In late 2023, a new study on the Portfolio diet was published. This study analysed data from over 200,000 participants over a 30-year period. To my knowledge, this is the first large-scale study investigating how adherence to the Portfolio diet in free-living people is associated with the risks of suffering from a heart attack or stroke.
The Portfolio diet is a whole food plant-based diet that includes four types of foods: viscous fibre, soy foods, nuts, and plant sterols. A 2003 randomised-controlled trial showed that high-compliance to the diet could reduce LDL-cholesterol by close to 30%, or almost as much as a first-generation statin. A later 2011 larger and longer randomised-controlled trial showed that under free-living conditions, adhering to the portfolio diet half the time was still able to deliver half the results and lower LDL-cholesterol by about 15%.
This latest study examined how adherence to the portfolio diet could lower cardiovascular disease or CVD risk by analysing data from more than 200,000 participants collected over a 30-year period, and I will be discussing three main takeaways from the study.
Before that, it might be instructive to understand more about the datasets that were used in this study. The participants in this study were all healthcare professionals, with about three-quarters being women from the first two Nurses Health Studies (NHS I and NHS II), and one-quarter being men from the Health Professionals Follow-Up Study (HPFS).
The two Nurses Health Studies and the Health Professionals Follow-Up Study are all large-scale studies started in the 1970s and 1980s, and are still on-going. What is amazing about these studies is that participants are requested to fill out a detailed questionnaire every two years on various aspects of their lifestyle and health conditions. They are also asked to complete a diet questionnaire every four years, as well as provide blood and urine samples about once every ten years! What is even more admirable is the dedication of the participants in responding to the requests to fill in follow-up questionnaires, with a response rate of around 90%! What that means is that the studies have generated an incredible amount of data that has produced many important findings, including one of the earliest links between smoking and poor health outcomes.
All that is to say that even though there are limitations to results from epidemiological data, these data do allow us to answer questions that cannot be obtained by randomised-controlled trials, since it would be nearly impossible to get funding to run a 30-year-long randomised-controlled trial with so many participants.
With that out of the way, what were the results from this update to the portfolio diet?
Number 1. The study found that greater adherence to the portfolio diet was associated with a 14% lower risk of cardiovascular disease, defined primarily as having a heart attack or stroke. In fact, the results mirrored the dose-respond trends demonstrated by the earlier randomised-controlled trials with respect to LDL-cholesterol. That is, the more one adhered to the portfolio diet, the greater the reduction in risk of getting a heart attack or stroke.
Number 2. As the data was collected from participants who were simply going about their everyday life, the participants in the study with the greatest adherence to the portfolio diet were actually eating amounts of portfolio foods that were still lower than the recommended amounts compared to the randomized-controlled trials. And as such, to achieve the levels similar to the group of participants with the highest intake of portfolio foods in the study, one could consume each day, and I quote “one-half cup of beans or 1 cup of soy milk, 1 cup of cooked oatmeal, one-half cup of eggplant, 0.5 to 1 ounce of nuts, and 1 tablespoon of olive oil.” And the researchers recommend that this be done to replace foods that are higher in saturated fat and cholesterol. In other words, to potentially achieve the 14% reduction in CVD risk, the amounts of portfolio foods to be eaten each day are actually very achievable!
Number 3. You might have noticed that the researchers mentioned foods like beans, eggplant, and olive oil, which do not seem to be on the list of portfolio foods from my earlier videos. In the randomised-controlled trials, viscous fibre from oats, barley and psyllium were highlighted, but in fact, there are other foods, including eggplant, that contain various kinds of viscous fibre. Soy protein was emphasised in the randomised-controlled trials, but all plant proteins, especially from legumes, are also encouraged as meat substitutes as part of the Portfolio diet. And finally, in 2010, the researchers performed a randomised-controlled trial to confirm the positive heart-healthy effects of monounsaturated fats, and added healthy plant oils such as olive oil as a component of the portfolio diet.
What this means is that the portfolio diet is actually quite expansive, and contains many more foods that are readily available and consumed in Asian cooking.
In fact, if you’re trying to increase the amount of viscous fibre in your diet, you could add the following items to your shopping cart. These would include vegetables like okra and eggplant, and fruits like apples and oranges. Okra and eggplant are widely available in this region, so add them onto your economy rice plates when you have lunch. And apples and oranges, which are what I like to call “oldies but goodies”, are great sources of a kind of viscous fibre called pectin. So, increase the amount of viscous fibre in your overnight oats by throwing in these fruits as well.
You could check out the video here as well: