Docosahexaenoic acid (DHA), an omega-3 fatty acid present in abundance in oily fish equivalent to mackerel and sardines, is believed to enhance cognitive operate by supporting connections between mind cells. Nonetheless, it has by no means been conclusively demonstrated that DHA taken as a dietary complement truly reaches the mind or gives measurable advantages in opposition to dementia.
In opposition to this backdrop, a analysis staff on the USC Faculty of Drugs has revealed the outcomes of a giant, two-year scientific trial involving older adults at elevated danger of creating Alzheimer’s disease. The examine discovered that whereas high-dose DHA dietary supplements do certainly attain the mind, they didn’t enhance reminiscence or cognitive operate, nor did they sluggish mind atrophy.
“Everybody hopes for a silver bullet to forestall Alzheimer’s illness, however we won’t say that fish oil dietary supplements shield mind well being,” said Hussein Naji Yassine, director of the Personalised Mind Well being Heart at USC. “Whereas omega-3s play an essential function in forming mind cell connections wanted for cognition, our outcomes don’t assist fish oil dietary supplements as a safety measure in opposition to Alzheimer’s.”
DHA Reached the Mind, However …
Yassine and his colleagues performed a randomized, double-blind, placebo-controlled trial involving 365 women and men between the ages of 55 and 80 who hardly ever ate fish. Practically half of the individuals (47 p.c) carried the APOE ε4 allele, the strongest genetic danger issue for late-onset Alzheimer’s illness. All individuals consumed lower than 200 mg of DHA per day via their food regimen.
Contributors had been randomly assigned to one in every of two teams. One group obtained a every day complement containing 2,000 mg of DHA, whereas the opposite obtained a placebo for twenty-four months. The placebo consisted of a combination of corn oil and soybean oil and was indistinguishable from the DHA complement in look, style, and odor. Neither the individuals nor the researchers knew which therapy every individual obtained.
The researchers first wished to find out whether or not DHA truly reached the mind. Measurements of DHA ranges within the cerebrospinal fluid, which surrounds the mind and spinal wire, confirmed that concentrations elevated by 17 p.c after six months within the DHA group. There was no distinction between carriers and noncarriers of the APOE ε4 allele, offering direct proof that high-dose DHA supplementation reaches the brains of cognitively wholesome older adults no matter APOE ε4 standing.
The outcomes had been very completely different, nevertheless, when it got here to cognitive operate and mind construction. After 24 months, individuals accomplished the Repeatable Battery for the Evaluation of Neuropsychological Standing, a standardized check of reminiscence and cognitive efficiency. No vital variations had been discovered between the DHA and placebo teams. Likewise, there have been no vital variations in adjustments in hippocampal quantity, a mind area essential for reminiscence and an early biomarker of Alzheimer’s illness.
Why Didn’t It Work?
The researchers recommend a number of attainable explanations for why DHA reached the mind however failed to provide measurable scientific advantages. One risk entails an enzyme that disrupts DHA metabolism within the mind. When an enzyme generally known as calcium-dependent phospholipase A2 (cPLA2) turns into activated, it might break down DHA earlier than it may be included into synaptic membranes—the buildings the place DHA is believed to play its most essential function in supporting cognitive operate.
One other attainable clarification is that many individuals had cardiovascular danger components equivalent to weight problems, hypertension, and bodily inactivity. The continual irritation related to these situations might have blunted the results of supplementation, making it tough for a single nutrient to provide measurable advantages.
The researchers additionally observe that the individuals had been comparatively younger, with a median age of 66, and skilled solely minimal cognitive decline over the course of the two-year examine. In consequence, there might merely have been too little decline in the course of the trial to detect any protecting impact from DHA supplementation.
