Sunny D (part 2)

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Experts hotly debate which diseases may truly be caused by vitamin D deficiency. Nevertheless the extent of the evidence and its consistency makes a powerful case for D-deficiency being an important cause of over a dozen chronic diseases and almost as many cancers

Diseases caused by vitamin D deficiency

Experts hotly debate which diseases may truly be caused by vitamin D deficiency. Nevertheless the extent of the evidence and its consistency makes a powerful case for D-deficiency being an important cause of over a dozen chronic diseases and almost as many cancers. Other important factors such as obesity, lack of exercise, or a diet containing too many calories, are also known to increase the risk of many of these diseases. But both obesity and lack of exercise are linked with D-deficiency and so the evidence is confused. Vitamin D, is stored in fat and becomes 'lost' in obese people, while people who take exercise often spend more time outdoors in the sun.

Nervous system diseases

Last year Professor John McGrath and others at the University of Queensland found that pregnant rats deprived of vitamin D give birth to baby rats with serious brain abnormalities. This work will eventually be seen to be as important as the discovery that folic acid deficiency during pregnancy causes severe spinal deformities (spina bifida) in offspring, or that thalidomide given to pregnant animals causes abnormalities of the limbs. The importance of their article published in Neuroscience (volume 118, pp641-653) has not yet been appreciated but it provides a means of understanding several neurological diseases which have puzzled doctors for more than a century.

Multiple sclerosis (MS), Schizophrenia, and Parkinson's disease - people with these diseases are more likely to have winter or spring birthdays. MS and Parkinson's diseases are more common in northern countries or states of America. People with MS have worse symptoms in winter and brain scans show an increase in damage to the brain of MS people in winter. Supplements of vitamin D given to babies may prevent MS and schizophrenia. A very severe form of Parkinson's disease occurs in people with dark skin living in the UK.

Alzheimer's disease and Amyotropic lateral sclerosis (motor neurone disease) are believed by some neurologists to be similar in the way they develop to Parkinson's disease but affecting different parts of the brain or nervous system. These diseases are several times more common in black people living in United States than in black people living in traditional societies in the Tropics. In northern countries there are more births of these two diseases in winter.

Autism - people with autism have winter birthdays more often than would be expected. The cause of the disease is a mystery, but increased winter birthdays could be an important clue suggesting that vitamin D deficiency in pregnancy is a cause, at least in a proportion of cases.

Autoimmune diseases

These are diseases in which the body is attacked by its own immune system. Such attacks are generally thought to be triggered by infection, but deficiency of vitamin D causing abnormal proliferation of cells and changes in the immune system may be a key factor. There are many of these diseases and some are quite rare. Only a few have been studied in depth.

Diabetes type 1 - a classic autoimmune disease. It is more common in northern countries and an increase in winter birthdays have been found in some places. Vitamin D supplements in pregnancy or first year of life protects against the disease and vitamin D may also delay progress of the disease after it has begun to cause problems.

Multiple sclerosis - another classic autoimmune disease - see details above.

Rheumatoid arthritis - people with this disease commonly have low levels of vitamin D in their blood. The more severe the disease the lower their vitamin D. Taking vitamin D has been found to reduce disease activity and relieve pain, as recently confirmed by results from the Iowa Women's Health Study.

Crohn's and other inflammatory bowel diseases - people with these diseases generally have low vitamin D. These diseases are more common in northern states of USA. Patients with these diseases often also have osteoporosis. Poor absorption of fat may make it difficult for people with these diseases to absorb vitamin D. Sunlight could be the best answer.

Heart and circulatory diseases

High blood pressure (hypertension) - a disturbance of calcium metabolism is often associated with high blood pressure. Vitamin D supplements and exposure to ultra-violet light have been found to reduce raised blood pressure.

Heart disease - low vitamin D levels in blood are associated with an increased risk of heart disease. Vitamin D may soon join the classic risk factors such as smoking and high fat diet. Risk of heart attacks and other symptoms is greatest in winter in the UK when vitamin D is lowest. Heart disease is low in alpine regions where high altitude provides greater exposure to ultra-violet light. Eskimos (Inuit) have less heart disease despite poor sunlight in the Arctic but they eat oily fish high in vitamin D every day.

Diabetes type 2 - low levels of vitamin D increase the risk of diabetes which is four or five times more frequent in Asian immigrants in the UK than in others. People who are overweight are at much increased risk of diabetes partly

because they have low vitamin D.


