This Made Everyone Worried About Omega-3s and Dementia

Recently there was a new study that made a lot of people concerned. Omega-3 supplementation was associated with faster cognitive decline in older adults. Of course, this is a eye-catching headline because all the previous data suggests that omega-3s have the opposite effect, that they protect your cognition and brain against aging. And for some reason, I kept seeing post after post from different people saying that omega-3s cause cognitive decline and that they're the worst thing for your body. The problem is that this study didn't show that omega-3s cause cognitive decline or degeneration. That's why I felt the need to make this video to clarify the confusion, and I'm going to analyze this study in greater detail to see what's true about it and what's not. First, the

study was published in collaboration with the Alzheimer's Disease Neuroimaging Initiative. The ADNI is a large public-private research initiative funded by the National Institute of Health and many partners. It is an observational study, not a randomized control trial. That's important to keep in mind because observational studies don't prove causality. They can be useful in directing your future research or supporting already established ideas. Now, the problem with this particular finding is that it contradicts previous findings. Of course, observational studies often find conflicting results. Many other observational studies have found that omega-3s are neuroprotective. They're associated with lower Alzheimer's risk and better cognitive function. The totality of evidence matters more than a single study. Interestingly, a previous 2023 meta-analysis of people in the same Alzheimer's Disease Neuroimaging Initiative cohort showed that long-term users of omega-3 supplements showed a 64% reduced risk of Alzheimer's disease. Among 103,000 participants in 48 studies, long-term omega-3 intake was seen to be associated with a 20% lower risk of all-cause dementia or cognitive decline. And what's even more important is that actual randomized control trials suggest that not only do omega-3 supplements not cause cognitive decline, but they can actually improve cognition. For example, this 2025 meta-analysis of 58 randomized controlled trials showed that omega-3 supplements led to modest improvements in cognitive function among adults. Each 2,000 mg a day of omega-3 supplementation improved attention, perceptual speed, language, primary memory, and global cognitive abilities significantly. This is very relevant because this new observational study it didn't randomize people in different groups. They didn't also control for other lifestyle variables and other health variables that can influence the outcomes. They did control for age, sex, APOE4 status, and cognitive impairment diagnosis. What they didn't control for was the omega-3 dose, the quality of the supplements, the EPA DHA ratio, their cardiovascular health, their metabolic health, their omega-3 status, and the reason why they started to take the omega-3s in the first place. In terms of the hierarchy of evidence, the meta-analysis of randomized controlled trials are at the top of the pyramid. They're the highest quality evidence. Observational studies, which this new study is, are somewhere in the middle and much lower in quality. So, in terms of quality of evidence, omega-3 supplements still have neuroprotective effects. There's no evidence that omega-3 supplements would prevent or treat Alzheimer's disease or dementia, but there's also no evidence that the omega-3s would harm cognition or lead to cognitive decline. And if you look at the totality of evidence, you find the opposite effect. So, why did this new

study see an association with cognitive decline from omega-3 supplementation? The likely explanation is reverse causation. People may start taking omega-3s because they already have heart problems or they notice cognitive decline. So, it's not omega-3s causing cognitive decline, it's people with already initiated cognitive decline starting to use omega-3s. The reason reverse causation is the most likely explanation is because the study didn't control for supplement dosage, reasons for starting to take omega-3s, baseline cardiovascular health, depression, baseline metabolic health, inflammation status, and their omega-3 status, all of which would influence the final outcome. In the general population, people who start taking omega-3s are still the ones who are concerned about their heart health because omega-3s are most commonly taken for heart health, and the general population is concerned with their heart health if they have a health scare or they have a family history of heart disease. You can find reverse causation in many other examples as well. People with low blood sugar often are seen to have a higher risk of mortality, but that's because people who often get to very low levels of blood sugar in the general population, I'm not talking about health optimizers, in the general population people who have low blood sugar usually have some disease that lowers their blood sugar like cancer or they're just malnourished like elderly people. Very old people, 70-80 years old people, they often undereat, they're malnourished, their blood sugar drops, and they die to the malnourishment because of not eating enough calories, not because of the low blood sugar. The same with the omega-3s. Omega-3s are known to have heart benefits, and people with some concern about their heart health already have cardiovascular complications that also reflects in brain aging. The brain is a cerebrovascular organ, and heart disease shows up in the brain the same way heart disease reflects in erectile dysfunction. It's the same vasculature.

