Healthy plant-based diet shows potential for prevention of cognitive decline

Key takeaways:

• Each 10-point increase in a healthy plant-based diet score was linked to a 30% lower risk for cognitive impairment.
• Each 10-point increase in an unhealthy plant-based diet score was linked to a 36% higher risk.

Adhering to a healthy plant-based diet for 3 years was associated with a reduced risk for cognitive impairment, but following an unhealthy plant-based diet was linked to a greater risk, according to recent study results.

Previous studies lack evidence on how changes in plant-based dietary quality impact the risk for cognitive impairment, Kai Ding, of Wuhan University’s School of Public Health in China, and colleagues wrote in the American Journal of Clinical Nutrition.

“Cognitive impairment is a common but easily overlooked condition in older adults characterized by impairments in multiple cognitive domains such as memory, reasoning, visuospatial abilities, and language,” Ding and colleagues wrote. “With the aging of the global population, the prevalence of dementia in the aging population constitutes a serious public health problem globally and carries a heavy economic burden.”

That means that finding modifiable risk factors of cognitive impairment “is crucial to prevent or delay the onset of dementia,” they wrote. One factor that has the potential to prevent cognitive impairment, they wrote, is dietary patterns emphasizing plant foods.

“Previous studies have shown some relationship between plant-based dietary patterns and cognitive function, namely that adhering to a healthful plant-based diet is associated with a lower risk of cognitive impairment,” Ding and colleagues wrote. “On the contrary, an unhealthful plant-based diet is detrimental to cognitive function.”

Since dietary patterns change over time, “it is unclear whether longitudinal changes in plant-based dietary quality are linked to incidence of cognitive impairment over time,” they wrote.

So, the researchers conducted a national community-based cohort study to better understand the relationship. The study included data from the Chinese Longitudinal Healthy Longevity Survey on 6,662 participants who did not have cognitive impairment in 2008 and were followed until 2018.

Ding and colleagues assessed cognitive impairment with the Mini-Mental State Examination and measured plant-based dietary quality with three indices:

• overall plant-based diet index (PDI);
• healthful plant-based diet index (hPDI); and
• unhealthful plant-based diet index (uPDI).

In the 10 years of follow-up, the researchers recorded 1,571 incident cases of cognitive impairment. They found that every 10-point increase in PDI and hPDI was associated with 26% and 30% lower risk of cognitive impairment. Every 10-point increase in uPDI, however, was associated with 36% higher risk.

Additionally, for participants with a large increase in PDI, hPDI and uPDI, the full-adjusted hazard ratios for cognitive impairment were 0.77 (95% CI, 0.64-0.93), 0.72 (95% CI, 0.6-0.86) and 1.5 (95% CI, 1.27-1.77), respectively, compared with participants whose plant-based diet had no change or was relatively stable over 3 years.

Among patients with a large decrease in PDI, hPDI, and uPDI, the HRs were 1.22 (95% CI, 1.02-1.44), 1.3 (95% CI, 1.11-1.54), and 0.8 (95% CI, 0.67-0.96) respectively.

Ding and colleagues additionally identified individual foods linked to lower incidence of cognitive impairment, including fruits, garlic, legumes, nuts, tea and vegetables. Among those associated with higher cognitive risk were fish, meat and sugar.

“A high-quality plant-based diet in older populations has the potential to prevent or delay cognitive decline,” the researchers concluded. “We call for intervention studies to validate our findings and further health policies to take action in practice.”