Consumption of canola oil is linked to weight gain and declines in memory and learning ability in mice that model Alzheimer’s disease, according to a new study published in the journal Scientific Reports.
Canola oil — a vegetable oil made from the rapeseed plant — is one of the most widely consumed vegetable oils in the world and has long been touted as a healthy alternative to saturated fats. However, surprisingly little is known about its effects on health. This study is the first to suggest that canola oil is more harmful than healthful for the brain.
“Canola oil is appealing because it is less expensive than other vegetable oils, and it is advertised as being healthy,” said lead researcher Domenico Praticò, M.D., professor in the Departments of Pharmacology and Microbiology and Director of the Alzheimer’s Center at Lewis Katz School of Medicine at Temple University (LKSOM).
“Very few studies, however, have examined that claim, especially in terms of the brain.”
In an attempt to understand how canola oil affects brain function, Praticò and co-author Elisabetta Lauretti, a graduate student in Pratico’s laboratory at LKSOM, focused on memory impairment and the formation of amyloid plaques and neurofibrillary tangles in an Alzheimer’s disease mouse model.
Amyloid plaques and phosphorylated tau, which is responsible for the formation of tau neurofibrillary tangles, contribute to neuronal dysfunction and degeneration and memory loss in Alzheimer’s disease. The mouse model was designed to mimic Alzheimer’s in humans, progressing from an asymptomatic phase in early life to full-blown disease in the older rodents.
In a previous study, the researchers used the same mouse model to investigate olive oil, the results of which were published earlier in 2017. In that study, they found that Alzheimer mice fed a diet enriched with extra-virgin olive oil had reduced levels of amyloid plaques and phosphorylated tau and experienced memory improvement.
For the new study, they wanted to determine whether canola oil is similarly beneficial for the brain.
The mice were divided into two groups at six months of age, before they had developed signs of Alzheimer’s disease. One group was fed a normal diet, while the other was fed a diet supplemented with the equivalent of about two tablespoons of canola oil per day.
The mice were evaluated at 12 months. One of the first differences observed was in body weight — mice on the canola oil-enriched diet weighed significantly more than mice on the regular diet.
Maze tests designed to gauge working memory, short-term memory, and learning ability revealed even more differences. The researchers found that the canola-consuming mice had experienced declines in working memory within that six month period.
Examination of brain tissue from the two groups of mice revealed that canola-consuming mice had greatly reduced levels of amyloid beta 1-40. Amyloid beta 1-40 is the more soluble form of the amyloid beta proteins. It generally is considered to serve a helpful role in the brain and acts as a buffer for the more harmful insoluble form, amyloid beta 1-42.
As a result of reduced amyloid beta 1-40, the canola-consuming mice further showed increased formation of amyloid plaques in the brain, with neurons engulfed in amyloid beta 1-42. The damage was accompanied by a significant decrease in the number of contacts between neurons, indicative of extensive synapse injury. Synapses, the spaces where neurons come into contact with one another, play a vital role in memory formation and retrieval.
The findings suggest that long-term consumption of canola oil is not beneficial to brain health.
“Even though canola oil is a vegetable oil, we need to be careful before we say that it is healthy,” said Praticò. “Based on the evidence from this study, canola oil should not be thought of as being equivalent to oils with proven health benefits.”
Source: Temple University Health System