‘Million dollar question’ remains unanswered
The fact that omega-6, considered neuroinflammatory, was associated with improved DSST score illustrates the complexity of this field, said Dr. McIntyre.
“We’re learning that when it comes to inflammation, many of the molecules in our brain that are implicated as anti-inflammatory can also be pro-inflammatory, so bad guys can be good guys and good guys can be bad guys.”
It speaks to the notion of homeostasis, he added. “Just like a seesaw; when you push this part down, that part goes up.”
The analysis showed the animal fluency score increased about 0.05 SD (around 0.3 score) with each SD (1.1 g/d) increase in dietary intake of omega-3.
There were no significant associations between other dietary fat intake and cognitive performance.
The researchers investigated the role of oxidative stress and antioxidant biomarkers (gamma glutamyl transpeptidase [GGT], bilirubin, uric acid, and vitamin D).
Cells produce oxidative radicals that are normally “mopped up” by our “innate antioxidant capability,” said Dr. McIntyre. “But in states of cognitive impairment, these oxidative stress markers accumulate and they exceed what the normal innate response is able to manage.”
The study showed GGT levels decreased with increased PUFA and omega-6 fatty acid intakes; levels of bilirubin decreased with increase in most dietary fat intakes; uric acid levels decreased with MUFA intake and omega-6/omega-3 ratio; and vitamin D levels increased with omega-3 fatty acid intake but decreased with SFAT intake.
Causal mediation analysis showed the association between dietary intake of fatty acids and DSST performance was partially mediated by GGT levels. However, Dr. McIntyre emphasized that this does not prove causality.
“The million dollar question is, is this the sole explanation for the association? In other words, is it the oxidative stress that caused the cognitive impairment and therefore correcting it improved it, or is it the case that oxidative stress is a proxy of other activities that are also taking place?”