Download A new government policy is needed for sunlight and vitamin D

C O N T R O V E R S I E S I N DE R M A T O L O G Y
DOI 10.1111/j.1365-2133.2006.07261.x
A new government policy is needed for sunlight and
vitamin D
O. Gillie
Health Research Forum, 68 Whitehall Park, London N19 3TN, U.K.
Correspondence
O. Gillie.
E-mail: [email protected]
Accepted for publication
15 December 2005
Conflicts of interest
None declared.
The British Isles are often thought to have a mild
climate—winters with little snow and temperatures generally
above freezing, while summers are seldom if ever uncomfortably hot. But in one respect the British climate is extreme: we
get very little bright sunshine. The British Isles are located so
far north that for 6 months of the year the sun is not strong
enough to enable vitamin D synthesis in exposed skin. In
summer the sky is often cloudy or overcast and, even when
the sun is strong and bright, the air temperature may be too
cold for clothes to be removed comfortably.
This lack of sunlight leads to a low vitamin D level in the
British and Irish population and this is now being recognized
as a major cause of ill health. And government advice to stay
out of the sun in the middle of the day, which is the best
time for vitamin D synthesis in the skin, adds to the problem.
In this article I consider the problem of vitamin D insufficiency from the earliest days of human settlement in these
islands up to the present day. I outline recent findings about
the consequences of vitamin D insufficiency for health. And I
suggest that optimum health is more likely to be achieved by
safe sunbathing without burning than by the SunSmart advice
presently advocated by government and Cancer Research UK
(CR-UK).
Europe some 20 000 years ago following the ice age.1 The climate of northern Europe provided a new evolutionary challenge
to humankind. In tropical Africa there is generally plenty of sunlight every day of the year whereas in northern Europe we have
a vitamin D winter when synthesis of the vitamin is impossible.
White skin synthesizes vitamin D six times faster than dark
skin,2 enabling efficient use to be made of short sunny periods
on cloudy days. A white skin also enables better use to be
made of the thin sunlight that we get at the beginning and
end of the summer season, thus extending the period when
vitamin D can be synthesized for growth and reproduction.
This must have given white skin a strong selective advantage
during the colonization of northern Europe.3 Low levels of
vitamin D are a cause of infertility4 and seem to be associated
with an increased risk of tuberculosis.5,6 These two factors
together were probably responsible for a strong selection pressure that fixed skin colour genes favouring greater production
of vitamin D, so enabling more successful reproduction and
enhanced survival of the species.
Women and children have lighter skins than adult men.7 It
has been suggested that this enables them to make best use of
small amounts of sunlight for good reproduction and growth
while men, who traditionally spent more time foraging in the
open, had darker skins that protected them from sun damage.
Evolution of white skin
Humans evolved in tropical Africa—we now know that for sure.
Modern human beings (Homo sapiens) first colonized northern
Oliver Gillie BSc PhD is former medical correspondent of the Sunday
Times and former medical editor of the Independent. He is the author of
Sunlight Robbery: Health Benefits of Sunlight are Denied by Current
Public Health Policy in the U.K. published by Health Research Forum
(http://www.healthresearchforum.org.uk).
1052
Industrial lifestyle brings low levels of
vitamin D
Our lifestyle has changed drastically in the last 200 years and
in the last 40 years it has changed with an accelerating pace.
Few people are now employed in agriculture or outside jobs.
We spend more time in cars, offices and houses, getting less
sun than ever, while air pollution in cities reduces the amount
of ultraviolet (UV) radiation that reaches ground level.
2006 British Association of Dermatologists • British Journal of Dermatology 2006 154, pp1052–1061
A new government policy is needed for sunlight and vitamin D, O. Gillie 1053
These problems of city life were recognized as the cause of
rickets early in the last century and in the 1930s, following
the discovery of vitamin D, margarine began to be fortified
with vitamin D. This largely prevented rickets, but in the last
30 years the disease has reappeared, mostly in the immigrant
population whose vitamin D levels are much lower as a result
of their skin colour.8
However, rickets is only the most florid manifestation of
vitamin D deficiency or insufficiency. Today 12% of adults of
working age in the U.K. are deficient in vitamin D and about
60% obtain insufficient vitamin D (B. Boucher, personal communication, 2005: summary of data on prevalence of vitamin
D deficiency and insufficiency in the U.K. taken from the
National Diet and Nutrition Survey data).9 In fact almost
everybody in the U.K. obtains suboptimal amounts of the vitamin. Over the last 10 years it has been realized increasingly
by a small number of scientists and doctors that vitamin D is
associated with many chronic diseases and is probably a significant cause of many of them—see Table 1 for details and references.
