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The Portfolio diet in combination with an NCEP Step II diet may reduce multiple cardiometabolic risk factors

Chiavaroli L, Nishi SK, Khan TA, et al. Portfolio dietary pattern and cardiovascular disease: A systematic review and meta-analysis of controlled trials Prog Cardiovasc Dis. 2018;61:43-53.

Review question

What is the effect of the Portfolio diet  in combination with the National Cholesterol Education Program (NCEP) Step II diet on LDL-cholesterol (bad cholesterol) and other risk factors for diabetes and cardiovascular disease (aka cardiometabolic risk factors), compared to the NCEP Step II diet alone?  

Background

The Portfolio diet is a plant-based diet consisting of four types of foods, which research has shown have a cholesterol-lowering effect: ≥ 45 g/day nuts (e.g., peanuts), ≥20 g/day viscous fibre that dissolves in water (e.g., comes from oats, barely, etc.), 2 g/day plant sterols (e.g., plant sterol-enriched margarine), and ≥ 50 g/day plant proteins (e.g., from soy or dried seeds such as beans, lentils or peas). This diet has been recommended in some guidelines developed by world leaders in the fields of diabetes and heart health. The NCEP Step II diet consists of 30% or less calories as total fat, less than 7% calories as saturated fat, and less than 200 mg/day of cholesterol, and is sometimes used with the Portfolio diet. The European Association for the Study of Diabetes, which has not made specific recommendations for the Portfolio diet, ordered a systematic review and meta-analysis to decide if changes to their recommendations were needed. The review focused on the Portfolio diet in combination with the NCEP Step II diet.

How the review was done

This is a systematic review and meta-analysis of five randomized controlled trials and non-randomized controlled trials published between 2002 and 2011, including a total of 439 participants.

• Participants were adults who were generally between 54-65 years of age and overweight, and who had high cholesterol, but no history of diabetes or cardiovascular disease.  
• Participants were on an NCEP Step II diet before the start of each study included in the review. Then, during each study, participants received one of two Portfolio diet-related approaches: 1) they were given food so they could follow either the standard Portfolio diet or an enhanced version that was high in monounsaturated fat (e.g., a type of fat found in sunflower oil or avocado); or 2) they were given either routine nutritional advice (two 40-60 minute clinic visits) or intensive nutritional advice (seven 40-60 minute clinic visits) from a dietician about incorporating foods from the Portfolio diet into their own diet.
• Researchers measured changes in: indicators for blood sugar control; LDL-cholesterol and other types of fat found in the blood (total cholesterol [TC], triglycerides [TG], non-HDL cholesterol, and HDL-cholesterol); apolipoprotein B [apoB] (helps transport fat); blood pressure; C-reactive protein [CRP] (a marker for inflammation); estimated 10-year risk of coronary heart disease; and body weight. 
• Results were compared to people in control groups who either received dietary advice on the NCEP Step II diet or food that met the criteria of the NCEP Step II diet so they could follow it.
• All trials included in the review received funding from both agency (e.g., government funded health research agencies) and industry (e.g., leaders in the field of diabetes) organizations.

What the researchers found

No trials that examined the effect of the Portfolio diet on measures of blood sugar control were found. Overall, the Portfolio diet in combination with an NCEP Step II diet was effective in reducing the following cardiometabolic risk factors in adults with high cholesterol, compared to the NCEP Step II diet alone:

• LDL-cholesterol, TC, TG, non-HDL- cholesterol, and apoB
• Systolic and diastolic blood pressure
• The inflammation marker CRP
• Estimated 10-year risk of coronary heart disease

However, there was no effect on HDL-cholesterol (aka good cholesterol), and weight. The evidence that supported the findings for LDL-cholesterol, TC, TG, non-HDL-C, apoB and weight was rated as being of high certainty, while the evidence for HDL-cholesterol, blood pressure, CRP, and 10-year coronary heart disease risk was rated as being of moderate certainty. More research with larger, higher quality studies is needed to confirm the findings in this review, and to establish the diet’s impact on actual heart-related events.   

Conclusion

The Portfolio diet in combination with the NCEP Step II diet may lower multiple cardiometabolic risk factors including LDL-cholesterol, the main target for cardiovascular disease prevention. These reductions may improve the estimated 10-year coronary heart disease risk.