A number of cancers are more common in northern countries of Europe and/or in northern states of the USA. These include cancer of the breast, ovary, womb, prostate, bowel, bladder, stomach, kidney, non-Hodgkin's lymphoma, and Hodgkin's lymphoma. Additional studies strongly support D-deficiency being a cause of breast, bowel and ovary cancer. In the UK some 20,000 people a year are estimated to die of cancer caused by vitamin D deficiency. Vitamin D seems to prevent cancer by preventing proliferation of cells and causing malignant cells to self-destruct.

Interesting fact: A study of 8596 women in the US found that those who had frequent exposure to the sun, either during work or recreation, had two thirds the risk of breast cancer compared with women who never exposed themselves to the sun. In Hawaii, the sunniest US state, only 9% of white women who get breast cancer die in the subsequent five years as compared with 16% dying within five years in other states.

Bone diseases

These are the diseases that every medical student knows are connected with vitamin D deficiency.

Rickets - once thought to be conquered, is now re-appearing. Immigrant groups are particularly vulnerable, but so are children of mothers who breast feed for long periods because breast milk is generally deficient in vitamin D whereas bottle milk is supplemented. Sun avoidance through fear of skin cancer has also been blamed by Professor Nick Bishop of Sheffield University. Children with rickets have been found to be three times more likely than others to develop diabetes type 1.

Osteoporosis, osteomalacia - vitamin D deficiency has long been accepted as a classic risk factor for these diseases. A trial has recently shown that a very large vitamin D supplement (100,000 international units) given every four months will protect old people against fractures. Osteoarthritis has also been linked to D deficiency.

Dental decay - Tooth decay is more severe in northern countries and in northern parts of the UK. Vitamin D reduces tooth decay in mice and rats. Vitamin D and calcium in pregnancy and early years when teeth are formed may be just as important as fluoride, tooth brushing and avoidance of too many sweet items, but somehow it has been forgotten.

Pain - nonspecific pain in muscles and skeleton, rheumatism, and low back pain, which are all very common in old people, may be the result of low vitamin D according to Gregory Plotnikoff of Minnesota Medical School (see Mayo Clinic Proceedings 2003;78:1463-1470).

Other diseases

Psoriasis - an unpleasant disease of the skin which is now treated with creams containing vitamin D or related substances and by exposure to sunlight or sunbeds.

Polycystic ovary disease - about one in five women of child bearing age suffer from this condition which causes abnormal periods, unwanted body hair and infertility. Seven of 14 women treated with vitamin D and calcium by Dr Susan Thys-Jacobs at St Lukes-Roosevelt Hospital recovered normal periods and two became pregnant. Dr Thys-Jacobs has also found that women with pre-menstrual syndrome including migraines are deficient in vitamin D and may respond to supplements plus calcium.

Infections - vitamin D enhances the activity of the immune system. Some evidence suggests that vitamin D protects against respiratory infections including pneumonia and tuberculosis. Could possibly protect against winter flu as well.

Safe sun bathing

Expose yourself to strong direct sun everyday when possible for at least 10 minutes provided you do not feel any unpleasant burning or baking sensation. The power of the sun varies greatly with the time of day, the time of year and the cloud cover. And so in cloudy weather or at off peak times a longer time, half an hour or even an hour or more, should be spent in the sun (in a bathing suit when possible) for optimum vitamin D synthesis in the skin. Avoiding the sun completely by covering up with clothes, covering up with suncream or always seeking the shade will cause vitamin D deficiency and risks serious disease.

The sun is strongest for two hours around solar midday (1pm in summer). People who have seldom or never sunbathed before should begin cautiously with just a few minutes exposure. Regular exposure will naturally lead to a tan which should not be a cause for any worry. A tan reduces the amount of sunlight penetrating the skin by about half and so a person who is tanned will be able to stay out safely in the sun for longer. People with a dark skin will need to stay in the sun for longer anyway - up to an hour or even more in full sun to get an optimum amount of vitamin D. But a dark or black skin can burn if it has not been regularly exposed to the sun in the past so care must be taken at first.

A person with a white skin will have made the maximum amount of vitamin D that can be made in one day after about 20 minutes in full sun. (This may take up to two hours or more for a person with a dark or black skin.) So after 20 minutes (or longer for darker skin) it is advisable to cover up, seek shade or use a high factor suncream - cover up earlier of course if the skin begins to get at all red or uncomfortable.

