Is a balanced diet the best defence
– or does the body need help?
February 8, 2005
Millions of people in Britain take food supplements,
adding up to an industry worth around £350 million
a year. These consumers believe their purchases are
helping to protect their health. But are they right
- or are they merely suckers who have swallowed some
skilful marketing?
The debate about the value of vitamin and mineral supplementation
shows no sign of abating. On one side are food scientists
and dieticians who insist that a balanced diet offers
all the nutrients we need, that serious vitamin and
mineral deficiency is rare in the developed world and
that the answer to bad eating habits is not a jar of
pills.
Ranged against them are nutritionists who claim that
many of us are not consuming a balanced diet and that
even if we were, higher doses of certain vitamins and
minerals than can be obtained through food give us an
extra boost and protect against disease.
"In principle, people in this country do not need
to take supplements, provided they are healthy and have
a normal balanced diet," says Dr Siân Astley,
research scientist at the Institute of Food Research.
"However, most people would probably say they are
not as healthy as they might be and that their diet
is lacking in some respects.
"You no longer see deficiency diseases like scurvy
in the Western world, but some people are walking around
with less than optimal levels of certain nutrients.
For example, teenage girls have an inadequate intake
of iron. The problem is that much of the data is about
avoiding deficiency rather than achieving optimal nutrition,
with the result that we have very little idea what we
do and don't need as individuals."
Ann Walker, senior lecturer in human nutrition at the
University of Reading, has found evidence in the British
National Diet and Nutrition Surveys that a sizeable
proportion of the population is not getting the Reference
Nutrient Intake - the recommended minimum amount - of
several vitamins and minerals, including iron, magnesium,
calcium, zinc, vitamin A and vitamin D.
"More than 50 per cent of women aged 15 to 18
are not reaching the target for calcium and this is
worrying because that is the age when we lay down bone.
This could have serious implications for osteoporosis
levels in the future," says Dr Walker. "Around
80 per cent of women do not make the magnesium targets.
A deficiency can lead to migraines, cramps, palpitations
and heart arrhythmias. It is unlikely that a GP would
pick up a magnesium deficiency as the cause of these
problems, but I know from my clinical practice that
people respond very well to supplementation."
Dr Walker blames poor diets for these deficiencies.
"Certain foods, such as fats and sugar, dilute
the impact of nutrients. Surveys show that our overall
energy intake has diminished and our micronutrient intake
will also be reduced. The fact that the average adult
eats fewer than three portions of fruit and vegetable
a day - compared with the recommended five - also has
an impact."
But is supplementation the answer to our nutritional
shortcomings? In some cases, yes. Folic acid has been
found to reduce neural tube defects in babies: the necessary
dose cannot always be obtained from food, so women planning
a family have been advised by the Government to take
a supplement. Those at risk of osteoporosis are prescribed
calcium and vitamin D. Women with heavy periods and
teenage girls may need extra iron. Older people are
less efficient at extracting the B vitamins from their
food and may benefit from supplementation.
But why stop there? There are many who swear that high
doses of vitamin C can prevent colds, that B6 can alleviate
pre-menstrual symptoms, and that the antioxidant vitamins
A, C and E can mop up the free radicals that lead to
cancer, heart disease and illnesses associated with
ageing. They believe it is only a matter of time before
nutritional supplements are widely used in therapeutic
doses as an alternative to pharmaceuticals.
So far, research has produced conflicting results.
Some trials suggest that people leading healthy lifestyles
who also take antioxidant supplements are at lower risk
of developing heart disease than those who do not take
supplements. However, a review of seven high-quality
trials published last year in The Lancet showed that
antioxidant supplementation actually increased death
rates from gastrointestinal cancers.
"We know that if you eat a diet high in vegetables,
fruit, wholegrains and plant-derived fats you have significantly
less chance of developing the diseases associated with
ageing," says Dr Astley. "But we do not see
the same effect when we isolate the antioxidant compounds
in a supplement. When you consume nutrients in a diet,
they seem to work synergistically, in harmony, like
the instruments in an orchestra."
Taking a handful of pills will not change a bad diet
into a good one, says dietician Lyndel Costain. "Helping
people to achieve a better diet can improve their health
in many ways and help to tackle obesity, diabetes, high
blood pressure and heart disease. Arguably, vitamin
pills are peripheral to the big issues: they appeal
to the worried well."
Costain accepts that a daily multivitamin is appropriate
for anybody on a restricted diet, including older people,
slimmers, those with specific food allergies and teenage
vegetarians. When 231 young adult prisoners - whose
diets are known to be poor - were given food supplements
in a double-blind, placebo-controlled trial, their behaviour
improved dramatically.
Dieticians and food scientists are concerned about
the high-dose tablets recommended by some nutritionists.
"We cannot make the assumption that because vitamins
and minerals are naturally occurring food products,
they are safe or that because a little of a nutrient
is good, more will necessarily be better," says
Dr Astley. "Aspirin is a natural substance that
can help in limited doses, but too much will kill you.
That is another reason why it is better to change your
diet: you cannot overdose on nutrients consumed as food."
The Government's Expert Group on Vitamins and Minerals,
whose job it was to decide on safe upper limits for
a wide range of nutrients, has warned against taking
more than 1,000mg a day of vitamin C, 1,500mg of calcium
or 17mg of iron and against long-term use of high doses
of B6. However, one expert in nutritional therapies
has described the group's recommendations as "excessively
and inappropriately restrictive". The debate looks
set to run for many years yet.
Source:www.telegraph.co.uk
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