214 The nutrition handbook for food processors It is time that the meat CRC story was laid to rest, so that we can get back to recommending that young women of childbearing age eat meat as a ready source of available iron (Hill, 2000) Nevertheless, it is sensible to consider that there must be an optimal range for meat intakes in order to ensure a balanced diet is achieved whilst optimal weight is maintained. From this practical perspective COMA's(1998)suggested intake range of 90-140 g cooked meat per day is sensible as a public health message he overemphasis on reducing meat, however, rather than encouraging greater accompanying plant food intake has served only to confuse the public(Hill, 1999b). Evidence suggests that the risk of cancer will be reduced to a greater extent by increasing intakes of fruit and vegetables than by lowering meat intakes Once again, the move towards pre-prepared meal solutions provides opportunity anufacturers to devel cipes with a healthy balance of meat and veg etable ingredients such that the nutritional profile of the dish is optimised. 9. 4 Concerns about fat Regular consumption of red meat is associated epidemiologically with increased risk of coronary heart disease, due to its fat composition. Conversely, a growing bank of evidence is showing that a healthy diet that includes lean red meat can produce positive blood lipid changes(Watts et al, 1988: Scott et al, 1990; Davidson et al, 1999; Beauchesne-Rondeau et al, 1999 ). blood cholesterol levels are increased by inclusion of beef fat, not lean beef in an otherwise low-fat diet Equal amounts of lean beef, chicken, and fish added to low fat, low saturated fat diets, similarly reduce plasma cholesterol and LDL-cholesterol levels in hyper- cholesterolaemic and normocholesterolaemic men and women Meat is a source of arachidonic acid(20: 4n-6), both in the lean and visible fat components(Duo et al, 1998). Assumptions that the 20: 4n-6 content of meat was responsible for increasing thrombotic tendencies in Western societies are too sim- plistic. The presence of large amounts of linoleic acid (18: 2n-6) in current diets results in plasma increases of linoleic and arachidonic acids only. However, in the absence of linoleic acid, the long chain n-6 and n-3 PUFAS present in lean meat can influence the plasma pool, increasing plasma eicosatrienoic acid (20: 3n- 6), 20: 4n-6, and eicosapentaenoic acid (20: 5n-3), and probably reducing throm- botic tendencies. It is the imbalance of n-6: n-3 PUFAS in the diet, brought about by excessive 18: 2n-6, that causes high tissue 20: 4n-6 levels, so encouraging metabolism to eicosanoids(Sinclair et al, 1994; Mann et al, 1997) Meat contributes between a third and a half of the uk daily cholesterol intake Chizzolini et al, 1999: British Nutrition Foundation, 1999). Meats cholesterol content is, for consumers, another negative influence on meats health image, although it is now accepted that dietary intake of cholesterol has little bearing on plasma cholesterol. A review of the cholesterol content of meat indicates sur prisingly that levels of cholesterol are generally not higher in fatty meat or meat
It is time that the meat CRC story was laid to rest, so that we can get back to recommending that young women of childbearing age eat meat as a ready source of available iron. (Hill, 2000) Nevertheless, it is sensible to consider that there must be an optimal range for meat intakes in order to ensure a balanced diet is achieved whilst optimal weight is maintained. From this practical perspective COMA’s (1998) suggested intake range of 90–140 g cooked meat per day is sensible as a public health message. The overemphasis on reducing meat, however, rather than encouraging greater accompanying plant food intake has served only to confuse the public (Hill, 1999b). Evidence suggests that the risk of cancer will be reduced to a greater extent by increasing intakes of fruit and vegetables than by lowering meat intakes. Once again, the move towards pre-prepared meal solutions provides opportunity for manufacturers to develop recipes with a healthy balance of meat and vegetable ingredients such that the nutritional profile of the dish is optimised. 