GC Links Blood DHA Levels to Brain Volume

Omega-3 fats in the blood, especially docosahexaenoic acid (DHA), have been linked to keeping the brain's physical structure healthy. However, most of what we know about this comes from Western countries, where people generally do not eat a large amount of fish and have relatively low omega-3 levels to begin with. Conversely, there is not much research on this topic from Japan, where people eat a lot more fish and typically have much higher omega-3 levels. Furthermore, few studies have looked at whether DHA and another omega-3 fat called eicosapentaenoic acid (EPA) affect the brain differently.

To bridge this knowledge gap, researchers examined how blood levels of EPA, DHA, and the two combined related to brain volume in older Japanese women, with serum concentrations of EPA and DHA measured using gas chromatography (GC). A paper based on this work was published in The Journal of Nutrition.¹

Why Is It Important to Study the Link Between Omega-3 Fatty Acids (like EPA and DHA) and Brain Health in Aging?

The risk of dementia and memory/thinking issues rises as people get older. Since dementia usually gets worse over time and there's currently no cure for it, figuring out what raises or lowers a person's risk is key to coming up with ways to help prevent it in the first place.²

Omega-3 fats that come from the sea, such asEPA and DHA, are types of fat mostly found in fish. Technically, the body can make some EPA and DHA on its own from another omega-3 fat called α-linolenic acid (ALA, found in foods like flaxseed), but this conversion process is not very efficient in humans. Research has shown that these omega-3s, especially EPA and DHA, are good for heart health and are also linked to slower mental decline as people age. A recent analysis that combined results from 48 long-term studies, covering more than 100,000 people total, found that eating more DHA or EPA was tied to a lower risk of cognitive decline. Specifically, the more omega-3s people consumed, the lower their risk tended to be; for every extra 100 mg per day, the risk of cognitive decline dropped by roughly 8-10%.^3-5

Does Blood DHA or EPA Level Relate to Brain Volume in Older Japanese Women?

This study looked at 527 women, all living independently in their communities, in Kusatsu City, Japan. They ranged in age from 60 to 85, with the average person being about 74 years old. To measure brain volume (including the total size of the brain, the gray matter, the white matter, and the hippocampus, a region tied to memory), researchers used MRI scans. Then, they grouped the women into four categories based on their blood levels of EPA, DHA, and EPA+DHA combined (from lowest to highest), and compared brain volume across these groups. To make sure the results were not skewed by other factors, they statistically accounted for factors such asage, head size, weight, education level, smoking and drinking habits, physical activity, and health conditions like diabetes, high blood pressure, and cholesterol medication use.¹

The results showed that women with higher blood levels of DHA tended to have more gray matter in their brains, and this pattern was statistically meaningful. EPA levels alone, however, didn't show this same connection. When looking at EPA and DHA together, there was a positive pattern with gray matter volume too, though it was a bit weaker and didn't quite reach the usual bar for statistical significance. There was no clear link, though, between any of these omega-3 measurements (EPA, DHA, or the two combined) and other brain measurements, including white matter volume, total brain size, or the size of the hippocampus.¹

“DHA,” wrote the authors of the paper,¹ “exhibited a stronger positive association with gray matter volume than EPA, for which associations were limited, supporting the importance of DHA-rich diets for healthy brain aging.”

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References

1. Kondo, K.; Kadota, A.; Torii, S. et al. Differential Associations of Docosahexaenoic and Eicosapentaenoic Acid with Brain Structure in Older Japanese Women. J Nutr. 2026, 101747. DOI: 10.1016/j.tjnut.2026.101747
2. Livingston, G, Huntley, J.; Liu, K. Y. et al. Dementia Prevention, Intervention, and Care: 2024 Report of the Lancet Standing Commission. Lancet 2024, 404 (10452), 572-628. DOI: 10.1016/S0140-6736(24)01296-0
3. Wei, B. Z.; Li, L.; Dong, C. W. et al. Alzheimer’s Disease Neuroimaging Initiative; Xu W. The Relationship of Omega-3 Fatty Acids with Dementia and Cognitive Decline: Evidence from Prospective Cohort Studies of Supplementation, Dietary Intake, and Blood Markers. Am J Clin Nutr. 2023, 117 (6), 1096-1109. DOI: 10.1016/j.ajcnut.2023.04.001
4. Lands, W. E.; Libelt, B.; Morris, A. et al. Maintenance of Lower Proportions of (n - 6) Eicosanoid Precursors in Phospholipids of Human Plasma in Response to Added Dietary (n - 3) Fatty Acids. Biochim Biophys Acta 1992, 1180 (2), 147-62. DOI: 10.1016/0925-4439(92)90063-s
5. Jack, C. R. Jr.; Knopman, D. S.; Jagust, W. J. et al. Hypothetical Model of Dynamic Biomarkers of the Alzheimer's Pathological Cascade. Lancet Neurol. 2010, 9 (1), 119-128. DOI: 10.1016/S1474-4422(09)70299-6