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KEY WORDS: AHA Scientific Statement diet fatty acids risk factors cardiovascular diseases
| INTRODUCTION |
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| EPIDEMIOLOGICAL, CLINICAL TRIAL, AND NONHUMAN PRIMATE EVIDENCE FOR THE RELATIONSHIP BETWEEN TYPE OF FAT AND CORONARY DISEASE |
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-linolenic acid) PUFAs are
protective. Trans fatty acids are strong predictors of
increased coronary risk compared with saturated fat or carbohydrates
(1)
The paradigm that dietary fats act exclusively via effects on serum
lipids and lipoproteins has been challenged (5
6
7
8)
. The
Lyon Diet Heart Study (5)
and the Indian Heart Study
(6)
have both shown in clinical trials that diet can
prevent fatal and nonfatal cardiovascular events in individuals with
CVD. In both trials, saturated fats were replaced with monounsaturated
fats and
-linolenic acid, an n-3 PUFA that is present in canola
(rapeseed) oil. Vegetables and fruits were increased in the diets in
these studies as well. In addition, fish and fish oil have been shown
to reduce all-cause mortality (7
,8)
and cardiovascular
death (8)
in patients who had myocardial infarction.
Studies have been conducted in primates to examine the effects of
dietary fatty acids on atherosclerosis (9
,10)
. Diets with
saturated, monounsaturated, and polyunsaturated (including both n-3 and
n-6) fatty acids have been evaluated. Coronary artery atherosclerosis
(as measured by intimal area) was less in the polyunsaturated fat than
in the saturated fat and monounsaturated fat groups. Monkeys fed
monounsaturated fat developed equivalent amounts of coronary artery
atherosclerosis as those fed saturated fat (9)
. LDL
cholesterol was similar in monkeys fed polyunsaturated and
monounsaturated fat and lower than in animals fed saturated fat.
However, there was an enrichment of cholesteryl oleate in plasma
cholesteryl esters of the monkeys fed the diet high in monounsaturated
fatty acids, which correlated with coronary artery cholesteryl ester
concentration, a measure of coronary artery atherosclerosis
(10)
. Activation of ACAT2 (the enzyme responsible for
cholesterol oleate formation and secretion by the liver) may explain
how dietary monosaturated fat promotes atherosclerosis out of
proportion to its effects on plasma LDL cholesterol levels. Both n-6
PUFAs (primarily linoleic acid) and n-3 PUFAs (principally
eicosapentaenoic acid and docosahexaenoic acid) have been shown to
confer protection. That a diet rich in monounsaturated fat resulted in
more atherosclerosis than a diet rich in polyunsaturated fat even
though plasma LDL and high-density lipoprotein (HDL) cholesterol
levels were comparable also suggests that nonlipid risk factors may
play a role in atherogenesis. Thus, additional studies with
cardiovascular end points that go beyond the measurement of surrogate
markers of CVD risk (ie, plasma lipids and lipoproteins) are needed to
evaluate the effects of fatty acids in humans. In this regard, there is
evidence in human subjects that a single high-fat meal (high in
monounsaturated fat or saturated fat) adversely affects endothelial
function, (11)
which is thought by
some to be an early event in the atherogenic process.
| EPIDEMIOLOGICAL AND CLINICAL TRIAL EVIDENCE FOR A RELATIONSHIP BETWEEN TYPE OF FAT AND CANCER RISK |
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| EFFECTS OF FATTY ACIDS ON INSULIN SECRETION AND ACTION |
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trans switch of the
double bond in the C16:1 and C18:1 fatty acids. Thus, there is
remarkable diversity in how individual fatty acids affect insulin
secretion. Consequently, these in vitro studies suggest that the type
and amount of circulating fatty acids may determine the insulin
secretory response. Importantly, saturated fat raises insulin
resistance. Unpublished data from a multicenter study in Europe showed
that individuals were more insulin sensitive when consuming a diet high
in monounsaturated fatty acids than when consuming an equivalent diet
high in saturated fat.
Increased intake of dietary fat reduces insulin action in experimental
animals, and this insulin resistance is associated with the
accumulation of triglyceride in muscle and liver. In animal models,
high-fat diets composed of fish oil or safflower oil have markedly
different effects on insulin action, and these differences may depend
on the ability of fatty acids in fish oil to upregulate lipid oxidation
in the liver. Mechanisms may involve increased translocation and
activation of specific protein kinase C isozymes (PKC-
and PKC-
)
that phosphorylate and reduce the activity of insulin signaling
intermediates (15
,16)
. In C2C12 cells (a murine muscle
cell line), oleate and palmitate have different effects on
insulin-stimulated glucose conversion to glycogen and different
effects on key components of the insulin signaling pathways
(17)
. On the other hand, in humans, varying the total fat
content of the diet does not affect insulin-mediated glucose
disposal (18)
. However, it is becoming increasingly
evident that specific fatty acids or their derivatives may have roles
other than as energy substrates involving regulation of enzyme activity
and gene expression in insulin-responsive tissues. More in vivo
studies in humans are needed.
