Canola oil linked to worsened memory and learning ability
in Alzheimer’s

Date:

December 7, 2017

Source:

Temple University Health System

Summary:

Canola oil is one of the most widely consumed vegetable
oils, yet little is known about its health effects. Now, a study links canola
oil consumption in the diet with worsened memory, worsened learning ability and
weight gain in mice which model Alzheimer’s disease. It’s the first study to
suggest that canola oil is more harmful than healthful for the brain.

Canola oil is one of the most widely consumed vegetable
oils in the world, yet surprisingly little is known about its effects on
health. Now, a new study published online December 7 in the
journal Scientific Reports by researchers at the Lewis Katz School of
Medicine at Temple University (LKSOM) associates the consumption of canola oil
in the diet with worsened memory, worsened learning ability and weight gain in
mice which model Alzheimer’s disease. The 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,” explained Domenico Praticò, MD, Professor in the Departments of
Pharmacology and Microbiology and Director of the Alzheimer’s Center at LKSOM,
as well as senior investigator on the study. “Very few studies, however,
have examined that claim, especially in terms of the brain.”

Curious about how canola oil affects brain function, Dr.
Praticò and Elisabetta Lauretti, a graduate student in Dr. Pratico’s laboratory
at LKSOM and co-author on the new study, focused their work 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 animal model was designed to recapitulate Alzheimer’s
in humans, progressing from an asymptomatic phase in early life to full-blown
disease in aged animals.

Dr. Praticò and Lauretti had previously used the same
mouse model in an investigation of 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 their latest
work, they wanted to determine whether canola oil is similarly beneficial for
the brain.

The researchers started by dividing the mice into two
groups at six months of age, before the animals 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 daily.

The researchers then assessed the animals at 12 months.
One of the first differences observed was in body weight — animals on the
canola oil-enriched diet weighed significantly more than mice on the regular
diet. Maze tests to assess working memory, short-term memory, and learning
ability uncovered additional differences. Most significantly, mice that had
consumed canola oil over a period of six months suffered impairments in working
memory.

Examination of brain tissue from the two groups of mice
revealed that canola oil-treated animals 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 beneficial role in the brain
and acts as a buffer for the more harmful insoluble form, amyloid beta 1-42.

As a result of decreased amyloid beta 1-40, animals on
the canola oil diet 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 areas where
neurons come into contact with one another, play a central role in memory
formation and retrieval.

“Amyloid beta 1-40 neutralizes the actions of
amyloid 1-42, which means that a decrease in 1-40, like the one observed in our
study, leaves 1-42 unchecked,” Dr. Praticò explained. “In our model,
this change in ratio resulted in considerable neuronal damage, decreased neural
contacts, and memory impairment.”

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,”
Dr. Praticò said. “Based on the evidence from this study, canola oil
should not be thought of as being equivalent to oils with proven health
benefits.”

The next step is to carry out a study of shorter duration
to determine the minimum extent of exposure necessary to produce observable
changes in the ratio of amyloid beta 1-42 to 1-40 in the brain and alter
synapse connections. A longer study may be warranted in order to determine
whether canola oil also eventually impacts tau phosphorylation, since no
effects on tau were observed over the six-month exposure period.

“We also want to know whether the negative effects
of canola oil are specific for Alzheimer’s disease,” Dr. Praticò added.
“There is a chance that the consumption of canola oil could also affect
the onset and course of other neurodegenerative diseases or other forms of
dementia.”

The research was funded in part by a grant from the Wanda
Simone Endowment for Neuroscience.

Story Source:

Materials provided by Temple University Health
System. Note: Content may be edited for style and length.

Journal Reference:

1.            Elisabetta
Lauretti, Domenico Pratic�. Effect of canola oil
consumption on memory, synapse and neuropathology in the triple
transgenic mouse model of Alzheimer’s disease. Scientific Reports,
2017; 7 (1) DOI: 10.1038/s41598-017-17373-3