102 The nutrition handbook for food processors The addition of minerals and other nutrients to foods to increase their nutri- tional value is widely practised. In the 1920s iodised salt was introduced in some countries to help combat endemic goitre. iodised salt, as well as other iodised foods such as bread and monosodium glutamate, are today widely used in part of the world where iodine deficiency diseases (IDD) are still endemic, such as India, and China, Papua New Guinea, Central Africa and the Andean region of South americ Legislation was introduced in several countries during World War II which required the addition of iron and calcium, as well as of certain water-soluble vitamins, to bread and flour in order to combat nutritional deficiencies caused by food restrictions. The success of these measures in improving health led to the extension of the legislation into peacetime. Some countries, such as the UK, still require that bread and flour be fortified with calcium and iron(Statutory Instrument, 1984) Bread and four are the only foodstuffs required by law to be fortified with minerals in the UK. There is, in addition, legal provision for the voluntary addi tion by food processors of other minerals to other foodstuffs, with the exception of alcoholic drinks. This has given manufacturers the opportunity to produce a variety of foods enriched with other minerals. Most ready-to-eat(RTE) breakfast cereals are enriched with iron and zinc. some varieties will also contain added iodine and other minerals. These are normally added at levels which are well below those which might cause toxic effects(Brady, 1996). Fortified RTE cereals have been shown to make a significant contribution towards meeting the nutri tional requirements of consumers for iron, as well as for copper, manganese and zinc (Booth et al, 1996). Currently a considerable amount of research is being carried out on methods, such as fortification of a variety of commonly used foods with minerals and other nutrients, as a way of improving nutritional status countries where deficiency problems regularly occur( Gibson and Ferguson 1998) In recent years there has been a growth in the production of foods, which have been deliberately selected or formulated to provide, according to their promotors, specific physiologic, health promoting and even disease-preventing benefits They have been given a variety of names such as ' designer food,'nutraceuti- cals, 'functional foodsand, officially in Japan, ' foods for specific health use FOSHU). Several of these products contain minerals such as selenium(Reilly, 1998) 4.5 Calcium Without an adequate supply of the macromineral calcium in the diet calcification of the skeleton will be adversely affected. During early growth and development the supply of calcium for this purpose is particularly critical and for this re the amount required by a child is proportionally greater than for an adult ( Nutrition Foundation, 1989)
The addition of minerals and other nutrients to foods to increase their nutritional value is widely practised. In the 1920s iodised salt was introduced in some countries to help combat endemic goitre. Iodised salt, as well as other iodised foods such as bread and monosodium glutamate, are today widely used in parts of the world where iodine deficiency diseases (IDD) are still endemic, such as India, and China, Papua New Guinea, Central Africa and the Andean region of South America. Legislation was introduced in several countries during World War II which required the addition of iron and calcium, as well as of certain water-soluble vitamins, to bread and flour in order to combat nutritional deficiencies caused by food restrictions. The success of these measures in improving health led to the extension of the legislation into peacetime. Some countries, such as the UK, still require that bread and flour be fortified with calcium and iron (Statutory Instrument, 1984). Bread and flour are the only foodstuffs required by law to be fortified with minerals in the UK. There is, in addition, legal provision for the voluntary addition by food processors of other minerals to other foodstuffs, with the exception of alcoholic drinks. This has given manufacturers the opportunity to produce a variety of foods enriched with other minerals. Most ready-to-eat (RTE) breakfast cereals are enriched with iron and zinc. Some varieties will also contain added iodine and other minerals. These are normally added at levels which are well below those which might cause toxic effects (Brady, 1996). Fortified RTE cereals have been shown to make a significant contribution towards meeting the nutritional requirements of consumers for iron, as well as for copper, manganese and zinc (Booth et al, 1996). Currently a considerable amount of research is being carried out on methods, such as fortification of a variety of commonly used foods with minerals and other nutrients, as a way of improving nutritional status in countries where deficiency problems regularly occur (Gibson and Ferguson, 1998). In recent years there has been a growth in the production of foods, which have been deliberately selected or formulated to provide, according to their promotors, specific physiologic, health promoting and even disease-preventing benefits. They have been given a variety of names such as ‘designer food’, ‘nutraceuticals’, ‘functional foods’ and, officially in Japan, ‘foods for specific health use’ (FOSHU). Several of these products contain minerals such as selenium (Reilly, 1998). 4.5 Calcium Without an adequate supply of the macromineral calcium in the diet calcification of the skeleton will be adversely affected. During early growth and development the supply of calcium for this purpose is particularly critical and for this reason the amount required by a child is proportionally greater than for an adult (British Nutrition Foundation, 1989). 102 The nutrition handbook for food processors