9.4 Concerns about fat Regular consumption of red meat is associated epidemiologically with increased risk of coronary heart disease, due to its fat composition. Conversely, a growing bank of evidence is showing that a healthy diet that includes lean red meat can produce positive blood lipid changes (Watts et al, 1988; Scott et al, 1990; Davidson et al, 1999; Beauchesne-Rondeau et al, 1999). Blood cholesterol levels are increased by inclusion of beef fat, not lean beef in an otherwise low-fat diet. Equal amounts of lean beef, chicken, and fish added to low fat, low saturated fat diets, similarly reduce plasma cholesterol and LDL-cholesterol levels in hypercholesterolaemic and normocholesterolaemic men and women. Meat is a source of arachidonic acid (20:4n-6), both in the lean and visible fat components (Duo et al, 1998). Assumptions that the 20:4n-6 content of meat was responsible for increasing thrombotic tendencies in Western societies are too simplistic. The presence of large amounts of linoleic acid (18:2n-6) in current diets results in plasma increases of linoleic and arachidonic acids only. However, in the absence of linoleic acid, the long chain n-6 and n-3 PUFAs present in lean meat can influence the plasma pool, increasing plasma eicosatrienoic acid (20:3n- 6), 20:4n-6, and eicosapentanoic acid (20:5n-3), and probably reducing thrombotic tendencies. It is the imbalance of n-6: n-3 PUFAs in the diet, brought about by excessive 18:2n-6, that causes high tissue 20:4n-6 levels, so encouraging metabolism to eicosanoids (Sinclair et al, 1994; Mann et al, 1997). Meat contributes between a third and a half of the UK daily cholesterol intake (Chizzolini et al, 1999; British Nutrition Foundation, 1999). Meat’s cholesterol content is, for consumers, another negative influence on meat’s health image, although it is now accepted that dietary intake of cholesterol has little bearing on plasma cholesterol. A review of the cholesterol content of meat indicates surprisingly that levels of cholesterol are generally not higher in fatty meat or meat 214 The nutrition handbook for food processors
Enhancing the nutritional value of meat 215 products. The cholesterol content of a meat is related to the number of muscle fibres so tends to be higher the more red the muscle 9.5 Reductions in the fat content of red meat Twenty years ago red meat and meat products were identified as major contri butor to fat intake in the UK. Most of the visible(subcutaneous) fat in the meat was consumed. In the early 1980s the red meat industry began to shift produc tion systems to favour less fat, reflecting more energy-efficient animal husbandry For many years now there has been emphasis on reducing the fat content of our diets and this continued consumer demand for less fat further prompted the meat industry to consider ways of reducing the fat content of meat. The fat content of the carcase has been reduced in Britain by over 30% for pork, making British pork virtually the leanest in the world, 15% for beef and 10% for lamb, with further reductions anticipated for beef and lamb over the next 5-10 years. The fat content of fully trimmed lamb, beef and pork is now 890, 5% and 4%o respe tively( Chan et al, 1995) These achievements are due to three factors: selective breeding and feeding practices designed to increase the carcase lean to fat ratio; official carcase clas sification systems designed to favour leaner production; and modern butchery techniques(seaming out whole muscles, and trimming away all intermuscular fat). It is easier to appreciate the process and extent of fat reduction by looking at the changes over time for a single cut of meat such as a pork chop(Fig 9. 1) The reduction in fat for pig meat is well illustrated by the trend downwards in P2 fat depth between the 1970s and the 1990s(P2 is fat depth at the position of the last rib)(Fig. 9.2). Since 1992 it has remained stable at around ll mm. Although updated compositional figures for British meat were published from 1986 onwards(Royal Society of Chemistry, 1986: 1993; 1996; Meat and Livestock Commission and Royal Society of Chemistry, 1990), it is only since updated supplements to the McCance and widdowson tables were published in 1995( Chan et al, 1995 and 1996), that the achievement of the meat industry in reducing the fat content of meat has been more widely acknowledged( Depart- ment Of Health, 1994b: Scottish Office, 1996: Higgs, 2000) A fat audit for the UK, commissioned by the Government's Ministry of Agri culture, Fisheries and Food to trace all fat in the human food