Chronic disease associated with inadequate
vitamin D levels
Evidence linking chronic disease with insufficient vitamin D,
or low exposure to sunlight, comes from several different scientific approaches which give similar answers. Studies of variation in chronic disease with latitude, altitude, season, skin
colour, holiday or lifetime exposure to the sun, and also case–
control studies all show an association between lower sun
exposure and disease.
While individual observations may be explained in various
ways there is only one conclusion that is consistent with all
these observations: a low gain in vitamin D, resulting either
from low exposure to sunlight or inadequate diet, is an
important risk factor for a number of chronic diseases (see
Table 1). In fact it is beginning to seem likely that a low gain
in vitamin D will prove to be a major lifestyle risk factor as
significant in causation of disease as smoking, obesity or
alcohol.
While vitamin D has long been known to be the cause
of the classic bone diseases—rickets, osteoporosis and osteomalacia—few doctors have been aware until very recently of
the link with cancer and other chronic diseases including multiple sclerosis, hypertension, diabetes, arthritis, autoimmune
disease and a multitude of other ills.10,11 The list is so long
that, regardless of evidence, it has aroused scepticism.
But it is now known that vitamin D is not simply processed
in the kidney to make the active hormone that controls calcium in bone. Some 30 or more tissues and organs have receptors for vitamin D.12 The vitamin is captured in these
tissues and processed into its hormone form which acts in a
paracrine fashion, both directly on local cell metabolism and
also on the genes, switching them on or off.13 Vitamin D actively controls certain genes involved in cell differentiation
and can switch on genes that programme cell death (apoptosis).
These are processes that play a crucial role in preventing initiation of clones of cells that may become malignant.14
Women in the U.K. (latitude 50–60) have a higher risk of
developing breast cancer than women in the relatively sunny
northern states of the U.S.A. (latitude 40–50), who in turn
have a higher risk of breast cancer than women living in subtropical Florida (latitude 25–30).15,16 Take a look at the
‘Cancer Maps’ on the National Cancer Institute website
[http://www3.cancer.gov/atlasplus/index.html (accessed 18
January 2006)]. As you head north from Florida towards Canada the death rates for prostate, breast and colon17 cancers
steadily increase. This correlation has been found for more
than 16 different cancers and cannot be explained by differences in diet, social class or race.15
These same cancers also tend to be more common in northern countries of Europe than they are in either the United
States or in the southern countries of Europe. Such geographical variation, attributable to differences in sun exposure, has
Table 1 List of diseases thought to be caused, at least in part, by low vitamin D levels. Low levels of vitamin D or insufficient sunshine may cause
or increase the risk of the diseases listed below, according to epidemiological and other evidence.10,11 The strength of the evidence varies
substantially for different diseases but satisfies many of the well-known criteria for causation considered by Sir Austin Bradford Hill.69
Cancer28,29,70
Nervous system diseases39,40,71–74
Circulatory and metabolic disease75,76
Reproductive disease4,77–83
Immune system disease
(autoimmune disease)11,56,84
Bone disease8,48,58,85–88
Pain89
Infections5,90
Breast, ovary, prostate, bowel (and intestinal polyps), pancreas, lymphoma, multiple myeloma
and thyroid cancers; possibly a risk factor in some 16 or more different cancers
Multiple sclerosis, schizophrenia and possibly other nervous system disease
Heart and blood vessel disease including heart failure and heart attack, hypertension, metabolic
syndrome (syndrome X) and diabetes type 2
Polycystic ovary syndrome, premenstrual syndrome including migraines, preeclampsia,
some infertility
Diabetes (type 1), rheumatoid arthritis, psoriasis; possibly plays a part in a number of other
autoimmune diseases
Rickets, osteoporosis, osteomalacia, osteoarthritis; may also be a risk factor for tooth decay
and tooth loss
Rheumatism, low back pain and other persistent nonspecific musculoskeletal pain is associated
with low vitamin D and/or unrecognized osteomalacia
Pneumonia and tuberculosis
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1054 A new government policy is needed for sunlight and vitamin D, O. Gillie
not generally been taken into account by those who have
studied geographical differences in diet. The Mediterranean
diet is reputed to protect against cancer and heart disease. But
at least part of what was thought to be the benefit of this diet
may actually come directly from the powerful Mediterranean
sun.
