Ask the Expert: The Portfolio Diet - Today's Dietitian Magazine

October 2018 Issue

Ask the Expert: The Portfolio Diet
By Toby Amidor, MS, RD, CDN
Today's Dietitian
Vol. 20, No. 10, P. 10

Q: Lately, I've been hearing about the Portfolio diet. What is it, what are its health claims, and is it effective?

A: The Portfolio diet is a modified vegan diet that includes a variety—or "portfolio"—of foods shown to lower cholesterol. The theory behind it is that when these cholesterol-lowering foods are eaten together, within a healthful diet, the diet as a whole can help lower LDL cholesterol. While many of the Portfolio diet's facets already are recommended for lowering cholesterol by organizations such as the American Heart Association (AHA), other aspects still are being investigated for efficacy.

The Diet
The Portfolio diet recommends including 2 g plant sterols, primarily from plant sterol–enriched margarine; 50 g nuts (about a handful); 10 to 25 g soluble fiber from a variety of plant foods; and 50 g soy protein daily along with regular physical activity. According to the diet's founder, David J. A. Jenkins, MD, a professor in the departments of nutritional sciences and medicine at the University of Toronto in Canada, all of these foods have been shown to lower cholesterol.

The Portfolio diet also substitutes soyfoods for animal-based products. Being a version of the vegan diet, it excludes meat, poultry, seafood, dairy, and eggs.

The Research
Most of the prescribed cholesterol-lowering foods in the Portfolio diet are backed up by well-designed studies and health organization recommendations. Plant sterols have been shown to reduce CVD by blocking the absorption of cholesterol in the small intestine, which can lower LDL cholesterol by 6% to 15% without lowering HDL levels. The consumption of plant sterols doesn't appear to interfere with the action of cholesterol-lowering medications such as statins.1 The efficacy of plant sterols is so strong that the National Cholesterol Education Program recommends people with high cholesterol consume 2 g daily.2

Nuts provide unsaturated fats, antioxidants, plant sterols, protein, and fiber and are linked to CVD prevention. Studies consistently have shown that regular consumption of nuts is associated with a reduced risk of CVD.3 According to the AHA, soluble fiber from fruits, vegetables, whole grains, legumes, and pulses are recommended in a heart-healthy diet, a prescription also in alignment with the Portfolio diet.4

In 2000, the AHA encouraged adding soy protein to a diet low in saturated fat and cholesterol; however, in 2006 they determined that newer research suggests that soy protein and soy isoflavones may not have strong cholesterol-lowering abilities. Furthermore, in 2017 the FDA released a statement questioning the relationship between soy and heart health and currently is reviewing the authorized health claim.5

Numerous studies have examined the effects of the Portfolio diet on lowering cholesterol. One study assessed the effects of the Portfolio diet in 351 participants randomized to follow a low-fat diet (control), or a cholesterol-lowering dietary portfolio that involved either two clinic visits (routine) or seven clinic visits (intensive), respectively, during a six-month period. Researchers found that the percentage of LDL cholesterol reductions for each of the dietary portfolio groups were significantly greater than the control diet.6 Another study examined the effects of a modified Portfolio diet in 30 subjects with type 2 diabetes using statin medications six weeks post coronary artery bypass surgery. This version of the Portfolio diet was low fat and included 8 g/1,000 kcal viscous fiber, 17 g/1,000 kcal soy protein, and 22 g/1,000 kcal almonds. This diet resulted in a 19% relative reduction in LDL cholesterol with no change in HDL cholesterol. Homocysteine levels also dropped significantly over the study period.7

Recommendations for Clients
The Portfolio diet recommends foods strongly linked to lowering cholesterol, with the exception of soy, for which the strength of the evidence behind the FDA's heart health claim is being reassessed. Including plant sterols, nuts, fruits, vegetables, whole grains, and legumes in a cholesterol-lowering diet already is recommended by the AHA and should be part of cholesterol-lowering recommendations for clients. However, consuming soyfoods in place of any cow's milk or other animal protein may not be the best choice for all clients. Practitioners should work with clients to determine their preferred protein sources (plant, lean animal, or a combination) and encourage consumption of low-fat milk, nonfat milk, and soymilk, per the recommendations of the 2015–2020 Dietary Guidelines for Americans.

— Toby Amidor, MS, RD, CDN, is the founder of Toby Amidor Nutrition (http://tobyamidornutrition.com) and a Wall Street Journal best-selling author. Her four cookbooks are Smart Meal Prep for Beginners, The Easy 5-Ingredient Healthy Cookbook, The Healthy Meal Prep Cookbook, and The Greek Yogurt Kitchen. She's a nutrition expert for FoodNetwork.com and a contributor to US News Eat + Run, Muscle&Fitness.com, and MensJournal.com.

References
1. Phytosterols: sterols & stanols. Cleveland Clinic website. https://my.clevelandclinic.org/health/articles/17368-phytosterols-sterols--stanols

2. National Institutes of Health, National Heart, Lung, and Blood Institute. Your guide to lowering your cholesterol with TLC. https://www.nhlbi.nih.gov/files/docs/public/heart/chol_tlc.pdf. Published December 2005. Accessed August 6, 2018.

3. Kris-Etherton PM, Zhao G, Binkoski AE, Coval SM, Etherton TD. The effects of nuts on coronary heart disease risk. Nutr Rev. 2001;59(4):103-111.

4. Meal planning: the high-fiber factor. American Heart Association website. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/meal-planning-the-high-fiber-factor. Updated April 26, 2018. Accessed August 6, 2018.

5. Statement from Susan Mayne, Ph.D., on proposal to revoke health claim that soy protein reduces risk of heart disease. US Food & Drug Administration website. https://www.fda.gov/newsevents/newsroom/pressannouncements/ucm582744.htm. Updated February 23, 2018. Accessed August 6, 2018.

6. Jenkins DJ, Jones PJ, Lamarche B, 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(8):831-839.

7. Keith M, Kuliszewski MA, Liao C, et al. A modified portfolio diet complements medical management to reduce cardiovascular risk factors in diabetic patients with coronary artery disease. Clin Nutr. 2015;34(3):541-548.