The Portfolio Diet: A Menu for Hyperlipidemia Treatment
The Portfolio Diet: A Menu for Hyperlipidemia Treatment
Abstract and Commentary
By Susan T. Marcolina, MD, FACP, Internist and Geriatrician, Issaquah, WA. Dr. Marcolina reports no financial relationships relevant to this field of study.
Synopsis: The cholesterol-lowering foods specified in the portfiolo diet of Jenkins et al are effective treatments for elevated LDL-C levels under real world living conditions. Not surprisingly, overall compliance with dietary instructions regarding portions of the four principal portfolio diet components (tree nuts, soy protein, soluble fiber, and plant sterols and stanols) was significantly associated with percentage reduction of LDL-C in participants completing the study.
Source: Jenkins DJA, et al. Effect of a dietary portfolio of cholesterol-lowering foods given at 2 levels of intensity of dietary advice on serum lipids in hyperlipidemia. A randomized controlled trial. JAMA 2011;306:831-839.
The portfolio diet effectively decreases elevated cholesterol levels under metabolically controlled conditions and its components (tree nuts, soy protein, soluble fiber, and plant sterols and stanols) are all FDA-approved foods that can claim heart-healthy benefits. This prospective single-blind, controlled, parallel-design study conducted across four Canadian medical centers evaluated the effects of two intensities of portfolio dietary counseling (intensive, consisting of seven total face-to-face counseling sessions, vs routine counseling with only two clinical counseling sessions over the 6-month study interval) compared to a control diet (dietary counseling focused on low fat dairy products, fruit, vegetables and whole grains, excluding specific portfolio components) on 345 hyperlipemic participants (62% female). Inclusion criteria specified men and postmenopausal women in the low (0-10%) and intermediate (10-19%) Framingham 10-year risk categories with LDL-C values ranging from 135-205 mg/dL and 116-178 mg/dL, respectively.
During the 6-month study period, dietitians counseled participants to follow weight-maintenance vegetarian diets from foods purchased in grocery and health food stores. Dietitian counseling sessions were 1 hour in duration for the initial visit and 30-40 minutes at subsequent ones. For the dietary portfolio interventions, dietitians incorporated the specific study foods into the 7-day food diaries of participants. To further facilitate the daily incorporation of the correct portions of each of the portfolio components, participants received a 7-day food checklist with an illustrated reference booklet (See Table 1). Consumption of peas, beans, and lentils also were encouraged. All participants received measuring utensils to facilitate portion control compliance. None of the participants took lipid-lowering medications during the study and all lost similar amounts of weight (average loss of 1.2 kg, 1.7 kg, and 1.5 kg for the intensive portfolio, routine portfolio and control diets, respectively). Adherence to the four portfolio components was estimated from 7-day food records kept by each participant, and mean adherence was found to be 46.4% for the intensive and 40.6% for the routine portfolio diets. Lipoprotein profiles and high sensitivity C-reactive protein (hsCRP) levels were obtained at weeks 0 and 24 after dietary treatments.
The investigators noted statistically significant average reductions in LDL-C levels of 13.1% (P < 0.001) and 13.8% (P < 0.001) for the routine and intensive portfolio diets, respectively from baseline compared to a 3.0% (P = 0.06) reduction in the control diet. The percentage LDL-C reductions for each dietary portfolio arm were significantly greater than the control diet with P < 0.001, for both. There were no significant changes in triglycerides or high-density lipoprotein cholesterol (HDL-C) levels. These results were comparable to LDL-C reductions obtained with a combination of a diet low in saturated fat and cholesterol plus first-generation statin therapy with lovastatin.1 The LDL-C decrements were accompanied by statistically significant decreases in the TC:HDL-C ratios of 8.2% and 6.6% for the routine and intensive dietary portfolio interventions, respectively. There were no significant differences between the dietary portfolio intensities on the lipoprotein profiles. None of the treatments significantly altered C-reactive protein (CRP) levels. The intensive dietary portfolio significantly reduced diastolic blood pressure an average of 2.1 mm compared to the control diet, but did not significantly reduce systolic blood pressure.
The authors concluded that hyperlipidemic patients could significantly lower their LDL-C with the portfolio diet and two sessions of dietary guidance and support over a 6-month period. Given that the patients bought and prepared their own foods during this time, the results demonstrate that this dietary intervention is both feasible for use in the outpatient primary care setting and produces important measurable improvements in LDL-C, an important risk factor for coronary artery disease. Since the patients in this study were predominantly white (79%), with low to intermediate cardiovascular risk, the findings cannot be generalized to other, more diverse, higher risk populations.
Commentary
Reducing cardiovascular morbidity and mortality is the objective for hyperlipidemia treatment and generally statins are the drugs best proven to accomplish this, particularly in patients with established cardiovascular disease ([CVD], secondary prevention), diabetes, and in patients without established CVD but at high risk for cardiovascular events (Framingham 10-year risk estimate > 20%). However, for patients at lower risk, as in this study, or for patients who have had adverse effects from or wish to avoid pharmacotherapy, counseling for diet and physical activity modification is the foundation for primary CVD prevention, since dietary approaches can lower total cholesterol, LDL-C, and triglyceride levels, and regular exercise can raise HDL-C levels and lower triglycerides. Thus, both approaches combine to improve the atherogenic lipoprotein profile as well as overall physical and cardiovascular fitness.2 Since this was not a clinical outcomes study, however, further evaluation is necessary to determine whether cholesterol reduction through the addition of portfolio foods to daily menus will be associated with a reduction in CVD events.