Taken alone, geographical or ‘ecological’ evidence can be
misleading. However, the geographical evidence from the
United States and Europe showing a link between digestive
system cancers and latitude is backed up by a similar study
from Japan.18 To get the same result in countries with such
different diets and cultures suggests that an unknown confounding factor is unlikely to be the cause. There is also substantial evidence supporting the association between cancer
and vitamin D using entirely different methodology: i.e. careful case–control studies.17,19–24 For example, British men who
have regular sunshine holidays or who sunbathe regularly are
less likely to suffer from prostate cancer than others who holiday at home or stay indoors. And if the men who take foreign
holidays and sunbathe do develop prostate cancer they do so
at an older age than men who have few foreign holidays and
sunbathe less.25
This research, undertaken by Professor Richard Strange and
others at the University of Keele, is what academics like to
describe as ‘robust’. Professor Strange was surprised to get
such a clear-cut result and worried that it might have been a
chance finding. So he repeated the survey and obtained exactly
the same result. There seems to be little doubt that investment
in sunshine holidays and careful sunbathing may stand a man
in good stead in preventing prostate cancer later in life.
Other evidence suggests that similar benefits from sunlight
exist for women. In Norway, women whose breast cancer is
diagnosed in the summer live longer than women whose
breast cancer is diagnosed in the winter, according to Professor Johan Moan of the University of Oslo.26 Prostate, colon,
lymph gland and lung cancer behave in a similar way in
Norway—summer-diagnosed illness does better than winterdiagnosed illness. Furthermore, the result for lung cancer has
been repeated by researchers at the Harvard School of Public
Health.27 People with nonsmall cell lung cancer, the commonest kind, are more than twice as likely to survive 5 years following diagnosis if their disease is first found in summer.
Higher consumption of foods containing vitamin D were also
found to improve survival of these lung cancer patients. It
appears that a higher level of vitamin D at the time of diagnosis aids treatment, possibly by facilitating apoptosis.
Edward Giovannucci, professor of public health at Harvard
and senior author of the lung cancer study, says in a wideranging review of vitamin D and cancer: ‘In vitro, animal and
clinical studies strongly indicate that vitamin D may have anticancer benefits, including against progression (such as metastasis) against a wide spectrum of cancers. Thus, vitamin D
could be potentially beneficial against either incidence or mortality, or both.’28
William Grant, an independent researcher, has calculated
that some 22 000 cancer deaths in the U.K. may be attributed
to insufficient sun exposure or too little vitamin D.29 Put
crudely, if we obtained as much sun in the U.K. as they do
in Florida we would have some 22 000 fewer cancer deaths
per year. But we do not need to go to live in Florida. People
living in the U.K. could obtain greater exposure to the sun,
and could reasonably expect to reduce their risk of cancer, if
they were encouraged to sunbathe by a positive public health
policy towards sunlight.
However, CR-UK remains sceptical of the link between cancer and insufficient vitamin D. Carolan Davidge, spokesman
for the charity, has insisted: ‘There is certainly no clear evidence that increasing the sun exposure of the general U.K.
population will reduce the incidence of common cancers.
Indeed it is irresponsible to suggest that prevention of these
cancers is a simple matter that could be achieved by sunbathing.’
Skin cancer
There is of course a risk of skin cancer for those who bake or
burn themselves in the sun. Those who expose pale untanned
skin to too much sun too quickly may have an increased risk
of skin cancer. But it has been known for a long time that
people who work outdoors and get regular exposure to the
sun are less likely to get melanoma, which is responsible for
the large majority of deaths from skin cancer.30 Recently one
study has found that people who have longer lifetime exposure to the sun without burning are less likely to get melanoma than those with less exposure.31 And most surprising of
all, another study has found that people with melanoma live
longer if they have previously had greater exposure to the
sun.32
So careful sunbathing, with measured exposure to the sun,
may actually reduce rather than increase the risk of melanoma,
reduce the overall risk of death from skin cancer, and improve
survival for those who do develop melanoma. This is consistent with evidence summarized above, which suggests that
vitamin D or sun exposure protects against many types of cancer and also increases survival of people who have developed
the disease.28
It has often been asserted that two-thirds of melanomas are
caused by exposure to the sun. However, this figure has been
challenged and other methods of analysis suggest that sun
exposure may account for as little as 10% of the risk.33
Indeed, C.B. Begg from the Department of Epidemiology and
Biostatistics, Memorial Sloan-Kettering Cancer Center, New
York, concluded in 2001 that the bulk of the variation in risk
of melanoma cannot be explained by known risk factors including sunlight.
