Portfolio diet delays heart risk and lowers cholesterol in young adults

New research shows that even modest adherence to the Portfolio Diet, a plant-based cholesterol-lowering strategy, can significantly reduce cardiovascular risk factors in young adults and may postpone heart disease onset by more than a decade.

Study: Portfolio diet and LDL-C in a young, multiethnic cohort: cross-sectional analyses with cumulative exposure modeling. Image Credit: Chiociolla / Shutterstock

University of Toronto researchers conducted a cross-sectional multiethnic cohort study to assess the portfolio diet's effect on a range of cardiovascular risk factors, including low-density lipoprotein cholesterol (LDL-C). The findings are published in the journal BMC Public Health.

Background

Cardiovascular disease is a leading cause of mortality worldwide. Several health conditions increase the risk of cardiovascular disease, including diabetes, obesity, hypertension, and hyperlipidemia.

Exposure to hyperlipidemia (high cholesterol) has been found to increase cardiovascular disease risk in a dose-dependent manner. Among various lipid molecules, LDL-C has been found to have a causal association with a higher incidence of cardiovascular disease. Thus, early management of hyperlipidemia starting at a younger age is an effective preventive strategy against cardiovascular disease.

The portfolio diet is a therapeutic, plant-based dietary strategy specifically designed to reduce blood cholesterol levels. It contains five types of cholesterol-lowering food components, including plant protein, viscous fiber, nuts, phytosterols, and monounsaturated fatty acids. Importantly, the Portfolio Diet Score also assigns reverse points for saturated fat and cholesterol intake from animal sources, so that lower intake of these foods is considered better adherence.

Existing clinical evidence indicates that a portfolio diet is highly effective in reducing several cardiovascular risk factors, including LDL-C, total cholesterol, triglycerides, C-reactive protein, and systolic and diastolic blood pressure in middle-aged adults.

Given the cardioprotective effect of the portfolio diet and the scarcity of information about its efficacy in ethnoculturally diverse populations, the current study was designed to evaluate the diet's associations with LDL-C and other established cardiovascular risk factors in an ethnoculturally diverse population of young adults.

Study design

The study analyzed data from 1,507 men and women in the Toronto Nutrigenomics and Health Study, a cross-sectional study investigating the impact of dietary intake and genetic variation on biomarkers of chronic disease among young Canadians with diverse ethnocultural backgrounds.

The participants' dietary intake was assessed using a validated food frequency questionnaire, and their adherence to the portfolio diet was assessed using the Portfolio Diet Score. Appropriate statistical analyses were carried out to determine the score's associations with LDL-C and other established cardiovascular risk factors.

It is important to note that, as a cross-sectional observational study, the design does not allow determination of causality.

Study findings

The study included participants of different ethnicities. Those with higher adherence to the portfolio diet were more likely to be Caucasian, with relatively fewer East Asian, South Asian, and other ethnicities in the highest adherence group.

Participants who adhered more strictly to the portfolio diet exhibited significantly lower levels of LDL-C, total cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C), and systolic and diastolic blood pressure.

Similarly, these participants exhibited lower body mass index (BMI), waist circumference, body weight, and fat mass index (FMI).

The study compared different magnitudes of dietary adherence and revealed that compared to low adherence, 50% and 100% adherence to the diet may delay the onset of increasing cardiovascular risk by 6 and 13 years, respectively.

However, the study did not find significant associations between adherence to the portfolio diet and HDL cholesterol (HDL-C), C-reactive protein (CRP), or fasting glucose levels overall.

Among the covariates analyzed in the study, sex and ethnicity showed strong influence on the association of portfolio diet with total cholesterol and fasting glucose, respectively. According to the findings, the diet's impact on total cholesterol was stronger among men than women. Similarly, the diet's impact on fasting blood glucose was stronger among East Asians and South Asians compared to other ethnicities.

Study significance

The study highlights the health benefits of a portfolio diet in terms of reducing the levels of several cardiovascular risk factors, including LDL-C, non-HDL-C, total cholesterol, systolic blood pressure, and diastolic blood pressure. The study also finds that the diet is effective in improving anthropometric measurements, including BMI, waist circumference, body weight, and FMI.

While the observed reductions in LDL-C were modest—approximately 0.1 mmol/L, or 4% lower among those in the highest compared to the lowest adherence groups—this is comparable to the minimum lipid-lowering seen for every dose doubling of a statin drug (a clinically approved lipid-lowering medication). This observation suggests that with larger differences in adherence to the diet, a meaningful association with LDL-C may be observed even in young adults.

Life transitions, including leaving home and leaving education, experienced by young adults are known to negatively impact diet quality. Healthy dietary interventions are, therefore, particularly vital in this age group to reduce lifetime exposure to cardiovascular risk factors.

The study recruited young adults from a large urban university campus, which may restrict the generalizability of the findings. The study analyzed self-reported data on diet, which may give rise to some measurement errors.

In general, study participants exhibited a lower consumption of portfolio diet components, which may have led to an underestimation of the strength of the observed associations.

In modelled projections, the study considered constant LDL-C levels over time because a single measure of LDL-C is available. Future longitudinal studies using multiple LDL-C measurements are needed for more reliable projections.

Because this was a cross-sectional study, the results reflect associations rather than causal relationships. Prospective longitudinal studies are needed to confirm these findings and to understand the long-term effects of early adoption of the portfolio diet on cardiovascular health.