Journal of the American College of Nutrition, Vol. 19, No. 3, 351-360 (2000)
Published by the American College of Nutrition
Incorporation of Lean Red Meat into a National Cholesterol Education Program Step I Diet: A Long-Term, Randomized Clinical Trial in Free-Living Persons with Hypercholesterolemia
Donald B. Hunninghake, MD,
Kevin C. Maki, PhD,
Peter O. Kwiterovich, Jr, MD,
Michael H. Davidson, MD,
Mary R. Dicklin, PhD and
Stephanie D. Kafonek, MD
The University of Minnesota Hospital and Clinics, Minneapolis, Minnesota (D.B.H.)
Chicago Center for Clinical Research, Chicago, Illinois (K.C.M., M.H.D., M.R.D.)
The Johns Hopkins University Lipid Clinic, Baltimore, Maryland (P.O.K., S.D.K.), Parke-Davis, Morris Plains, New Jersey (S.D.K.)
Address reprint requests to: Kevin C. Maki, PhD, Chicago Center for Clinical Research, 515 North State Street, Suite 2700, Chicago, Illinois 60610.
 |
ABSTRACT
|
|---|
Objective: Clinicians often recommend that intake of all meat, particularly red meat, be reduced in conjunction with a low-fat, low-cholesterol diet to reduce low-density lipoprotein (LDL) cholesterol. This study was designed to determine the long-term effects of lean red meat (beef, veal and pork) compared to lean white meat (poultry and fish) consumption on lipoprotein concentrations in free-living hypercholesterolemic subjects consuming a National Cholesterol Education Program (NCEP) Step I diet.
Methods: A randomized, crossover design was utilized. Hypercholesterolemic men and women (LDL cholesterol between 3.37 and 4.92 mmol/L) (triglycerides <3.96 mmol/L) (n = 145) were counseled to consume 
80% of their 170 g/d meat intake as either lean red meat or lean white meat for two 36-week phases, separated by a four-week washout period of free meat selection. Subjects were instructed to follow an NCEP Step I diet throughout the study.
Results: There were no significant differences in lipid concentrations between the lean red meat and lean white meat phases. LDL cholesterol was 4.02 ± 0.04 (SEM) and 4.01 ± 0.04 mmol/L in the white and red phases, respectively; this represented a decrease of 
2% from baseline concentrations (p < 0.01). Total cholesterol also declined by 1% from baseline (p < 0.05), and high-density lipoprotein (HDL) cholesterol rose over the study period by 2% to 3% from baseline to reach concentrations of 1.37 ± 0.03 mmol/L and 1.38 ± 0.03 mmol/L in the white and red phases, respectively (p < 0.001). Triglycerides were not altered by treatment.
Conclusions: Consumption of lean red meat or lean white meat, as part of an NCEP Step I diet, is similarly effective for reducing LDL cholesterol and elevating HDL cholesterol concentrations in free-living persons with hypercholesterolemia.
Key words: LDL cholesterol, diet, hypercholesterolemia, meat, lipid-lowering
|
INTRODUCTION
|
|---|
Epidemiological studies have demonstrated that the risk for developing coronary artery disease, the single most important cause of morbidity and mortality in the United States, is strongly associated with blood cholesterol concentrations [1–4]. Evidence clearly supports the benefits of reducing elevated low-density lipoprotein (LDL) cholesterol both in persons with and without coronary artery disease [3,5–7]. Therefore, reduction of LDL cholesterol is the primary target of cholesterol-lowering therapy. Dietary intervention is a cornerstone in the management of high blood cholesterol concentrations.
The National Cholesterol Education Program (NCEP) developed dietary guidelines with the aim of preventing and controlling coronary heart disease risk. The NCEP Step I diet has as its focus a restriction of total fat to 
30% of energy intake and saturated fatty acids to 8% to 10% of energy intake. Additionally, these guidelines recommend monounsaturated and polyunsaturated fatty acid intakes 10% and 15% of total calories, respectively, dietary cholesterol intake <300 mg/d and maintenance of desirable body weight [8].
In creating the Step I recommendations, the NCEP expert panel recognized the importance of a balanced diet incorporating a wide variety of popular foods [8]. Unfortunately, in order to meet the saturated fatty acid restrictions of the Step I diet, these guidelines have often been oversimplified by health care practitioners and the media to a suggestion to limit intake of all meat, particularly red meat [9–11]. Studies indicate that the relative amounts of different types of fat, and not the meat source itself (i.e., red meat versus white meat), is the factor related to blood lipid concentrations [12–16]. With the increased availability of lean meat products, red meat can be as low in fat, or in some cases even lower, than white meat.