| EFFECTS OF FATTY ACIDS ON HEMOSTATIC FACTORS AND PLATELET FUNCTION |
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Several hemostatic factors are influenced by dietary components
(19
,20)
. For example, when a high-fat diet is replaced
by a lower-fat, higher-fiber diet, the activity of factor VII
decreases and the capacity of the endogenous fibrinolytic system
increases. Studies of the relationship of dietary fatty acids and
hemostatic factors generally show that hemostatic proteins are not
affected by changes in the type of dietary fat, such as saturated,
monounsaturated, trans, or n-6 polyunsaturated fats.
Platelets play several roles in atherosclerosis, including exacerbating the atherosclerotic process, adhering to ruptured or eroded lesions, and participating in the formation of an occlusive thrombus. Lipids are an important constituent of the platelet membrane. Lipids are also important in the intracellular signaling of platelets. Many studies have explored the relationship of dietary fatty acids and platelet function. The majority of studies have been performed in small numbers of human subjects and in animal models. However, interpretation of results is difficult because different methods have been used to estimate platelet function, there has been inconsistency in assessment of platelet lipid composition, and there have been questions regarding the relationship of in vitro assays to in vivo activity. The composition and duration of the dietary manipulations have been inconsistent across studies. There are few population-based epidemiological data because of difficulty in assessing platelet function and diet composition in these studies.
In general, the composition of the platelet membrane appears to reflect the fatty acid composition of the diet. Diets rich in n-3 fatty acids appear to cause platelets to aggregate less at a fixed dose of agonist or to require more agonist to aggregate. There are some data to support a deleterious effect of dietary stearic acid on platelet aggregation. It appears that within the context of the usual diet, there may be some effects of dietary fatty acids on both the coagulation proteins and the platelet membrane. However, these effects are minor, and the clinical meaning of such effects is unclear.
| EFFECTS OF FATTY ACIDS ON BLOOD PRESSURE |
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| FATTY ACIDS AND ENDOTHELIAL ACTIVATION |
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| DIETARY FAT INTAKE |
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Because of challenges associated with collecting accurate food
consumption data, there is a pressing need to identify reliable markers
of fat and fatty acid intake. Evidence indicates that adipose tissue
fatty acid composition is a suitable biomarker for habitual type of
dietary fat intake (25
,26)
.
| MODIFICATION OF OILS FOR IMPROVED HEALTH BENEFITS |
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-linolenic (18:3 n-6) and
stearidonic acids (18:4 n-3). Long-chain n-3 fatty acids in the
form of stearidonic acids, the 18:4 n-3 precursor to eicosapentaenoic
acid and docosahexaenoic acid, could provide a more effective n-3 fatty
acid than
-linolenic acid. In addition, vegetable oilderived
stearidonic acids could be used as an alternative to fish oil to
provide long-chain n-3 fatty acids with enhanced stability and
taste that can be incorporated into a wide variety of foods. | DIETARY FAT RECOMMENDATIONS: WHERE WE ARE AND WHERE WE COULD GO |
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30% of energy as fat,
10% of energy as saturated fatty
acids, up to 10% of energy as PUFAs, and <300 mg of cholesterol per
day (28| CONCLUSION |
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Technologies are emerging that will enable the production of designer fats and oils that have a modified fatty acid profile that provides both nutritional and processing benefits. Based on a large body of evidence, it is apparent that the optimal diet for reducing risk of chronic diseases is one in which saturated fatty acids are reduced and trans fatty acids from manufactured fats are virtually eliminated. Because of the growing health benefits recognized for unsaturated fatty acids, it is likely that a mixture of these fatty acids in the diet will confer the greatest health benefits within the context of a total fat intake that is considered moderate. Given the limited amount of evidence to date on the effect of individual fatty acids on many of the variables discussed in this meeting summary, it is not possible to incorporate specific advice on all the points raised into population-wide dietary guidelines. As the evidence base strengthens, it will be important to reevaluate the current guidelines on a regular basis and modify them, if necessary, in light of substantive new findings.
| APPENDIX 1 |
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Welcome/Opening Remarks, Discussant, and Conference Discussion (Closing): Robert H. Eckel, MD, University of Colorado, Health Sciences Center, Division of Endocrinology, Denver, Colo.
Overview: Rationale for Dietary Fat Guidelines: Scott M. Grundy, MD, PhD, University of Texas Southwestern Medical Center at Dallas, Dallas, Tex.