There are a few tantalizing clues suggesting other causes of
melanoma. For example, it has been found in a number of
countries that melanoma, like breast cancer, is more common
in higher social classes.34 And melanoma, like breast cancer,
has been found in some studies to be associated with greater
height.35–37 This suggests that some of the ideas being considered as causes of breast cancer, such as increased levels of
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A new government policy is needed for sunlight and vitamin D, O. Gillie 1055
insulin or insulin-like growth factors in the blood, could profitably be considered in connection with melanoma and indeed
in vitro evidence suggests that such hypotheses are biologically
plausible.38
Multiple sclerosis—a disease of dark winter
days
Multiple sclerosis (MS) has long puzzled doctors and scientists
seeking to understand how it may be caused. At last epidemiology has come up with an explanation. It has been proven,
so far as it is possible with epidemiology, that low exposure
to sunlight is a major cause, and possibly the major cause, of
MS. In the northern hemisphere, MS is more common in the
most northern countries with longest winters: it is more common in Canada than in the United States and more common
in Scotland than it is in England.39,40 In Australia MS is some
five times more common in Tasmania in the relatively cold
south of the country than it is in Queensland in the subtropical or tropical north.41
Increased exposure to the sun seems to protect against MS.
People who get nonmelanoma skin cancer, an indication of
extended sun exposure, have half the risk of developing MS
compared with healthy controls.42 And observations of MS
lesions in the brain have shown that the lesions increase in
winter when MS symptoms are known to become worse and
vitamin D levels in the blood are lowest.43 But most challenging of all to those concerned with public health: children born
in late winter or early spring have a greater risk of developing
MS later in life than children born at other times. This may be
explained by low vitamin D levels in the mother’s body at the
end of pregnancy increasing the risk of developing MS.40
Professor George Ebers, the Oxford neurologist who has
been in the forefront of this research, says: ‘We have done all
we can by way of epidemiological studies to pinpoint the
cause of MS. There can be no doubt about the strong link
with low levels of exposure to sunlight. Insufficient vitamin D
could be the cause but we have not proved that yet. We now
need to undertake trials.’
A policy based on misunderstanding
Fear of skin cancer has led to a policy of recommending
reduction in exposure to the sun with consequent reduction
of vitamin D levels for those who follow such advice. CR-UK
insists that casual exposure of the hands and face for about
10–15 min two or three times a week will provide people in
the U.K. with sufficient vitamin D.44 But this advice is based
on outdated information and a contradiction.
CR-UK’s recommendation of 10–15 min casual exposure to
the sun is actually calculated on the basis of an exposure at
noon when the sun is strongest. However, their SunSmart programme recommends use of sun cream and avoidance of the
sun for 2 h each side of solar noon—that is between 11 AM
and 3 PM British Summer Time. If the SunSmart advice is followed, casual exposure to the sun will occur only before or
after the 4-h period around midday, in which case very little,
if any, vitamin D will be obtained. And 10–15 min will certainly not provide sufficient vitamin D.
There is another problem with the scientific reasoning
behind CR-UK’s advice. CR-UK’s calculation assumes that a
person needs only 200 IU of vitamin D per day, a figure that
is out of date (E. Yong, Cancer Research UK, personal communication,
2005;
see:
http://www.healthresearchforum.org.uk, accessed 23 January 2006). This figure, which
recurs in the literature on vitamin D, seems to originate from
the amount of vitamin D in a teaspoon of cod liver oil. A
hundred years ago a teaspoon per day of the dreaded but
potent substance was found to be sufficient to cure rickets,
and ever since the teaspoon has been taken as a basis for calculating the daily requirement of vitamin D.
However, such simple reckoning has now been superseded
by the pharmacokinetic studies of Heaney and others which
show that 3000–5000 IU vitamin D per day are needed for
optimum health.45 If Heaney’s scientific investigation of vitamin D requirement is accepted, as it is by experts in vitamin D,
then CR-UK’s calculation is out by a factor of more than ten.
The policy of Government and CR-UK on sunlight is also
based on an assertion, made in a report published by the
National Radiological Protection Board (NRPB) in 2002,46 that
casual exposure of hands and face to the sun will provide sufficient vitamin D (E. Yong, Cancer Research UK, personal
communication, 2005). However, the reference provided by
NRPB to support this claim fails to provide any cogent evidence.10
The reference describes observations of nine elderly patients
who lived on a hospital ward near Nottingham where they had
access to a sunny terrace.47 At the end of summer, three of the
old people in this study had blood levels of vitamin D of
< 22Æ5 nmol L)1 and so would be expected to suffer severe
D-deficiency during the following winter. All the others except
one had levels of D < 40 nmol L)1, which could not be expected to remain above danger levels during the following winter.
Only one of the nine elderly people maintained a reasonably
healthy summer level of D at 79Æ4 nmol L)1 and he had spent
many hours in his garden after discharge from hospital.
In fact, contrary to NRPB’s assertion, this data illustrates
that an optimal level of vitamin D cannot be maintained by
most people in the U.K. simply by casual exposure of hands
and face.