More than 40 years ago, the lipid-lowering effect of a diet containing corn oil as the primary fat source was shown to be unaffected by the addition of 100 g of lean meat per day [17]. Since that time, studies conducted to compare directly the effects of lean red meat (beef and/or pork) with lean white meat (chicken and/or fish), have demonstrated equivalent effects of these meats on lipid concentrations of subjects with normal, borderline or high blood cholesterol concentrations [12,15,18–24].
Despite the large body of convincing evidence and the leaner cuts of red meat now available, controversy over the relationship between red meat consumption and coronary heart disease risk factors continues to affect the nutritional counseling provided to many hypercholesterolemic persons [11]. To simplify the NCEP dietary recommendations regarding intakes of specific nutrients, patients are frequently advised to eliminate certain foods in their diet. The elimination of favorite foods and limited food choices are often cited by patients as reasons for discontinuing diet therapy [25]. Since beef is one of the most popular meats consumed in the United States, unnecessary recommendations for its exclusion may reduce adherence to a low-fat diet and thus defeat its long-term effectiveness.
Most of the investigations conducted to date on the lipid-altering effects of meat have utilized tightly controlled institutional or metabolic ward settings to demonstrate the equivalency of lipid responses between short term lean red meat and lean white meat consumption [23,24]. Though providing valuable information, this approach has given little insight into the real-life scenario of counseling free-living hypercholesterolemic patients to implement long-term lifestyle changes by incorporating lean meats into the NCEP Step I diet. The present two-year randomized, crossover clinical trial was designed to examine the effects of incorporation of either lean red meats (beef, veal, pork) or lean white meats (poultry and fish) into an NCEP Step I diet, among free-living subjects with mild-to-moderate hypercholesterolemia. Results of the first phase (year 1) of the crossover study have been reported in detail elsewhere [26].
|
MATERIALS AND METHODS
|
|---|
Screening and Diet Stabilization
Participants were recruited from the Minneapolis, Minnesota, (The University of Minnesota Hospital and Clinics), Chicago, Illinois, (Chicago Center for Clinical Research) and Baltimore, Maryland, (The Johns Hopkins University Lipid Clinic) metropolitan areas for this randomized, multi-site clinical trial. The study protocol was reviewed and approved by an Institutional Review Board for each investigative site, and procedures were carried out in accordance with the Helsinki Declaration of 1975 as revised in 1983. Men and women (18 to 75 years of age) who met the initial screening criteria, as determined by a telephone interview, were asked to discontinue all lipid-lowering drugs or therapies [fish oil supplements, niacin/nicotinic acid (>250 mg/d), psyllium (>10 g/d), or oat bran (>1/3 cup/d)], with approval from their physicians, for at least six weeks prior to an orientation and screening visit at their respective clinical research center. Individuals who were pregnant or lactating, vegetarians, current smokers, abused alcohol (>14 drinks per week) or used recreational drugs were excluded from the study.
At screening (week -4), a written informed consent form was signed by each participant after the conditions and procedures of the study had been explained to them. Additionally, at the screening visit, participants completed a medical history questionnaire and underwent physical examination and laboratory procedures including hematology, blood chemistry, urinalysis (with a urine pregnancy test for women of childbearing potential) and a fasting blood lipid profile [total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol and triglycerides]. Exclusion criteria assessed during the medical history and physical examination included body mass index 35 kg/m2, diabetes mellitus, atherosclerotic disease, cancer, hypothyroidism or other endocrine disorder, or any hematological, hepatic, gastrointestinal or immune disorder. Volunteers meeting the inclusion criteria were administered the Oregon Health Sciences University Diet Habit Survey, an indicator of typical eating habits [27], and were instructed to maintain their usual diets throughout a four-week diet stabilization period.
After two weeks of diet stabilization (week -2), subjects returned to their respective clinic site to have vital signs and body weight checked and for another blood lipid profile measurement. Lipid criteria for inclusion in the study, based on an average of the two measurements obtained at weeks -4 and -2, included LDL cholesterol between 3.37 and 4.92 mmol/L and serum triglycerides 3.96 mmol/L. If LDL cholesterol concentrations varied by more than 15% between visits at weeks -4 and -2, an additional lipid profile clinic visit at week -1 was scheduled. If values from week -2 and week -1 did not meet the lipid eligibility criteria, the subject was dropped from the study.
At the week -2 visit, subjects were asked to complete a three-day diet record (including one weekend day) during the remaining two weeks of the diet stabilization period. Subjects received instructions regarding the completion of diet records from a nutritionist, who utilized food models to illustrate portion sizes.
