Wednesday 30 October 2013

Why is smoking more dangerous for the poorest in society?

We know that cigarette smoking causes lung cancer. What we do not usually know is that the poorest socio economic groups are worst affected. Does Vitamin D hold the answer?

If you are poor, smoking is dangerous! Another burden for the poorest people in our society. Things are not always quite so simple as they first appear.

A study from Denmark, the Copenhagen Men's Study, looked at among many other things the number of deaths from lung cancer, the analysis taking account of social class of those who died. The subjects of this long-term survey were divided into just three simple social groups - low, medium, and high social class, and they were followed up for 17 years.

The outcome was very different depending on social class, more so than might have been expected. Those in the highest social class had the best outcome, that is the lowest incidence of lung cancer. Those in the lowest social class had the worst outcome, the highest incidence of lung cancer. Those in the intermediate social group had the intermediate incidence of lung cancer. There was no difference in the number cigarettes smoked in the three groups, nor was there any difference in inhalation.

We can see in the figure the cumulative incidence of lung cancer in the three groups, low social group in the highest incidence line.

Copenhagen study

This might not surprise us, as we are now accustomed to hearing that the poor, socio-economically disadvantaged, have the worst health and the shortest lives, at least in northern Europe and the USA. But this social class effect is to my mind astounding. 1.6% of the smokers in the high social class developed lung cancer. 6.7 %, four times as many in the low social class developed lung cancer, a huge difference.

How low social class and poverty translate into poor health is usually difficult to understand, unless we enter into dubious victim blaming, something that defies biological plausibility. But in this case there is not accepted biological plausibility to explain this big difference.

Unless, that is, we consider the fact that poor low social class groups have the lowest exposure to the sun and the lowest vitamin D levels, for a variety of reasons based on disposable income, housing, leisure opportunities.

I suggest that differential levels of sun exposure probably explain this huge difference in lung cancer rates. Vitamin D, by stimulating immunity, reduces cancer risk and improves survival.  There are more observations of lung cancer risk that involve the sun and I will bring these to attention in future posts, shortly.


Hein HO, Suadicani P, Gyntelberg F. Lung cancer risk and social class. The Copenhagan Male Study – 17 year follow up. Dan Med Bull 1992; 39:173-176.

Please note that smoking is now banned in public places in many countries.

Wednesday 16 October 2013

Is the sun dangerous?

All that we eat comes from the sun. Photosynthesis within the green parts of plants gives rise to the synthesis of sugars and oils. We eat fruit and vegetables, we enjoy olive oil and other oils, and we drink wine - as Galileo called it "sunshine wrapped up in water".  In Europe, and probably in North America, about 75% of agricultural produce goes into animal feed (probably too much) and so all our meat comes originally from the sun. 

The same occurs in the sea. Plankton and similar simple organisms absorb the sunlight and grow, starting the food chain through fish of increasing sizes, ultimately finishing as our food (again, too much of it). 

The point is that the sun is essential for life. But there is always a downside and the sun can be responsible for destruction. Fire!

Picture a forest fire for example in Australia, in this case Tasmania. The vast amount of energy released is energy that the forest biomass acquired from the sun and it is stored in its structure. The amount of energy is immense, but so is the amount of energy that radiates from the sun on to the surface of the earth.

The higher the altitude the greater amount of sunlight energy at ground level. Compared to sea level, at a higher altitude less of the energy from the sun will be absorbed by its passage through the atmosphere. The higher the altitude of residence the better the health.

But in the aftermath of a fire there is rain. This is the result of evaporation of water from the sea, again an effect of the sun. The vegetation regenerates after a massive fire.

And so of course the sun is dangerous, but the advantages obviously outweigh the dangers. The Earth survives sun-related fires.

It is the same with human beings. The sun is essential in providing us with food and rain. It also provides us with something essential - Vitamin D.

