SYMPOSIUM: THE ROLE OF THE NUTRITIONAL AND HEALTH BENEFITS IN THE MARKETING OF DAIRY PRODUCTS Potential for Enhancing the Nutritional Properties of Milk Fat DENISE Y. NEY Department of Nutritional Sciences University of Wisconsin-Madison Madison 53706
Cholesterol Education Program,VLDL = very low density lipoprotein.
ABSTRACT
Milk fat has been identified as a hypercholesterolemic fat because it contains cholesterol and is primarily saturated. However, Werent types of dietary saturated fats do not have equivalent effects on plasma cholesterol levels rele vant to ingestion of polyunsaturated fats. Research suggests that the hypercholesterolemic effect of saturated fats in human diets is largely due to 12, 14, and 16 carbon chain length fatty acids. Evidence also suggests that stearic acid (ct8:O) is as effective as oleic acid (c18: ,.,+) in lowering plasma cholesterol levels when either replaces palmitic acid (C1k.)in the diet of men. Milk fat has a unique fatty acid profile with approximately 10% short- and mediumchain length saturated fatty acids ( 4 2 carbons) and 35% of total fatty acids from stearic and oleic acids. The contribution of milk products to fat and cholesterol intake in the typical American diet is less than that provided by other animal products. This paper will review the recommendations of the National Cholesterol Education Program, the effects of milk fat ingestion on blood cholesterol, and the rationale and feasibility of three approaches to mod@hg the lipid composition of milk fat. (Key words: milk fat modification, saturated fat, blood cholesterol)
INTRODUCTION
Abbreviation key: CHD = Coronary heart disease, HDL = high density lipoprotein, LDL = low density lipoprotein. NCEP = National
Received October 1, 1990. Accepted January 8, 1991.
1991 J Dairy Sci 7440024012
Coronary heart disease (CHD) is a multifactorial disease that causes more than 500,000 deaths each year in the United States. Coronary heart disease is the result of atherosclerosis, in which deposits of cholesterol and other lipids, along with cellular reactions, thicken artery walls. Epidemiological studies have repeatedly demonstrated a clear association between elevated sem cholesterol levels and an increased risk of mortality from CHD. This epidemiological evidence has resulted in the completion of several national clinical trials that were designed to test the hypothesis that a reduction in plasma cholesterol levels would reduce the development of atherosclerosis and its progression to CHD. Interpretation of many recent clinical trials remains cmtroversial with respect to the efficacy of lowering blood cholesterol levels by dietary means (26, 31). However, there is substantial evidence that increased blood levels of low dmsity lipoprotein (LDL) cholesterol are causally related to an increased risk of CHD and that lowering of total and LDL cholesterol levels will reduce the incidence of CHD (41). Dietary therapy is regarded as the primary approach for lowering elevated blood cholesterol levels (41). Dietary recommendations to reduce elevated serum cholesterol levels emphasize a reduced intake of total fat, saturated fat, and cholesterol. Because milk fat contains primarily saturated fat and a small amount of cholesterol, butter and full fat dairy products are eliminated in cholesterol-reducing diets. The marketing of dairy products to health conscious consumers presents a challenge. Efforts to provide consumers with accurate nutritional information regarding the role of milk fat in
4002
SYMPOSTUM: HEALTH BENEmTS AND PRODUCT MARKETING
4003
TABLE?1. Recommendations of the adult treatmeot panel of tbe National Cholesterol Education Rogram based on serum total and low density lipoprotein (LDL) cholester~l.~
cholesterol (mg/dl) LDL
Total
Risk cateeorv ~
Desirable Borderline without CHD' or two other risk factors3.4 With CHD or two other risk factors High Without CHD or hvo other risk factors With CHD or two other risk factors
RCCOmIWlldatiOIU
DiaflnoEis
Diet
~
a00
430
200-239 130-159
224.0
2160
Remeasme in 5 yr
Recheck annually
Initiate diet if LDUlM)
Lipoprotein assay
Initiate diet if LDL >I30
Lipoprotein assay
Initiate diet
Lipoprotein assay
Initiate diet
'Adapted with p d s i o n of the publisher from Ney (36). TIE cardiovascnlar System. Pages 339-397 in CIinicul Num'tion und Dietetics, 2nd ed. P. J. Zeman, ed. MacMllan, New York, NY. ~ H =D~oronaryheart disease k i s k factors include d e sex, family history of premature CHD,hypertension, low levels of high density lipoproteins ( 4 5 mg/dl). diubetes mellitus, cacbrovascular or paiphaal vascular disease, severe obesity (230% overweight), and cigarette smoking. 4Children with plasma cholesterol levels exceeding thc 75th percenhle or 176 WdI sb,ould be considered for dietmy counseling.Drug therapy for hypercholesterolemia in children should only be considered for those children with plasma cholesterol levels exceeding the 95th parentile or 200 Wdl and only afta dietary hterventim has been llnsaccessfnl (7).