Treatment Period (Phases I and II)
Three-hundred eighty-two persons were screened to provide the eligible two-hundred-two individuals randomly assigned to either the lean red meat (n = 95) or lean white meat (n = 107) treatment group during Phase I. At the randomization visit (week 0), subjects were instructed to consume 170 g of meat, 5 to 7 days per week, for 36 weeks (Phase I) as part of an NCEP Step I diet. The meat consumption guidelines were based on the NCEP Step I diet recommendation of up to 170 g per day of lean meat, including red meat, poultry, fish, or shellfish [8]. Subjects in the lean red meat group were instructed to consume at least 80% of their total meat in the form of lean beef, veal or pork. Subjects randomized to the lean white meat group were similarly instructed, except that at least 80% of their meat consumption was to be lean white meat defined as poultry or fish. Lamb was included in the 20% of other meat consumed by both groups during the treatment period. Baseline (week -2 to 0) three-day diet records and the results of the Diet Habit Survey administered at screening were reviewed with each subject at the randomization visit. Detailed instructions were provided on following an NCEP Step I diet. Subjects were also provided with an American Heart Association booklet, food scales, handouts and videotapes to aid their understanding of the prescribed diet. A nutritionist counseled the participants regarding selection and preparation of appropriate meats and completion of Daily Meat Consumption Logs.
At the end of 36 weeks, all subjects were allowed to choose their meat consumption freely while complying with a NCEP Step I diet for a four-week washout period. At week 40, all subjects crossed over to the other treatment, e.g., lean red meat group switched to lean white meat and lean white meat group switched to lean red meat. At the first visit of the crossover period (week 40), subjects completed a Diet Habit Survey and received reinforcement diet instruction. Subjects continued to follow their new study diets for the remaining 36 weeks of the study (Phase II).
Subjects returned to the clinic at weeks 4, 12, 20, 28 and 36 during the first phase of the study, week 38 at the midpoint of the washout phase and weeks 40, 44, 52, 60, 68 and 76 during the second phase of the study. The clinic visit included measurement of body weight, vital signs and fasting blood lipid profiles, reinforcement of dietary advice and assessment of concomitant medication use and adverse events. Additionally, visits at weeks 36 (end of Phase I) and 76 (end of Phase II) included safety laboratories (hematology, blood chemistry and urinalysis), a physical examination and an electrocardiogram.
Dietary Compliance
Throughout the treatment period, subjects maintained Daily Meat Consumption Logs to monitor the types and cuts of meat consumed, methods of preparation and portion sizes. A subject was deemed compliant with his or her recommended meat consumption if at least 80% of the total meat intake over a one-month period came from the appropriate meat and if the subject consumed between 795 g and 1306 g of meat per week over that period. Three-day diet records were completed between each clinic visit. Quantitative (computerized) analysis of dietary records was completed at weeks 0, 4, 20, 36, 40, 44, 60 and 76 by the Nutrient Analysis Center at the Chicago Center for Clinical Research, using the University of Minnesota Nutrition Data System 2.7 software. Diet records and results of the computerized analysis of the diet record from the previous clinic visit were reviewed with the subject at each visit. Between clinic visits, at weeks 8, 16, 24, 32, 48, 56, 64 and 72, telephone interviews were conducted to further monitor and encourage compliance with the study protocol. The Diet Habit Survey was administered over the telephone four times during treatment at weeks 16, 32, 56 and 72. Compliance with the fat and cholesterol guidelines of the NCEP Step I diet was determined using the cholesterol-saturated fat score of the Diet Habit Survey. A value of 60 or higher is consistent with the recommendations for intakes of <30% of total energy from fat and <300 mg/d of cholesterol [27].
Lipid Analysis
Fasting (12 hours) blood collection was completed at each clinical research site according to previously described procedures [26]. Serum total cholesterol, HDL cholesterol and triglycerides were measured enzymatically by a central laboratory (Medical Research Laboratories, Cincinnati, OH), which participates in the Centers for Disease Control and Prevention lipid measurement standardization program [28]. Low-density lipoprotein cholesterol in mg/dL was calculated using the Friedewald equation [LDL cholesterol = total cholesterol - HDL cholesterol - (triglycerides/5)] [29] and converted to mmol/L utilizing the factor of 0.02586. Results were blinded from investigators throughout the treatment period, though clinic sites were notified by the central laboratory if the LDL cholesterol of any subject exceeded 5.68 mmol/L.