Pregnant women should sunbathe in this way at least three times a week if they can, but in the British climate it is only for a few weeks each year that there is clear sunshine enabling people to sunbathe at their convenience - so it is advisable to take a supplement too (see below). Babies can be safely taken into weak sunlight (avoiding 11am to 3pm) in only their nappies (no suncream) for between 5-10 minutes a day, according to Professor Nick Bishop of Sheffield University. A total of 30 mins per week may be sufficient to give them adequate vitamin D. If the child is taken into the sun fully clothed without a hat or gloves then two hours per week is needed to obtain adequate vitamin D. A baby with dark skin will need longer in the sun.

Experts disagree about older children. Some suggest allowing children to run around freely in weak sunlight but put on suncream, full clothes and hat from 11 am, taking care to avoid full sun during the four hours round midday. Others believe that for optimum health children should be fully exposed in a swimsuit to full midsummer sunlight for some 15 - 30 minutes a day without any suncream, so long as they do not burn.

How to prevent vitamin D deficiency year round

Sunlight is too weak in the UK to provide any useful vitamin D between about October and the end of March, and summer stores of the vitamin are used up quickly, dwindling by half within about six weeks. We obtain small amounts of vitamin D from margarine, butter, eggs, liver, a few breakfast cereals and from oily fish. But most people do not eat oily fish and many do not eat much of the other items either. So about 90% of our vitamin D comes from the sun unless we take a supplement. A vitamin D supplement is advisable year round for most people in the UK except regular sunbathers who should still take a winter supplement.

Existing recommendations on vitamin D supplements are based on guesswork and what can now be seen as faulty science. They are totally outdated. Natural exposure to sunlight produces in excess of 20,000 international units (iu) of vitamin D in the body in one day and supplements of 10,000iuper day have been taken for five months without any problems. Several experts in the United States agree that a supplement of 2,000iuper day is needed to maintain summer levels of vitamin D through the winter.

Pregnant and nursing mothers: Substantial supplementation of pregnant and nursing mothers is needed in the UK climate for optimum health of babies. But how much vitamin D they should take is a matter of debate. Dr Bruce Hollis and Dr Carol Wagner of the Department of Pediatrics at Medical University of South Carolina, Charleston, which is on the same latitude as North Africa, believe that pregnant or breast-feeding women should take at least 2000iuper day and they recommend 4,000iu for breast-feeding mothers. They say this is the minimum needed to provide adequate amounts of vitamin D in mothers' milk. However Professor Nick Bishop suggests following the more cautious official British recommendation of 400 units a day for ethnic minority women and says he is not sure whether women with white skins need take a supplement. Cod liver oil is not suitable for pregnant women in larger than recommended doses because of its high vitamin A content.

Children: Babies aged 0-6 months are advised by UK government guidelines to take 340iu of vitamin D per day as NHS vitamin drops. This is particularly important if the mother is breast feeding because bottled milk is supplemented with vitamin D while breast milk is generally deficient especially in winter. UK government guidelines suggest 280iu/day for infants aged 6 months to three years. Less than is recommended for babies which is not logical. Dr Hollis recommends 4-500iuper day for children up to five years old. But Professor Nick Bishop suggests the American Academy of Pediatrics recommendation of 200iuper day for children under five between mid-October and mid-April. A large teenager should probably take an adult dose of 2,000iuexcept when outdoors regularly in full summer sun.

Old people are almost always seriously deficient in vitamin D especially when living in institutions. 2000iu per day is advised by several American experts. Dr Peter Selby of Manchester Royal Infirmary prescribes 800iuper day, taken as vitamin D plus calcium tablets, for his patients with osteoporosis but this may be taken as a minimum.

Obtaining vitamin D

Tablets containing 1000iu vitamin D may be obtained over the internet from Doses are also quoted in micrograms (µg), 40iu = 1µg. The vitamin can be bought in the UK as calcium and vitamin D tablets, but several large tablets have to be taken to get a dose of 2000iu. For some but not all benefits of vitamin D the diet must also contain adequate calcium which may be obtained from four or five portions of dairy produce a day (milk, yoghurt, cheese) or from calcium tablets. Children may be given cod liver oil (which also supplies very useful omega 3 fatty acids) either as capsules, as an oil, or as an orange flavoured syrup (from Seven Seas) that is quite palatable, especially if served from the refrigerator. A teaspoon of syrup providing 200iuis the dose recommended on the bottle, but a desertspoon provides something like 400-500iuwhich is a more suitable dose for a child between about 5 and 10 years old.

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