Bones, human importance

Bone tissue is created from the minerals and organic molecules that entered the body through drinking water and food and the chemistry of human bone holds information on the diet and life history of the deceased individual. Both the elemental and the isotopic composition of bone are important in studies concerned with dietary reconstruction. Elemental analyses focus on the mineral portion of bone, while isotopic studies are usually aimed at the organic part. Isotopic analyses are also used to study place of origin and past climate as recorded in tooth and bone. The role of archaeological chemistry in the study of prehistoric bones is discussed in further detail in Chap. 4 on Methods, and several examples are provided in Chap. 7, Environment and Diet. 

The absorption, distribution, and accumulation of lead in the human body may be represented by a three-part model (6). The first part consists of red blood cells, which move the lead to the other two parts, soft tissue and bone. The blood cells and soft tissue, represented by the liver and kidney, constitute the mobile part of the lead body burden, which can fluctuate depending on the length of exposure to the pollutant. Lead accumulation over a long period of time occurs in the bones, which store up to 95% of the total body burden. However, the lead in soft tissue represents a potentially greater toxicological hazard and is the more important component of the lead body burden. Lead measured in the urine has been found to be a good index of the amount of mobile lead in the body. The majority of lead is eliminated from the body in the urine and feces, with smaller amounts removed by sweat, hair, and nails. 

Four of the main-group cations are essential in human nutrition (Table A). Of these, the most important is Ca2+. About 90% of the calcium in the body is found in bones and teeth, largely in the form of hydroxyapatite, CatOH)2 - SCa PO. Calcium ions in bones and teeth exchange readily with those in the blood about 0.6 g of Ca2+ enters and leaves your bones every day. In a normal adult this exchange is in balance, but in elderly people, particularly women, there is sometimes a net loss of bone calcium, leading to the disease known as osteoporosis. 

A partial solution to this dilemma could be that a large proportion of the protein-rich foods (meat, eggs) consumed by these people came from animals that were themselves fed a C4 diet. We know that dogs typically share the same diet as humans (Katzenberg 1989 Cannon et al. 1999) and are important components of the diet in some sites (eg., Cuello Hammond 1991 van der Merwe et al, this volume). It is unlikely that all the meat consumed by Maya peoples was derived from pure C4 consumers, however, as we have evidence for at least some C3-based animal bones that are presumed to be waste from food preparation. This should a subject of future study to test for the degree of domestication (and consequent feeding on maize) of meat-supplying animals such as turkeys. 

Advanced Seminar volume reflects the greatly expanded awareness of the importance of diet reconstruction for understanding past human health and behavior. It also reflects the growing number of applications of stable isotope and trace element analyses of bones and teeth. 

Similar to the human studies, the animal studies are not entirely consistent, due to the different study designs (source and dose of soy protein/isoflavones time, method and length of administration age of rats, etc.). Nevertheless, a certain number of conclusions may be drawn. Overall, soy extracts or pure isoflavones show an osteoprotective effect in the ovariectomized rat model of menopausal bone loss. The time of administration is important and they must be given at the time of ovariectomy which allows prevention but not reversal of bone loss. Although the OVX-induced bone loss in the rat is a... 

Milk is an excellent source of calcium, phosphorus, riboflavin (vitamin B2), thiamine (vitamin Bl) and vitamin B12, and a valuable source of folate, niacin, magnesium and zinc (Food Standards Agency, 2002). In particular, dairy products are an important source of calcium, which is vital for maintaining optimal bone health in humans (Prentice, 2004). The vitamins and minerals it provides are all bioavailable (i.e. available for absorption and use by the body) and thus milk consumption in humans increases the chances of achieving nutritional recommendations for daily vitamins and mineral intake (Bellew et al., 2000). 

The balance between excess and insufficient zinc is important. Zinc deficiency occurs in many species of plants and animals, with severe adverse effects on all stages of growth, development, reproduction, and survival. In humans, zinc deficiency is associated with delayed sexual maturation in adolescent males poor growth in children impaired growth of hair, skin, and bones disrupted Vitamin A metabolism and abnormal taste acuity, hormone metabolism, and immune function. Severe zinc deficiency effects in mammals are usually prevented by diets containing >30 mg Zn/kg DW ration. Zinc deficiency effects are reported in aquatic organisms at nominal concentrations between 0.65 and 6.5 pg Zn/L of medium, and in piscine diets at <15 mg Zn/kg FW ration. Avian diets should contain >25 mg Zn/kg DW ration for prevention of zinc deficiency effects, and <178 mg Zn/kg DW for prevention of marginal sublethal effects. 

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