Higher blood levels of omega 3 fatty acids found in seafood are associated with a higher likelihood of healthy ageing among older adults, finds a US study published by The BMJ today.
With populations across the world living longer, there is a growing focus on healthy ageing - a meaningful lifespan without major chronic diseases and with good physical and mental function.
Previous studies suggest that omega 3 polyunsaturated fatty acids (n-3 PUFAs) derived from seafood and plants may have beneficial effects on the body that could promote healthy ageing, but results are inconsistent.
So a team of US researchers, led by Heidi Lai at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, set out to investigate the association between circulating blood levels of n-3 PUFAs and healthy ageing among older adults.
The study involved 2,622 adults who were taking part in the US Cardiovascular Health study from 1992 to 2015. Average age of participants at the start of the study (baseline) was 74 years, 63% were women and 11% were from non-white groups.
Blood levels of n3-PUFAs were measured at baseline, 6, and 13 years. These included eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and alpha linolenic acid (ALA). The main dietary sources of EPA, DHA and DPA come from seafood, while ALA is found mainly in plants (nuts, seeds, and leafy green vegetables).
Based on these measurements, participants were split into five groups (quintiles) of circulating blood n-3 PUFA levels, from lowest to highest.
Through review of medical records and diagnostic tests, the researchers found that 89% of the participants experienced unhealthy ageing over the study period, while 11% experienced healthy ageing - defined as survival free of major chronic diseases and without mental or physical dysfunction.
After taking account of a range of other social, economic, and lifestyle factors, the researchers found that levels of seafood-derived EPA in the highest quintile were associated with a 24% lower risk of unhealthy ageing than levels in the lowest quintile.
For DPA levels, the top three quintiles were associated with an 18-21% reduction in the risk of unhealthy ageing. However, seafood-derived DHA and plant-derived ALA were not associated with healthy ageing.
A possible explanation for this effect is that n-3 PUFAs help to regulate blood pressure, heart rate and inflammation, explain the authors.
They point out that this was an observational study, so no firm conclusions can be drawn about cause and effect, and they cannot rule out the possibility that some of the observed risk may be due to other unmeasured factors.
The study had a long (up to 22 years) follow-up period, and results remained largely unchanged after further analyses.
As such, they say that, among older adults, higher levels of circulating n-3 PUFAs from seafood were associated with a lower risk of unhealthy ageing.
"These findings encourage the need for further investigations into plausible biological mechanisms and interventions related to n3-PUFAs for maintenance of healthy ageing, and support guidelines for increased dietary consumption of fish among older adults," they conclude.
In a linked editorial, Professor Yeyi Zhu at Kaiser Permanente Northern California Division of Research and the University of California and colleagues say this study makes a valuable contribution to our understanding of the effect n3-PUFAs might have on ageing. But they caution against using these findings to inform public health policy or nutritional guidelines.
We live in challenging times, when lifespans are increasing but healthy lifespans are not, they write. "Following the World Health Organization's policy framework for healthy ageing, any evidence-based clues to improve health in later life are welcome but additional efforts to accelerate this area of research are essential," they conclude.
Externally peer-reviewed? Yes (research), No (linked editorial)
Type of evidence: Observational