Statistical Analysis
Analyses were conducted using the JMP 3.1 (SAS Institute, Cary, NC) and Statview 4.5 (Abacus Concepts, Berkeley, CA) statistical analysis packages. Two sided p-values <0.05 were used to denote statistical significance.
Chi-square tests and analysis of variance were used to assess comparability of baseline characteristics between treatment groups. The initial statistical models contained terms for treatment, time, treatment-time interaction, study center and treatment-study center interaction. No evidence of treatment-time or treatment-study center interactions was detected (p > 0.10). In addition, a test for sequence effect showed that the responses were independent (p > 0.10) of treatment sequence [30]. Therefore, data from the three sites were pooled and mean blood lipid concentrations during treatment were used in the final statistical models.
The primary data analyses reported here include all patients who entered the crossover phase of the study and completed at least one post-crossover clinic visit. The outcome variables of interest, blood lipid concentrations (total, LDL and HDL cholesterol and triglycerides) were averaged for all visits completed by each subject during the respective treatment periods. A repeated measures analysis of variance (ANOVA) model was used to compare mean values between treatment conditions and to assess possible interaction by study site. Results from a per protocol analysis, in which data from patients who were deemed non-compliant were excluded, were similar to those from the primary analyses.
The potential interactions of treatment with age, gender, obesity, dietary fat consumption, baseline LDL concentration, body weight change and phase of menstrual cycles with lipid response were tested by individual entry of terms and interaction terms for each of these factors into the ANOVA models.
|
RESULTS
|
|---|
Subjects and Demographics
Forty-two (21%), of the two-hundred two randomized subjects, dropped out of the study prior to completion of Phase I. Of these, 18 were in the lean red meat group and 24 were in the lean white meat group. Reasons reported for study discontinuation included inability to follow the diet (n = 15), scheduling problems (n = 11), loss to follow-up (n = 7), private medical advice or newly prescribed medication (n = 5), personal reasons (n = 2), surgery (n = 1) and relocation (n = 1). Details of Phase I of this study are reported elsewhere [26]. Twenty-nine (18%) of the subjects who entered Phase II dropped out of the study prior to its completion. Of these subjects, eight were in the lean white meat group during phase II and 21 were in the lean red meat group during phase II. Reasons reported for study discontinuation included lost to follow up (n = 6), new medication use (n = 6), noncompliance with clinic visits or scheduling problems (n = 4), unable to follow diet (n = 4), relocation (n = 3), new job or work conflicts (n = 3), newly diagnosed disease (n = 2) and surgery (n = 1).
One-hundred, forty-five subjects completed at least one blood draw in Phase II and were included in the crossover data analyses. Baseline demographic and anthropometric characteristics of each treatment group in Phase II are shown in Table 1. Treatment groups did not differ in mean age, body mass index, gender and race distribution or alcohol intake.
Serum Lipids
Serum lipid concentrations at baseline (average of values obtained at weeks -4, -2 and 0), during Phase I (average of values obtained at weeks 4 through 36) and during Phase II (average of values obtained at weeks 40 through 76) are summarized in Table 2. Mean LDL and HDL cholesterol concentrations at each time point from screening to the end of the study are presented graphically in Fig. 1 and Fig. 2, respectively. Tests for the effect of sequence indicated that there was no relationship between treatment sequence and the lipid response (p > 0.05). Therefore, further analyses were conducted by grouping subjects into lean red meat and lean white meat phases.
View this table:
[in this window]
[in a new window]
|
Table 2. Lipid Concentrations at Baseline and during Phase I and Phase II Treatment Periods according to Treatment Sequence*
|
|
View larger version (24K):
[in this window]
[in a new window]
|
Fig. 1. Low-density lipoprotein (LDL) cholesterol concentrations (Mean ± SEM) from screening to the end of the two-year crossover study of hypercholesterolemic men and women consuming an NCEP Step I diet which incorporated either predominantly lean red meat or predominantly lean white meat as the meat source. Treatment phases are shown connected.
|
|
View larger version (23K):
[in this window]
[in a new window]
|
Fig. 2. High-density lipoprotein (HDL) cholesterol concentrations (Mean ± SEM) from screening to the end of the two-year crossover study of hypercholesterolemic men and women consuming an NCEP Step I diet which incorporated either predominantly lean red meat or predominantly lean white meat as the meat source. Treatment phases are shown connected.
