The virtues of Vitamin D: It's time we saw the light

[Guest guest]

http://news.independent.co.uk/health/article2974479.ece

There's no such thing as a cure-all, but Vitamin D comes pretty close. Jeremy

Laurance explains how a little sunshine could help you live a lot longer

Published: 18 September 2007

It may not be the first supplement to be called a " wonder vitamin " , but it is

one of the few to have lived up to the name. Last week, the biggest review of

the role of vitamin D in health found that people who took supplements of the

vitamin for six years reduced their risk of dying from all causes.

 

 

Overall mortality

 

It was the proof that researchers had been waiting for. Earlier studies had

suggested that vitamin D played a key role in protecting against cancer, heart

disease and diabetes - conditions that account for 60 to 70 per cent of all

deaths in the West. The new study, by scientists from the International Agency

for Research on Cancer in Lyon and the European Institute of Oncology in Milan

and published in Archives of Internal Medicine, shows that it does. The review

of 18 trials involving 57,000 people found that those who took the supplements

had an 7 per cent lower risk of death overall during the six-year period of the

study.

 

Edward Giovannucci, a professor of nutrition at the Harvard School of Public

Health, said that the research added " a new chapter in the accumulating evidence

for the beneficial role of vitamin D on health " . He called for a debate on the

merits of " moderate sun exposure, food fortification with vitamin D and higher

dose supplements for adults " .

 

Vitamin D is important because we are often short of it. Most healthy

individuals get all the vitamins and minerals they need from eating a balanced

diet, but vitamin D is the exception. It is made by the action of sunlight on

the skin, which accounts for 90 per cent of the body's supply. Very little comes

from food.

 

But the increasing use of sunscreens and the decreasing amount of time spent

outdoors, especially by children, has contributed to what many scientists

believe is an increasing problem of vitamin D deficiency. In the winter, the sun

in Britain is barely strong enough to make the vitamin, and by spring, say

scientists, 60 per cent of the population is deficient (defined as a blood level

below 30ng per millilitre).

 

 

Colds and flu

 

The traditional advice for avoiding these winter ailments has been to swallow

large quantities of vitamin C. But we may have been turning to the wrong

vitamin. Researchers from Winthrop University Hospital in Mineola, New York,

found that giving supplements of vitamin D to a group of volunteers reduced

episodes of infection with colds and flu by 70 per cent over three years. All

the participants were Afro-Caribbean women whose dark skin means that they make

less vitamin D. The researchers said that the vitamin stimulated " innate

immunity " to viruses and bacteria. The decline in vitamin D levels between

November and March could be the " seasonal stimulus " that accounts for the peak

in colds and flu in the winter. " Since there is an epidemic of vitamin D

insufficiency in the US, the public health implications of this observation

could be great, " the researchers wrote.

 

 

Heart disease

 

High rates of heart disease in Scotland have been blamed on the north's weak

sunlight and short summers. Differences in sunlight may also explain the higher

rates of heart disease in England compared with southern Europe. Some experts

believe that the health benefits of life in the Mediterranean may have as much

to do with the sun there as with the regional food.

 

A study of almost 10,000 women over 65 by the University of California found

that those who took vitamin D supplements had a 31 per cent lower risk of dying

of heart disease; researchers at the University of Bonn found lower levels of

vitamin D in patients with chronic heart failure.

 

Vitamin D works by lowering insulin resistance, which is one of the major

factors in heart disease. It is also used by the thyroid gland, which secretes a

hormone that regulates the body's levels of calcium, which in turns helps

regulate blood pressure.

 

 

Cancer

 

A 40-year review of research found that a daily dose of vitamin D could halve

the risk of breast and bowel cancer, two of the biggest cancer killers.

Scientists from the University of San Diego reviewed 63 scientific papers

published since the 1960s and concluded that there was a need for " public health

action " to boost vitamin D levels. They said that a daily dose of 1,000

international units (25 micrograms) was needed; the recommended level in the US

is currently only 400 units. Vitamin D deficiency " may account for several

thousand premature deaths from colon, breast, ovarian and other cancers

annually, " they wrote in the American Journal of Public Health.

