南加州大学医学院的一项为期两年的临床试验显示，尽管高剂量的DHA（一种在多脂鱼类中富含的Omega-3脂肪酸）补充剂确实能够进入老年人的大脑，但它们并未能改善记忆力或认知功能，也没有减缓脑部萎缩。

该研究涉及365名55至80岁且少吃鱼的受试者，其中近半数携带阿兹海默症的主要遗传风险基因APOE ε4。结果显示，补充组的脑脊髓液DHA浓度在六个月后增加了17%，但两年后其认知表现与海马回体积变化与安慰剂组相比并无显著差异。

研究人员指出，补充剂无效可能与大脑中cPLA2酶分解DHA、受试者自身的血管风险因素，或是其年龄较轻且认知退化不明显有关。目前，规律运动、充足睡眠和均衡饮食等健康生活方式仍是预防阿兹海默症最有效的方法。

A two-year clinical trial conducted by the USC School of Medicine revealed that while high-dose DHA (an omega-3 fatty acid abundant in oily fish) supplements successfully reach the brains of older adults, they do not improve memory or cognitive function, nor do they slow brain atrophy.

The study involved 365 participants aged 55 to 80 who rarely ate fish, with nearly half carrying the APOE ε4 allele, the strongest genetic risk factor for Alzheimer's. Although DHA levels in their cerebrospinal fluid increased by 17% after six months, no significant differences in cognitive tests or hippocampal volume were observed compared to the placebo group after 24 months.

Researchers suggested that the lack of efficacy could be due to the cPLA2 enzyme breaking down DHA, pre-existing cardiovascular risk factors, or the relatively young age of the cohort. Currently, established lifestyle measures such as regular exercise, quality sleep, and a balanced diet remain the most effective ways to prevent Alzheimer's disease.