chain provides a more accurate picture than National Food Survey(NFS)(Ministry of Agriculture Fisheries and Food, 1981-99)data for identifying principal sources of fat in the diet, between 1982 and 1992(Ulbricht, 1995). It illustrates that whereas the fat contributed by red meat decreased by nearly a third, that from fats and oils as a group increased by a third to contribute nearly half of our fat intakes(Fig. 9.3) This striking picture is lost in NFS data since vegetable fats(in particular)are consumed within a broad range of end products-from chips(so here they are hidden within the vegetables section) to meat products (so here they artificially inflate the apparent fat contributed by meat)
products. The cholesterol content of a meat is related to the number of muscle fibres so tends to be higher the more red the muscle. 9.5 Reductions in the fat content of red meat Twenty years ago red meat and meat products were identified as major contributors to fat intake in the UK. Most of the visible (subcutaneous) fat in the meat was consumed. In the early 1980s the red meat industry began to shift production systems to favour less fat, reflecting more energy-efficient animal husbandry. For many years now there has been emphasis on reducing the fat content of our diets and this continued consumer demand for less fat further prompted the meat industry to consider ways of reducing the fat content of meat. The fat content of the carcase has been reduced in Britain by over 30% for pork, making British pork virtually the leanest in the world, 15% for beef and 10% for lamb, with further reductions anticipated for beef and lamb over the next 5–10 years. The fat content of fully trimmed lamb, beef and pork is now 8%, 5% and 4% respectively (Chan et al, 1995). These achievements are due to three factors: selective breeding and feeding practices designed to increase the carcase lean to fat ratio; official carcase classification systems designed to favour leaner production; and modern butchery techniques (seaming out whole muscles, and trimming away all intermuscular fat). It is easier to appreciate the process and extent of fat reduction by looking at the changes over time for a single cut of meat such as a pork chop (Fig. 9.1). The reduction in fat for pig meat is well illustrated by the trend downwards in P2 fat depth between the 1970s and the 1990s (P2 is fat depth at the position of the last rib) (Fig. 9.2). Since 1992 it has remained stable at around 11 mm. Although updated compositional figures for British meat were published from 1986 onwards (Royal Society of Chemistry, 1986; 1993; 1996; Meat and Livestock Commission and Royal Society of Chemistry, 1990), it is only since updated supplements to the McCance and Widdowson tables were published in 1995 (Chan et al, 1995 and 1996), that the achievement of the meat industry in reducing the fat content of meat has been more widely acknowledged (Department Of Health, 1994b; Scottish Office, 1996; Higgs, 2000). A fat audit for the UK, commissioned by the Government’s Ministry of Agriculture, Fisheries and Food to trace all fat in the human food chain provides a more accurate picture than National Food Survey (NFS) (Ministry of Agriculture, Fisheries and Food, 1981–99) data for identifying principal sources of fat in the diet, between 1982 and 1992 (Ulbricht, 1995). It illustrates that whereas the fat contributed by red meat decreased by nearly a third, that from fats and oils as a group increased by a third to contribute nearly half of our fat intakes (Fig. 9.3). This striking picture is lost in NFS data since vegetable fats (in particular) are consumed within a broad range of end products – from chips (so here they are hidden within the vegetables section) to meat products (so here they artificially inflate the apparent fat contributed by meat). Enhancing the nutritional value of meat 215
216 The nutrition handbook for food processors 1950s-1970s30 Breed an 1990s213 butchery 195 Total back fat trim Traditional butchery intermuscular eam cutting Further cooking loss trimmed 3.5 Fig 9.1 Change in fat content of pork loin for 100g of raw edible tissue(Adapted from Higgs JD and Pratt J, 1998)(McCance and Widdowson, 1940, 1960, 1978: Royal Society of Chemistry, 1995: MLC/RSC report to MAFF, 1990) ear Fig 9.2 Average P2 fat depth of British slaughter pigs 1972-1995
