Linked to a reduced risk of heart disease, stroke, diabetes, rheumatoid arthritis, Alzheimer’s and certain cancers, it’s easy to see why olive oil – especially extra virgin – is popular with health-conscious people.
But what’s in olive oil that makes it a healthy choice, and how in particular can it maintain good brain function?
Credit is usually given to its abundance of plant chemicals, but maybe we should focus on one very special substance in olive oil. Then again, maybe we shouldn’t. Keep reading and I’ll explain…
A Key Component of Cell Membranes
The phytochemicals in olive oil show strong antioxidant and anti-inflammatory properties, but there’s also evidence the fatty acid that makes up 73 percent of the total oil content is also important. It’s a monounsaturated fatty acid (MUFA) called oleic acid.
Oleic acid is a key building block of the brain and nervous system. It accounts for up to 30 percent of the fatty acid content of adult cell membranes and helps keep them pliable. Oleic acid also plays a role in nerve growth and repair.
It’s also required for the myelin sheath that covers nerve cells, allowing electrical impulses to be transmitted quickly and efficiently.
But unlike alpha-linolenic acid (omega 3) and linoleic acid (omega 6) that must come from the diet, oleic acid (omega 9) is not an “essential” fat or lipid, because the body makes its own as required. So, does it matter how much we obtain from food?
A research group from Italy set out to answer this question. Based on cognitive tests and food intakes of 278 people aged 65 to 84 without dementia, the researchers concluded that a high MUFA diet — where oleic acid was the prominent fat — protected against age-related cognitive decline.1
However, the study was small, took information from one time point, and involved people from a rural community who ate a typical Mediterranean diet high in olive oil. The study isn’t sound enough to be the final word on the subject, and even the authors admitted the benefits could have come from the phytochemicals in the olive oil, not just oleic acid.
Fortunately, we have additional evidence. Two rigorously controlled studies in 32 adults aged 18 to 40 were carried out by researchers from the University of Vermont. Lowering the saturated fat content of their diet and replacing it with oleic acid positively affected the participants’ mood. In particular, it reduced anger and hostility.2 (Given the state of our politics, maybe the whole population should be required to eat more olive oil.)
Two other studies link MUFU intake from food with reduced depression,3 4 and a trial involving 20 adolescent boys with ADHD found higher levels of oleic acid in the blood was linked to an improved temperament.5
These studies suggest oleic acid intake from dietary sources has a positive impact on the brain, but it takes lab work to seek out more definitive findings.
In tissue from autopsies, Japanese scientists found a significant 6.2 percent decline in oleic acid in the brains of patients who had been suffering from major depressive disorder, when compared to a normal brain.6
Biochemists from the University of Western Ontario, Canada found MUFAs — mainly oleic acid — inhibit the production of amyloid beta brain plaques in both lab-cultured tissue and in mice engineered to succumb to Alzheimer’s.7
Another Canadian research group compared post-mortem brain samples from people who while living had suffered from either mild cognitive impairment (MCI), Alzheimer’s, or who were cognitively healthy when they died. They found the MCI samples were 70 percent lower and the Alzheimer’s samples were 80 percent lower in oleic acid compared to the healthy controls.
That’s a remarkable finding that might send me racing to the olive oil section of the supermarket.
But nothing in science ever seems to be simple. In the superior temporal region of the brain — mainly responsible for processing sounds — and the mid frontal cortex — involved with memory and decision making — oleic acid was 10 to 20 percent higher in the Alzheimer’s samples.8
And when a group of neuroscientists in the UK compared the fatty acid composition of cellular membranes in 58 normal and 114 Alzheimer’s brains, they found increased oleic acid in the frontal and temporal cortex of the diseased brains.9
Adding to the confusion are two important recently published papers. They concern Parkinson’s disease.
Oleic Acid Makes Parkinson’s Worse
The researchers found that oleic acid led to the build-up of a protein called alpha-synuclein in neurons, promoting toxicity in both cellular and animal models of Parkinson’s.
Cells convert stearic acid to oleic acid by way of an enzyme called SCD when the body makes its own oleic acid. Inhibiting SCD lowered levels of oleic acid and thereby reduced alpha-synuclein, protecting the neurons from harm.
Since these studies refer to oleic acid made in the cells themselves – NOT derived from the diet — they may have little or nothing to do with what we consume. But nobody knows for sure.10
As scientists from China point out, “The brain contains thousands of lipid species, but the complex lipid compositional diversity and the function of each of lipid species are currently poorly understood.”11
Since this is the case, and the body makes it as required, I’m going to venture a cautious opinion: eating additional oleic acid is not a brain health priority. We get a plentiful supply in our diets in any case. Apart from olive oil, other good sources are milk, eggs, cheese, red meat, poultry, avocado, nuts and seeds.
Significant amounts are also found in cooking oils, which means many junk foods such as fries and potato chips also supply oleic acid.
And last but not least, I want to say that olive oil is a very healthy food in spite of the mixed findings on oleic acid. Because the body makes its own AND gets abundant amounts from other sources, the presence of oleic acid in olive oil is probably a sideshow. Tons of evidence – including some of the studies above – clearly point to major health benefits from a diet rich in olive oil.