All vitamin D comes from the sun. This can be by its direct effect on our skin. Vitamin D is produced by the sun acting on its precursor 7-dehydrocholesterol, which is synthesised not just by our skin but by plankton in the surface of the sea. Vitamin D thereby enters the fish food chain, or perhaps from mammals that we eat. But the great majority of our vitamin D should come from the action of the sun on our skin.

And don't forget that the sun acting directly on our skin also produces nitric oxide, which is necessary for at least cardio-vascular health.

It is essential that we expose our skin to the sun if we wish to avoid vitamin D deficiency, the alternative being that we take fish oil vitamin D supplements by mouth. Once again there is a danger but the advantages of exposure to the sun outweigh dangers probably several hundred-fold.

The obvious and main danger is acute sunburn, and those with a fair skin must be very conscious of this. The main danger is in the summer, in locations closer to the equator than where we usually live, and also at high altitudes. Pigmented skin, either inherited or occurring in response to sun exposure, is protective against burn but not completely so. 

The sun is best avoided at mid-day in these situations - the song goes that "Mad dogs and Englishmen go out in the mid-day sun....", and there is much truth in this (song by Noel Coward). 

"Mad dogs" are dogs with rabies, which have thereby lost their reason and so they can be found out in the mid-day sun, whilst well dogs are sensibly resting in the shade. "Englishmen" refers to men from England who are living in India.

The title of the song is taken from a poem by Rudyard Kipling, who spent many years living in India and is perhaps best known for his "Jungle Book" and "Just So Stories" for children. The song indicates that men recently arrived from England have not yet learned of the strength of the sun in sub-tropical as opposed to sub-arctic places of residence. The northern parts of the UK are at a latitude further north than anywhere in China, about the same latitude as the southern parts of Hudson Bay and the fringes of the Antarctic. British people are used to gentle sun and we are often not adequately careful when we visit more southerly countries such as India and Spain.

Remember that in the middle of the day it is the parts of the body that face upwards that have maximum exposure - the top of the head, the nose, the ears, the shoulders if not covered, the tops of the feet if not wearing shoes. If exposure is prolonged, these should be protected  by hat and clothes or by strong factor creams. 

Lying flat in the sun - sunbathing - is not to be encouraged and is not necessary for adequate vitamin D production. Normal activities in the sun are adequate. Lying in the sun means exposure of much more of the body to direct overhead sun and can cause serious burn. 

In the mornings and evenings the sun intensity is much less and protection will not be necessary. A rule of thumb is that if your shadow is longer than your height then the sun will not cause burn.

Also note that there is no danger in what is called a "physiological erythema", a temporary reddening of the skin after sun exposure. This should not be equated with sunburn, which is by definition painful. Reddening of the skin after a hot bath is not a scald!

The sun, like all radiation, can cause DNA damage to cells in the skin. This is stated as a reason for avoidance of all exposure to the sun. Not so. The body is built to repair DNA damage over a period of a few hours. This is part of the overall physiological self-correcting process of the body. The sun is not new and we have survived as a species for millennia despite the historic absence of sun-block creams and misinformed government advice.

Sun exposure should start in the early spring when sun intensity is adequate to produce vitamin D synthesis but unlikely to cause burn.  It will encourage the gradual development of a protective tan and vitamin D actually activates tanning genes.

Advice to use high factor sun creams before going out of the house is ridiculous and in respect of children it is likely to lead to vitamin D deficiency. Restrict but do not avoid completely exposure of the skin to the sun. Avoid prolonged high intensity sun exposure, not all sun exposure.

You will be wondering about skin cancer. Melanoma is not the result of sun exposure - see a further post shortly. Non-melanoma skin cancers, the mild and not dangerous basal cell and squamous cell cancers are the price to be paid for being fair-skinned and having a good outdoor life. They tend to occur in later life and the most important thing is for bald men to take great care of their scalp with protective creams and a hat.

