Trans fats could be bad for the brain...
A high-fat diet could harm the brain. And trans-fats, such as those
found in margarine, and which are often used to increase the shelf-life
of foods, are the worst culprits, suggests a new study.
Ann-Charlotte Granholm of the Medical University of South Carolina
in Charleston, US, says she became concerned about trans-fats after
seeing how they are made.
Hydrogen is bubbled through an oil, and metals such as zinc and
copper are added to made it solid at room temperature. The resulting
greyish fat is then bleached and coloured to make it look more appealing,
she says.
Zinc and copper are known to build up in the brain of people with
Alzheimer’s disease, she says, and there are signs that high
fat diets could contribute to the risk of this disease. “I
became concerned about what these fats were doing to our children,
who are given French fries at school every day.”
Granholm compared rats on a high-fat diet of about 12% soybean
oil with those on a high trans-fat diet, containing 10% hydrogenated
fat and 2% cholesterol, so that any effects seen could be attributed
to the type of fat, not the weight of the animals.
It is hard to compare this level directly with human diets, but
this sort of proportion would be considered to give a high risk
of heart disease in humans, she says.
Rats on the high trans-fat diet showed learning difficulties, she
reports. When the animals were required to remember the position
of hidden platforms in a water-filled maze, the animals on the trans-fat
diet learned more slowly and made more errors, particularly as the
task was made harder. They are about five times worse at the task,
she says, than those animals on the soybean oil.
The brains of the animals also showed signs of damage in a region
called the hippocampus, which is important for learning and memory.
“The high trans-fat diet may cause loss of a neural protein,”
she says. She also found that the brains of rats on this diet showed
signs of inflammation.
This is a pilot study, stresses Granholm, and it is not clear yet
whether these changes are temporary or reversible.
Barry Levin, an expert on obesity from the Veterans Affairs Medical
Center in East Orange, New Jersey, adds: “We must regard these
as preliminary studies.”
There may be many factors involved - insulin levels, obesity, lack
of exercise - rather than the fats themselves. “And we all
work on rats, so we can not necessarily extrapolate this to humans.”
But he agrees that there are many reasons to be cautious about a
high fat diet.
Granholm suggests preferentially eating natural foods, rather than
those with additives to increase shelf life. “A longer shelf-life
may make for a shorter life span for humans,” she cautions.
Current UK recommendations for trans fats are 4.4g per day for
women, the same amount detected by Which? in a KFC meal. A McDonalds
McNuggets and regular fries meal contains 3g, while 2.5g came in
for Saxby’s short pastry, the same as for Tesco’s gluten-free
toffee fudge shortbread.
Of the 30 products tested, a Sainsbury’s treacle tart bought
from the bakery counter, a McVitie’s Penguin biscuit and Morrisons
pork pie were bottom of the table with 0.2g of trans fat per portion.
In Europe Which? pointed out that McVities have removed trans fatty
acids from biscuit dough, but they are still present in cream fillings.
UK retailer Sainsbury’s has already switched to low trans-fat
pastry (although 1.8g found in its puff pastry minced beef pie),
and while KFC branches run directly by KFC use oil that contains
trans fats, the franchised shops use non-hydrogenated vegetable
oil.
For more information, the European Food Safety Authority have published
a detailed report on trans fatty acids.
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