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Lean meat as part of a cholesterol-lowering diet
Prog. Lipid Res. Vol. 25, pp. 219-220, 1986
0163-7827/86/$0.00 +0.50 © 1986 Pergamon Journals Ltd
Printed in Great Britain. All rights reserved
LEAN MEAT AS PART OF A CHOLESTEROL-LOWERING DIET K. O'DF_~,* A. J. SINCLAIR,~" M. NIALL:~ and K. TRAIANEDES:~ *Department of Medicine, Royal Melbourne Hospital, Victoria, Australia tDepartment of Agriculture Victoria, Veterinary Research Institute, Parkville, Australia ~Department of Medicine, Repatriation General Hospital, Heidelberg, Victoria, Australia
INTRODUCTION
Diets of traditionally living Aborigines in northern Australia were often rich in meat (kangaroo, reptiles, birds) and yet there is no evidence that they were associated with hypercholesterolemia or other risk factors for occlusive vascular disease. Indeed, we have shown that when westernized diabetic Aborigines reverted temporarily to a traditional diet, rich in lean red meat (kangaroo), there was an improvement in all of the metabolic abnormalities of diabetes including the hyperlipidemia. MATERIALS AND METHODS
In order to investigate these observations in more detail under controlled conditions, we conducted dietary studies in 4 healthy adult Caucasians who consumed 500 g kangaroo meat/day for two weeks as part of a low-fat, isocaloric, weight-maintaining diet. Each study lasted for 4 weeks: week 1 on the usual diet, weeks 2 and 3 on the kangaroo meat diet and week 4 on the usual diet (Table I). The kangaroo meat contained 1.5% fat, 40% of which was polyunsaturated. 2 Food intake was weighed and recorded throughout the study to facilitate the accurate calculation of dietary composition. Fasting blood samples were taken before and at weekly intervals during the study for the measurement of lipoprotein lipids and plasma fatty acid composition. RESULTS AND DISCUSSION
The mean fat intake was 35% of energy during weeks 1 and 4 and fell to 6% during the 2 weeks on the kangaroo meat diet. The P/S ratio was 0.6 on the usual diet and rose to 1.1 on the kangaroo meat diet. The cholesterol intake remained constant at about 300 mg/day throughout the study. Despite this, mean total plasma cholesterol fell in all subjects during the diet (4.5 ± 0.5mM before, 3.7 ± 0.4mM after, mean ± SEM) and returned rapidly to baseline levels (4.5 + 0.5 mM) one week after resuming the normal diet (p < 0.001). The concentration (and proportion) of linoleic acid (LA) fell in both phospholipid (PL) and cholesteryl ester (CE) fractions in all 4 subjects and similarly there was a consistent but smaller rise in the concentration (and proportion) of arachidonic acid (AA) in all 4 TAnL~ I. Experimental Design Normal diet
Low-fat diet
Normal diet
Week 1
2
3
4
500 g kangaroo meat per day; isocaioric with week 1 and 4 Fat intake: 35% of energy
6.4% energy
32% of energy
P:S 0.6
1.1
0.5
219
K. O'Dea et al.
220
TAma 2. The Percentage Content of Selected PUFA in PL and CE in 4 Normal Adults Fed a Diet Rich in Kangaroo Meat Diet
Normal diet
Week
1
2
3
4
26 + 4t 56 + 6 11 + 2 7+2 6+ 1 1 +0.2
17 + 2t 45 +__6t 15 + 2t 10+2# 7+ 2 2+0.5
16 + 2t 43 + 7t 15 _ 2t 12+2t 7+ 2 2+0.5
24 + 3 55 + 6 12 __+2 8+2 6+ l 1 +0.2
Linoleic acid Arachidonic acid
PL CE PL CE PL CE
Low-fat Kangaroo diet
Normal diet
Long-chain n - 3 PUFA (20:5, 22:5 and 22:6) *The results are shown as the percentage of the PL or CE fatty acids. Each result is the mean + SD. tSignifieantly different from value on normal diet (p < 0.01).
subjects (Table 2). There was a slight rise in the level o f the long-chain n - 3 polyunsaturated fatty acids ( P U F A ) in b o t h fractions. The plasma fatty acid patterns had returned to baseline levels one week after resuming the n o r m a l diet. Despite the k a n g a r o o meat containing m o r e than twice as m u c h L A as A A , the concentration and p r o p o r t i o n o f L A in plasma phospholipids and cholesteryl esters fell and that o f A A rose. This m a y indicate the preferential i n c o r p o r a t i o n o f A A into structural lipids when it is available in the diet. T h e fall in L A could simply reflect the greatly reduced total L A intake during the k a n g a r o o m e a t diet relative to the usual diet. The fatty acid c o m p o s i t i o n o f platelet lipids showed similar but less p r o n o u n c e d changes in L A and AA. This study highlights, firstly, that it is possible to have a diet containing a large quantity o f red meat but which is very low in fat with a high P/S ratio, and, secondly, that even in subjects with l o w - t o - n o r m a l cholesterol concentrations, this diet rich in lean meat was associated with a rapid fall in plasma cholesterol concentration despite the cholesterol content o f the diet remaining c o n s t a n t t h r o u g h o u t . These results have i m p o r t a n t implications for red meat producers and suggest that the development o f very lean meats (similar to wild meats) could o v e r c o m e m u c h o f the present opposition to red m e a t by health professionals and the public. REFERENCES 1. O'DEA, K. Diabetes 33, 596--603 (1984). 2. SXNCLAIR,A. J., SLAYrERY,W. J. and O'DEA, K,, J. Sci. Fd. Agric. 33, 77t-776 (1982).