Analysis and Interpretation of the Epidemiological and Clinical Trial Scientific Evidence for Fatty Acid Relationships/Effects on Disease End Points: Thomas A. Pearson, MD, PhD, Department Chair, Community and Preventive Medicine, Albert D. Kaiser Professor, University of Rochester, Rochester, NY.
Epidemiological and Clinical Trial Evidence for the Relationship Between Type of Fat and CVD Risk: Frank Sacks, MD, Associate Professor of Nutrition, Harvard School of Public Health, Department of Nutrition, Boston, Mass; Tim Byers, MD, Professor, Department of Preventive Medicine and Biometrics, University of Colorado School of Medicine, Denver, Colo.
Fatty Acids in Atherosclerosis: Lawrence L. Rudel, PhD, Department of Pathology, Wake Forest University School of Medicine, Section of Comparative Medicine, Winston-Salem, NC.
Effects of Fatty Acids on Lipids and Lipoproteins: Margo A. Denke, MD, Associate Professor, University of Texas Southwestern Medical Center at Dallas, Dallas, Tex.
General Discussion and AHA Dietary Guidelines: Ronald M. Krauss, MD, Senior Scientist and Head of the Molecular Medicine Department, University of California at Berkeley, Lawrence Berkeley National Laboratory, Berkeley, Calif.
Insulin Secretion: Daniel T. Stein, MD, Albert Einstein College of Medicine, Bronx, NY.
Insulin Action: Greg Cooney, PhD, Senior Research Fellow, Metabolism and Diabetes Program, Garvan Institute of Medical Research, St. Vincents Hospital, Sydney, Australia.
Hemostatic Factors: Peter Marckmann, MD, DSc, Associate Professor, Research Department of Human Nutrition, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Platelet Function: Russell P. Tracy, PhD, Professor of Pathology and Biochemistry, Director, Laboratory for Clinical Biochemistry Research, University of Vermont, Colchester, Vt.
Vascular Reactivity: Robert A. Vogel, MD, Herbert Berger Professor of Medicine and Head, Division of Cardiology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Md.
Blood Pressure: Lawrence J. Appel, MD, MPH, The Johns Hopkins University, Baltimore, Md.
Fatty Acids in the Diet and Food Supply: Eileen Kennedy, DSc, United States Department of Agriculture, Office of Research, Education & Economics, Washington, DC.
Biomarkers to Assess Fatty Acid Intake: Hannia Campos, PhD, Assistant Professor, Harvard School of Public Health, Department of Nutrition, Boston, Mass.
New Technologies to Manipulate Dietary Fatty Acids: Virginia Ursin, PhD, Nutrition Sector, Monsanto Company, Calgene Campus, Davis, Calif.
Technologies to Modify Fatty Acids: Mike Rudrum, PhD, Unilever Research Vlaardingen, Vlaardingen, The Netherlands. Discussant: Barbara V. Howard, PhD, President, Medlantic Research Institute, Washington, DC.
Dietary Recommendations for Fatty Acids: Peter L. Zock, PhD, Wageningen Center for Food Sciences, Nutrition and Health Program, Wageningen University, Wageningen, The Netherlands.
Dietary Recommendations for Fatty Acids: Gabriele Riccardi, MD, Institute of Internal Medicine and Metabolic Diseases, Second Medical School, University of Naples, Napoli, Italy.
Recommendations for Dietary Fat: Where We Are and Where We Could Go: Alice H. Lichtenstein, DSc, Professor of Nutrition, HNRC/Tufts University, Boston, Mass.
| FOOTNOTES |
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| REFERENCES |
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1.
Hu FB, Stampfer MJ, Manson J, et al Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med 1997;337:1491-1499
2. Sacks FM. Dietary prevention trials. In: Hennekens CH, Buring JE, Manson JE, Ridker PM, eds. Clinical Trials in Cardiovascular Disease: A Companion to Braunwalds Heart Disease. Philadelphia, Pa: WB Saunders Co; 1999: 423431.
3. Keys A, Anderson JT, Grande F. Serum cholesterol response to changes in diet, IV: particular saturated fatty acids in the diet. Metabolism 1965;14:776-787
4. Hegsted DM, McGandy RB, Myers ML, et al Quantitative effects of dietary fat on serum cholesterol in man. Am J Clin Nutr 1965;17:281-295[Medline]
5.
De Lorgeril M, Salen P, Martin JL, et al Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Heart Study. Circulation 1999;99:779-785
6. Singh RB, Rastoqi SS, Verma R, et al Randomised controlled trial of cardioprotective diet in patients with recent acute myocardial infarction: results of one year follow up. BMJ 1992;304:1015-1019
7. Burr ML, Fehily AM, Gilbert JF, et al Effects of changes in fat, fish and fibre intakes on death and myocardial reinfarction: Diet And Reinfarction Trial (DART). Lancet 1989;2:757-761[Medline]
8. GISSI Investigators Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione TRIAL: Gruppo Italiano per lo Studio della Sopravvivenza nellInfarto miocardico. Lancet 1999;354:447-455[Medline]
9.