Nonpharmacologic treatment of hyperlipidemia with the Therapeutic Lifestyle Changes approach has been a recommended initial treatment by the Adult Treatment Panel III of the National Cholesterol Education Program (NCEP) for more than a decade based upon its review of the available evidence in 1999.3 The Mediterranean diet also has been recognized as a heart-healthy diet that emphasizes intake of tree nuts, monounsaturated fats (such as olive oil), fish, fresh fruit, and vegetables; limited intake of red meat and poultry; and moderate consumption of red wine.
The portfolio diet of Jenkins et al provides a multifaceted approach to improving lipoprotein profiles that offers patients the option to adopt a few or all of the components, depending upon their motivation, food tolerances, underlying cardiovascular risk factors, and lipoprotein levels. The four food elements of this diet contribute toward lipid-lowering effects. Tree nuts have an FDA-approved health claim for decreasing risk of heart disease if eaten as part of a diet low in saturated fat and cholesterol. Since they are calorically dense, a 22.5 g serving most days of the week should be incorporated isocalorically. Almonds are used in the portfolio diet, but walnuts or pecans consumed isocalorically as a 1.5 ounce serving are also FDA approved for the primary prevention of heart disease. Brazil nuts, macademia nuts, cashews, and some types of pine nuts, however, are excluded because of their high saturated fat content.4
Plant sterols or phytosterols have a chemical structure similar to cholesterol and compete for absorption in the digestive tract. Intake of 2 g of plant sterols reduces LDL cholesterol by approximately 10%, while higher doses do not further augment cholesterol-lowering effects. They are available commercially in the form of spreads such as Promise and Benecol.5
Soy protein promotes enhanced insulin sensitivity in addition to its beneficial effects on lipoprotein profiles.6
Other foods recommended in the portfolio diet, such as fruits and legumes, are low glycemic index foods and rich sources of antioxidants and soluble fiber.
In a separate randomized, controlled, 1-month crossover study separated by a 2-week washout, Jenkins et al evaluated the effects of the daily addition of 454 g of strawberries (112 kcal) in place of sweets or an isocaloric portion of oat bran bread to the portfolio diets of hyperlidemic subjects.7 The strawberry supplementation reduced oxidative damage to LDL-C, measured as thiobarbituric acid-reactive substances, while maintaining the reductions of LDL-C and TC/HDL-C from the portfolio diet and enhancing its palatability.8,9
Another specific fruit enhancement to the portfolio diet is the addition of kiwis, particularly if triglyceride levels are not at NCEP goal. In a small Norwegian randomized, crossover study, consumption of 2 kiwi fruit/day for 28 days reduced triglyceride levels by 15% and platelet aggregation by collagen by 18% compared to the control group.10
The present study demonstrated that two moderately short counseling sessions over a 6-month period on the portfolio diet (routine portfolio counseling) are suitable in the ambulatory setting and produce measurable, statistically significant lowering of LDL-C levels and salutary effects on HDL-C in free living (and eating) adults. The study subjects did not have any serious adverse reactions to the prescribed diet, although soy and tree nut allergies are valid reasons for eliminating one or more elements of the diet. Only two study subjects experienced skin rashes, one from soy and one from almonds, and both had positive skin tests that required them to discontinue study participation.
The portfolio diet offers versatile ways in which hyperlipidemic individuals can use daily food choices as opportunities to improve their LDL-C numbers and possibly their CVD risk. Testing the portfolio diet in more diverse patients with clinical outcomes may clarify the use of these specific foods for cardiac risk reduction.
References
1. Jenkins DJ, et al. Effects of a dietary portfolio of cholesterol-lowering foods vs lovastatin on serum lipids and C-reactive protein. JAMA 2003;290:502-519.
2. Katcher HI, et al. Lifestyle approaches and dietary strategies to lower LDL-cholesterol and triglycerides and raise HDL-cholesterol. Endocrinol Metab Clin North Am 2009;38:45-78.
3. Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 2001;285:2486-2497.
4. U.S. Food and Drug Administration. FDA moves forward on qualified health claims 2003 July 15. Press Release. March 31, 2004.
5. Katan MB, et al. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clin Proc 2003;78:965-978.
6. Jayagopal V, et al. Beneficial effects of soy phytoestrogen intake in postmenopausal women with type 2 diabetes. Diabetes Care 2002;25:1709-1714.
7. Jenkins DJA, et al. The effect of strawberries in a cholesterol-lowering dietary portfolio. Metab Clin Exp 2008;57:1636-1644.
8. Cao G, et al. Serum antioxidant capacity is increased by consumption of strawberries, spinach, red wine or vitamin C in elderly women. J Nutr 1998;128:2383-2390.
9. Hannum SM. Potential impact of strawberries on human health: A review of the science. Crit Rev Food Sci Nutr 2004;44:1-17.
10. Duttaroy AK, Jorgensen A. Effects of kiwi fruit consumption on platelet aggregation and plasma lipids in healthy human volunteers. Platelets 2004;15:287-292.
The cholesterol-lowering foods specified in the portfiolo diet of Jenkins et al are effective treatments for elevated LDL-C levels under real world living conditions. Not surprisingly, overall compliance with dietary instructions regarding portions of the four principal portfolio diet components (tree nuts, soy protein, soluble fiber, and plant sterols and stanols) was significantly associated with percentage reduction of LDL-C in participants completing the study.Subscribe Now for Access
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