 

The research showed that African Americans with darker skins and people living

in the north-eastern US, where it is less sunny, were more likely to be

deficient in vitamin D, and had higher cancer rates. This could explain why

black Americans die sooner that whites from cancer, even after allowing for

differences in income and access to health care.

 

In June, the Canadian Cancer Society recommended that adults start taking

vitamin D supplements to reduce their risk of cancer.

 

 

Rickets

 

This is the disease traditionally linked with vitamin D deficiency. A century

ago, the typical bow-legged gait of children whose bones had softened and

deformed in the absence of the vitamin was a common sight. Cod liver oil, which

contains vitamin D, was introduced as a welfare food in 1942 and virtually

eliminated the condition. Now, rickets is reappearing. Last June, doctors in

Dundee reported five cases in ethnically Asian children; dark skin produces

vitamin D more slowly than lighter skin.

 

Vitamin D is crucial for the absorption of calcium, which is the building

material for new bones. As well as leading to rickets, deficiencies can

contribute to poor tooth formation, stunted growth and general ill health.

 

The National Institute for Clinical Excellence is consulting on a proposal to

recommend supplements for certain pregnant women at risk: vegans and women who

cover their skin for religious reasons. Supplements are already recommended for

infants at risk, and are available free to families on income support and

jobseeker's allowance.

 

 

Diabetes

 

Vitamin D supplements given to babies born in Finland reduced their risk of Type

1 diabetes by 80 per cent. Researchers followed 12,000 children born in 1966

until 1997 and found that those who developed rickets, indicating vitamin D

deficiency, were three times more likely to become diabetic. Vitamin D is

believed to act as an immunosuppressive agent, which may prevent an overly

aggressive response from the immune system from destroying insulin-producing

cells in the pancreas.

 

In Oxford, the number of five-year-olds with diabetes has increased fivefold,

and the number of 15-year-olds with it has doubled. Doctors say that this

increase is too steep to be caused by genetic factors, and must be due to

changes in the environment. " Our research shows that an alarmingly high number

of people in the UK do not get enough vitamin D, " said Elina Hypoponen, from the

Institute of Child Health in London, who led the Finland study. " In winter, nine

out of 10 adults have sub-optimal levels. "

 

 

Multiple sclerosis

 

The idea that sunlight might protect against MS arose because the condition is

more common in countries further from the equator: gloomy Chicago has a higher

rate than sunny Florida, for example. Cloudy Scotland has the highest rate of MS

in the world. Scots born in May, after the long, dark winter, have an

above-average risk, while those born in November, after the summer holidays,

have the lowest risk.

 

Sir Donald Acheson, former UK Chief Medical Officer, published a study in 2004

suggesting that people who spent more time in the sun had a lower risk than

those who stayed out of it. Published in the Journal of Epidemiology and

Community Health, it concluded that a certain level of exposure to the sun might

be necessary throughout the year.

 

 

Autism

 

Could vitamin D deficiency be behind the explosion in autism? John Cannell, a

psychiatrist and vitamin D advocate, thinks so. The evidence is circumstantial,

but Cannell says that medical advice to avoid the sun and cover up since the

1980s has paralleled the rise in autism. Flagging levels of vitamin D could be

the decisive factor. Dr Richard Mills, research director at the National

Autistic Society, said: " There has been speculation about autism being more

common in high-latitude countries that get less sunlight, and a tie-up with

rickets has been suggested - observations which support the theory. "

 

How to get it - and how much you should take

 

* 90 per cent of the body's supply of vitamin D is generated by the action of

sunlight on the skin.

 

 

* Vitamin D lasts for around 60 days in the body, so it needs regular topping

up.

 

 

* Twenty minutes twice a week in the sun with exposed hands, arms and face is

adequate to maintain reserves.

 

 

* There is no recommended supplementary dose in the UK.

 

 

* In the US, the recommended supplementary dose is 400 international units a

day.

 

 

* Some scientists say that 1,000 international units of vitamin D a day may be

necessary to prevent disease.

 

 

* Vitamin D supplements cost around 5p a day.