Exposure to the sun over a long period of time can lead to sun damage called solar or actinic keratosis. It is not dangerous. People with solar keratosis have a reduced risk of multiple sclerosis, due to high levels of exposure to the sun. Non-melanoma skin cancers are also associated with better health and longer life expectancy, again due to sun exposure, a good thing.

Further details on various skin cancers and the influence of the sun are to follow.

Friday 4 October 2013

Vitamin D supplements - when and what to take

Ideally we obtain all our vitamin D by the action of the sun on our skin but this involves two variable factors: the sun and the skin. There are variations of the sun, or strictly speaking the amount of sunlight energy per unit area at ground level or on our skin. The two major geographic variable factors are: 
  • distance from the equator, the greater the distance (strictly at the spring and autumn equinox, that is outside the tropics) the less the energy; 
  • the altitude of residence, the higher the altitude the greater the energy. 

The principle is that the greater the depth of atmosphere through which the sunlight must travel, the more energy is lost. This is minimised by high altitude and an overhead sun, and there are health benefits from high altitude residence.

The other factor is that a hypothetical ray of light from an overhead sun will light a circular spot on the surface of the earth. A  hypothetical ray from a sun that is low in the sky will cast light on an elongated spot. In other words the energy from the lower sun will be spread over a larger surface area, and so less energy per square metre. Even small increases in altitude are effective in urban areas there is always a layer of polluted atmosphere close to the ground, as can be see in London, England, and Linz, Austria. It is only when above this layer that it can be appreciated.

Linz, Austria, looking south across the Danube
London, looking north from Greenwich

The climate also has an influence on the sun energy that we receive. Cloud cover reduces sunlight penetration, and this is important in the north-western parts of the UK, especially the west of Scotland, where there are serious health problems. Atmospheric pollution also interferes with sunlight penetration, especially particulate pollution from smoke, also known to have a detrimental effects on health.

We can see the variation of sunlight over the UK. The variations is hours of sunlight, which in the absence of cloud is the same everywhere. The effect of cloud can be seen in the west of Scotland and north-west England to a lesser extent.The effect on health can also be seen, just in England. Premature deaths are greater in number in the north-west where there is less sun. 

The energy of sunlight at ground level is a a different thing, being greatest closer to the equator and at higher altitudes. The variations can be seen in this comprehensive review, the source of which is "Sustainable Energy without the Hot Air", a remarkable book by David MacKay (available on the internet but also in printed form.

You will see that Edinburgh is the city second only to Anchorage, Alaska, for the least sunlight energy at ground level. Not very good for solar energy and not good for health. Glasgow probably has less sun energy. North west European cities are low in sun energy. They are are habitable only because they are kept warm by the Gulf Stream, bringing warm water from the tropics. Edinburgh is further north than anywhere in China. It is the same latitude as Siberia and Hudson Bay.

Variations of human behaviour also influence our exposure to the sun. Clothing is most obvious and those who extensively  cover their skin with clothing, usually for religious reasons with the examples of Jews and Muslims. There is also the amount of time spent out of doors and these days there are fewer outdoor workers. In hot countries indoor air conditioning is very tempting. And of course the use of sun-block creams prevents vitamin D synthesis in the skin.

One way to deal with this has been Sunshine Clinics, where children have been exposed to the ultra-violet light of which they have been deficient. The present-day equivalent are sun-beds, but children are not allowed it use them. They are generally frowned upon by the misguided "sun cancer police". However regular sun-bed users have excellent blood levels of vitamin D.

There are people who have traditionally lived in northern latitudes with little sun, particularly Inuits of northern Canada and those of the coastal communities in Scotland and northern Scandinavia. They have been surrounded by seas teeming with fish, by good chance an excellent source of vitamin D. Their health deteriorated when fish became a much smaller part of their diets, the result of “modernisation” and movements of the village populations to cities.

