great passion to reduce the hidden hunger and they have developed more than 50 varieties which are QPM (Quality protein Maize) and more than 40 pro vit A varieties have been developed. Despite being tedious and hectic work institutes are working on alleviating the hidden hunger from the world. CIMMYT has developed and launched the zinc biofortified cultivars in maize in more than 60 countries and more than 35 million people are consuming the biofortified food. Pakistan is also working on different projects related to biofortification and the future seems to be bright and healthy.