Rudel LL, Parks JS, Sawyer JK Compared with dietary monounsaturated and saturated fat, polyunsaturated fat protects African green monkeys from coronary artery atherosclerosis. Arterioscler Thromb Vasc Biol 1995;15:2101-2110
10. Rudel LL, Hains JL, Sawyer JK, et al Hepatic origin of cholesteryl oleate in coronary artery atherosclerosis in African green monkeys: enrichment by dietary monounsaturated fat. J Clin Invest 1997;100:74-83[Medline]
11. Vogel RA Brachial artery ultrasound: a noninvasive tool in the assessment of triglyceride-rich lipoproteins. Clin Cardiol 1999;22(6 suppl):II34-II39[Medline]
12.
Willet WC Diet and health: what should we eat?. Science 1994;264:532-537
13.
Schatzkin A, Lanza E, Corle D, et al Lack of effect of a low-fat, high-fiber diet on the recurrence of colorectal adenomas: Polyp Prevention Trial Study Group. N Engl J Med 2000;342:1149-1155
14. Stein DT, Stevenson BE, Chester MW, et al The insulinotropic potency of fatty acids is influenced profoundly by their chain length and degree of saturation. J Clin Invest 1997;100:398-403[Medline]
15. Griffin ME, Marcucci MJ, Cline GW, et al Free fatty acid-induced insulin resistance is associated with activation of protein kinase C theta and alterations in the insulin-signaling cascade. Diabetes 1999;48:1270-12741[Abstract]
16. Schmitz-Peiffer C, Browne CL, Oakes ND, et al Alterations in the expression and cellular localization of protein kinase C isozymes epsilon and theta are associated with insulin resistance in skeletal muscle of the high-fat-fed rat. Diabetes 1997;46:169-178[Abstract]
17.
Schmitz-Peiffer C, Craig DL, Biden TJ Ceramide generation is sufficient to account for the inhibition of the insulin-stimulated PKB pathway in C2C12 skeletal muscle cells pretreated with palmitate. J Biol Chem 1999;274:24202-24210
18. Howard BV. Diet, insulin resistance, and atherosclerosis. In: Baba S, Kaneko T, eds. Diabetes. New York: Elsevier Science BV; 1995: 446450.
19.
Pearson TA, LaCava J, Weil HF Epidemiology of thrombotic-hemostatic factors and their associations with cardiovascular disease. Am J Clin Nutr 1997;65(5 suppl):1674S-1682S
20. Marckmann P. Diet, blood coagulation and fibrinolysis. Dan Med Bull 1995;42:410-425[Medline]
21. Appel LJ, Miller ER, III, Seidler AJ, et al Does supplementation of diet with "fish oil" reduce blood pressure?. A meta-analysis of controlled clinical trials. Arch Intern Med. 1993;153:1429-1438
22. Morris MC, Sacks FM. Dietary fats and blood pressure. In: Swales JD, ed. Textbook of Hypertension. Oxford, UK: Blackwell; 1994: 605618.
23.
De Caterina R, Liao JK, Libby P. Fatty acid modulation of endothelial activation. Am J Clin Nutr 2000;71(suppl 1):213S-223S
24.
Kennedy ET, Bowman SA, Powell R. Dietary-fat intake in the US population. J Am Coll Nutr 1999;18:207-212
25. FarquharJW Ahrens, EH Jr Effects of dietary fats on human erythrocyte fatty acid patterns. J Clin Invest 1963;42:675-685
26. Dayton S, Hashimoto S, Dixon W, et al Composition of lipids in human serum and adipose tissue during prolonged feeding of a diet high in unsaturated fat. J Lipid Res 1966;7:103-111[Abstract]
27. Knutzon DS, Knauf V. Manipulating seed oils for polyunsaturated fatty acid content. In: Harwood J, ed. Plant Lipid Biosynthesis: Fundamentals and Agricultural Applications. Cambridge, UK: University Press; 1998: 287. Society for Experimental Biology Seminar Series 67.
28. Summary of the second report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. JAMA. 1993;269:30153023.
29. Nutrition and Your Health: Dietary Guidelines for Americans, 2000. Available at: http://www.usda.gov/cnpp/DietGd.pdf. Accessed December 22, 2000.
30.
Krauss RM, Eckel RH, Howard B, et al AHA dietary guidelines: revision 2000: a statement for healthcare professionals from the Nutrition Committee of the American Heart Association. Circulation 2000;102:2284-2299
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