Just in case there were any doubts about the importance of vitamin D – the ‘sunshine’ vitamin – two major studies published last week confirmed just how essential it is for good health.

One study found that people with higher levels in their blood were more likely to survive cancer, the other that having very low levels increased your risk of cardiovascular disease.

Previous research has linked high levels with fighting off infection and helping with all sorts of chronic problems. But there is a catch: we make most of our vitamin D when our skin is exposed to fairly strong sunlight and we can get more from oily fish and a few foods like cereals that have been fortified with it.

But to obtain the benefits suggested by this new research you have to have a level in your blood that is four or five times higher than we in the UK can get from occasionally exposing our face and hands to the sun on the way to work or having the odd meal of oily fish.

Now a new and controversial book by an American doctor suggests that taking even higher levels of the vitamin – 10 to 15 times the recommended amounts – can work wonders.

Dr James Dowd, who works at the Arthritis Institute of Michigan, has been prescribing vitamin D to people suffering from chronic disorders such as arthritis, back pain and headaches and the result, he claims, is a huge improvement in their symptoms.

In his book, The Vitamin D Cure, Dr Dowd describes a number of success stories using this approach. One of his patients, Barbara, for instance, was obese, and suffered from arthritis in one leg as well as high blood pressure.

As Dowd explains: “In the past I would have given her anti-inflammatory drugs, pain medication, a pill to lose weight and drug treatment for hypertension.”

But several years earlier he himself began to suffer symptoms of joint pain and fatigue and after researching other treatments, devised a very different “and much more effective approach”.

He believes that he, like Barbara and millions of others in America and Europe, was seriously deficient in vitamin D and was eating foods that were making his condition worse.

He devised the ‘Vitamin D Cure’ which he used on himself, and patients such as Barbara.

Dr Dowd says: “Within six weeks she told us that she could hardly believe how much better she felt.”

The cure involves a high dose supplement of vitamin D and simple dietary changes, including cutting out wheat and cheese and encouraging a greater variety of fruit, vegetables and protein. It also involves a certain amount of exercise.

“It sounds almost magical,” Dowd admits, “but in fact it’s just common-sense medicine based on good science; the sort that has eluded many physicians for decades.”

Dr Dowd says his approach works for patients complaining of a wide range of symptoms.

“Many of them are obese and have been diagnosed with high blood pressure, diabetes, osteoarthritis, osteoporosis and autoimmune diseases.

“Usually they believe their problems are down to their genes or just because they are getting older. In most cases this is selfdefeating nonsense.”

Vitamin D is essential for good bone health, but as research now suggests, it is also important in chronic conditions such as cardiovascular disease and cancer.

Quite why is not clear. However, we do know that the level of vitamin D in our bloodstreams is dropping, partly because of concerns about the link between sun and skin cancer.

It has been estimated that in America and the UK as many as 90 per cent of the population are not getting nearly enough vitamin D from the sun and diet can’t make up for the shortfall.

We spend most of our days in offices – modern glass doesn’t allow the vitamin D-producing ultra violet B rays through – and for four to six months of the year the sun isn’t high enough in the sky to stimulate production in the skin when you do go outdoors.

This is why Dr Dowd recommends his patients take a supplement containing anywhere between 4,000 and 6,000 international units (IUs) a day. He says it is the only way to get their blood levels up to a point where the real benefits begin to kick in.

However vitamins don’t work like a drug; you can’t just take a three or four 1000IU pills a day and assume that all will be well. Vitamin D works alongside three other minerals: potassium, magnesium and calcium, which are best obtained from your diet. Without these, vitamin D doesn’t work as well.

Unfortunately, the typical American and British diets rarely have enough of these minerals either, says Dr Dowd.

He’s also concerned that the normal western diet makes our blood too acid – as a result calcium is leached out of our bone to ‘neutralise’ our blood.

Two of the major culprits for raising the acid levels are grainbased food – especially wheat – 5 and, in particular, cheese, which he describes as the ‘The king of junk foods’.

But the most wide-ranging and serious effect of too much acid is that levels of various stress hormones, such as cortisol, rise. This in turn raises the amount of unhealthy fat stored in your abdomen, and increases the risk of diabetes.

Dr Dowd recommends a good intake of protein from lean meat along with nuts and seeds. While this protein also has an acidic effect, it has many other benefits and its acid count can be easily balanced by an increase in fruit and vegetables, he adds.

Nutritionists and doctors are dismissive of the ‘acid’ theory of foods – especially cutting out grains and cheese, both nutritionally important foods. But of greater concern is the quantity of Vitamin D Dr Dowd prescribes.

The amount of vitamin D you have in your blood is measured in ‘nanomoles per litre’, written nmol/L. The amount you get from a supplement is usually measured in international units, written IU.

A blood level of 25 is the official amount needed to prevent bonedamaging rickets – to achieve this you need an intake of about 400 IU a day. The UK Food Standards

Agency cautions against supplementing with amounts over 1,000IU because high levels have been linked with excess calcium which can damage bones and kidneys.

However, these safety levels are controversial. A recent article in the prestigious New English Journal of Medicine recommended that people take 2,600IU per day.

One Canadian expert, Reinhold Veith, of the Department of Laboratory Medicine and Pathobiology at the University of Toronto, says that 40,000IU could be a toxic dose but only if taken over a long time.

Dr Dowd himself says: “People worry about taking too much vitamin D but it is hard to overdose. Toxicity is highly unlikely with an intake of less than 10,000IU a day.”

A spokesperson for the British Nutritional Foundation pointed out that the safe upper limit for supplementing according to the American Institute of Medicine was 2,000 IU and warned of dangers of going above that.