What Are Fish Oil Supplements Good For? Here’s Your Crash Course
What Are Fish Oil Supplements Good For? Here’s Your Crash Course
鱼油补充剂到底有什么用？这里有一份速成指南
Docosahexaenoic acid (DHA), an omega-3 fatty acid found in abundance in oily fish such as mackerel and sardines, is thought to improve cognitive function by supporting connections between brain cells. However, it has never been conclusively demonstrated that DHA taken as a dietary supplement actually reaches the brain or provides measurable benefits against dementia.
二十二碳六烯酸（DHA）是一种在鲭鱼和沙丁鱼等油性鱼类中含量丰富的欧米伽-3脂肪酸，人们认为它可以通过支持脑细胞之间的连接来改善认知功能。然而，目前从未有确凿证据表明，作为膳食补充剂摄入的DHA能够真正到达大脑，或在预防痴呆症方面提供可衡量的益处。
Against this backdrop, a research team at the USC School of Medicine has published the results of a large, two-year clinical trial involving older adults at elevated risk of developing Alzheimer’s disease. The study found that while high-dose DHA supplements do indeed reach the brain, they did not improve memory or cognitive function, nor did they slow brain atrophy.
在此背景下，南加州大学（USC）医学院的研究团队发表了一项为期两年的大型临床试验结果，受试者为患阿尔茨海默病风险较高的老年人。研究发现，虽然高剂量DHA补充剂确实能到达大脑，但它们并未改善记忆力或认知功能，也未能减缓大脑萎缩。
“Everyone hopes for a silver bullet to prevent Alzheimer’s disease, but we can’t say that fish oil supplements protect brain health,” said Hussein Naji Yassine, director of the Personalized Brain Health Center at USC. “While omega-3s play an important role in forming brain cell connections needed for cognition, our results do not support fish oil supplements as a preventive measure against Alzheimer’s.”
“每个人都希望找到预防阿尔茨海默病的‘灵丹妙药’，但我们不能说鱼油补充剂能保护大脑健康，”南加州大学个性化大脑健康中心主任侯赛因·纳吉·亚辛（Hussein Naji Yassine）表示，“尽管欧米伽-3在形成认知所需的脑细胞连接方面发挥着重要作用，但我们的研究结果并不支持将鱼油补充剂作为预防阿尔茨海默病的手段。”
DHA Reached the Brain, But …
DHA到达了大脑，但是……
Yassine and his colleagues conducted a randomized, double-blind, placebo-controlled trial involving 365 men and women between the ages of 55 and 80 who rarely ate fish. Nearly half of the participants (47 percent) carried the APOE ε4 allele, the strongest genetic risk factor for late-onset Alzheimer’s disease. All participants consumed less than 200 mg of DHA per day through their diet.
亚辛及其同事进行了一项随机、双盲、安慰剂对照试验，受试者为365名年龄在55至80岁之间、很少吃鱼的男女。近一半的参与者（47%）携带APOE ε4等位基因，这是迟发性阿尔茨海默病最强的遗传风险因素。所有参与者每天通过饮食摄入的DHA均少于200毫克。
Participants were randomly assigned to one of two groups. One group received a daily supplement containing 2,000 mg of DHA, while the other received a placebo for 24 months. The placebo consisted of a mixture of corn oil and soybean oil and was indistinguishable from the DHA supplement in appearance, taste, and smell. Neither the participants nor the researchers knew which treatment each person received.
参与者被随机分配到两组。一组每天服用含有2000毫克DHA的补充剂，另一组服用安慰剂，持续24个月。安慰剂由玉米油和大豆油混合而成，在外观、味道和气味上与DHA补充剂无法区分。参与者和研究人员都不知道每个人接受的是哪种治疗。
The researchers first wanted to determine whether DHA actually reached the brain. Measurements of DHA levels in the cerebrospinal fluid, which surrounds the brain and spinal cord, showed that concentrations increased by 17 percent after six months in the DHA group. There was no difference between carriers and noncarriers of the APOE ε4 allele, providing direct evidence that high-dose DHA supplementation reaches the brains of cognitively healthy older adults regardless of APOE ε4 status.