the context of a total diet and the availability of a variety of low fat dairy products are likely to enhance consumption of dairy products. The objectives of this review are 1) to summarize the rationale and recommendations of the National Cholesterol Education Rogram (NCEP),2) to review the effects of milk fat ingestion on blood cholesterol, and 3) to discuss the potential for enhancing the lipid profile of milk fat from a nutritional perspective. Natlonal Cholesterol Educatlon Program
In 1988, the National Hear&, Lung, and Blood Institute published recommendations for an NCEP (41) that was designed to reach and influence both health professionals and the public. The goal of the NCEP is to reduce the prevalence of elevated blood cholesterol in the United States, thereby contributing to the reduction of CHD morbidity and mortality. The recommendations of this program include that all American adults have their serum cholesterol level determined at least every 5 yr @able 1). Individuals with a serum cholesterol level of 240 mg/dl or higher are suggested to
be at high risk for the development of CHD. Those with serum cholesterol levels between 200 and 239 mddl are suggested to be at borderline high risk; levels of less than 200 mg/d are classified as desirable. Based on this classification system, it is estimated that over half of the American public will be evaluated as having borderline or high blood cholesterol levels. Decisions regarding treatment include lipoprotein analysis to determine serum LDL cholesterol concentrations and assessment of the presence of risk factors for CHD other than high blood cholesterol levels (Table 1). Drug therapy for hypercholesterolemia is usually not recommended until a 6-mo trial of intensive dietary therapy and counseling have failed to reduce LDL cholesterol levels below 160 to 190 mg/dl (41). Drug therapy is added to dietary therapy, not substituted for it. Dietary Recommendations. Dietary recommendations for individuals with blood cholesterol levels greater than 200 mg/dl or LDL cholesterol levels greater than 130 mg/dl are referred to as the StepOne diet, as summarized in Table 2. The relative importance of Journal of Dairy Science Vol. 74, No. 11, 1991
4004
NEY
TABLE 2. Diem Recommendations of the National Cholesterol Education Rogram. Nulrient
Ammt
Total fat Saturated fat Polyunsaturated htty acids Monounsaturated fatty acids Carbohydrates Rotein
Less than 30% of total calories Less than 105% of total calories Up to 10% of total calories 10 to 15% of total calories 50 to 604b of total Calories 10 to 205% of total calories
Cholesterol Total calories
W d To achieve and maintaiu desirable weight
-
'Adapted from the Report of the National Cblesterol Education Program Expert Panel on Detection,Evaluation and Treatment of High Blood Cholesterol in Adults (41). Also referred to as the Step-One therapeutic diet.