|
|
The results of the combined Phase I and II analyses are shown in Table 3 and Table 4. There were no significant differences in lipid concentrations between the lean red meat and lean white meat phases. LDL cholesterol decreased 1.9% from baseline to a concentration of 4.01 ± 0.04 (SEM) mmol/L during the lean red meat phase (p = 0.002). For the lean white meat phase, LDL cholesterol was 4.02 ± 0.04 mmol/L which represented a 2.0% decline from baseline (p < 0.001). Total cholesterol was also significantly reduced from baseline concentrations by 0.9% in the lean red meat phase and 1.2% in the lean white meat phase (p = 0.042 and p = 0.010, respectively). HDL cholesterol concentrations were elevated from baseline in both phases by 2.8% (p < 0.001) and 2.2% (p < 0.001) for the lean red and lean white meat phases, respectively. Subjects in both phases also had a 3% decrease in the total cholesterol/HDL cholesterol ratio (p < 0.001 in both the red and white phases). Triglycerides were not altered by treatment. The average of LDL cholesterol values from the final two visits in the lean red phase and lean white phase were virtually identical, 4.03 ± 0.04 and 4.02 ± 0.04 mmol/L, respectively. The mean individual difference between treatment phases was 0.02 mmol/L, representing a difference of <0.5%.
View this table:
[in this window]
[in a new window]
|
Table 4. Percent Change in Serum Lipid Concentrations from Baseline to Lean Red Meat Phase and Lean White Meat Phase*
|
|
Compliance
The cholesterol-saturated fat score of the Diet Habit Survey (determined by adding scores for the questions related to cholesterol and saturated fat intakes), administered twice during each phase of the study, was significantly elevated from baseline at each administration during both treatment phases (p < 0.001) (Table 5). Scores at baseline and at each administration of the survey were greater than 60, indicating compliance with the NCEP Step I diet at baseline and throughout the duration of the study.
View this table:
[in this window]
[in a new window]
|
Table 5. Diet Habit Survey Cholesterol-Saturated Fat Scores at Baseline and Two Time Points during each Phase of the Study according to Treatment Phase*
|
|
Results of analyses of randomly selected meat logs from consecutive seven-day periods between each clinic visit are shown in Table 6. In general, all subjects consumed at least 80% of their total meat according to treatment group assignment. Furthermore, subjects were generally compliant with consumption of an average of 120 g to 170 g per day (170 g per day, 5 to 7 days per week) of meat. Total meat consumption was significantly lower in the lean white meat group, compared to the lean red meat group, during weeks 21 to 28 (p < 0.001) and 29 to 36 (p = 0.002), the last time points of Phase I. Total meat consumption was significantly higher in the lean white meat group, compared to the lean red meat group, during weeks 61 to 68 (p < 0.001), the next to the last time point of Phase II.
Results of three-day diet record analyses at baseline and during treatment are shown in Table 7. At baseline, there were no significant differences in dietary intake observed between subjects who were randomized to either the lean red meat or lean white meat treatment groups. During treatment there were small, but statistically significant, differences between the lean red meat and lean white meat phases in the intake of several nutrients. Compared to the lean white meat phase, subjects reported a higher energy intake during the lean red meat phase of the study (p = 0.004) and consumed a larger percentage of their energy from total fat and both saturated (18:0 and 12:0 to 16:0) and monounsaturated fatty acids (p < 0.001). During the lean white meat phase, intakes of polyunsaturated fatty acids (p < 0.001), carbohydrate (p = 0.025) and protein were greater than during the lean red meat phase (p < 0.001).
View this table:
[in this window]
[in a new window]
|
Table 7. Results of Three-day Diet Record Analyses at Baseline and during Lean Red Meat and Lean White Meat Phases*
|
|
Body Weight
Body weight was similar at baseline between subjects randomized to the lean red meat group or the lean red meat group and did not change significantly in either group over the duration of the trial. Mean total weight gain from screening to the end of the first phase of the study was <0.5 kg and from screening to the end of the second phase of the study was <1.0 kg (p > 0.05). Body weight changes in the lean red meat and lean white meat phases did not differ.
|
DISCUSSION
|
|---|
The results of this study demonstrate similar lipid responses between hypercholesterolemic patients who were counseled to incorporate either lean red meat (beef, pork, veal) or lean white meat (poultry and fish) into an NCEP Step I diet. In fact, this 76-week clinical trial indicated that the 1% reductions in total cholesterol, 2% reductions in LDL cholesterol, 3% reductions in total cholesterol/HDL cholesterol ratio and 2–3% elevations of HDL cholesterol were nearly identical between the two lean meat treatment phases. Similar findings have been reported previously in short term investigations conducted under tightly controlled conditions. Scott and colleagues [23,24] directly compared the blood lipid responses to lean beef versus chicken and/or fish consumption in men with borderline or frank hypercholesterolemia. In two randomized, clinical trials this group demonstrated similar blood cholesterol reductions in men consuming lean beef versus chicken, or chicken and fish. As in the present study, lean meats were incorporated into diets containing less than 30% of energy from fat and less than 10% of energy from saturated fatty acids. Though both of these four-to-five week studies were conducted in free-living populations, in neither study did the subjects select or prepare their own foods. Therefore, the average decrease in plasma total cholesterol concentrations of 7.6% and 11% for the beef and chicken treatment groups, respectively, is not directly comparable to the more modest reductions demonstrated in this trial of free-living subjects selecting and preparing their own foods.