Sources of vitamin D
An adult in the U.K. obtains an average of about 150 IU vitamin D per day from food (B. Boucher, personal communication, 2005). About half of the vitamin D in the average U.K.
diet comes in margarine and fortified breakfast cereals
(B. Boucher, personal communication, 2005), but many
people do not eat these foods. Furthermore Kellogg’s, the
cereal manufacturers, has recently stopped fortifying many of
its products with vitamin D because of regulations in other
European countries and the need for efficient production.
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1056 A new government policy is needed for sunlight and vitamin D, O. Gillie
Oily fish, the food richest in vitamin D, is eaten by relatively few people in the U.K. Even Norwegians or Icelanders,
who eat much more fish than we do, cannot get enough vitamin D just from their diet. Only Inuit (Eskimos), who eat oily
fish or other marine produce at virtually every meal, and
Lapps, who get their vitamin D from reindeer meat, get most
of their vitamin D from the diet.
Vitamin supplements available over the counter in the U.K.,
typically providing about 200 IU per day, may double the
amount of vitamin D obtained by mouth. This is enough to
prevent gross bone disease, such as rickets or osteomalacia,
but is not enough to prevent osteoporosis or the many other
ills linked to low vitamin D.48 Much more vitamin D is needed
for optimum health. So sunlight remains the major source of
vitamin D for people in the U.K. who achieve anything near
healthy blood levels of the vitamin.
The vitamin D budget for people living in the British
Isles needs to be calculated on an annual basis because in
winter no vitamin D can be gained from the sun. Between
3000 and 5000 IU of vitamin D a day are required for
optimum health,45 but 1000 IU per day may be taken to
be the minimum desirable gain in vitamin D according to
international experts. So, reckoned annually, the minimum
desirable gain is 365 000 IU. Vitamin D has a half life of
6–8 weeks and so a large store needs to be accumulated in
summer to last through the winter. In the British Isles sufficient summer levels to provide the minimum desirable level
year round are likely to be reached only with the help of
active sunbathing.
The sun is generally strong enough in southern England to
provide vitamin D for 26 weeks between the first week of
April and last week of September. However, April is generally
too cold for sunbathing, and throughout the summer cold
winds or cloud frequently prevent sunbathing in southern
England. The summer season is substantially shorter in Scotland where, in addition, the sun is less intense and there are
more cold days.
Casual exposure of the hands, arms and face two or three
times a week, as suggested by CR-UK and Diffey49 might supply 1 MED (minimum erthythemal dose) to an adult in southern England, weather and time permitting. So over the
26 weeks of summer such casual exposure may supply up to
26 000 IU of vitamin D. If this exposure could be increased
from three to seven times per week then at most 61 000 IU
could be obtained over the summer while some 55 000 IU
(150 IU per day) on average might be obtained annually from
food. This adds up to 116 000 IU of vitamin D gained annually and leaves our subject with another 249 000 IU to find if
he or she is to obtain the minimum desirable amount of vitamin D.
In fact it makes no sense to try to increase the gain in vitamin D by increasing exposure of hands, arms and face. Excessive sun exposure may cause skin ageing and so it is
preferable, as in radiology, to spread the dose. In this case the
dose may be spread over all parts of the body by active sunbathing while protecting the face which tends to get over-
exposed. It is obviously advantageous to protect the face as
age is largely judged from facial appearance. Failure to recognize the advantage of spreading the UV dose over the whole
body is a serious flaw in the advice given by the SunSmart
programme.
Active sunbathing that exposes the whole body may supply
up to 10 000 IU per day50,51 in summer. To obtain something approaching the optimum annual amount of vitamin D
in the U.K. (without travelling abroad) a person would have
to sunbathe in a swim suit on about 100 sunny summer days.
This is, for practical purposes, impossible even for a dedicated
nudist.
There are about 26 weeks (182 days) when the sun is
potentially strong enough for sunbathing in the U.K., but in
less than half of these will the sky be clear and the air warm
enough for sunbathing. It may be possible to sunbathe wearing minimum clothing on 25 days over the summer, an average of once per week. If so, and 10 000 IU can be obtained
each time, then the extra 249 000 IU of vitamin D that are
needed to attain the minimum desirable annual level could be
accumulated during the course of a summer. However, with
our uncertain weather in the U.K. weeks may pass by without
clear sun. So it makes sense to sunbathe whenever possible
wearing as few clothes as possible if vitamin D sufficient for
good health is to be obtained.
Choosing a sun exposure policy
The SunSmart programme, which advises against sun exposure
in the middle of the day, is ill-suited to our climate. SunSmart
is based on a model programme developed in Australia
where the sun is a great deal stronger. The SunSmart recommendation that 10–15 min of sun on the face, arms and
hands two or three times a week is sufficient for good health
in the U.K. does not even provide the minimum requirement
of vitamin D.
