CHAPTER 1
The importance of minerals in the human diet
KĆ©sia Diego Quintaes1 & Rosa Wanda Diez-Garcia2
1 Federal University of Ouro Preto, Nutrition School, Department of Clinical and Social Nutrition, Ouro Preto, MG, Brazil
2 University of SĆ£o Paulo, RibeirĆ£o Preto Medical School, RibeirĆ£o Preto, SP, Brazil
Mineral nutrients are indispensible to the maintenance of life. A mineral element is considered essential when deficient ingestion results in harm or suboptimal function, and if supplementation with physiological levels of this specific element prevents or repairs this damage. Human nutritional requirements demand at least 23 mineral elements, and there are various methods available to establish the nutritional status of minerals. The required daily quantities of mineral nutrients are small, particularly when compared with nutrients such as carbohydrates and lipids. The minimum and maximum mineral contents necessary to produce adverse effects can vary widely between different mineral nutrients. Chosen food regimens are related to geographical availability, and the corresponding biodiversity. Biological adaptive processes, constrained by the regional diversity of diets, have over time established existing nutritional requirements. Nutritional recommendations define mineral consumption values that are not easily achieved with the contemporary Western diet. Scientific evidence suggests that nutrient supplements cannot replace a healthy diet, with the consumption of a wide variety of nutritious foods being the best way to maintain health and prevent chronic disease. There is scope for significant additional study of the role of minerals in the human diet, and their impact on human health.
1.1 Historical aspects
Mineral nutrients are essential for the proper functioning of every organism on earth. The interactions between mineral elements in biological systems and their role in mediating the chemical and biological reactions fundamental to life are still being discovered. Archaeological evidence of the feeding habits adopted by our human predecessors has been discovered by fossil studies from different periods and sites. Determination of the minerals in mineralized prehistoric human remains reveals the dietary conditions and food habits, and also the environmental and living conditions, of the population. Understanding the feeding habits adopted by our ancestors helps to elucidate the evolution of the species [1ā3].
The availability and distribution of foods and their preparation indicate the preferences of the population and provide knowledge of the social organization practised [1]. The main tool used to unravel the past is archaeological chemistry (archaeochemistry), which has been useful in discovering the practices and lifestyles of past human populations, including their feeding habits [3]. Human remains studied using archaeochemistry, be it via the recovery of tools or paintings or analysis of the concentration of the chemical elements and their isotopic forms, help us understand the role of the biocultural system resulting from the interaction between humans and their environment [4]. The definition of marker elements is essential for archaeochemistry to contribute to the reconstruction of human history, and of the respective feeding practices adopted.
Bones and teeth are body structures considered as indicators of the exposure of humans to minerals [5, 6]. Although bones present numerous analytical difficulties with regard to the separation and characterization of the constituent minerals, they are the target of much research to determine the form of feeding practised by our ancestors. It is known that the geochemistry of modern vertebrate bones is directly related to the consumption of food and water: the composition of bone represents the principal food items ingested over the 10ā30 years preceding death, varying as a function of the rate of bone renewal of the anatomical part under study. Because of its minimum annual renewal rate of 10%, bone is considered a monitor of some trace elements throughout life. However, because of its morphology, bone exhibits a marked turnover of cortical tissue (32%) and of trabeculated tissue (4.3%) and thus shows greater susceptibility to post-mortem changes [2, 6].
In addition, the form of the mineral incorporated into the bones can be distinct for the various elements. Reconstruction of the diet consumed based on the mineral composition of bones requires that the diagenetic process has not altered bone composition over time. In fossils, the concentrations of the elements Fe, Mn and Cu can be increased due to diagenesis of the soil in which the individuals were buried [2].
The bone concentration of trace elements such as Sr and Ba has been used to discriminate between herbivorous and omnivorous food patterns, where a low Sr level indicates low consumption of foods of animal origin, especially fish [2, 5, 7]. It is worth pointing out that the Sr and F contents suffer progressive post-mortem alterations, and can be enriched due to diffusionāadsorption processes [3], whereas variations in the Sr content of bones of the same individual suggests seasonal or geographical changes in the diet [8].
It is known that the majority of Mg in the human organism comes from foods of animal origin [7]. One of the functions of Mg in the human is its involvement in cell metabolism, and insufficient amounts appear to affect the senescence process negatively [9]. Because of the high level of Zn in blood and meat, a diet based on meat could induce a higher level of this element. However, high levels of Zn can also be found in certain legumes and vegetables and can lead to erroneous interpretation of the diet [2].
The choice of a food regime or types of food is related to the foods available locally and to the biodiversity encountered, ...