each dietary recommendation is controversial. Evidence from human studies suggests that dietary cholesterol is the least important lipid variable affecting serum cholesterol level (9, 34). Investigations with humans in the wtpatient setting suggest that dietary cholesterol has little or no effect on senun cholesterol levels, but investigations performed under metabolic ward conditions have demonstrated a rise in serum total cholesterol levels with increasing intake of cholesterol (15). The quantitative relationship between cholesterol intake and blood cholesterol levels remains unclear. Keys et al. (24) noted that the serum total cholesterol response is correlated to the square root of cholesterol intake, but Hegsted et aL (18, 19) and Mattson et al. (33) reported a linear relationship. Evidence also suggests considerable variability among individuals in the response of blood cholesterol to dietary cholesterol intake; however, we currently have no means of screening individuals for sensitivity to dietary cholesterol other than a trial of diet. Data from the United States Department of Agriculture (20, 21, 22, 23) indicate that average daily intake of dietary cholesterol is 304 and 435 mg for women and men, respectively. The intake for men is 45% higher than the recommended intake of less than 300 mgld of cholesterol. Saturated Fat. A large number of investigations have demonstrated that saturated fatty acids, compared with polyunsaturated fat or carbohydrate, raise serum total and LDL cholesterol concentrations. Current intake of saturated fatty acids as a proportion of calories for adults is 13.2% (20, 21, 22, 23). The NCEP recommends that less than 10% of calories be Journal of Dairy Science Vol. 74. No. 11, 1991
derived from saturated fat daily. Concerning the quantitative relationship between intake of saturated fatty acids and serum cholesterol response, the Keys equation (25) suggests that a decrease in intake of saturated fatty acids is twice as effective in lowering serum cholesterol concentrations as an increase in polyunsaturated fatty acids. Hegsted et al. (19) noted a similar response. Equation of Keys et al. (25) is as follows:
A Cholesterol (mddl) = 2.7AS - 1.35AP + 1.5AC1E mg/ 1OOOkcalperd Equation of Hegsted et al. (19) is as follows:
A Cholesterol (mg/dl) = 2.16AS - 1.65AP + .068AC&d where
S
= saturated fatty acids (percentage
of total calories), P = polyunsaturated fatty acids (percentage of total calories), and C = dietary cholesterol.
In spite of recommendations to reduce intake of saturated fat, not all types of saturated fatty acids raise blood cholesterol relative to dietary polyunsaturated fats. Research suggests that the chain length of a saturated fatty acid affects its ability to raise blood cholesterol when consumed in the diet. Keys et al. (25) demonstrated that the hypercholesterolemic effect of saturated fat in human diets is largely due to 12, 14, and 16 carbon chain length
4005
SYMPOSIUM: HEALTH BENEFITS AND PRODUCT MARKETING
TABLE 3. Fatty acid distribution (96) of selected dietary fats.' ___
~~~
~
Cholesterol Education Program,VLDL = very low density lipoprotein.
ABSTRACT
Milk fat has been identified as a hypercholesterolemic fat because it contains cholesterol and is primarily saturated. However, Werent types of dietary saturated fats do not have equivalent effects on plasma cholesterol levels rele vant to ingestion of polyunsaturated fats. Research suggests that the hypercholesterolemic effect of saturated fats in human diets is largely due to 12, 14, and 16 carbon chain length fatty acids. Evidence also suggests that stearic acid (ct8:O) is as effective as oleic acid (c18: ,.,+) in lowering plasma cholesterol levels when either replaces palmitic acid (C1k.)in the diet of men. Milk fat has a unique fatty acid profile with approximately 10% short- and mediumchain length saturated fatty acids ( 4 2 carbons) and 35% of total fatty acids from stearic and oleic acids. The contribution of milk products to fat and cholesterol intake in the typical American diet is less than that provided by other animal products. This paper will review the recommendations of the National Cholesterol Education Program, the effects of milk fat ingestion on blood cholesterol, and the rationale and feasibility of three approaches to mod@hg the lipid composition of milk fat. (Key words: milk fat modification, saturated fat, blood cholesterol)
INTRODUCTION
Abbreviation key: CHD = Coronary heart disease, HDL = high density lipoprotein, LDL = low density lipoprotein. NCEP = National
Received October 1, 1990. Accepted January 8, 1991.
