Consumption of a plant-based diet rich in lignans is associated with a lower risk of coronary heart disease (CHD), new research suggests.
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In a prospective cohort study that followed almost 214,108 men and women who were free of CHD and cancer at baseline, increased long-term intake of lignans, polyphenolic substances produced by plants, was associated with significantly lower risk of total CHD in both men and women.
The benefit was increased in participants with a greater intake of fiber, suggesting that synergistic effects between the two might exist in relation to CHD reduction.
The results were published online in the Journal of the American College of Cardiology.
“Lignan is an estrogen-like molecule, so it exerts some estrogenic effects which are cardioprotective. It also has anti-inflammatory properties,” first author Yang Hu, ScD, a research fellow at the Harvard School of Public Health, Boston, said in an interview.
“Our results that showed an inverse association between lignan consumption and heart disease risk were expected, because it is known that lignans, which are predominantly from plant-based foods, like whole grains, fruit, vegetables, red wine, and coffee, are all associated with lower CHD risk,” Dr. Hu said.
What is novel about the current study is that it established a threshold for lignan consumption, above which there is no CHD benefit, he said.
“It is not a matter of the more you consume, the lower your risk. There is a certain amount of lignan you have to reach, after which there is no more benefit,” Dr. Hu said.
Dr. Hu and associates prospectively followed 214,108 men and women in three cohorts who did not have cardiovascular disease or cancer at baseline. The cohorts were the Health Professionals Follow-Up Study, Nurses’ Health Study, and Nurses’ Health Study II.
Diets were assessed using the Food Frequency Questionnaire every 2-4 years at follow-up visits.
During 5.5 million person-years of follow-up, Dr. Hu and associates documented 10,244 CHD cases, including 6,283 nonfatal myocardial infarctions and 3,961 fatal CHD cases.
The results showed that higher total lignan intake, and all individual lignan intake as well, were associated with significantly lower risk of total CHD.
Participants with higher total lignan intake were older and had more favorable health and lifestyle profiles including lower body mass index, lower prevalence of hypertension and hypercholesterolemia, high levels of physical activity, and better diet quality.
Overall, the pooled hazard ratios of CHD were 0.85 (95% confidence interval, 0.79-0.92) for total lignans, 0.76 (95% CI, 0.71-0.82) for matairesinol, 0.87 (95% CI, 0.81-0.93) for secoisolariciresinol, 0.89 (95% CI, 0.83-0.95) for pinoresinol, and 0.89 (95% CI: 0.83- 0.95) for lariciresinol (all P values for trend ≤ .003).
In addition, nonlinear relationships were found for total lignan, matairesinol, and secoisolariciresinol: The risk reduction plateaued at intakes above approximately 300 mcg/d for total lignan; 10 mcg/d for matairesinol, and 100 mcg/d for secoisolariciresinol.
The inverse associations for total lignan intake were more apparent among participants with higher total fiber intake.
In addition, lignan intake was more strongly associated with plasma concentrations of enterolactone when fiber intake was higher.
Dr. Hu said a next avenue of research will explore the synergistic association between lignans and fiber in further lowering CHD risk.
Lignans are exclusively metabolized by gut microbiota, Dr. Hu noted. “This opens another avenue of research because we can take further steps to see how the gut microbiota compositions and fiber interact with the production of lignans and how these might affect disease risk for other conditions, such as diabetes.”