People in the U.K. who are influenced by the SunSmart
advice will obtain substantially less than average exposure to
the sun and should expect to suffer a corresponding deficit in
vitamin D unless they take a large supplement by mouth.
Therefore it seems quite likely that SunSmart may be causing
substantial ill health and is quite possibly causing more cancer
deaths than it is preventing.
It also worth remembering that sunlight is the normal and
natural source of vitamin D for human beings and, unlike special foods or supplements, it is free. There should be very
good reasons for issuing instructions which prevent people
from utilizing a natural source of vitamin. SunSmart claims to
reduce deaths from skin cancer but it may do this by only a
few hundred per year. The risk of skin cancer may be reduced
equally well by less extreme measures that encourage safe sun
exposure (without burning) and at the same time boost vitamin D levels30–32 with substantial benefits in prevention of
cancer of all kinds.
I have developed guidance for sunbathers which I call the
SunSafe advice (Table 2). This advice has been produced with
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A new government policy is needed for sunlight and vitamin D, O. Gillie 1057
Table 2 The SunSafe advice
1
2
3
4
5
6
7
8
Sunbathe safely without burning—every day if you can
The middle of the day is a good time for sunbathing in the U.K.a
Start by sunbathing for 2–3 min each side; gradually increase from day to day
Don’t use sun cream while sunbathing
If feeling hot or uncomfortable expose a different area, cover up, move into
the shade—or use sun cream
When abroad, where the sun is generally stronger, expose your body for shorter
times until you find out how much is safe
Children benefit from sun exposure, but need guidance
A tan is natural and is generally associated with good health
a
The sun is strongest in the middle of the day and so maximum synthesis of vitamin D
occurs in the shortest possible time. This is important in our climate because intermittent
cloud or overcast skies often decrease intensity of UV. Furthermore at the beginning and
end of the summer the sun is strong enough for vitamin D synthesis only at midday. The
lunch hour is often the most convenient time to sunbathe.
safety, optimum health and reduction of skin cancer as primary considerations. SunSafe advises people in the U.K. to
sunbathe as often as they can, while taking care to avoid
burning, and so maximizes the vitamin D that they can obtain.
The advice is based on up-to-date information about vitamin
D requirements together with an up-to-date assessment of
causes and risks of skin cancer. The advice is conservative,
reflecting the positive health advice on sunlight widely advocated in the U.K. before SunSmart was introduced.
SunSafe advice may reasonably be expected to reduce some
of the 22 000 cancer deaths in the U.K. that can be attributed
to insufficient sunlight, as well as much other chronic disease.
I believe that SunSafe advice is safer than CR-UK’s SunSmart
advice because it recognizes the importance of vitamin D for
health. While SunSmart advice may be effective in reducing
skin cancer it is unwise to advocate it without also recommending that those who follow it take a 1000 IU vitamin D
supplement per day. Such advice has not been given hitherto
and such supplements can be obtained only from abroad.
The SunSmart advice has consistently been promoted with
the slogan: ‘There is no such thing as a safe or healthy tan.’ This
slogan was adopted in 1994 by the U.K. Skin Cancer Prevention
Working Party,52 although no direct evidence was offered then
or since that a tan is actually linked with disease of any kind. A
campaign launched in the U.K. in 1989 (‘Are you dying to get a
SunTan’) even went so far as to suggest a suntan was associated
with death.53 In fact some evidence suggests that a deep tan,
particularly in childhood and the adolescent years, is associated
with protection against melanoma,30,54 and sunburn in childhood is actually associated with a reduced risk of prostate cancer
and multiple sclerosis in later life.25,55 The 1989 campaign is a
classic example of ‘shroud waving’, a poorly established scare
story promulgated through the media with the intention of
frightening the public and changing behaviour.
While it is true that sun exposure causes death of skin cells
and this is associated with tanning there is no reason to
believe this is other than a normal process; and no evidence
has been forthcoming to suggest that tanning leads directly to
any harmful consequences. A tan is an inevitable consequence
of sun exposure, and greater sun exposure, which leads to a
deeper tan, has been shown to be linked with better health.
So a good tan may be a fair index of good health. This certainly is the common belief, and it does no favours to the credibility of science or medicine to deny common belief when
there is scientific evidence to support it.
Insufficient vitamin D and/or sunlight during childhood
appears to increase the risk of diabetes type 1,56 multiple
sclerosis55,57 and poor bone development.58 Insufficient vitamin D and/or sun exposure may produce greater effects on
children and young people than on adults because it is needed
for active growth, and such effects cannot be expected always
to be reversible by the provision of increased vitamin D later
in life. Because sunlight is a major source of vitamin D it
seems obvious that children should not be denied the opportunity for safe exposure to the sun in the middle of the day
when the sun is strong enough to induce synthesis of the vitamin.