Minerals 103 4.5.1 Calcium absorption Uptake of calcium from food in the gut is not very efficient. Only about 30% is sorbed, with 70% lost in faeces. Absorption is a complex process, which is under the control of the cholecalciferol(vitamin D)-parathyroid hormone system Calcium is transported across the intestinal mucosa bound to a special carrier protein. Synthesis of this protein is stimulated by an activated form of cholecal- ciferol, 1, 25-dihydroxycholecalciferol (1, 25-DHCC) If vitamin D levels are low, calcium absorption will be restricted and a deficiency will occur. To be absorbed. calcium must be in the soluble ionic form. Several food components can prevent this happening. These include phytic acid (inositol hexaphosphate) in cereals, and oxalate in certain dark green vegetables, such as spinach, and in rhubarb. Uronic acid in dietary fibre can have a similar effect, as can free fatty acids and certain other dietary factors, including sodium chloride and a high protein intake 4.5.2 Functions of calcium in the body Over 99%o of body calcium is in the skeleton, where it both provides structural support and serves as a reservoir for maintaining plasma levels. Calcium in plasma plays a number of roles, for example in muscle contraction, neurous- cular function and blood coagulation. To maintain these roles, calcium levels in the plasma must be very stable. If for any reason they are altered, they are imme- diately restored to normal levels by an increased secretion of parathyroid hormone and the formation of 1, 25-DHCC. In children this increase in plasma calcium means that less of the mineral goes into bones, while in adults calcium is withdrawn from the skeleton. In either case there can be significant implica tions for bone structure 4.5.3 Osteoporosis Osteoporosis is a condition which is characterised by loss of bone tissue from the skeleton and deterioration of bone structure with enhanced bone fragility and increased risk of fracture. It is relatively common in the elderly, especially females, but may also occur in the young. In the UK one in three women and one in twelve men over the age of 50 years can expect to have an osteoporotic frac ture during the remainder of their lives(Prentice, 2001 ). The causes of osteoporosis, in spite of extensive research, remain elusive. The higher rate in women seems to be associated with a number of factors: the lower skeletal mass in women compared to men, a greater rate of calcium loss and a fall in oestrogen production with age. Lifetime history is also important. Higher intakes of calcium, especially in adolescence and early adulthood, ensure greater bone density. In addition, physical exercise can help increase calcium deposition, while high consumption of alcohol, coffee, meat, salt and cola beverages may contribute to decreased bone density(Sakamoto et al, 2001) Although there is considerable debate about the effectiveness of calcium sup
4.5.1 Calcium absorption Uptake of calcium from food in the gut is not very efficient. Only about 30% is absorbed, with 70% lost in faeces. Absorption is a complex process, which is under the control of the cholecalciferol (vitamin D)-parathyroid hormone system. Calcium is transported across the intestinal mucosa bound to a special carrier protein. Synthesis of this protein is stimulated by an activated form of cholecalciferol, 1,25-dihydroxycholecalciferol (1,25-DHCC). If vitamin D levels are low, calcium absorption will be restricted and a deficiency will occur. To be absorbed, calcium must be in the soluble ionic form. Several food components can prevent this happening. These include phytic acid (inositol hexaphosphate) in cereals, and oxalate in certain dark green vegetables, such as spinach, and in rhubarb. Uronic acid in dietary fibre can have a similar effect, as can free fatty acids and certain other dietary factors, including sodium chloride and a high protein intake. 4.5.2 Functions of calcium in the body Over 99% of body calcium is in the skeleton, where it both provides structural support and serves as a reservoir for maintaining plasma levels. Calcium in plasma plays a number of roles, for example in muscle contraction, neuromuscular function and blood coagulation. To maintain these roles, calcium levels in the plasma must be very stable. If for any reason they are altered, they are immediately restored to normal levels by an increased secretion of parathyroid hormone and the formation of 1,25-DHCC. In children this increase in plasma calcium means that less of the mineral goes into bones, while in adults calcium is withdrawn from the skeleton. In either case there can be significant implications for bone structure. 4.5.3 Osteoporosis Osteoporosis is a condition which is characterised by loss of bone tissue from the skeleton and deterioration of bone structure with enhanced bone fragility and increased risk of fracture. It is relatively common in the elderly, especially females, but may also occur in the young. In the UK one in three women and one in twelve men over the age of 50 years can expect to have an osteoporotic fracture during the remainder of their lives (Prentice, 2001). The causes of osteoporosis, in spite of extensive research, remain elusive. The higher rate in women seems to be associated with a number of factors: the lower skeletal mass in women compared to men, a greater rate of calcium loss and a fall in oestrogen production with age. Lifetime history is also important. Higher intakes of calcium, especially in adolescence and early adulthood, ensure greater bone density. In addition, physical exercise can help increase calcium deposition, while high consumption of alcohol, coffee, meat, salt and cola beverages may contribute to decreased bone density (Sakamoto et al, 2001). Although there is considerable debate about the effectiveness of calcium supMinerals 103