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WELLNESS AND NUTRITION
How
Vitamin D May Help In The Battle Against Cancer
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.
Steve
Smith