Dietary intervention studies in free-living hypercholesterolemic populations provide a more accurate comparison for the present trial. An investigation of the efficacy of NCEP Step II diet therapy (saturated fatty acids restricted to 7% of total calories) in free-living, moderately hypercholesterolemic subjects who selected and prepared their own foods, demonstrated a 5% reduction in LDL cholesterol compared to persons consuming a self-selected diet [31]. Similarly to the present study, this group utilized extensive dietary education and monitoring. However, the actual lipid response in this free-living population was less than that expected based on results from metabolic ward studies.
Suboptimal compliance with dietary recommendations is frequently related to a less-than-satisfactory LDL cholesterol reduction. However the tool utilized in the current study to measure compliance with the cholesterol and saturated fat restrictions of the NCEP Step I diet, the Diet Habit Survey, suggested excellent adherence to the diet throughout the duration of the trial. The Diet Habit Survey is an indicator of typical eating habits. Cholesterol-saturated fat scores 60 on the Diet Habit Survey represent adherence to the cholesterol and saturated fat restrictions of the diet [27]. Mean baseline cholesterol-saturated fat scores were above 60 for both groups; this suggested that many subjects were following NCEP diet recommendations prior to entry into the study. Scores at both the first and second administrations of the survey were higher than baseline in both phases, but did not differ between phases. The lack of a difference between phases further supports the finding of no difference between lean red meat and lean white meat phases in lipid response or changes in body weight.
An additional tool utilized in this study to estimate dietary compliance was the three-day diet record. According to diet records, mean intakes of total fat, saturated fats and cholesterol at baseline were 32% of energy, 10.5% of energy and 245 mg/d, respectively. Diet analyses indicated that, compared to the lean white meat phase, during the lean red meat phase subjects had higher energy intakes (7255 kJ/d versus 6941 kJ/d), and larger intakes of total fat (28.4% versus 26.0% of total energy), 12:0 to 16:0 fatty acids (6.2% versus 5.3% of total energy), 18:0 fatty acids (2.5% versus 2.1% of total energy) and monounsaturated fatty acids (11.2% versus 9.7% of total energy). Though the differences between lean red and lean white meat phase intakes were statistically significant, they were quantitatively small and did not apparently result in differences in body weight or serum lipid responses.
To assess the expected effect of the differences in dietary intake on lipid responses, the following equation, published by Kris-Etherton and Yu, was applied utilizing the individual responses of subjects, rather than the means reported above [32].
 |
In this equation 12:0–16:0 represents the percentage of energy intake from cholesterol-raising fatty acids, 18:0 is the percentage of energy from stearic acid, M is the percentage of energy from monounsaturated fatty acids, and P is the percentage of energy from polyunsaturated fatty acids. Results in mg/dL were converted to Systéme International units of mmol/L utilizing a factor of 0.02586. The predicted difference in LDL cholesterol response between lean red meat and lean white meat phases was 0.03 mmol/L which was nearly identical to the actual difference detected between phases. Since this equation has no term for differences in cholesterol intake, an additional calculation was performed using a factor of 0.44 mg/dL to account for the influence of each one-mg/d difference in dietary cholesterol intake per 1000 kcal of energy [32]. Incorporation of this factor into the previous equation indicated that the predicted difference between lean red meat and lean white meat groups was 0.01 mmol/L. Therefore it is evident that the small differences noted in the intakes of dietary components had no clinically relevant effect on LDL cholesterol levels.