216 The nutrition handbook for food processors 30 21.3 19.5 7.9 3.9 3.5 1950s – 1970s 1990s Breed and feed changes Cutting plant and Modern retail trimming butchery Traditional butchery Seam cutting Further cooking loss lean + intermuscular fat only fully trimmed lean only fully trimmed lean only Total back fat trim Trimming, cooking loss and plate waste Fig. 9.1 Change in fat content of pork loin for 100 g of raw edible tissue. (Adapted from Higgs JD and Pratt J, 1998) (McCance and Widdowson, 1940, 1960, 1978; Royal Society of Chemistry, 1995; MLC/RSC report to MAFF, 1990) 1972 74 76 78 80 82 84 86 88 90 92 1994 Year 5 10 15 20 25 P2 (mm) Fig. 9.2 Average P2 fat depth of British slaughter pigs 1972–1995
Enhancing the nutritional value of meat 217 Dietary fat Fig. 9.3 Total fat available for consumption(UK) from different food sources. (Ulbricht TLV,1995) The fat content of meat products can vary considerably, dependent on the pro- portion of lean and fat present and the amount of added non-meat fat(Higgs and Pratt, 1998). Traditional types such as sausages, pastry-covered pies and salami are high in fat(up to 50%) but modern products include ready meals and pre- pared meats that can be low in fat(5%). The trend downwards in fat for red meat is reflected in the reduced fat content of a number of meat products, such as hams and sausages. Some reduced-fat meat products are now available although the potential for product development in this area has not been fully exploited 9.6 Fatty acids in meat The fatty acid composition of food, including meat, has become increasingly important in recent years because of concerns with the effects they have on human
The fat content of meat products can vary considerably, dependent on the proportion of lean and fat present and the amount of added non-meat fat (Higgs and Pratt, 1998). Traditional types such as sausages, pastry-covered pies and salami are high in fat (up to 50%) but modern products include ready meals and prepared meats that can be low in fat (5%). The trend downwards in fat for red meat is reflected in the reduced fat content of a number of meat products, such as hams and sausages. Some reduced-fat meat products are now available although the potential for product development in this area has not been fully exploited. 9.6 Fatty acids in meat The fatty acid composition of food, including meat, has become increasingly important in recent years because of concerns with the effects they have on human Enhancing the nutritional value of meat 217 24 20 16 12 8 4 0 1982 1992 Year Dietary fat kg Dairy fat Fats and oils Red meat Fish Eggs Chocolate Poultry meat Cereals Nuts Fig. 9.3 Total fat available for consumption (UK) from different food sources. (Ulbricht TLV, 1995)
218 The nutrition handbook for food processors health. Fatty acids play a role in many conditions such as CHD, cancer, obesity, diabetes and arthritis. These roles can be protective, causative or relatively neutral, depending on the disease, the fatty acid, and the opposing effects of other dietary components. Current dietary advice emphasises balancing the intake of the different fatty acids. The Department of Health( COMA, 1994)has recom mended a reduction in the intake of saturated fat and an increase in the intake of unsaturated fat. Within the unsaturated fatty acids it is recommended to increase he omega-3(n-3) PUFAS relative to the omega-6(n-6) PUFAS 9.6.1 Saturated fatty acids Probably the main misconception about meat fat is that it is assumed to be totally saturated. Meat contains a mixture of fatty acids both saturated and unsaturated and the amount of saturated fat in meat has been reduced in recent years. At the present time, less than half the fat in pork and beef and 51% of the fat in lamb is saturated. The saturated fat contributed to the diet from red meat and meat products has gradually fallen from 24%o in 1979 to 19.6% in 1999. Carcase meats now provide 6.7% of total saturated fat intake(Ministry Of Agriculture Fisheries And Food, 1981). In reality, even this figure is an overestimate, since there is a disproportionate wastage in terms of trimming, cooking losses and plate waste (Leeds et al, 1997) The predominant saturated fatty acids in meat are stearic acid(C18: 0) and palmitic acid (C16: 0). In general terms, saturated fats are known as the" fats as they tend to raise blood cholesterol and cause atherosclerosis. However, not all saturated