The portfolio diet: A smart investment for your heart

The portfolio diet, which emphasizes plant foods rich in fiber and healthy fats, was conceived some 20 years ago. Since then, many studies have documented the diet's ability to lower harmful LDL cholesterol. But because none of those trials lasted any longer than six months, the portfolio diet's long-term returns were unknown. Now, new research suggests that the more closely you follow a portfolio-style eating pattern, the greater your protection against heart disease and stroke.

Published Nov. 28, 2023, in Circulation, the study included more than 210,000 people who enrolled in three Harvard-led health studies in the 1980s and 1990s. Using data from diet questionnaires the participants filled out every four years, researchers scored each person's diet based on how well it complied with the portfolio eating pattern. After 30 years of follow-up, researchers compared the scores with the participants' health outcomes. People with higher scores (that is, those who followed the diet most closely) had a 14% lower risk of heart disease compared to those with lower scores.

"A lot of different foods can lower LDL cholesterol, but only by a little bit — about 5% to 10%. The idea behind the portfolio diet was to combine many of these foods together to get a larger reduction," says registered dietitian Andrea Glenn, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health and a co-author of the study.

Earlier studies found that the portfolio diet may lower LDL cholesterol by as much as 30%. In the new study, people with higher portfolio diet scores not only had better cholesterol profiles, they also had lower blood levels of C-reactive protein and other inflammatory substances compared to people with lower scores, says Glenn. Inflammation is a key player in the buildup of fatty plaque inside arteries — the root cause of most heart attacks.

What's in the portfolio diet?

The diet discourages foods from animal sources, particularly red and processed meat, high-fat dairy, and eggs, which means it's naturally low in saturated fat and dietary cholesterol, both of which raise LDL cholesterol in the body. The featured foods fall into five main categories. Here's a rundown, including ways to incorporate them into your meals.

Plant protein. This includes beans, lentils, and peas (collectively known as legumes), with a specific focus on foods made from soybeans, says Glenn. In 1999, the FDA authorized a health claim for soy protein, noting that consuming at least 25 grams daily as part of a diet low in cholesterol and saturated fat may lower the risk of heart disease. Soy protein comes in many different forms: edamame (whole, green soybeans often sold frozen in pods), soy milk, soy yogurt, tofu, or tempeh (fermented soybeans). But there are many other legumes to choose from, including black beans, pinto beans, chickpeas (garbanzo beans), lentils, and split dried green peas.

Nuts and seeds. All nuts — including almonds, cashews, hazelnuts, pecans, pistachios, walnuts — are included. So are all sorts of seeds: chia, flax, hemp, pumpkin, sunflower, sesame.

Viscous fiber. Viscous fiber is a type of soluble fiber that has a somewhat sticky quality, says Glenn. "It's found in grains like oats and barley, certain vegetables such as eggplant and okra, and fruits like apples, oranges, berries, and persimmons," she says. One of the best sources is psyllium seed husks, which transform into a viscous gel when dissolved in water. People may be familiar with psyllium because the powdered husks are the key ingredient in Metamucil, which helps treat constipation, says Glenn. But you can buy plain psyllium seed husk in stores.

In the intestines, viscous fiber binds to bile acids, which carry fats from your small intestine into the large intestine for excretion. This triggers your liver to create more bile acids—a process that requires cholesterol. If the liver doesn't have enough cholesterol, it draws more from the bloodstream, in turn lowering your circulating LDL. In addition, viscous fiber is fermented in the gut into short-chain fatty acids, which may also inhibit cholesterol production.

Plant sterols. Also known as phytosterols, these exist naturally in nuts, soybeans, peas, and canola oil. Plant sterols have a structure similar to cholesterol; eating them helps limit the amount of cholesterol your body can absorb. Margarine enriched with plant sterols, such as Benecol, provides a concentrated dose. But you have to eat quite a bit (about four tablespoons daily) to make a difference, says Glenn. It tastes similar to other types of margarine and can be used as a spread for toast and in sandwiches.

Monounsaturated fats. Used in place of saturated fats, these fats help lower cholesterol. Extra-virgin olive oil is the top recommendation; other good options include canola, soybean, or "high-oleic" sunflower or safflower oils. Stock a variety of these oils for use on salads and in cooking and baking. Avocados are also rich in monounsaturated fat.

You don't need to embrace every aspect of the diet to reap benefits, says Glenn. "But we saw a dose-related response in the study, which means that the more of these foods were added to the diet, the lower the risk of cardiovascular disease we observed," she says.

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