Upon review, a U.S. study of what happened to mice bred for Alzheimer’s symptoms when canola oil was added to their diet doesn’t translate to a risk for people, researchers and the Canola Council of Canada say.
The mouse study, which was published last week by researchers from Temple University in Philadelphia, examined mice genetically modified to model Alzheimer’s disease when given chow with canola oil and said it found them more prone to certain markers of the disease than the same type of mice on regular chow.
Emphasizing the mouse study is not the same as a human clinical trial, the Canola Council on Wednesday put forward a list of concerns and criticisms of the Temple study from Canadian and U.S. researchers.
The mice tested in both the control and canola oil groups in the Temple study were genetically engineered to develop three characteristics of Alzheimer’s disease: memory impairment, amyloid plaques and neurofibrillary tangles. The Temple team subjected the mice to maze tests as well as physical exams and brain tissue tests.
The Temple team had written that “chronic exposure to the canola-rich diet” — which it described as “the human equivalent of about one tablespoon of canola oil daily” in the mouse chow — resulted in a “significant increase in body weight and impairments in (the mice’s) working memory together with decreased levels of post-synaptic density protein-95, a marker of synaptic integrity.”
In brain tissue samples, the Temple team also reported “greatly reduced” levels of amyloid beta 1-40, the more soluble form of the amyloid beta proteins, in the canola oil group. Amyloid beta 1-40, the team said, is considered to act as a buffer for the “more harmful” insoluble form, amyloid beta 1-42.
“Animal models of Alzheimer’s lack predictive validity,” Richard Bazinet, an associate professor in the University of Toronto’s department of nutritional science, said in a Canola Council release Wednesday.
For example, he said, “we have a series of major phase-III clinical trials with drugs in Alzheimer’s disease. The drugs ‘worked’ in the animal models, but failed in humans.”
“This mouse model is a huge stretch from what you may see in humans,” Peter Jones of the University of Manitoba’s Richardson Centre for Functional Foods and Nutraceuticals said in the same release.
The Canola Council also cited a published critique of the Temple study by Kevin Folta, a horticultural sciences professor at the University of Florida, in which he wrote that the Temple paper “does not show in any way that there is a causal link to disease in humans. Not even close.”
Out of six measures and three different tests, the canola oil-fed mice were different for one test and showed about a 20 per cent difference in behaviour, the council quoted Folta as saying. “The researchers refer to this as ‘significant deficits of working memory’ but this slight difference in one test is inconsistent with this claim.”
As for the reported weight gain, the council said, that’s “not surprising given that the canola oil diet was higher in calories than the control diet.”
Also, Jones said, the control and canola oil diets fed to the mice “were not balanced for fat content… We know that higher fat diets are more palatable and lead to increased food intake and weight gain, which is what happened here.”
Furthermore, he said, “animals with greater body fat will elicit reduced food-seeking behaviour which may, independent of any fat-induced action, well explain the differences in brain chemistry and memory.”
The notion that canola oil worsens Alzheimer’s symptoms “in no way reflects what the data present,” Folta said. “What the data show is that mice fed more calories from oil that get overweight behave slightly differently in one of several neurological tests and has a subset of biochemical changes that are consistent with (Alzheimer’s)… these results do not indicate any ill effect on human health, and show slight effects on messed-up mice.”
In its paper, the Temple team had said it was led to test the mice’s response to a canola oil diet after the same team’s separate study in June reported “reduced levels of amyloid plaques and phosphorylated tau and experienced memory improvement” in mice fed a diet enriched with extra-virgin olive oil, against the same type of mice fed regular chow.
“The contrast in the study of canola oil with olive oil is completely inappropriate without a group fed olive oil being tested” directly alongside the canola oil group, Jones said Wednesday. “This is an absurd overreach of what the data provide without testing both oils side by side.”
But the Temple team’s canola oil study “does not include an olive oil group,” the council said Wednesday, “therefore, comparisons between canola and olive oils are limited except that they are both predominantly composed of monounsaturated fat.”
Moreover, the council said, “the mice fed olive oil in the first study also gained more weight than the control group.”
The council on Wednesday also criticized Temple’s announcement of the study results. The council cited a critical article by Health News Review which said Temple’s headline “jumps way ahead of what the research actually shows” and that the study “doesn’t say anything meaningful for consumers.” — AGCanada.com Network