Vitamin D's importance in maintaining strong, healthy bones
through its interaction with the essential mineral,
calcium, is well known. But the vitamin is also vital for
the health of the nervous and immune systems, in regulating
insulin levels and blood pressure, and even as a possible
protector against certain common cancers.
The best known and most serious disease associated with
vitamin D deficiency is rickets, which arises when the
deficiency causes blood calcium levels to fall too low, and
the body to respond by stripping the bones of calcium
leading to loss of bone density and malformation.
Interestingly, studies have shown that the geographical
pattern of the incidence of rickets is very similar to
those for both breast and colon cancer, suggesting a
possible (though not fully understood) link between vitamin
D deficiency and these diseases. One 5 year study which
grouped 120,000 people by levels of vitamin D intake
reported that men in the highest intake group had a 29%
lower incidence of colon cancer than those in the lowest
intake group and similar results have been observed in
breast cancer research. Relatively high blood levels of
active form vitamin D have also been associated with a
lower risk of pre-cancerous growths (polyps) in the colon
whereas lower levels of vitamin in the blood have been
associated with an increased risk of prostate cancer.
Vitamin D is known to be essential for a healthy immune
system and has been shown to be particularly important in
helping prevent auto-immune diseases - those in which the
body's immune system attacks and destroys its own cells,
wrongly having identified them as invaders. Type 1
(insulin dependent) diabetes, rheumatoid arthritis and
multiple sclerosis are examples of serious diseases which
fall into this category and a number of research studies
suggest that a generous intake of vitamin D may be a
significant mitigating factor.
Blood levels of vitamin D have also been shown to be
inversely correlated with blood pressure, and some research
suggests that high dose supplements of vitamin D of (1,600
IU per day) may help this, although orthodox medicine, as
ever, is cautious about definitively acknowledging any
direct causal link.
The traditional view was that adequate supplies of vitamin
D can be synthesised in the skin upon its exposure to
sunlight. But the problem is that a large proportion of
the population in the affluent world lives in latitudes
which provide very limited sunlight for six months of the
year. People commonly work indoors and tend to use high
factor sunblocks on the rare occasions on which they might
expose significant areas of skin to the sun.
It is a cruel irony that this concern about skin cancer may
lead to the ill-health associated with vitamin D deficiency
and may even increase the risk of other cancers. But in
these circumstances the usual assumptions about vitamin D
production in the body appear questionable at best, if not
downright complacent. And the situation is even worse for
the elderly, who may not only enjoy even less exposure to
the sun than the young, but are less able to make use of
that which they do obtain.
Moreover, there are relatively few good natural food
sources of vitamin D, and the best source, oily fish such
as sardines, mackerel and salmon is one which many people,
and perhaps children in particular, often find unpalatable.
The situation has improved somewhat with the fortification
of milk, orange juice, bread and some cereal products, but
it may still be difficult for individuals to ensure they
obtain a sufficient intake of the vitamin, particularly
because the amounts added to different foods and drinks are
very variable.
Since the amount of vitamin D required from food will vary
greatly depending on the amount of exposure to sunlight
enjoyed by the individual, it has not been deemed possible
to determine a Recommended Dietary Allowance (RDA) for
vitamin D. But the Food and Nutrition Board has suggested
200 IU (5mcg) for infants, children, and adults up to 50,
rising to 400 IU for the 50-70s, and 600 IU for the over
70s, as an "Adequate Intake" of the vitamin from food on
the assumption that none is being obtained from sunlight.
Orthodox opinion, however, seems to regard these
suggestions as too conservative. And even for those
individuals fortunate enough to enjoy regular exposure to
good quality sunlight, the intake of 400 IU (10 mcg) of
vitamin D as part of a multi-vitamin and multi-mineral
supplement is recommended. For the over 65s, those with
less than optimal liver or digestive health, those living
in less advantageous climates and those who spend the
majority of their time in indoor occupations a
supplementary dose of a further 400 IU, for a total of 800
IU is strongly advised.
For maximum effect, however, vitamin D supplementation
should be always be combined with adequate dietary calcium
- supplemented if necessary to achieve an intake of 1,000 -
1,200 mg per day of this essential mineral.
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Steve Smith is a freelance copywriter specialising in
direct marketing and with a particular interest in health
products.
Find out more at
http://www.sisyphuspublicationsonline.com/LiquidNutrition/In
formation.htm