0163-7827/86/$0.00 +0.50 © 1986 Pergamon Journals Ltd
Printed in Great Britain. All rights reserved
LEAN MEAT AS PART OF A CHOLESTEROL-LOWERING DIET K. O'DF_~,* A. J. SINCLAIR,~" M. NIALL:~ and K. TRAIANEDES:~ *Department of Medicine, Royal Melbourne Hospital, Victoria, Australia tDepartment of Agriculture Victoria, Veterinary Research Institute, Parkville, Australia ~Department of Medicine, Repatriation General Hospital, Heidelberg, Victoria, Australia
INTRODUCTION
Diets of traditionally living Aborigines in northern Australia were often rich in meat (kangaroo, reptiles, birds) and yet there is no evidence that they were associated with hypercholesterolemia or other risk factors for occlusive vascular disease. Indeed, we have shown that when westernized diabetic Aborigines reverted temporarily to a traditional diet, rich in lean red meat (kangaroo), there was an improvement in all of the metabolic abnormalities of diabetes including the hyperlipidemia. MATERIALS AND METHODS
In order to investigate these observations in more detail under controlled conditions, we conducted dietary studies in 4 healthy adult Caucasians who consumed 500 g kangaroo meat/day for two weeks as part of a low-fat, isocaloric, weight-maintaining diet. Each study lasted for 4 weeks: week 1 on the usual diet, weeks 2 and 3 on the kangaroo meat diet and week 4 on the usual diet (Table I). The kangaroo meat contained 1.5% fat, 40% of which was polyunsaturated. 2 Food intake was weighed and recorded throughout the study to facilitate the accurate calculation of dietary composition. Fasting blood samples were taken before and at weekly intervals during the study for the measurement of lipoprotein lipids and plasma fatty acid composition. RESULTS AND DISCUSSION
The mean fat intake was 35% of energy during weeks 1 and 4 and fell to 6% during the 2 weeks on the kangaroo meat diet. The P/S ratio was 0.6 on the usual diet and rose to 1.1 on the kangaroo meat diet. The cholesterol intake remained constant at about 300 mg/day throughout the study. Despite this, mean total plasma cholesterol fell in all subjects during the diet (4.5 ± 0.5mM before, 3.7 ± 0.4mM after, mean ± SEM) and returned rapidly to baseline levels (4.5 + 0.5 mM) one week after resuming the normal diet (p < 0.001). The concentration (and proportion) of linoleic acid (LA) fell in both phospholipid (PL) and cholesteryl ester (CE) fractions in all 4 subjects and similarly there was a consistent but smaller rise in the concentration (and proportion) of arachidonic acid (AA) in all 4 TAnL~ I. Experimental Design Normal diet
Low-fat diet
Normal diet
Week 1
2
3
4
500 g kangaroo meat per day; isocaioric with week 1 and 4 Fat intake: 35% of energy
6.4% energy
32% of energy
P:S 0.6
1.1
0.5
219
K. O'Dea et al.
220
TAma 2. The Percentage Content of Selected PUFA in PL and CE in 4 Normal Adults Fed a Diet Rich in Kangaroo Meat Diet
Normal diet
Week
1
2
3
4
26 + 4t 56 + 6 11 + 2 7+2 6+ 1 1 +0.2
17 + 2t 45 +__6t 15 + 2t 10+2# 7+ 2 2+0.5
16 + 2t 43 + 7t 15 _ 2t 12+2t 7+ 2 2+0.5
24 + 3 55 + 6 12 __+2 8+2 6+ l 1 +0.2
Linoleic acid Arachidonic acid
PL CE PL CE PL CE
Low-fat Kangaroo diet
Normal diet
Long-chain n - 3 PUFA (20:5, 22:5 and 22:6) *The results are shown as the percentage of the PL or CE fatty acids. Each result is the mean + SD. tSignifieantly different from value on normal diet (p < 0.01).
subjects (Table 2). There was a slight rise in the level o f the long-chain n - 3 polyunsaturated fatty acids ( P U F A ) in b o t h fractions. The plasma fatty acid patterns had returned to baseline levels one week after resuming the n o r m a l diet. Despite the k a n g a r o o meat containing m o r e than twice as m u c h L A as A A , the concentration and p r o p o r t i o n o f L A in plasma phospholipids and cholesteryl esters fell and that o f A A rose. This m a y indicate the preferential i n c o r p o r a t i o n o f A A into structural lipids when it is available in the diet. T h e fall in L A could simply reflect the greatly reduced total L A intake during the k a n g a r o o m e a t diet relative to the usual diet. The fatty acid c o m p o s i t i o n o f platelet lipids showed similar but less p r o n o u n c e d changes in L A and AA. This study highlights, firstly, that it is possible to have a diet containing a large quantity o f red meat but which is very low in fat with a high P/S ratio, and, secondly, that even in subjects with l o w - t o - n o r m a l cholesterol concentrations, this diet rich in lean meat was associated with a rapid fall in plasma cholesterol concentration despite the cholesterol content o f the diet remaining c o n s t a n t t h r o u g h o u t . These results have i m p o r t a n t implications for red meat producers and suggest that the development o f very lean meats (similar to wild meats) could o v e r c o m e m u c h o f the present opposition to red m e a t by health professionals and the public. REFERENCES 1. O'DEA, K. Diabetes 33, 596--603 (1984). 2. SXNCLAIR,A. J., SLAYrERY,W. J. and O'DEA, K,, J. Sci. Fd. Agric. 33, 77t-776 (1982).