Regarding the larger apparent reduction from baseline in energy intake during the lean white meat phase compared with the lean red meat phase, it should be noted that red meat varies in its fat content to a much larger extent than white meat. These variations may not be completely accounted for in diet records and/or the nutrient database used for analysis, possibly creating a bias in the estimated fat intake. More than 80% of the difference in reported energy consumption between phases can be attributed to higher apparent fat intake during the lean red meat phase. Since no difference in body weight was observed between phases, the possibility of a systematic bias cannot be ruled out.
|
CONCLUSION
|
|---|
The results of this 76-week clinical trial demonstrate the equivalent lipid-lowering efficacy of counseling free-living, hypercholesterolemic persons to incorporate either lean red meat (beef, pork, veal) or lean white meat (poultry and fish) into an NCEP Step I diet. These results confirm the findings previously reported for the first phase of the trial [26]. Additionally, this investigation adds to the accumulating body of evidence that demonstrates the similarity of lipid responses to lean red meat and lean white meat consumption. Long-term dietary changes are difficult to institute. Findings from this study suggest that the lipid-lowering effects of a low-fat diet are not compromised by incorporation of lean red meats. The common practice of excluding red meat from low-fat diets should probably be replaced with specific instructions on the appropriate replacement of meats high in fat with leaner meats, which may facilitate long-term compliance.
|
ACKNOWLEDGMENTS
|
|---|
This research was funded by the National Cattlemen’s Beef Association. The authors wish to thank Julie Kong, MS, RD, Julie Rink, RD, Cindy Miglieri RD, Andrea Druetzler, MS, RD, Rebecca Westereng, RD, LD, Mary Patz, RD, Kathleen R. Shultz, RD, LD and Liz Johnston, MPH, RD, LD for their help with the conduct of the study.
|
FOOTNOTES
|
|---|
Abbreviations: ANOVA = analysis of variance, HDL = high-density lipoprotein cholesterol, LDL = low-density lipoprotein cholesterol, NCEP = National Cholesterol Education Program.
This research was funded by the National Cattlemen’s Beef Association.
Received November 1, 1999.
Revised February 1, 2000.
Accepted February 1, 2000.
|
REFERENCES
|
|---|
- Drexel H, Amann FW, Beran J, Rentsch K, Candinas R, Muntwyler J, Luethy A, Gasser T, Follath F: Plasma triglycerides and three lipoprotein cholesterol fractions are independent predictors of the extent of coronary atherosclerosis. Circulation 90: 2230–2235, 1994.[Abstract/Free Full Text]
- Genest J, McNamara J, Salem D, Schaefer E: Prevalence of risk factors in men with coronary artery disease. Am J Cardiol 67: 1185–1189, 1991.[Medline]
- Holme I: An analysis of randomized trials evaluating the effect of cholesterol reduction on total mortality and coronary heart disease incidence. Circulation 82: 1916–1924, 1990.[Abstract/Free Full Text]
- Sarrett A, Patsch W, Sorlie P, Heiss G, Bond M, Davis C: Associations of lipoprotein cholesterols, apolipoproteins A-I and B, and triglycerides with carotid atherosclerosis and coronary heart disease. The Atherosclerosis Risk in Communities (ARIC) Study. Arterioscler Thromb 14: 1098–1104, 1994.[Abstract/Free Full Text]
- Downs JR, Clearfield M, Weis, Whitney E, Shapiro DR, Beere PA, Langendorfer A, Stein EA, Kruyer W, Gotto Jr AM: Primary prevention of acute coronary events with lovastatin in men and women with average cholesterol levels: results of AFCAPS/TexCAPS. Air Force/Texas Coronary Atherosclerosis Prevention Study. JAMA 279: 1615–1622, 1998.[Abstract/Free Full Text]
- Law M, Wald N, Thompson S: By how much and how quickly does reduction in serum cholesterol concentration lower risk of ischaemic heart disease? Br Med J 308: 367–372, 1994.[Abstract/Free Full Text]
- Scandinavian Simvastatin Survival Study Group: Randomized trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian simvastatin survival study (4S). Lancet 344: 1383–1389, 1994.[Medline]
- The Expert Panel: "Second Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II)." Washington, DC: US Dept of Health and Human Services, 1993.
- Chait A, Brunzell JD, Denke M, Eisenberg D, Ernst ND, Franklin Jr FA, Ginsberg H, Kotchen TA, Kuller L, Mullis RM, et al.: Rationale of the Diet-Heart Statement of the American Heart Association and Report of the Nutrition Committee. Circulation 88: 3008–3029, 1993.[Free Full Text]
- Hunt J, Kristal A, White E, Lynch J, Fries E: Physician recommendations for dietary change: their prevalence and impact in a population-based sample. Am J Public Health 85: 722–726, 1995.[Abstract/Free Full Text]
- McIntosh W, Fletcher R, Kubena K, Landmann W: Factors associated with sources of influence/information in reducing red meat by elderly subjects. Appetite 24: 219–230, 1995.[Medline]
- Morgan S, Sinclair A, O’Dea K: Effect on serum lipids of addition of safflower oil or olive oil to very-low-fat diets rich in lean beef. J Am Diet Assoc 93: 644–648, 1993.[Medline]
- Bonanome A, Grundy S: Effect of dietary stearate on plasma cholesterol and lipoprotein levels. N Eng J Med 318: 1244–1248, 1988.[Abstract]
- Denke M: Role of beef tallow, an enriched source of stearic acid, in a cholesterol-lowering diet. Am J Clin Nutr 60: 1044S–1049S, 1994.[Abstract/Free Full Text]
- O’Dea K, Traianedes K, Chisolm K, Leyden H, Sinclair A: Cholesterol-lowering effect of a low-fat diet containing lean beef is reversed by the addition of beef fat. Am J Clin Nutr 35: 2734–2741, 1981.
