Duvall 1 The Role of Monounsaturated Fatty Acids in Cardiovascular Disease and Diabetes Mellitus Type 2 By Jovan Duvall May 21 st 2012 NUTR 420
Duvall 2 Introduction American s waistbands are not the only thing increasing. Issues of chronic diseases such as cardiovascular disease (CVD) and Diabetes Mellitus Type 2 are also on the rise and topping off the United States list of leading causes of death 1. Recent research has lead to the idea that monounsaturated fatty acids (MUFAs) may be helpful to decrease risks for both cardiovascular disease (CVD) and diabetes mellitus type 2 (T2DM) when used as a replacement for dietary saturated fatty acids (SFAs). What are Monounsaturated Fatty Acids? Monounsaturated fatty acids are fatty acid chains with a single double bond and are liquid at room temperature 2. Common forms of MUFAs are palmitoleic acid (16:1n- 7) and oleic acid (18:1n-9) 2. MUFAs are commonly consumed as dietary oils such as olive and canola varieties, but are also found in avocados, nuts and seeds, and selected animal products 2. Monounsaturated Fatty Acids and Cardiovascular Disease MUFAs have made many news headlines in the form of the Mediterranean diet. Compared to the American diet, the Mediterranean diet replaces many SFAs with MUFAs. Both epidemiological and randomized clinical studies have shown the Mediterranean diet to have an inverse effect on coronary heart disease risk 2. This has lead researchers to the conclusion that perhaps dietary fat quality is more important than dietary fat quantity 2. Main predictive biomarkers for CVD risk include elevated low-density lipoprotein cholesterol (LDL-C), and the total cholesterol (TC): high-density lipoprotein
Duvall 3 cholesterol (HDL-C) 2. Inflammatory markers such as oxidation of LDL-C may also be helpful in determining CVD risk 3. One review of over 147 articles reported that when MUFAs are used to isocalorically replace dietary SFAs, there is a decrease in serum LDL-C, a preservation of HDL-C and improvements in TC:HDL-C 2. A smaller study of 37 volunteers demonstrated supporting evidence of this review and found that both low and high fat diets that replaced SFAs with MUFAs resulted in a decrease in TC, LDL-C and LDL-C:HDL-C 4. The study also reported a decrease in LDL- C susceptibility to oxidation. However, the small study correlated these diets to a decrease in HDL-C, which the researches attributed to the replacement of SFAs with cisunsaturated fatty acids causing a lowering of the TC:HDL-C 4. This was however, a very small study on a very specific population of volunteer participants ages 18-34y 4. A second review of comparative size concluded that there is not a strong association between MUFAs and coronary heart disease (CHD), a subset of cardiovascular disease 5. The review also reported that some studies associated MUFAs with an increased risk of CHD, but concluded that this increase was likely due to mutual dietary sources of MUFAs and SFAs in dairy and animal products 5. This review indicates that simply consuming more MUFAs may not decrease CVD risk, but replacing SFAs with MUFAs may 5. A third review of around 100 articles concluded that MUFAs raise HDL-C, lower LDL-C, decrease LDL-C susceptibility to oxidation, reduce other inflammatory biomarkers and also could have an antihypertenstive effect and improve insulin sensitivity 6. The review also noted that excessive reductions in SFAs may not be
Duvall 4 necessary for some populations such as active, non-overweight subjects with no risk factors and may also not be necessary for overweight subjects 6. Overall MUFAs appear to be beneficial in reducing risk factors for CVD across many populations and study sizes. It has been demonstrated that MUFAs lower LDL-C and LDL-C oxidation, raise or preserve HDL-C, improve the TC:HDL-C, reduce TC, reduce inflammatory biomarkers, and may be antihypertensive and improve insulin sensitivity. Monounsaturated Fatty Acids and Diabetes Mellitus Type 2 Current literature debates whether a diet high in carbohydrates (CHO) or high in MUFAs is more beneficial to patients with T2DM. One technical review reported that both diets high in MUFA and diets low in fat and high in CHO show improvements in glucose tolerance and lipids when compared to diets high in SFAs 7. These two diets are also shown to decrease plasma LDL-C equivalently 7. The review then stated that the high caloric intake from high MUFAs diets compared to a diet high in CHO is of concern to diabetic patients due to excess energy and weight gain 7. A second review concluded that while the optimal ratio of SFAs and MUFAs in a diabetic diet is unknown, improving lipid quality should be a major strategy for preventing and managing T2DM 8. The review further concluded that replacing SFAs with MUFAs encourages improvements in insulin sensitivity, reduced diabetes risk, lowers serum LDL-C:HDL-C ratio and Triacylglycerols 8. This second review offers many explanations for why MUFAs are effective in the prevention and management of T2DM. One method is that dietary fat composition affects cell membranes, which can
Duvall 5 alter cellular functions such as membrane fluidity, ion permeability, insulin receptor binding or affinity 8. This in turn could affect insulin sensitivity at both the tissue and whole body levels 8. Conclusion Evidence supports that MUFAs appear to be beneficial for decreasing CVD risks by lowering LDL-C and LDL-C oxidation, raising or preserving HDL-C, improving the TC:HDL-C, reducing TC, reducing inflammatory biomarkers, and possibly aiding as an antihypertensive and also improving insulin sensitivity. MUFAs have also been shown to decrease T2DM risks including increasing insulin sensitivity and glucose tolerance when used as replacement for SFAs. I would recommend replacing SFAs with MUFAs to patients concerned about CVD and T2DM. I would, however, emphasize the importance of watching the amount of total fat consumption and total caloric intake when avoiding weight gain or combating obesity.
Duvall 6 References 1.Center for Disease Control and Prevention. Leading Causes of Death. January 2012. Available from: http://www.cdc.gov/nchs/fastats/lcod.htm. Accessed May 15, 2012. 2. Gillingham L, Harris-Janz S, Jones P. Dietary Monounsaturated Fatty Acids Are Protective Against Metabolic Syndrome and Cardovascular Disease Risk Factors. Lipids. 2011;46:209-228. 3.Mahan K, Escott-Stump S, Raymond J. Krause s Food and the Nutrition Care Process. Missouri: Elsevier Saunders;2012. 4. Egert S, Kratz M, Kannenberg F, Fobker M, Wahrburg U. Effects of high-fat and lowfat diets rich in monounsaturated fatty acids on serum lipids, LDL size and indices of lipid peroxidation in healthy non-obese men and women when consumed under controlled conditions. European Journal Of Nutrition [serial online]. February 2011;50(1):71-79. Available from: Academic Search Premier, Ipswich, MA. Accessed May 21, 2012. 5. Erkkila A, de Mello V, Riserus U, Laaksonen D. Dietary fatty acids and cardiovascular disease: An epidemiological approach. Progress in Lipid Research. January 2008;47:172-187. 6. Lecerf J. Fatty Acids and Cardiovascular Disease. Nutrition Reviews. April 2009;67(5):273-283. 7. Franz M, Bantle J, Beebe C, Brunzell J, Chiasson J, Holzmeister L, Hoogwerf B, Mayer-Davis E, Mooradian A, Purnell J, Wheeler M. Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related Complications. Diabetes Care. January 2002; 25 (1). 8. Riserus U, Willett W, Hu F. Dietary Fats and Prevention of Type 2 Diabetes. Progress in Lipid Research. October 2008;48:44-51.