Let's also cover what did the study actually find. They found that omega-3 supplementation users had faster deterioration in major cognitive tests. They had worsening in MMSE, ADAS-Cog 13, and CDR-SB, which are standard cognitive tests. However, the non-omega-3 exposed group also saw worsening of the tests over the course of years. It's just the omega-3 group saw worse results. The important point here is that they also used PET scans to measure actual brain pathology in these people, and they found no association between omega-3 use and progression in Alzheimer's or neurodegeneration as measured by amyloid deposition, tau accumulation, and brain gray matter atrophy. There was no difference between the groups in actual physical degradation of the brain or pathological changes towards Alzheimer's. The only thing they did see in the omega-3 users was reduced FDG PET metabolism. FDG PET measures glucose metabolism and is often interpreted as synaptic activity and neuronal function. This would be an explanation as to why there was a cognitive decline in the omega-3 users. However, you have to interpret these findings very carefully. Reduced FDG PET metabolism is not the same thing as increased Alzheimer's pathology. Remember, the study found no increase in amyloid or tau proteins, which are the core pathological hallmarks of Alzheimer's disease. So, the omega-3 users weren't progressing towards Alzheimer's, at least not any faster than the control group who wasn't taking omega-3s. FDG PET metabolism is influenced by many things related to overall metabolic health, vascular health, metabolic disease, depression, aging, inflammation, and heart health. It's impossible to claim that omega-3s caused the lower brain metabolism of FDG PET because it's not a controlled study and the relevant factors weren't controlled for. If omega-3s were truly causing cognitive decline or leading towards Alzheimer's pathology, you would see it in the hallmarks of Alzheimer's disease, such as in the tau protein and amyloid, but there was no effect on these markers. A lot of people also

speculated that the reason these omega-3 users saw cognitive decline was because of these oxidized fish oil or rancid omega-3s that they were taking. However, that's a pretty far-fetched assumption. Yes, omega-3s are prone to oxidation and they can be easily oxidized. But then again, the omega-3 users didn't see any actual brain degeneration beyond what's normal. They saw the same effects on the hallmarks of Alzheimer's and brain atrophy as the control group. So, if there was increased brain inflammation, you would have seen it in greater tau and amyloid protein accumulation. And secondly, there's no evidence that even regular commercial omega-3 supplements cause inflammation. If anything, the omega-3s attenuate oxidative stress and inflammation. A 2022 umbrella meta-analysis that looked at 32 meta-analyses of randomized controlled trials, which includes dozens of studies, found that supplementation with omega-3s can improve inflammatory biomarkers, such as CRP, TNF alpha, and IL-6. That's a massive amount of studies, and it's a consistent finding. And if that's not enough, then we also have a study that looks at the effects of consuming oxidized rancid fish oil. They found that consuming oxidized fish oil every day for 3 to 7 weeks resulted in no changes in markers of oxidative stress, inflammation, or lipid peroxidation, the oxidation of lipids. But, they did find a significant increase in plasma levels of EPA and DHA, which reflects a higher omega-3 status. What's important about this study is that they also used fish oil that was oxidized in a way that's not possible with your everyday means. It was way more oxidized by exposing it to insane amounts of heat and oxygen that you wouldn't be able to get from your gas station fish oil that's been sitting on the shelf for a little bit. So, even this highly oxidized fish oil didn't cause any increase in inflammation. I'm not saying that you should buy the gas station fish oil. It's still a lower quality product compared to a pharmaceutical grade fish oil or omega-3 supplementation, but it just highlights that even this highly oxidized artificially oxidized fish oil didn't cause any inflammation. So, the argument that omega-3 supplements cause inflammation is not real, backed up by dozens of randomized controlled trials. And you should definitely buy higher quality omega-3 supplements that come in a dark glass bottle, that are ideally fresh, not years old, and that haven't been exposed to heat, oxygen, or sunlight. Overall, this study didn't

prove that omega-3s cause cognitive decline. It's an uncontrolled observational study, and the results are probably cause of reverse causation. That's the most likely explanation. Omega-3 users had no change in Alzheimer's pathology or brain degeneration compared to non-users. So, the cognitive decline was because of something else other than neurodegeneration, most likely reverse causation. The totality of evidence suggests that omega-3 supplements have neuroprotective effects, and they might reduce cognitive decline as shown by randomized controlled trials, which are higher quality evidence than observational cohort studies. Omega-3s don't cause inflammation, even highly oxidized fish oil doesn't, And pharma grade omega-3 supplements are even less likely to do so. And the totality of evidence suggests that high quality omega-3s lower inflammation and oxidative stress. The reason I made this video is because I think omega-3s are one of the lowest hanging fruit for most people. Most people don't eat enough seafood, they have a sub-optimal omega-3 index, and based on the studies we know, having a low omega-3 index increases your risk of dying to heart disease, Alzheimer's, and to all other causes. Even smokers who had a high omega-3 index make up for some of the harm that they get from smoking. Whereas smokers with a low omega-3 index die sooner. And the problem is that on social media you have these headlines, people who didn't read the study or they don't understand the methodology of the study, they say that omega-3 supplements cause cognitive decline when there's no evidence for that. And the totality of evidence suggests the opposite. You don't have to start taking omega-3s if you eat enough seafood, but if you don't eat seafood and you don't take omega-3 supplements, you probably have a sub-optimal omega-3 index. That's why I think omega-3s are a god tier supplement for most people. Check out my video where I rank 100 other supplements from worst to best.