Hippocrates, the father of modern medicine, was the first person to acknowledge
that the food we eat has a direct effect on our health. Now, over 2000 years
after his death, we are beginning to understand how right he was. In a new study
carried out at the University of California, Los Angeles (UCLA), rats fed a
high-fructose diet for just six weeks were less able to learn and retain
information. They found it tougher to negotiate a maze with just one exit. The
rats had been fed high-fructose corn oil, a ubiquitous ingredient in processed
drinks and foods churned out by the food industry, particularly in the United
This is perhaps one of the most direct demonstrations that an
ever-present foodstuff has the potential of affecting the way we think. Fructose
is the sugar that occurs naturally in fruits and is the favored sweetener of the
food and drink industry worldwide. Our consumption of it has risen exponentially
from the modest levels associated with seasonal fruits to an average yearly per
capita consumption in the US of more than 45 kilograms of refined sugar, over
half of which is fructose. The rest of the world is not far behind.
Fructose is problematic, because unlike glucose, its consumption does not
elicit the body's appropriate hormonal response to eating. It actually
suppresses the effect of insulin and the brain chemicals that signal we are full
and no longer hungry. And, therein lies the problem. Insulin affects the brain
by controlling the blood levels of its primary fuel, glucose. Insulin receptors
are also richly distributed throughout some areas of the brain, including those
associated with regulating food intake and cognitive function.
A quick scan through the research journals shows that the latest study is not
on its own in pointing a finger at fructose. At the end of last year, Dr.
Xingwang Ye and colleagues from Tufts University in Boston reported in the
British Journal of Nutrition that the level of habitual sugar intake in
non-diabetic participants aged over 45 was inversely related to memory and
cognitive performance. And in March and April this year, a series of separate
studies showed that insulin resistance is associated with greater cognitive
decline and reduced brain volume in non-diabetic older people.
Pretty much all of the evidence in this area relates to older adults, whether
we might see the same effects in younger people is an open question, since high
levels of fructose are unlikely to have detrimental effects in the short term.
Even the six weeks of fructose consumption that damaged the brains of the rats
in the UCLA experiment would equate to several years in human terms. Fructose is
not the only problematic component in our contemporary diet. There are plenty of
studies showing that consuming high levels of bad saturated fats, found
primarily as meat and dairy animal fats and as a range of oils added to
processed food, also predispose us to poorer mental function later in life.
The UCLA research did offer one crumb of comfort.
When fed a slightly healthier diet with more omega-3 fatty acids, the effect of
fructose on the rat's brains was reduced. There is also a lot of research
showing that a diet close to that enjoyed by our ancestors in evolutionary
terms, for instance, the so-called `Mediterranean diet' typified by lots of
natural fruit, vegetables and legumes, can protect against natural cognitive
decline as we get older. So, if you hope to retain your intelligence into old
age, you could do worse than follow Hippocrates's adage "let
food be thy medicine".