- Watts GF, Ahmed W, Quiney J, Houlston R, Jackson P, Iles C, Lewis B: Effective lipid lowering diets including lean meat. Br Med J 296: 235–237, 1988.
- Malmros H, Wigand G: The effect on serum cholesterol of diets containing different fats. Lancet ii: 1–8, 1957.
- Denke MA, Grundy SM: Individual responses to a cholesterol-lowering diet in 50 men with moderate hypercholesterolemia. Arch Int Med 154: 317–325, 1994.[Abstract]
- Flynn MA, Heine B, Nolph GB, Naumann HD, Parisi E, Ball D, Krause G, Ellersieck M, Ward SS: Serum lipids in human diets containing beef or fish and poultry. Am J Clin Nutr 34: 2734–2741, 1981.[Abstract/Free Full Text]
- Flynn M, Naumann H, Jrause G, Ellersieck M: Dietary "meats" and serum lipids. Am J Clin Nutr 35: 935–942, 1982.[Abstract/Free Full Text]
- Marckmann P, Jepersen J, Leth T, Sandstrom B: Effect of fish diet versus meat diet on blood lipids, coagulation and fibrinolysis in healthy young men. J Intern Med 229: 317–323, 1990.
- O’Brien B, Reiser R: Human plasma lipid responses to red meat, poultry, fish, and eggs. Am J Clin Nutr 33: 2573–2580, 1980.[Free Full Text]
- Scott L, Kimball K, Wittels EH, et al.: Effects of a lean beef diet and of a chicken and fish diet on lipoprotein profiles. Nutr Metab Cardiovasc Dis 1: 25–30, 1991.
- Scott L, Dunn J, Pownall H, Brauchi DJ, McMann MC, Herd JA, Harris KB, Savell JW, Cross HR, Gotto Jr AM: Effects of beef and chicken consumption on plasma lipid levels in hypercholesterolemic men. Arch Intern Med 154: 1261–1267, 1994.[Abstract]
- Carmody TP, Matarazzo JD, Istvan JA: Promoting adherence to heart-healthy diets: a review of the literature. J Compliance Health Care 2: 105–124, 1987.
- Davidson MH, Hunninghake D, Maki KC, Kwiterovich PO, Kafonek S: A long-term, randomized clinical trial to compare the effects of lean red meat versus lean white meat on serum lipids among free-living persons with hypercholesterolemia. Arch Int Med 159: 1331–1338, 1999.[Abstract/Free Full Text]
- Connor S, Gustafson J, Sexton G, Becker N, Artaud-Wild S, Connor W: The Diet Habit Survey: a new method of dietary assessment that relates to plasma cholesterol changes. J Am Diet Assoc 92: 41–47, 1992.[Medline]
- Myers G, Cooper G, Winn C, Smith S: The Centers for Disease Control-National Heart, Lung, and Blood Institute Lipid Standardization Program. An approach to accurate and precise lipid measurements. Clin Lab Med 9: 105–135, 1989.[Medline]
- Friedewald W, Levy R, Frederickson D: Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 18: 499–502, 1972.[Abstract]
- Pocock SJ: "Clinical Trials: A Practical Approach." New York: Wiley Medical Publications, 1983.
- Hunninghake DB, Stein EA, Dujovne CA, Harris WS, Feldman EB, Miller VT, Tobert JA, Laskarzewski PM, Quiter E, Held J, et al.: The efficacy of intensive dietary therapy alone or combined with lovastatin in outpatients with hypercholesterolemia. N Engl J Med 328: 1213–1219, 1993.[Abstract/Free Full Text]
- Kris-Etherton PM, Yu S: Individual fatty acid effects on plasma lipids and lipoproteins: human studies. Am J Clin Nutr 65 (Suppl): 1628S–1644S, 1997.[Abstract/Free Full Text]
TOP
ABSTRACT
INTRODUCTION