研究人员首先想确定DHA是否真的到达了大脑。对环绕大脑和脊髓的脑脊液中DHA水平的测量显示，DHA组在六个月后浓度增加了17%。APOE ε4等位基因携带者与非携带者之间没有差异，这提供了直接证据，证明无论APOE ε4状态如何，高剂量DHA补充剂都能到达认知健康的老年人的大脑。
The results were very different, however, when it came to cognitive function and brain structure. After 24 months, participants completed the Repeatable Battery for the Assessment of Neuropsychological Status, a standardized test of memory and cognitive performance. No significant differences were found between the DHA and placebo groups. Likewise, there were no significant differences in changes in hippocampal volume, a brain region critical for memory and an early biomarker of Alzheimer’s disease.
然而，在认知功能和大脑结构方面，结果却大相径庭。24个月后，参与者完成了“神经心理状态评估可重复电池”（RBANS），这是一项针对记忆力和认知表现的标准化测试。DHA组和安慰剂组之间没有发现显著差异。同样，在海马体体积的变化上也没有显著差异，而海马体是记忆的关键脑区，也是阿尔茨海默病的早期生物标志物。
Why Didn’t It Work?
为什么没起作用？
The researchers suggest several possible explanations for why DHA reached the brain but failed to produce measurable clinical benefits. One possibility involves an enzyme that disrupts DHA metabolism in the brain. When an enzyme known as calcium-dependent phospholipase A2 (cPLA2) becomes activated, it may break down DHA before it can be incorporated into synaptic membranes—the structures where DHA is thought to play its most important role in supporting cognitive function.
研究人员提出了几种可能的解释，说明为什么DHA到达了大脑却未能产生可衡量的临床益处。一种可能性涉及一种破坏大脑中DHA代谢的酶。当一种被称为钙依赖性磷脂酶A2（cPLA2）的酶被激活时，它可能会在DHA整合到突触膜（DHA被认为在支持认知功能方面发挥最重要作用的结构）之前将其分解。
Another possible explanation is that many participants had cardiovascular risk factors such as obesity, hypertension, and physical inactivity. The chronic inflammation associated with these conditions may have blunted the effects of supplementation, making it difficult for a single nutrient to produce measurable benefits.
另一种可能的解释是，许多参与者患有肥胖、高血压和缺乏运动等心血管风险因素。与这些疾病相关的慢性炎症可能削弱了补充剂的效果，使得单一营养素难以产生可衡量的益处。
The researchers also note that the participants were relatively young, with an average age of 66, and experienced only minimal cognitive decline over the course of the two-year study. As a result, there may simply have been too little decline during the trial to detect any protective effect from DHA supplementation.
研究人员还指出，参与者相对年轻，平均年龄为66岁，在两年的研究过程中仅经历了轻微的认知衰退。因此，试验期间的衰退可能太小，以至于无法检测到DHA补充剂的任何保护作用。
The researchers further point out that the Covid-19 pandemic may also have affected the interpretation of the results, as 38 percent of participants dropped out before completing the trial. In addition, because the study was conducted at a single center, caution is warranted when generalizing the findings to broader populations.
研究人员进一步指出，新冠疫情可能也影响了对结果的解读，因为38%的参与者在完成试验前中途退出。此外，由于该研究是在单一中心进行的，在将研究结果推广到更广泛的人群时需要谨慎。
Going forward, the research team plans to focus on understanding how DHA is metabolized within the brain, conducting studies in people with preclinical Alzheimer’s disease, incorporating more sensitive biomarkers of neurodegeneration—such as plasma phosphorylated tau and neurofilament light chain—and exploring personalized treatment strategies based on gut microbiome composition and APOE genotype.
展望未来，研究团队计划专注于了解DHA在大脑内的代谢方式，对阿尔茨海默病临床前阶段的人群进行研究，纳入更敏感的神经退行性生物标志物（如血浆磷酸化Tau蛋白和神经丝轻链），并探索基于肠道微生物群组成和APOE基因型的个性化治疗策略。
Rather than relying on dietary supplements to prevent dementia, the findings suggest that, at present, the most effective way to reduce the risk of developing Alzheimer’s disease may still be to focus on well-established lifestyle measures, including regular physical activity, adequate high-quality sleep, and a balanced diet.
研究结果表明，目前预防痴呆症最有效的方法或许并非依赖膳食补充剂，而是专注于已被证实有效的健康生活方式，包括规律的体育锻炼、充足的高质量睡眠以及均衡的饮食。