However, the SunSmart programme has warned of a special
risk to children and young people from exposure to the sun
and advises extra special protection for children against the
sun. In fact, evidence that there are special risks to children
from sun exposure are conflicting. Much of the evidence suggests that there is no special association between melanoma
and exposure to the sun in childhood.59,60 Indeed one study
has found that outdoor activities in childhood are associated
with a lower risk of melanoma.61 Of course, care must be
taken that children do not overexpose themselves and suffer
sunburn. This requires vigilance because children themselves
generally do not understand the risks.
There may be other risks from the application of the SunSmart advice. Some parents, influenced by this advice, dress
their children in Foreign Legion style caps and special suits
that envelope the whole body except for the hands and face
which are covered with sun cream. Children dressed in this
way are likely to be at risk of vitamin D deficiency unless they
also take a large vitamin D supplement. CR-UK has yet to
2006 British Association of Dermatologists • British Journal of Dermatology 2006 154, pp1052–1061
1058 A new government policy is needed for sunlight and vitamin D, O. Gillie
warn the public of the risks that may ensue from the use of
such sun-suits and the adoption of its SunSmart advice without also taking a large vitamin D supplement.
Reply to Brian Diffey
I welcome the opportunity to reply to some of the points
made by Brian Diffey in his accompanying article.62 Diffey
compares the incidence of and mortality from various cancers
in the U.K. with incidence and mortality in Australia and New
Zealand. He uses these figures to question other observations
which suggest sunlight is beneficial in the prevention of cancer.
On the face of it comparing observations on the populations
of Australia or New Zealand with the U.K. may seem appropriate because the ancestors of the large majority of people in
these countries came from the U.K. Therefore the possibility
of genetic differences may generally be ignored. But international comparisons of this kind are subject to difficulties of
interpretation for a number of reasons.
Most epidemiologists will agree that cancers are multifactorial in their causation. Sunlight is only one of several factors
influencing cancer incidence. It cannot be assumed in comparing cancer incidence in Australia and New Zealand with the
U.K. that the difference found is the consequence of the differing strength of sunlight in the three countries. To understand the difference in cancer incidence between these
countries all possible causes need to be examined because one
cause may mask another.
The U.K., like other European countries, was affected by
World War II in a way that Australia and New Zealand largely
avoided. The German submarine patrols in the Atlantic had a
devastating effect on food supplies to the U.K. which were
then, as now, largely imported. Rationing of food was introduced in the U.K. in January 1940 and lasted long after the
war. It was abolished in a series of stages and finally ended
when meat rationing ceased in 1954. Frugal habits with
regard to food were established by this wartime experience
and continued in families for many years, at least until the
1960s and 1970s. The generations raised in those relatively
frugal times are the ones who are now in the age group that
is providing most of the cancer statistics.
A plentiful diet in childhood and later is now recognized as
a risk factor for a number of cancers, including melanoma,
whereas a restricted diet in childhood, as caused by rationing,
is associated with a reduced risk of cancer.63,64 These concepts
are well supported by animal work. It has long been known
from animal experiments that restriction of calories inhibits
the development of cancer.65,66
The association between obesity and cancer has been well
documented and the evidence is sufficient for obesity to have
been designated ‘causal’ for cancers of the colon and breast by
the International Agency for Research on Cancer. It has been
suggested that overeating is the largest avoidable cause of cancer after smoking.67 But increased risk of cancer has also been
associated with higher birth weight, accelerated or catch-up
growth, and greater birth length or adult height—all of which
are consequences of overeating or a more plentiful supply of
food.63
Therefore the general dietary history of a country is relevant
if cancer incidence or mortality of countries are to be compared. It cannot be safe to assume that the diets of people in
Britain and Australia or New Zealand have been generally
comparable over the last 65 years. Australia and New Zealand
are food-producing countries, which have generally had food
surpluses and food has therefore been cheap. Furthermore,
they did not suffer shortages during World War II. Whereas
in the U.K., extra food beyond that needed for bare survival
has at times been unobtainable, while at other times it may
have been relatively more expensive.
Similar considerations apply to the statistics, quoted by Diffey, which show an increase in the incidence of breast, colon
and prostate cancer, as well as melanoma, in the U.K. over
past decades. The increasing availability of food in the U.K.
over the decades following World War II may well be a major
driving factor behind the increasing incidence of certain cancers, but other factors such as instruction to avoid exposure to
sunlight in the middle of the day and insufficient vitamin D
could also be involved. Population level data of the kind
quoted by Diffey have proved to be useful in the past for the
generation of hypotheses and in defining public health problems that need to be tackled.68 However, such data cannot be
employed reliably to refute a hypothesis as Diffey has done,
because there are too many possible interpretations and such
data are too readily subject to confounding.
