1.1 Introduction
Selenium (Se) is an essential micronutrient for human and animal healthy due to its capabilities to support antioxidant defence systems. However, problems related to the deficiency of Se are emerging issue for human health worldwide and plant species differ considerably in their susceptibility to high concentrations of Se, and certain plant species can be able to accumulate Se to astonishingly high concentrations. Selenium is one of various compounds and chemical elements important to ensure the quality of food, together with proteins, carbohydrates, fats, vitamins, iron (Fe), iodine (I), and zinc (Zn) (Rayman et al. 2012). Genetic breeding programs can contribute positively to the development of improved crop varieties. However, problems of nutritional deficiencies are experienced by almost half the world’s population, especially Fe, I, Se, vitamin A and Zn in developing countries (Rayman et al. 2012).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Selenium (Se) is an important trace element having biological functions of utmost importance for human health. Different from the other (semi) metals, it is incorporated into proteins by a co-translational mechanism as part of the amino acid selenocysteine (SeCys), the 21st amino acid used for protein synthesis in humans, whereas only a few of them have been functionally characterized. Most Se-proteins participate in antioxidant defence and redox state regulation, particularly the families of more specific essential roles, such as iodothyronine deiodinases (DIOs) which are involved in thyroid hormones metabolism, GPx4 which is essential for spermatogenesis, and selenophospathe synthetases 2 (SPS2) participating in Se-protein biosynthesis.
Other Se-proteins may be involved in important biological processes, but their exact mechanism of action is still yet to be fully understood. Despite the scarce knowledge of the precise biochemical functions, a very large number of studies have been carried out in the last two decades showing that insufficient Se levels, and particularly Se-proteins, are associated with several human diseases including cancer, diabetes, cardiovascular and immune system disorders. In most cases, the link lies in the contrast to the oxidative stress that may be booth causing or caused by the disease. In this context, it is important to decipher whether and adequate Se status may contrast the risk factors for health disorders, or Se supplementation may improve therapy when Se metabolism is altered.
Despite many studies that have suggested a beneficial effect from Se supplementation to general health protection, most of them have remarked that it is limited to general health protection; most of them have remarked that it is limited to the initially inadequate Se status. Conversely, care should be taken when using supplements because excessive Se intake leads to toxic effects, and recent studies have shown that even sub-toxic doses may be negatively impacting, for example by increasing the risk of type 2 diabetes.
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Effects of Selenium Toxicity and Deficiency on Humans.
1.3 Statement of Problems
Investigation revealed that selenium toxicity is a problem of smaller magnitude, but has its own set of devastating effects in different areas across the world. A solution to both of these problems is to focus on development of Se-enriched dietary plant material. Furthermore, Se bioavailability in soil has a direct impact on the Se concentrations of the plants that are locally produced and consumed, and thereby on the daily Se intake of humans. The results from an increasing number of clinical studies highlight the health risks associated with too low a daily Se intake, a problem that may affect a billion or more people.
1.4 Aim and Objectives of Study
The aim of the study is to investigate the Effects of Selenium Toxicity and Deficiency on Humans. In achieving this aim, the following specific objectives were laid out as follows:
- To investigate the influence of selenium toxicity and deficiency on human’s body;
- To examine the factors that affect the content of selenium in different foods; and
- To compile some information about selenium for humans and other mammals, and the need for a sufficient daily selenium intake.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- What do you understand by selenium toxicity and deficiency on human body?
- What is the influence of selenium toxicity and deficiency on humans?
- What are the factors that affect the content of selenium in different foods?
1.6 Significance of Study
This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.7 Scope of Study
The scope of the research is focused on the Effects of Selenium Toxicity and Deficiency on Human Body.
1.8 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
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