Study Shows Plant Lignans, Found in Flaxseed, Whole Grains, and Coffee, May Reduce Type 2 Diabetes Risk

The findings from 3 large prospective US cohorts, published in JAMA Network Open, suggest individual plant lignans appear to be beneficial in reducing the risk of type 2 diabetes, highlighting the importance of including lignan-rich foods—such as flaxseed products, whole grains, and coffee—in one's diet for diabetes prevention.

Lignans, which are prevalent in flaxseeds, sesame seeds, whole grains, and certain vegetables, are known for their antioxidant and anti-inflammatory properties. Lignans are phytoestrogens commonly found in Western diets and may be linked to the risk of developing type 2 diabetes. Considering this, Siyue Wang, Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, and colleagues sought to prospectively investigate associations between lignan intake and incidence of type 2 diabetes.

For this purpose, the researchers conducted a population-based cohort study using data from various studies, including the Nurses’ Health Study (NHS, 1984-2018), NHSII (1991-2019), and the Health Professionals Follow-Up Study (HPFS, 1986-2020), along with 496 participants from the Men’s Lifestyle Validation Study (MLVS). All participants were free of T2D, cardiovascular disease, and cancer at the study's outset. Data analysis took place between November 2022 and July 2023.

Lignan intake was evaluated through a validated food frequency questionnaire, which participants updated every 2 to 4 years. In the MLVS, lignan consumption was recorded using two sets of 7-day diet records.

The study identified new cases of T2D based on the American Diabetes Association diagnostic criteria. Cox proportional hazard models were employed to examine the associations between lignan intake and T2D, adjusting for multiple variables.

The study revealed the following findings:

• The current study included 201 111 participants (mean age, 44.7 years; 80.2% female participants) from the HPFS, NHS, and NHSII studies. The median total lignan intake of the highest quintile ranged from 355.1 μg/d in NHS to 459.9 μg/d in HPFS at the median follow-up time.
• 20,291 incident cases of T2D were identified over 5 068 689 person-years.
• Higher lignan intake was inversely associated with T2D incidence, except for lariciresinol.
• The multivariable-adjusted pooled hazard ratios (HRs) for the highest vs lowest quintiles were 0.87 for total lignans, 0.72 for secoisolariciresinol, 0.92 for pinoresinol, 0.93 for matairesinol, and 0.99 for lariciresinol.
• Secoisolariciresinol intake exhibited a significant inverse association with T2D risk among individuals with obesity (HR, 0.75 for body mass index [BMI] ≥30 versus HR, 0.82 for BMI <25) and premenopausal women (HR, 0.67 for premenopausal women versus HR, 0.82 for the past use of hormones).
• Dietary lignan assessed with 7DDRs was associated with lower HbA1c levels, as well as lower C-reactive protein levels and better lipid profiles.

The findings suggest that higher overall lignan intake, particularly from secoisolariciresinol, matairesinol, and pinoresinol (but not lariciresinol), is significantly linked to a lower risk of type 2 diabetes. The protective effect of secoisolariciresinol was notably more pronounced among individuals with obesity and premenopausal women.

"These results highlight the importance of a plant-based diet rich in lignan-containing foods, such as flaxseed products, whole grains, and coffee, for the primary prevention of type 2 diabetes," the researchers concluded.

Reference:

Wang S, Hu Y, Liu B, Li Y, Wang M, Sun Q. Lignan Intake and Type 2 Diabetes Incidence Among US Men and Women. JAMA Netw Open. 2024;7(8):e2426367. doi:10.1001/jamanetworkopen.2024.26367