Diffey argues that British adults spend an average of only
14 min engaging in activities outdoors and therefore will not
have time to sunbathe. The 14 min is apparently a year-round
average. On sunny summer days the average person may well
spend two or three times as long in the open air, and many
people will happily spend much longer outdoors. As little as
5–10 min exposure to the sun in the middle of the day in
midsummer is long enough to obtain some useful vitamin D
if some clothes are removed.
Certainly, as Diffey points out, many people do not go outdoors a great deal and both adults and children generally walk
outside less than they used to do. However, it is not necessary
to walk in order to sunbathe. Most people actually enjoy sunbathing and so can be expected to respond to positive advice
suggesting that they do so by sitting or lying in the sun. But I
recognize that there is no one way of improving vitamin D
status that will appeal to all and so I believe it is also important to increase fortification of food with vitamin D and bring
official advice on use of vitamin D supplements up to date.
Diffey’s Figure 4 shows that blood levels of vitamin D do
not vary greatly with season or latitude. On the basis of this
Diffey arrives again at the nihilistic conclusion that nothing
much that anyone can do will make a lot of difference to their
vitamin D level. However, there are two reasons for the similar levels of vitamin D in such different places as Norway and
Australia. The first is that in industrial societies we all live similar lives wherever we are and whatever the season, and the
2006 British Association of Dermatologists • British Journal of Dermatology 2006 154, pp1052–1061
A new government policy is needed for sunlight and vitamin D, O. Gillie 1059
second reason is that cancer societies around the world have
for the last 20 years or so advised the public to avoid the sun
in the middle of the day when it is strongest.
If on the other hand people are told that sunlight is a normal and natural source of vitamin D and that safe exposure to
the sun in the middle of the day in the U.K. is possible and
beneficial then they are likely to expose themselves more to
the sun and obtain more vitamin D. People enjoy sunbathing
and so it is not difficult to persuade them to do it and they
can be instructed in how to do it safely.
The SunSafe advice provided here is not simply theoretical,
as Diffey suggests; it is well based in observational evidence
which is available in the scientific literature. This contrasts
with the SunSmart advice, which is in my view based on a
narrow interpretation of outdated evidence. Furthermore, the
SunSmart advice is not supported by any kind of document
spelling out its rationale and providing a review of scientific
evidence that might justify it.
Finally, Diffey suggests that the SunSafe message might
make cancer patients see their cancer as self-imposed and
blame themselves for not getting sufficient sunlight, or that
patients might move away from friends and family to a sunny
country in the belief that this might extend their life. Whatever public stance is taken on such issues people who are so
inclined may find ways of blaming themselves. People with
melanoma, for example, may and often do blame themselves
for having had too much exposure to the sun, not realizing
that they might as well blame over-consumption of food or
lack of exercise.
It would be wrong to tell doctors to deny a link between
sunlight and melanoma on the grounds that patients might
blame themselves. For the same reason it would be just as
wrong to deny the link between lack of sunlight, low levels of
vitamin D and cancer. And if this convinces some cancer
patients to take a winter sunshine holiday no harm would be
done. Sunshine holidays will provide additional vitamin D
which on available evidence might provide some extra months
or even years of life. Doctors must be able to say what they
believe to be true, albeit in the kindest possible way, if they
are to maintain the confidence of their patients.
Conclusion
A wealth of evidence suggests that insufficient vitamin D is a
cause of a wide variety of chronic diseases including several
types of cancer. The majority of people in the U.K. and most
other industrial countries have suboptimal levels of vitamin D.
The cost of low vitamin D levels and consequent disease is
probably billions of pounds per year in the U.K. A new government policy to develop increased levels of vitamin D in the
population could be readily implemented and would not be
unpopular. It would involve increased fortification of a wider
variety of foods with vitamin D, revision of recommended
supplements of vitamin D for people of all ages, and encouragement of safe sunbathing. Continuation of the government’s
SunSmart policy, which is administered by Cancer Research
UK, is unwise because it risks reducing vitamin D levels in the
population and in so doing may be expected to increase the
risk of certain cancers, multiple sclerosis and much other
chronic disease.
Note added in proof
Since this article was completed several reviews of vitamin D
and chronic disease have appeared which will be helpful to
the reader. Particularly useful are those by Holick91, by Garland et al.92 and a series of papers published to mark 25 years
since the first formal recognition of the connection between
insufficient sunlight and bowel cancer.93–97
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