THE PORTFOLIO DIET FOR PEOPLE WITH TYPE 2 DIABETES

The Portfolio Diet is a plant-based dietary approach designed to lower cholesterol levels and reduce the risk of common cardiovascular diseases like heart disease and stroke. As the name suggests, it includes a select “portfolio” of foods, comprised of 5 key pillars, each consumed daily:

1. 50 g of plant-based proteins such as soy, soy milk and other legumes;
2. 20 g of viscous fibre from foods such as oats, barley, berries, apples and citrus fruit;
3. 45 g of nuts and seeds;
4. 2 g of phytosterols (plant sterols) that reduce cholesterol absorption through fortified foods or supplements; and
5. 45 g of avocado and healthy plant-based oils high in monounsaturated fat.

It was conceived by Dr. David J.A. Jenkins based at the University of Toronto. Regular readers of GI News will know that Dr Jenkins was also behind the original Glycemic Index (GI) research, so perhaps unsurprisingly, the Portfolio Diet is also rich in low glycemic index foods and beverages.
Randomized controlled trials in humans have shown that the Portfolio Diet results in clinically meaningful reductions in low-density lipoprotein (LDL) cholesterol (“bad” cholesterol), equivalent to statin medications (1). Additionally, observational studies have shown that the Portfolio Diet is associated with improvements in blood glucose levels and reduced incidence (development of new cases) of type 2 diabetes and cardiovascular disease (2,3).

While the scientific evidence for cardiovascular benefits are compelling, it has mostly been conducted in people without diabetes. Recently, the University of Toronto team decided to see if the Portfolio Diet would help blood glucose management in people with type 2 diabetes (4).

A total of 267 adults (average 62 years old) with type 2 diabetes received either a low-GI or a high-cereal fibre diet for either 6 months or 3 years as part of 2 randomised controlled trials. The low-GI diets included the dietary advice to consume lower-GI foods, including oats, barley, oat bran and psyllium breads, peas, beans, chickpeas and lentils, pasta, and vegetables and fruit, particularly eggplant and okra and temperate climate fruit. Adherence to the Portfolio Diet was measured using a validated clinical Portfolio Diet Score (c-PDS).

The researchers found that at 6 months, greater adherence to the Portfolio Diet led to lower glycated haemoglobin (HbA1c) levels. Indeed, every 7.5-point (30%) increase in the c-PDS was associated with a 0.3% reduction in HbA1c, with nuts and seeds and plant proteins (i.e., legumes) having the greatest impact.

While not for everyone, a predominantly vegetable-based diet high in plant-based proteins and low GI carbohydrates can help significantly improve blood glucose management in people with type 2 diabetes.

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