Just as genetic differences between individuals determines our
susceptibility to disease, genes may also determine how our bodies react
to different nutrients or anti-nutrients in our food. The pioneering
field of studying how nutrition and genes interact and the implications
for dietary modification is called “nutrigenomics.” The completion of
the Human Genome Project in April last year has opened doors to a better
understanding of how our genes work and to what extent they are affected
by the environment, including the food we eat. It seems likely that one
day, dietitians and doctors will be able to prescribe diets to suit
individual needs, based on individual genetic
profiles.
Gene Link
Last year, a team of researchers at the
University of Wisconsin knocked out a gene called SCD-1 from mice and
created a foodie’s dream - a mouse that didn’t get fat, no matter how
much of a high-fat diet it ate. In addition, the mouse did not
accumulate fat in the liver or other tissues where they would contribute
to health problems under normal circumstances. A human equivalent of the
SCD-1 exists and might conceivably explain a predisposition to
overweight and obesity in a some (albeit a minority) of people, and why
some people are more susceptible to the negative health complications of
obesity.
Colon cancer is another example: While about 5%
of colon cancer cases are directly linked to inherited susceptible
genes, there are genes that work less directly. These genes make the
individual more susceptible to the effects of food, which can either
aggravate or protect the person from cancer.
Genetic mutations have been noted to alter iron
absorption, leading to iron overload in some people. These mutations
increase the intestinal absorption of dietary iron above the normal
level by about 10%. People with this mutation have a lower minimum daily
requirement for iron than other people, and identifying these
individuals early in life enables them to make more informed decisions
about their dietary choices.
The list goes on - heart disease, hypertension,
diabetes - individual genetic differences explain why populations eating
similar diets exhibit a wide disparity in their propensity to disease.
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It would seem that foods that have a protective
function for some individuals may have no effect or even turn out to be
detrimental to others because of genetic variation. This helps to
explain why elements of standard dietary advice, such as increasing
dietary fibre, or limiting salt intake may work well for some people,
but have little of the desired effect on others.
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Furthermore, researchers in the field have found
evidence that the foods that people eat can also directly interact with
their genes and affect the instructions such genes send out to the body.
Such variations in genetic makeup, could be responsible for slower or
faster metabolism of nutrients, leading to the production of toxic or
carcinogenic compounds in the body, or protective factors such as
increased production of heart protective lipoproteins.
Nevertheless, the early findings of this
pioneering research should not be interpreted as a reason to abandon
established healthy eating advice: Most of the foods we eat, impact on
multiple body functions, and there is still much scientists do not
understand about how specific food components impact body functions. For
example, those individuals with normal blood pressure or those with high
blood pressure which is not lowered by a low-salt diet may gain other
benefits, not yet identified by limiting sodium intake. Similarly, while
a low-fat diet may not lower blood-cholesterol levels for people whose
genes are not sensitive to this, they almost certainly will gain other
health benefits from low saturated fat diets, such as reduced risk of
colon, pancreatic and breast cancer, and more effective weight
management.
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In the near future, nutrigenomics might pave the
way for more tailored, and effective, personalised dietary
recommendations. After all, according to the US Centre of Excellence for
Nutritional Genomics, the desired outcome of nutrigenomics is the use of
personalised diets or intelligent nutrition (i.e., knowledge of
nutritional status, nutritional requirement and genetic profile) to
prevent or delay the onset of disease and optimise and maintain human
health.
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The Future of Food Research and Development?
Hate the taste of oat-bran or wish that
ice-cream did more for you? Research into genes could help to identify
ways to develop special foods for individuals to make healthy diets more
appealing by improving taste or by adding health benefits to favourite
foods.
Our understanding and knowledge of the role
functional foods can play in personal health has been growing for some
years. Functional foods, containing biologically active compounds that
offer the potential of enhanced health or reduced risk of disease, may
work by helping to counteract the effects of certain genes and even
delay the development of some chronic diseases or health problems.
Nutrigenomics research therefore, may be highly complementary to the
research and development work in the field of functional foods.
Similarly, food biotechnology research and
developments in the future will not merely incorporate additives to
enhance the nutrition value of processed foods but perhaps could also
lead to the development of foods with specific nutritional effects
designed to meet the genetically programmed needs of the
individual.
And it is not only the human genome that is
providing clues. Scrutinising the genes of plants and microbes could
help scientists find new proteins or compounds with potential health
benefits.
At the same time, knowledge of how these
individual compounds work might tell us more about which compounds
should be taken individually - perhaps as an extract - and which ones
work better consumed in actual foods. Who knows, scientists might find
that some antioxidants taken in pill form work just as well as the real
thing, and some work best in cooked, raw foods or even when used in
specific recipes!
The Future of Dietary Advice?
One day in the near future, a genetic test may
be the first thing a dietitian performs before designing a specific
diet. Information from the human genome may enable doctors and
dietitians to draw up individual profiles of disease susceptibility and
nutritional interaction to design personalised diet plans to enhance
nutrition or reduce the risk to diseases, not just based on a person's
age, nutritional status and requirements and lifestyle but also on
his/her genetic profile.
One of the most exciting aspects of
nutrigenomics research is its potential to identify those at risk of
developing chronic degenerative diseases such as stroke, heart disease,
diabetes, before symptoms have developed, and design a tailor-made diet
and lifestyle to prevent or delay its onset. Currently, with limited
understanding of who is at greatest risk, many individuals only receive
or act on medical advice once symptoms have developed, and physiological
damage is irreversible. Recognising those at risk, before any symptoms
or physiological damage has developed and drawing up diet and lifestyle
recommendations for prevention could save individuals from years of
ill-health, and public health budgets a great deal of money.
There may also be diets for specific short-term
goals. An athlete, for instance, may be given a diet matched with his
genetic profile to enhance performance.
Already there are companies working on
developing systems that would track how a person’s genes function, based
on food and health supplement intakes and how these genetic functions
affect health. This information may eventually be used to prescribe a
mix of foods for a certain genetic profile to protect a person from
disease or enhance his/her health status.
So go ahead and enjoy that ice-cream cone - just
one, mind you - and remember the oat-bran at breakfast. Your genes would
certainly approve.
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Before you get ready to revamp your entire food
cupboard in anticipation of new information, nutritionists agree that no
matter what your genes may say, the benefits of eating a balanced,
varied diet, bolstered with generous helpings of fruits, vegetables and
whole wheat grains while limiting your intake of saturated fat, along
with prevention of overweight and regular physical activity will always
remain the wisest strategy for long-term health.
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