So, scientists did clinical trials on people after finding that it
caused heart and liver damage in laboratory animals? Seems unlikely,
but then, considering how much profit could be made by convincing
people to eat what is basically an industrial oil, maybe that is what
happened.

Following that logic, the traditional diet of the Chamorro people of
Guam must be safe to eat as well. The problems they suffered with
Parkinsons disease, ALS and dementia must have had nothing to do with
chronic exposure to the phytotoxins in the food they were eating after
all.

The point is that a lot of traditional foods are quite toxic, and
probably do cause long-term health problems for those eating them. If
rapeseed oil causes heart and organ damage in rats and pigs, then it's
a fair bet that it does the same in humans, irrespective of whether
it's used in chinese cooking or not. In any case, the chinese eat such
a wide variety of foodstuffs (anything from cats and dogs to nests made
from bird spit), that rapeseed oil is unlikely to have aver been their
main source of dietary fat.

As the saying goes, "the dose makes the poison". The Chamorro people
only started becoming ill in great numbers after they acquired guns,
which allowed them to hunt fruit bats (a local delicacy) far more
effectively than before. The fruit bats had absorbed and concentrated a
poison from the seeds of the cycad tree, which was their main food
source. The Chamorroans also used the seeds to make flour, but this
isn't though to have given them enough of the poison to make them ill.
It is only when they began hunting the fruit bats with guns that their
intake of the poison became great enough to produce illness.

Canola and other vegetable oils have been so heavily promoted as
"healthy" and are so widely used in processed foods, that people are
consuming them in far larger quantities than ever before. I've also
heard that there are other very long-chain fatty acids found in
vegetable oils that can inhibit the same enzymes affected by erucic
acid.

If you look at the epidemiology of the heart disease epidemic in
Western countries, coronary heart disease as a cause of death was
extremely rare when people had butter and lard as their main source of
dietary fat. Then, late in the 19th century, industrialisation was
applied to agriculture and it became possible to manufacture vegetable
oils very cheaply. It was found that by adding hydrogen to vegetable
oil, it could be converted into a solid - margarine - that could be
used as a cheap substitute for butter. Vegetable oil consumption
soared, and soon after, doctors noticed increasing numbers of their
patients dying from heart attacks. As vegetable oil consumption
continued to increase, so did the incidence of heart disease and within
the space of a few decades, CHD went from a rare condition to being the
commonest cause of death in Westernised countries.

To be fair, there were other changes in diet and lifestyle occurring at
the same time which probably contributed to the heart disease epidemic,
but the fact remains that it has occurred at the very time that
vegetable oil consumption is at its highest.

-Hugh