CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 3, May/June 2010
168
AFRICA
Your Life and Your Heart
Sunshine and the cardiovascular benefits – a dose of sunshine!
God said, ‘Let there be light’, and there
was light.
(Gen.1:3)
Without sunlight, there would be no life
as we know it. Early human societies
rightly paid homage to the sun. Many
millennia later, and for a host of different
reasons, we are again regarding our sun
with special interest. That exposure to
sunlight is capable of generating a variety
of beneficial effects in our skin is an area
of exciting discovery – not least for the
cardiovascular practitioner.
Vitamin D from sunshine
Rickets is making a comeback in many
parts of the world, even in so-called
civilised and fully westernised countries.
That sunlight impinging on the skins of
humans generates an anti-rachitic vitamin
was discovered some 90 years ago, but
ignorance of its vital functions and fear
of skin neoplasms from sun exposure
have brought about the tragic increase in
rickets.
In the late 1990s, John Jacob Cannell,
an exemplary social activist, began work-
ing as a psychiatrist at Atascadero State
Hospital, where quite serendipitously he
noted that those of his patients who
received UV radiation from a ‘sterilising’
light source, enjoyed far better resist-
ance to respiratory infections and better
psychiatric health. This reawakened his
interest in clinical nutrition. His nutri-
tional studies led to several discoveries
about the overlooked need for vitamin D,
and inspired him to create the Vitamin
D Council (
/)
in 2003 to promote the vital need for
adequate vitamin D.
Structurally, the various forms of vita-
min D are secosteroids, and should be
regarded as hormones, as they are gener-
ated in our skins, from where they circu-
late around our bodies. The major meta-
bolic product produced in many organs is
calcitriol. This highly active secosteroid
hormone targets over 2 000 genes, which
is about 10% of the human genome.
Ongoing research continues to impli-
cate vitamin D deficiency as a major
predisposing factor in the pathology of
at least 17 varieties of cancer, as well
as heart disease, stroke, hypertension,
autoimmune diseases, diabetes mellitus,
depression, chronic pain, osteoarthritis,
musculoskeletal instability, osteoporosis,
muscle weakness, muscle wasting, birth
defects, periodontal disease, predispo-
sition to tuberculosis, other microbial
diseases and more. A virtual plethora of
data supports the importance of adequate
bodily levels of calcidiol in reducing
overall morbidity and mortality.
1-6
A quick
perusal of these open full-text reviews
assures us that every bodily system bene-
fits from adequate levels of calcidiol,
and that with insufficiency, every bodily
system suffers.
It is of great importance that we appre-
ciate that foodstuffs, of whatever sort,
are poor providers of this vitamin, even
in the modern world where several coun-
tries vitamin D-fortify milk and other
commodities for human consumption.
In the three years since a contribu-
tion to this
Journal
alerting physicians
to the cardiovascular risks of a vitamin D
deficit, titled ‘Vitamin D – the forgotten
vitamin – and the cardiovascular physi-
cian’,
7
the data dealing with vitamin D
have burgeoned almost explosively. A
quick search in Pubmed using just the
term ‘vitamin D’, showed that in February
2010, some seven articles per day were
published. Google the term ‘vitamin D’,
and we get more than 12 million hits!
Nevertheless exposure to vitamin D data
via various African clinical journals,
which presumably are the most widely
read journals on this continent, is decid-
edly minimal or completely absent.
Unpigmented human skin produces
approximately 10 000 to 25 000 IU of
vitamin D in response 20 to 30 minutes’
summer sun exposure – 50 times more
than the US government’s recommenda-
tion of 200 IU per day. Short-wave UVB
from sunlight acts on the skin precursor
7-dehydrocholesterol to generate, by a
fascinating variety of mechanisms, vari-
ous forms of vitamin D. Chemically these
various forms of vitamin D are secos-
teroids; i.e., steroids in which one of
the bonds in the steroid rings is broken.
Therefore, what sunlight generates is a
series of secosteroid hormones that circu-
late in our body and act via different vita-
min D receptors (VDRs), which are found
in almost every cell.
Calcidiol is the important circulat-
ing form that is measured to ascertain
adequacy or otherwise. Plasma levels of
calcidiol should be
>
30 ng/ml, while
levels greater than 100 ng/ml are very
difficult to obtain. A study of highly sun-
exposed young people in Hawaii conclud-
ed that the highest 25 (OH)D concentra-
tion produced by natural UV exposure
seems to be approximately 60 ng/ml (150
nmol/l).
8
The magic of our bodily organi-
sation is that there has never been a
reported case of vitamin D intoxication
due to excessive sun exposure, such as
in lifeguards, sun worshippers, etc. The
reason is that once the skin makes enough
vitamin D, the sun destroys the excess.
In 2003, Gomez produced evidence
that secondary hyperparathyroidism is
almost non-existent when 25 (OH)D
levels exceed 30 ng/ml (requiring 3 000
IU/day).
9
Dr Vieth cited six studies that
concluded, if the aim is to keep para-
thyroid hormone concentrations low, 25
(OH)D levels should exceed 28 ng/ml (70
nmol/l).
10
Of special significance to Africa is the
fact that persons with highly pigmented
skin are particularly at risk of vitamin
D deficiency, and require at least five
times longer sun exposure to generate the
same amount of Vitamin D than would be
generated in unpigmented skins.
Data presented at the March 2010
scientific sessions of the American
College of Cardiology inAtlanta, Georgia,
indicate
inter alia
, that adequate levels of
calcidiol provide cardiovascular benefits
of the same order as statin therapy or
normalisation of blood pressure in hyper-
tensive persons.
Findings from a study presented at the
American Heart Association’s scientific
conference on 16 November in Orlando,
