You’ve probably heard that there is good cholesterol (HDL) and bad cholesterol (not HDL or LDL). But did you know that one of the places in the body where this division is most evident is the brain? Recent studies reveal the role of cholesterol in maintaining organ health and accelerating its decline. The composition of fat is related to these various effects.
For a long time, cholesterol’s role in the brain was viewed as sinister, especially because of its association with vascular accidents in the organ. However, over the past decade, studies have shown that the brain depends on it to function well.
The organ consists of about 60% fat and needs fat to maintain the structure of neurons and transmit electrical signals. But this does not mean there is any fat.
“It is a complex division and depends on the quality of this cholesterol,” explains neurologist Marco Tullio Pedatella, neurology coordinator at the Einstein Israelita Hospital in Goiânia.
“It’s not just about thinking in general levels, even the ratio of proteins bound to HDL cholesterol has an impact on the effects it will bring to the brain.”
Therefore, the balance is delicate. If, on the one hand, good fats are essential for the formation and maintenance of neuronal functions, then on the other hand, excess fats, especially the types of LDL that accumulate in droplets in the organ, are associated with inflammation and cognitive decline.
When cholesterol protects or harms
Many studies have been conducted to understand the effects of this distinct role of cholesterol in the brain.
One of them, conducted by researchers at the University of Texas in the United States, and published in the Journal of Clinical Medicine in October 2024, revealed that HDL may have a neuroprotective effect.
Imaging tests on 1,800 adults showed that those with higher levels of HDL had, on average, a larger volume of gray matter in the brain, which may be associated with better preservation of cognition with aging. This beneficial association was maintained even in patients who had the ApoE4 gene associated with Alzheimer’s disease.
Another research, published in the journal Immunity in July 2025, was dedicated to “bad” LDL cholesterol. Research has revealed that having high levels of this type of fat between the ages of 40 and 65 significantly increases the risk of developing Alzheimer’s disease and other forms of dementia in the coming decades.
According to research by neuroscientists at Purdue University, also in the United States, excess fat can paralyze microglia, which are defense cells in the brain.
They discovered that the lipid enzyme DGAT2 accumulates in these cells and reduces their ability to clear amyloid plaques, accumulations of proteins closely linked to Alzheimer’s disease. The study also discovered, in laboratory cells, that by eliminating fatty enzymes, the cellular function of these brain “cleaners” is fully restored.
“These results reinforce the importance of maintaining a balanced lipid metabolism to maintain brain health throughout life,” highlights cardiologist Fabiana Hanna Rashid, specialist in atherosclerosis, from Einstein Israelita Hospital.
“Cholesterol imbalance in the brain affects communication between neurons, impairs synaptic function and can contribute to cognitive decline.”
The good news is that keeping cholesterol under control — especially LDL — can reduce the risk of cognitive decline. Studies show that using statins and dietary changes not only helps protect the heart, but also helps delay or even prevent dementia.
Cholesterol in the brain only
Although the body produces cholesterol in various tissues, the brain is “special.” It is made there and does not freely cross the blood-brain barrier, which isolates the nervous system, which is why its levels may differ from those in the rest of the body.
“Cholesterol in the brain has its own metabolism, and only derivatives such as 24S-hydroxycholesterol can cross this barrier,” Pedatella explains. This separation helps protect the nervous system from sudden changes in circulating fats.
However, systemic disorders in the body associated with lipid levels, such as metabolic syndrome, can indirectly affect cholesterol metabolism in the brain. For example, individuals with abdominal obesity, high blood pressure, and low blood HDL levels often have reduced brain volume.
“While healthy fats are essential for cognitive function and brain health, low HDL levels associated with other metabolic problems have been linked to decreased cognitive performance in trials, so we need to further investigate whether reversing or improving metabolic syndrome can benefit brain health and in what ways,” Rashid says.
Furthermore, the time in life at which cholesterol levels rise appears to determine the risk of future dementia.
“The effect of cholesterol levels on dementia risk is most significant when exposure occurs in midlife,” the neurologist warns. After age 70, this association weakens, and higher levels may be linked to a better prognosis in some studies.
These discrepancies suggest that there is still much to understand. “There is a lack of longitudinal studies able to distinguish between the cause and effect of cholesterol in the brain. It is also necessary to study how early interventions, such as balanced diets and metabolic control, can preserve brain function,” highlights the Einstein cardiologist.
In the meantime, it is useful to follow the rule: taking care of cholesterol through good nutrition, drug treatments when necessary, and physical activity is not just a matter of the heart; It is also an investment in health as a whole, including the brain.
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