Diet-Vitamins Potential Damage to Body's Defences
Vitamins Potential Damage to Body's Defences
Nov. 26, 2013 — Vitamin supplements are a billion-dollar
industry. We want to stay healthy and fit and help our bodies with this. But
perhaps we are achieving precisely the opposite?
"We believe
that antioxidants are good for us, since they protect the cells from
oxidative stress that may harm our genes. However, our bodies have an enormous inherent ability to
handle stress. Recent research results show that the body's responses to stress in
fact are important in preventing our DNA from eroding. I fear that the fragile balance in our cells can
be upset when we supplement our diet with vitamin pills, says Hilde
Nilsen to the research magazine Apollon. Nilsen is heading a research group at
the Biotechnology Centre, University of Oslo.
Maintenance of genes
Our DNA - the genetic code that makes us who we are - is
constantly exposed to damage.
In each of the hundred trillion cells in our body, up to two
hundred thousand instances of damage to the DNA take place every day. These may
stem from environmental causes such as smoking, stress, environmental pathogens
or UV radiation, but the natural and life-sustaining processes in the organism
are the primary sources of damage to our DNA.
How can the repair of damage to our DNA help us stay healthy
and live long lives?
A small worm provides the answer
To answer this question, Hilde Nilsen and her group of
researchers have allied themselves with a small organism - a one
millimetre-long nematode called Caenorhabditis elegans (C. elegans). This
roundworm, which lives for
only 25 days, is surprisingly sophisticated with its 20,000 genes; we humans
only have a couple of thousand more.
C. elegans is a fantastically powerful tool, because we can
change its hereditary properties. We can increase its ability to repair DNA
damage, or we can remove it altogether. We can also monitor what happens when
damage to DNA is not repaired in several hundred specimens and through their
entire lifespan. Different "repair proteins" take care of various
types of damage to the DNA. The most common ones are repaired by "cutting
out" and replacing a single damaged base by itself or as part of a larger
fragment.
Affecting lifespan with the aid of genes
In some specimens that do not have the ability to repair the
damage, the researchers observe that the aging process proceeds far faster than
normal. Is it because the damage accumulates in the DNA and prevents the cells
from producing the proteins they need for their normal operation? Most
researchers have thought so, but Hilde Nilsen doubts it.
One of the genes studied by the researchers has a somewhat
shortened lifespan: on average, this mutant lives three days less than normal.
Translated into human terms, this means dying at the age of 60 rather than at
70. -"We were surprised when we saw that these mutants do not in fact
accumulate the DNA damage that would cause aging. On the contrary: they have
less DNA damage. This happens because the little nematode changes its
metabolism into low gear and releases its own antioxidant defences. Nature uses
this strategy to minimize the negative consequences of its inability to repair
the DNA. So why is this not the normal state? Most likely because it comes at a
cost: these organisms have less ability to respond to further stress ‒ they are
quite fragile.
Hilde Nilsen and her colleagues have now -for the very first
time -"shown that this response is under active genetic control and is not
caused by passive accumulation of damage to the DNA, as has been widely
believed.
This provides an opportunity to manipulate these processes.
And that's exactly what we have done: we have re-established the normal
lifespan of a short-lived mutant by removing other proteins that repair damage.
Hence, the cause could not be accumulation of damage, since there is no reason to
assume that a mutant with no other alternative ways to repair its DNA will be
less exposed to damage. There must be something else.
The researchers have gone on to discover that this
"something else" in fact is the other repair proteins. They believe
that the proteins inhibit damage that they fail to repair completely.
The consequence is that they establish a barrier - a road
block. This triggers a cascade of signals that reprogram the cell.
Wouldn't this imply that the repair proteins defy their own
purpose -"after all, the result is a shorter lifespan?
We need to remember that most likely, the purpose of the DNA
repairs is to ensure that we produce healthy offspring -"not necessarily
that we live as long as possible after our reproductive age interval.
Initiating a survival response that reinforces the antioxidant defences means
that a lack of ability to repair the DNA has less impact than it would
otherwise have on our reproduction. To the species as a whole, it's a small
cost that some individuals will be less good at handling stress and have a
shorter life.
Because this is an active process within the cells, the
researchers refer to it as reprogramming.
"We have found several proteins that trigger this
reprogramming. The process has the same effect as a reduction in caloric
intake, which we know helps increase the lifespan in many species. In other
words, there are two routes to a long life. When we stimulate both of these two
routes in our nematode at the same time, we can quadruple its normal lifespan,"
Nilsen says.
Can do great harm
The balance between oxidants and antioxidants is crucial to
our physiology, but exactly where this equilibrium is situated varies from one
person to the next.
"This is where I start worrying about the synthetic
antioxidants. The cells in our body use this fragile balance to establish the
best possible conditions for themselves, and it is specially adapted for each
of us. When we take
supplements of antioxidants, such as C and E vitamins, we may upset this
balance," the researcher warns.
"It sounds intuitively correct that intake of a
substance that may prevent accumulation of damage would benefit us, and that's
why so many of us supplement our diet with vitamins. Our research results
indicate that at the same time, we may also cause a lot of harm. The health authorities recommend
that instead, we should seek to have an appropriate diet. I'm all in favour of
that. It's far safer for us to take our vitamins through the food that
we eat, rather than through pills," Hilde Nilsen states emphatically.
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