fats are equal in their effects on blood cholesterol. For instance, stearic acid does not appear to raise blood cholesterol (Bonanome and Grund 1988)or other thrombotic risk factors(Kelly et al, 1999, 2001). Stearic acid prominent saturated fat in meat, for example; it accounts for approximately one third of the saturated fat in beef. Similarly, palmitic acid, another major saturated fat in meat does not consistently raise blood lipids. On the other hand, myristic acid(C14: 0)is the most atherogenic fatty acid, having four times the cholesterol raising potential of palmitic acid(Ulbricht, 1995). Myristic acid is found only in minor quantities in meat 9.6.2 Monounsaturated fatty acids Meat contains a mixture of unsaturated fatty acids, polyunsaturated fatty acids and monounsaturated fatty acids(MUFAs ). MUFAs are the dominant unsaturated fatty acid in meat and they account for approximately 40%o of the total fat in meat It is a neglected fact that meat and meat products are the main contributors to 1UFAS in the British diet, supplying 27% of total MUFA intake(Ministry Of Agriculture Fisheries And Food, 1999). MUFAs are considered to be neutral with respect to blood cholesterol levels. The principal MUFA in meat is oleic acid (cis C18: 1n-9), which is also found in olive oil and is associated with the health Mediterranean diet
health. Fatty acids play a role in many conditions such as CHD, cancer, obesity, diabetes and arthritis. These roles can be protective, causative or relatively neutral, depending on the disease, the fatty acid, and the opposing effects of other dietary components. Current dietary advice emphasises balancing the intake of the different fatty acids. The Department of Health (COMA, 1994) has recommended a reduction in the intake of saturated fat and an increase in the intake of unsaturated fat. Within the unsaturated fatty acids it is recommended to increase the omega-3 (n-3) PUFAs relative to the omega-6 (n-6) PUFAs. 9.6.1 Saturated fatty acids Probably the main misconception about meat fat is that it is assumed to be totally saturated. Meat contains a mixture of fatty acids both saturated and unsaturated and the amount of saturated fat in meat has been reduced in recent years. At the present time, less than half the fat in pork and beef and 51% of the fat in lamb is saturated. The saturated fat contributed to the diet from red meat and meat products has gradually fallen from 24% in 1979 to 19.6% in 1999. Carcase meats now provide 6.7% of total saturated fat intake (Ministry Of Agriculture Fisheries And Food, 1981). In reality, even this figure is an overestimate, since there is a disproportionate wastage in terms of trimming, cooking losses and plate waste (Leeds et al, 1997). The predominant saturated fatty acids in meat are stearic acid (C18:0) and palmitic acid (C16:0). In general terms, saturated fats are known as the ‘bad’ fats as they tend to raise blood cholesterol and cause atherosclerosis. However, not all saturated fats are equal in their effects on blood cholesterol. For instance, stearic acid does not appear to raise blood cholesterol (Bonanome and Grundy, 1988) or other thrombotic risk factors (Kelly et al, 1999, 2001). Stearic acid is a prominent saturated fat in meat, for example; it accounts for approximately one third of the saturated fat in beef. Similarly, palmitic acid, another major saturated fat in meat does not consistently raise blood lipids. On the other hand, myristic acid (C14:0) is the most atherogenic fatty acid, having four times the cholesterol raising potential of palmitic acid (Ulbricht, 1995). Myristic acid is found only in minor quantities in meat. 9.6.2 Monounsaturated fatty acids Meat contains a mixture of unsaturated fatty acids, polyunsaturated fatty acids and monounsaturated fatty acids (MUFAs). MUFAs are the dominant unsaturated fatty acid in meat and they account for approximately 40% of the total fat in meat. It is a neglected fact that meat and meat products are the main contributors to MUFAs in the British diet, supplying 27% of total MUFA intake (Ministry Of Agriculture Fisheries And Food, 1999). MUFAs are considered to be neutral with respect to blood cholesterol levels. The principal MUFA in meat is oleic acid (cis C18:1n-9), which is also found in olive oil and is associated with the healthy Mediterranean diet. 218 The nutrition handbook for food processors