There have a been a number of convincing studies in recent years showing that the old adage “you are what you eat” is pretty accurate. But if you weren’t quite convinced to cut back on donuts and choke down some kale, a new study from the University of Illinois might do so: It shows that blood levels of certain molecules that are touted to be healthy—omega-3s, lycopene, B-vitamins, among others—actually correlated not only to cognitive function but also to how the brain functions.
“The basic question we were asking was whether diet and nutrition are associated with healthy brain aging,” said study author Aron Barbey in a statement. “And instead of inferring brain health from a cognitive test, we directly examined the brain using high-resolution brain imaging.” (He and his team did have the participants carry out cognitive tasks, which is important, and discussed below.)
The study was published this week in the journal NeuroImage.
The researchers measured blood levels of nutritional biomarkers in the blood of 115 healthy participants (aged 65-75), including omega-3 and omega-6 fatty acids, lycopene (found in highest concentrations in tomatoes and watermelon), folate (in leafy greens), carotenoids (in red, yellow, and orange veggies), riboflavin, vitamin B12, and vitamin D. The team chose these because they represent many of the healthy compounds from the Mediterranean diet.
They scanned the participants’ brains to view high-resolution images of neural networks, including how the various networks were connected in each participant, and found a correlation between having higher blood levels of many of the nutrients of interest and having better connectivity in certain brain regions. In particular, higher levels of omega-3s, omega-6s and carotene were linked to better network efficiency.
“Efficiency has to do with how information is communicated within the network,” Barbey said. “We looked at ‘local efficiency’ – how well information is shared within a spatially confined set of brain regions – and also ‘global efficiency,’ which reflects how many steps are required to transfer information from any one region to any other region in the network. If your network is more efficiently configured, then it should be easier, on average, to access relevant information and the task should take you less time.”
The team also had the participants take tests to measure cognition, overall intelligence, memory, and executive function—and they were able to correlate these scores with brain connectivity and levels of the nutritional biomarkers. Omega-3, omega-6, lycopene, carotenoids, and vitamins B and D all correlated to aspects of cognition, and most were also connected to brain function.
For instance, omega-3s were linked to general intelligence andto connectivity in the fronto-parietal network, which governs goal-directed behaviors and attentional focus. Omega-6 fatty acids and lycopene were linked to executive function and to the dorsal attention network. (Additionally, lycopene and omega-3s and -6s were linked to several tests of memory function, vitamins B and D to executive function, and carotenes were linked to intelligence scores.)
“Our study suggests that diet and nutrition moderate the association between network efficiency and cognitive performance,” said Barbey. “This means that the strength of the association between functional brain network efficiency and cognitive performance is associated with the level of the nutrients.”
In other words, the connection between cognition and brain activity can at least partially be explained by the levels of biomarkers in the blood.
The study has a couple of limitations—one being that most participants were white, educated, and in good health. They study would need to be repeated in a more diverse population before drawing more solid conclusions. Additionally, a big caveat is that it’s only correlational, meaning that we don’t know which came first, the brain/cognitive health or the good nutrition/blood biomarkers. There could be reverse causation going on here, so that people who were smarter to begin with ate foods that were healthier, which then showed up in their blood. To really know whether causation was play, you’d have to assign people to eat healthily or poorly over time, which might have some ethical issues.
Still, the study confirms what others have in the past—that eating well may well keep the brain healthy and, in so doing, boost cognition. There are lots of reasons why this is logical, and researchers have laid out many of the biochemical mechanisms behind it, from how lycopene may reduce inflammation to how omega-3s help keep neurons’ membranes more permeable. And plenty of studies have illustrated the flip-side: That unhealthy foods (especially sugar) is linked to reduce brain volume, and poorer cognition.
While science continues to map out all the connections, it’s probably wise to do what we’ve been told for ages—eat well when you can, but don’t beat yourself up if occasionally you can’t.
