When we consider a healthy dietary pattern, whether that be for overall health or to prevent Alzheimer’s disease, it’s imperative that we consume healthy fats. For those that paid attention to nutrition messaging in the 80’s, the idea of consuming dietary fats might still make you feel uncomfortable, as for at least a decade or so, all dietary fat was demonized, leading to a low fat food product craze. As I sit here writing this in 2025, the research is abundantly clear: we need fat in our diet; we need healthy fats along with healthy proteins and carbohydrates if we want to prevent dementia and other chronic diseases.
So that brings up the question, what is “healthy” fat? If you’ll bear with me, I want to give you a very brief lesson in organic chemistry, which will help me make this answer clearer. You may have heard terms like “saturated fat” or “unsaturated fat”. These are organic chemistry terms, with the “saturation” referring to the saturation of the carbon molecules with hydrogen. While understanding what this looks like may not matter much, the takeaway point is that the chemical composition of the various fatty acids is different. It is this chemical composition (along with the other compounds within the food itself) that determines whether a fat is healthy or unhealthy.
The most critical fat for brain health is called omega-3 fatty acids, or more specifically, preformed EPA and DHA. Omega-3 fats are polyunsaturated fats, meaning that they have multiple places where the carbon chain of the fatty acid is not saturated with hydrogen. Omega-3 fats can be found in foods like flaxseeds, chia seeds, and walnuts. Preformed EPA and DHA can be found in fatty fish like salmon and sardines, and in algae, which is where the fish derive it from.
Over half of our brain’s weight is made up of fat, specifically omega-3 fatty acids, and this reservoir decreases when we do not consume a source of preformed DHA and EPA. These omega-3 fats are needed to maintain the health of our neurons. Thus, if we want to keep our brain healthy, we must get regular sources of preformed EPA and DHA. We can do this by eating fatty fish several times per week, and that is an option. It is not, however, a sustainable option for our planet, as we already overfish our oceans. If everyone in the world were to all of a sudden eat fatty fish multiple times per week, we would cause further harm to an already deteriorating ecosystem. My recommendation is to get your EPA and DHA through a supplement. For most people, a fish or algae oil supplement that provides 1-1.5 grams of EPA and DHA is adequate to keep their levels within the optimal range. There are some potential side effects and drug nutrient interactions, so if you don’t take an omega-3 supplement and are considering starting one, you should speak with your medical doctor first. I should also note that this dose may not be adequate for everyone. The best way to know for sure would be to test your omega-3 index, which measures the amount of omega-3 in your red blood cell membranes. An optimal range is at least 8%.
Saturated fats appear to be the most harmful to brain health, although the dose matters. Saturated fats are found in animal products like meat, eggs, and dairy products, but also in tropical oils like coconut and palm. High intakes of saturated fats are correlated with increased risk of developing dementia. We also see increased risk of other chronic diseases of aging, such as cardiovascular disease, with higher saturated fat intake. With cardiovascular disease, the impact of dose is more clearly elucidated, with the increased risk occurring when intake reaches a critical threshold that lies around 8-9% of total calories from saturated fat. Hopefully future research will identify if such a critical threshold exists with regard to dementia. Regardless, decreasing intake of animal products appears wise from another dietary fat standpoint: trans fats. When most of us think of trans fats, we think of Crisco, or other margarines that were so often used in baked goods. Fortunately, in a win for public health, the FDA banned the use of artificial trans fats (called partially hydrogenated oils) in 2015, so they are no longer used in the US food supply. This was an incredible move, given that the research connecting trans fats with poor health outcomes in humans was overwhelmingly robust. So we no longer need to worry about trans fats coming from artificial production, but naturally occurring trans fats still exist. These are found primarily in animal products, but they can also be created when you cook an oil past its smoke point for an extended period of time (think about frying oil used to cook fries in a fast food restaurant that’s left frying all day long and rarely changed).
There’s tons of misinformation out there about dietary fats. Perhaps the most pervasive myth is that seed oils like canola oil, sunflower oil, and soybean oil are inflammatory or otherwise harmful. Seed oils are typically high in omega-6 fatty acids, which are also often vilified. This is an interesting nutrition myth because essentially all of the scientific literature available (and this has been overwhelmingly studied) shows benefit to consumption of seed oils. Randomized controlled trial after randomized controlled trial looking at the intake of seed oils either show no difference in biomarkers of inflammation and cardiometabolic health compared to other monounsaturated plant oils, or they show biochemical benefits when compared to intake of saturated fats like butter.
I think the reason for this massive area of misinformation stems from an appeal to nature fallacy. This logical fallacy explains when we assume that something is healthier because it is more “natural.” While at first glance it may seem that something more natural is better, we have to look to the science to help us determine what foods are most healthful. Normally when I speak to people about this concept at the Amos Institute, I hear the argument, “but we didn’t evolve to eat foods that are not made in nature!” And that’s true. But evolution cared only about us reaching reproductive age so that we could ensure the survival of our species. Our early human ancestors that we refer to when discussing evolution did not live long enough to develop and die from chronic diseases of aging like Alzheimer’s and Dementia. So the argument that evolution should guide our understanding of what is and is not healthy for healthspan and longevity is nonsensical. Of course, nutrition science is highly nuanced. As I mentioned in the beginning of this article, the type of fatty acid is not the only thing that determines the health implications. We also have to look at the company that the fat keeps. So if omega-6 seed oils are found in a food that’s also high in sugar and refined carbohydrates (which is often the case in hyperpalatable processed foods), the overall health implications will still be deleterious.
At the end of the day, we need a full healthy dietary pattern. Fat, while an important part of a healthy diet, is not the end all be all. We need all of the components of a healthy dietary pattern to be in place. But in terms of fats, focus on foods like extra virgin olive oil, nuts, seeds, avocados, and fatty fish. Consider an omega-3 supplement to make sure you’re meeting your needs of preformed EPA and DHA. Avoid fatty cuts of meat, butter, cream, or cooking with animal fat like lard or tallow. Finally, avoid deep fried foods or cooking oils for extended periods of time.
