CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 3, May/June 2010
AFRICA
169
Florida, found that patients with very
low levels of vitamin D (calcidiol) were
77% more likely to die, 45% more likely
to develop coronary artery disease, and
78% were more likely to have a stroke
than patients with normal levels. Patients
with very low levels of calcidiol were also
twice as likely to develop heart failure
compared with those with normal calcidi-
ol levels. Startlingly, insufficient calcidiol
levels were associated with almost zero
responsiveness to atorvastatin therapy,
11
and therefore perhaps to other stains as
well.
Therefore it is no exaggeration to
claim that an increased risk of morbidity
and mortality is associated causally with
inadequacy of vitamin D.
Sunshine on the skin generates
other vital agents
Sunlight on our skin generates another
vital substance – nitric oxide (NO).
12
While UVB is responsible for the skin
production of the vitamin D entities, UVA
radiation releases nitric oxide from our
skin. The results from the 1970s MRC
Hypertension trial showed that sunlight
lowered blood pressure, with lowering
effects consistently greater in the summer
months than in the wintertime. Human
skin is found to be a notable store of
nitric oxide moieties, and these are readily
mobilised by sun exposure, and delivered
around our bodies to provide vasodilation
and cardiovascular protection.
The extremely short half-life of NO
(measured in nanoseconds) is compen-
sated for by giving rise to the formation
of other longer-lived metabolites such as
nitrites, nitrates and nitrosothiols that are
found in the circulation. Our epidermis is
rich in sulphydryls, which readily forms
nitrosated products, and these are found
at concentrations that are notably higher
than those in the plasma. UVA mobi-
lisation of these entities can lead to an
increase in plasma nitrite levels of 40%.
There is evidence too that vitamin D
can enhance the formation of NO from a
multiplicity of sources. But also intrigu-
ing is the discovery that sunlight-stimulat-
ed formation of melatonin modulates the
formation and activity of NO.
Hypertension, ischaemic heart disease,
stroke, the metabolic syndrome, and type
2 diabetes are major causes of morbidity
and mortality, and while excessive sun
exposure carries real risks, there would
seem to be no real substitutes for regular
small doses of sunshine onto our bodies.
True, we can supplement with vitamin
D
3
or D
2
, and even supplement with the
amino acids L-arginine and L-citrulline to
provide endogenous sources of NO-type
moieties, but are we then mimicking all
that sunlight can do? Unlikely!
Cautious and regular UV exposure
may well allow for major reduction in the
annual burden of cardiovascular disease,
and would be absolutely cost effective.
Such exposure should begin in early child-
hood, and should never be omitted, espe-
cially during pregnancies. The prevention
of sunburn is essential if we are to gain
the real benefits of sun exposure.
Let us rejoice at the availability of
free healthful sunshine, and take it all to
heart! Cardiovascular clinicians in their
praiseworthy holistic approaches to their
patients need to ensure that they add the
arrows of sunshine to their therapeutic
quivers.
John L Straughan
continued on p.170
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