There is a wealth of evidence that omega-3 fats such as DHA, found in salmon and other fish, play a role in both brain and heart health. In fact, infant formulas are supplemented with a type of DHA because it is critical to newborns' brain development.
Now, a new study published in JAMA Neurology has shown an association between low levels of DHA and cerebral amyloidosis, a precursor of the beta-amyloid plaques common in the brains of people with Alzheimer's disease.
The researchers took blood samples and conducted Amyvid PET scans of the brains of 61 seniors who did not show signs of cognitive impairment. (These scans, which were developed with early support from the Alzheimer's Drug Discovery Foundation, image beta-amyloid plaques in the brain.) They found that people with cerebral amyloidosis had 23 percent less DHA in their systems.
The researchers also took MRIs of study participants' brains and discovered that the brains of people with high levels of DHA were larger in the areas that atrophy in those with Alzheimer's disease. These high-DHA patients also did better on a memory test than those with lower levels. All participants were part of the ongoing Harvard Aging Brain Study, which is being conducted at multiple research centers.
More evidence of the connection between DHA levels and dementia risk can be found in early results from the Multidomain Alzheimer Preventive Trial (MAPT study), which the Alzheimer's Drug Discovery Foundation is helping to advance. Older adults in this study with mild cognitive impairment (MCI) and low blood DHA levels who were given DHA supplements in combination with nutritional counseling, exercise, and cognitive and social stimulation had slower cognitive decline than others who did not receive these interventions.
Should you take DHA, and if so, when? Research shows that the timing of DHA supplementation matters. A number of studies have looked at DHA supplementation in people who already have dementia. The supplements did not benefit these individuals, suggesting that their disease process was too far along for it to make a difference. In the aforementioned studies, however, it appears that in clinically normal people or those in the earliest stages of cognitive impairment, DHA may be helpful. This body of evidence suggests that older adults with recent memory problems should ask their physicians about having their DHA levels tested, just as they are tested for vitamin B12 or vitamin D deficiency. The red blood cell DHA test may be more relevant. Patients with low levels may benefit more from taking DHA-rich supplements such as fish oil or purified DHA.
While more research is needed to demonstrate the value of routine DHA screening for all seniors, these studies suggest it may play a role in helping slow the progression of very early Alzheimer's disease.