Because of little sun and in many places less fish, vitamin D deficiency is very common at present, and it is appreciated that a supplement taken by mouth is often necessary. The need for this can be seen from testing the blood level. Vitamin D is continually being consumed by body metabolism, especially inactivation of its active form to prevent excess levels. The amount required is to match the amount consumed and this appears to be about 2,500 units per day. As vitamin D is absorbed and stored in body fat it can be taken in larger doses at longer intervals. Perhaps the most convenient is a weekly dose of 20,000 units. An EU report of 2002 (no longer on the EU website) and a more recent eastern European report both recommended 2,000 – 2500 units per day. More cautious advice is 10,000 units each week rather than 20,000 units. 

IU = International Units

The use of “units” goes back to the time when vitamin D itself could not be measured chemically. Its activity was measured by its ability to heal rickets in young rats bred to be vitamin D deficient. It might have been that one unit per day was that which would heal rickets in a young vitamin D deficient rat. Today we can measure vitamin D but the use of “units” tends to persist. One microgram of vitamin D is equivalent to 40 units.

If blood levels of vitamin D are particularly low, less than 10 ng/ml (25 mol/L), then it is usual to give initially a higher dose of 20,000 units daily for two weeks so as to correct the deficiency rapidly, and then to reduce to 20,000 units weekly for long-term maintenance.

The higher range of the dose stated is the most effective.

We can see some graphs illustrating serial blood levels when treatment is given. These serial tests are not necessary in usual life or clinical practice but they have been part of gaining experience in the use of vitamin D. 

You will see that after an initial high daily dose to correct the deficiency a steady state is reached. This can now be seen to be predictable, thereby removing this need for frequent measurements of blood level.

We can also see that if vitamin D supplement is stopped when a good blood level is achieved, then the blood level drops back to its natural level. The natural level of an individual level is a reflection and a result of the individual's lifestyle and place of residence. In young people in particular it can be a result of inheritance, inadequate transfer of vitamin D across the placenta before birth.

The natural variation throughout the year is lost when the supplement continues throughout the year but this is not a problem. It is better to avoid the winter dip of vitamin D levels, which are associated with more illness in the winter than in the summer. The action of the sun on the skin will inactivate any excess of vitamin D that might occur in the summer. 

Taking vitamin D 20,000 units (= 500 micrograms) per week produces an excellent blood level without any excess. This can be seen in the results of 172 people receiving this supplement. Each vertical line represents one person. The blue represents the pre-treatment natural level. You will see that about half of these had a blood level of less than 10 ng/ml, very low levels, representing their residence in the north-west of England, many (but minority) of South Asian ethnicity. The adjacent pink line represents the blood level of vitamin D achieved after taking the supplement for three months. 

The response is good and only two reached a blood level of marginally greater than 100 ng/100ml (250 ng/L), a level that is not dangerous but greater than necessary by present understanding. There is a variation in response as shown by the blood levels in people receiving the same supplement, although it cannot be assumed that all took what they were prescribed. Biological variation can be due to a genetic variation of VDP – Vitamin D Binding Protein. A fat soluble substance like vitamin D will not dissolve in an aqueous medium such as the blood plasma and it must carried attached to a protein. This is a general principle and it applies to virtually all medicines. Vitamin D requires a specific protein, similar to thyroid hormone that requires specific thyroid binding globulin (TBG). These proteins are synthesised by genetically controlled metabolic processes. What it means is that when we measure the blood level of vitamin D, that is just what we are measuring. Strictly speaking we  are not measuring whether there is real deficiency of vitamin D but it is the best measure that we have. VDP deficiency, like all genetic abnormalities, is rare and low blood levels of vitamin D should be corrected. The expected target range might not be reached for above reason. If the blood level of vitamin D is measured before starting a supplement then it is reasonable but not essential to repeat the test after three or six months. Do not be concerned if the blood level is not well into the ideal range 40–60 ng/ml (100–150 mol/L) as the important thing is that the correct supplement is being taken.  

There are many vitamin D supplements. 

The most convenient and effective is the 10,000 unit capsule, taking one or two each week, as a long term supplement.