Vitamin D’s power to strengthen bones and muscles has been well known for years. But now there’s increasing evidence that it may exert a positive influence over many other parts of the body.
New Danish research has confirmed that vitamin D, known as the “sunshine vitamin” because 90% of it is made in the skin when it’s exposed to sunlight, can help lower blood pressure.
The study on 112 patients at the Holstebro Hospital in Denmark found that taking a vitamin D supplement led to a “significant reduction” in blood pressure.
And just last week, a study by the Medical Research Council’s lifecourse epidemiology unit found that the children of women who were deficient in vitamin D during pregnancy were fatter as they grew older than children born to women who weren’t vitamin D deficient.
The studies add to a growing body of research which suggests vitamin D may keep the immune system healthy, and reduces the risk of some cancers, while being deficient in the vitamin may increase the risk of chronic health conditions such as multiple sclerosis, diabetes and cardiovascular disease.
The lifecourse epidemiology unit’s director, Professor Cyrus Cooper, says that in the last 10 years there’s been an increasing amount of research into vitamin D and health problems such as diabetes, obesity, blood pressure, heart disease, auto-immunity and multiple sclerosis.
“There’s been a lot linking vitamin D in observational data with all those outcomes,” he says.
“They’re interesting, because the vitamin D receptor is found on lots of different cell types, including cells of the immune system, the vascular system and smooth muscle, so it’s conceivable that it has cardiovascular, immune and other effects.”
However, he stresses that these effects need to be “demonstrated rigorously” in clinical trials.
In the meantime, Prof Cooper says people should be aware of how to get vitamin D – mainly from exposure to UVB rays from sunlight in the summer months and, to a much lesser extent, eating oily fish.
Currently, the Department of Health estimates up to a quarter of the population has low levels of vitamin D. This is thought to be because people are spending less time outdoors; sunscreen is often applied when it’s sunny, preventing the synthesis of vitamin D in the skin, and more people are keeping their skin covered for cultural reasons.
You’re unlikely to know you have low vitamin D levels without having a blood test, as the effects tend to become apparent over the longer term. As well as the health implications currently being researched, like multiple sclerosis, high blood pressure and obesity, it’s known that vitamin D ensures people absorb enough calcium to keep bones and teeth healthy, so low levels can lead to brittle bones and osteoporosis.
Children with low levels of vitamin D are also at risk of the bone-weakening disease rickets, known for causing bow legs. They can even be born with the condition if their mother has vitamin D deficiency during pregnancy, and this was highlighted in December when the parents of four-month-old Jayden Wray were cleared of his murder after it emerged at their trial that the baby’s numerous fractures, including the head injury that killed him, were likely to have been caused by undiagnosed rickets. Baby Jayden is thought to have been born with the condition, which was eradicated in the UK in Victorian times but is now on the increase again, because his mother had an undiagnosed vitamin D deficiency.
As well as pregnant women, those at risk of vitamin D deficiency include breastfeeding women, children under five years, the over-65s, those who have low or no exposure to the sun, like people who cover their skin for cultural reasons, who are housebound or do night shifts, and people who have darker skin, such as those of African and South Asian origin, because their bodies can’t make as much vitamin D.
Official advice currently only recommends that those at risk take vitamin D supplements, although the independent Scientific Advisory Committee on Nutrition is currently reviewing the recommendations. However, the results aren’t expected until 2014.
The best way of all to increase vitamin D levels is to get out in the sun. However, over-exposure to the sun can, of course, lead to skin damage and cancer.
Deborah Mason, spokeswoman for the British Association of Dermatologists, warns that excessive sun exposure is the main cause of skin cancer.
But she says: “Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer.
“The time required to make sufficient vitamin D is typically short and less than the amount of time needed for skin to redden and burn. Regularly going outside for a matter of minutes around the middle of the day without sunscreen should be enough.”
She says people should get to know their own skin to understand how long they can spend outside without risking sunburn, and adds: “When it comes to sun exposure, little and often is best, and the more skin that’s exposed, the greater the chance of making sufficient vitamin D before burning.”