1991 J Dairy Sci 7440024012
Coronary heart disease (CHD) is a multifactorial disease that causes more than 500,000 deaths each year in the United States. Coronary heart disease is the result of atherosclerosis, in which deposits of cholesterol and other lipids, along with cellular reactions, thicken artery walls. Epidemiological studies have repeatedly demonstrated a clear association between elevated sem cholesterol levels and an increased risk of mortality from CHD. This epidemiological evidence has resulted in the completion of several national clinical trials that were designed to test the hypothesis that a reduction in plasma cholesterol levels would reduce the development of atherosclerosis and its progression to CHD. Interpretation of many recent clinical trials remains cmtroversial with respect to the efficacy of lowering blood cholesterol levels by dietary means (26, 31). However, there is substantial evidence that increased blood levels of low dmsity lipoprotein (LDL) cholesterol are causally related to an increased risk of CHD and that lowering of total and LDL cholesterol levels will reduce the incidence of CHD (41). Dietary therapy is regarded as the primary approach for lowering elevated blood cholesterol levels (41). Dietary recommendations to reduce elevated serum cholesterol levels emphasize a reduced intake of total fat, saturated fat, and cholesterol. Because milk fat contains primarily saturated fat and a small amount of cholesterol, butter and full fat dairy products are eliminated in cholesterol-reducing diets. The marketing of dairy products to health conscious consumers presents a challenge. Efforts to provide consumers with accurate nutritional information regarding the role of milk fat in
4002
SYMPOSTUM: HEALTH BENEmTS AND PRODUCT MARKETING
4003
TABLE?1. Recommendations of the adult treatmeot panel of tbe National Cholesterol Education Rogram based on serum total and low density lipoprotein (LDL) cholester~l.~
cholesterol (mg/dl) LDL
Total
Risk cateeorv ~
Desirable Borderline without CHD' or two other risk factors3.4 With CHD or two other risk factors High Without CHD or hvo other risk factors With CHD or two other risk factors
RCCOmIWlldatiOIU
DiaflnoEis
Diet
~
a00
430
200-239 130-159
224.0
2160
Remeasme in 5 yr
Recheck annually
Initiate diet if LDUlM)
Lipoprotein assay
Initiate diet if LDL >I30
Lipoprotein assay
Initiate diet
Lipoprotein assay
Initiate diet
'Adapted with p d s i o n of the publisher from Ney (36). TIE cardiovascnlar System. Pages 339-397 in CIinicul Num'tion und Dietetics, 2nd ed. P. J. Zeman, ed. MacMllan, New York, NY. ~ H =D~oronaryheart disease k i s k factors include d e sex, family history of premature CHD,hypertension, low levels of high density lipoproteins ( 4 5 mg/dl). diubetes mellitus, cacbrovascular or paiphaal vascular disease, severe obesity (230% overweight), and cigarette smoking. 4Children with plasma cholesterol levels exceeding thc 75th percenhle or 176 WdI sb,ould be considered for dietmy counseling.Drug therapy for hypercholesterolemia in children should only be considered for those children with plasma cholesterol levels exceeding the 95th parentile or 200 Wdl and only afta dietary hterventim has been llnsaccessfnl (7).
the context of a total diet and the availability of a variety of low fat dairy products are likely to enhance consumption of dairy products. The objectives of this review are 1) to summarize the rationale and recommendations of the National Cholesterol Education Rogram (NCEP),2) to review the effects of milk fat ingestion on blood cholesterol, and 3) to discuss the potential for enhancing the lipid profile of milk fat from a nutritional perspective. Natlonal Cholesterol Educatlon Program
In 1988, the National Hear&, Lung, and Blood Institute published recommendations for an NCEP (41) that was designed to reach and influence both health professionals and the public. The goal of the NCEP is to reduce the prevalence of elevated blood cholesterol in the United States, thereby contributing to the reduction of CHD morbidity and mortality. The recommendations of this program include that all American adults have their serum cholesterol level determined at least every 5 yr @able 1). Individuals with a serum cholesterol level of 240 mg/dl or higher are suggested to
be at high risk for the development of CHD. Those with serum cholesterol levels between 200 and 239 mddl are suggested to be at borderline high risk; levels of less than 200 mg/d are classified as desirable. Based on this classification system, it is estimated that over half of the American public will be evaluated as having borderline or high blood cholesterol levels. Decisions regarding treatment include lipoprotein analysis to determine serum LDL cholesterol concentrations and assessment of the presence of risk factors for CHD other than high blood cholesterol levels (Table 1). Drug therapy for hypercholesterolemia is usually not recommended until a 6-mo trial of intensive dietary therapy and counseling have failed to reduce LDL cholesterol levels below 160 to 190 mg/dl (41). Drug therapy is added to dietary therapy, not substituted for it. Dietary Recommendations. Dietary recommendations for individuals with blood cholesterol levels greater than 200 mg/dl or LDL cholesterol levels greater than 130 mg/dl are referred to as the StepOne diet, as summarized in Table 2. The relative importance of Journal of Dairy Science Vol. 74, No. 11, 1991
4004
NEY
TABLE 2. Diem Recommendations of the National Cholesterol Education Rogram. Nulrient
Ammt
Total fat Saturated fat Polyunsaturated htty acids Monounsaturated fatty acids Carbohydrates Rotein
Less than 30% of total calories Less than 105% of total calories Up to 10% of total calories 10 to 15% of total calories 50 to 604b of total Calories 10 to 205% of total calories
Cholesterol Total calories
W d To achieve and maintaiu desirable weight
-
'Adapted from the Report of the National Cblesterol Education Program Expert Panel on Detection,Evaluation and Treatment of High Blood Cholesterol in Adults (41). Also referred to as the Step-One therapeutic diet.
each dietary recommendation is controversial. Evidence from human studies suggests that dietary cholesterol is the least important lipid variable affecting serum cholesterol level (9, 34). Investigations with humans in the wtpatient setting suggest that dietary cholesterol has little or no effect on senun cholesterol levels, but investigations performed under metabolic ward conditions have demonstrated a rise in serum total cholesterol levels with increasing intake of cholesterol (15). The quantitative relationship between cholesterol intake and blood cholesterol levels remains unclear. Keys et al. (24) noted that the serum total cholesterol response is correlated to the square root of cholesterol intake, but Hegsted et aL (18, 19) and Mattson et al. (33) reported a linear relationship. Evidence also suggests considerable variability among individuals in the response of blood cholesterol to dietary cholesterol intake; however, we currently have no means of screening individuals for sensitivity to dietary cholesterol other than a trial of diet. Data from the United States Department of Agriculture (20, 21, 22, 23) indicate that average daily intake of dietary cholesterol is 304 and 435 mg for women and men, respectively. The intake for men is 45% higher than the recommended intake of less than 300 mgld of cholesterol. Saturated Fat. A large number of investigations have demonstrated that saturated fatty acids, compared with polyunsaturated fat or carbohydrate, raise serum total and LDL cholesterol concentrations. Current intake of saturated fatty acids as a proportion of calories for adults is 13.2% (20, 21, 22, 23). The NCEP recommends that less than 10% of calories be Journal of Dairy Science Vol. 74. No. 11, 1991
derived from saturated fat daily. Concerning the quantitative relationship between intake of saturated fatty acids and serum cholesterol response, the Keys equation (25) suggests that a decrease in intake of saturated fatty acids is twice as effective in lowering serum cholesterol concentrations as an increase in polyunsaturated fatty acids. Hegsted et al. (19) noted a similar response. Equation of Keys et al. (25) is as follows:
A Cholesterol (mddl) = 2.7AS - 1.35AP + 1.5AC1E mg/ 1OOOkcalperd Equation of Hegsted et al. (19) is as follows:
A Cholesterol (mg/dl) = 2.16AS - 1.65AP + .068AC&d where
S
= saturated fatty acids (percentage
of total calories), P = polyunsaturated fatty acids (percentage of total calories), and C = dietary cholesterol.
In spite of recommendations to reduce intake of saturated fat, not all types of saturated fatty acids raise blood cholesterol relative to dietary polyunsaturated fats. Research suggests that the chain length of a saturated fatty acid affects its ability to raise blood cholesterol when consumed in the diet. Keys et al. (25) demonstrated that the hypercholesterolemic effect of saturated fat in human diets is largely due to 12, 14, and 16 carbon chain length
4005
SYMPOSIUM: HEALTH BENEFITS AND PRODUCT MARKETING
TABLE 3. Fatty acid distribution (96) of selected dietary fats.' ___
~~~
~
