Vitamin D, and more especially a deficiency in it, is probably the last thing on our minds at the moment as many of us are enjoying the warm summer sunshine. But a report suggests that, come Autumn and Winter, many Britons will experience low levels of this vital vitamin.
The often dull British weather is the source of much complaint, but is it actually having a negative impact on our health? According to the government’s Scientific Advisory Committee on Nutrition (SACN), the lack of sunshine in Autumn and Winter is leaving many of us with worryingly low levels of vitamin D.
Do we need Vitamin D Supplements?
It is estimated that one in five British adults, and one in six children, have low levels of the vitamin. SACN investigated the link between such deficiency and various health problems, including musculoskeletal health problems, heart disease, type 1 diabetes, cancer and multiple sclerosis. Those deduced to be most at risk of health problems related to vitamin D deficiency were pregnant women, children up to the age of 5, and adults over the age of 65. Those with darker skin and those who generally do not expose their skin to sunlight very often are also less likely to have healthy levels of vitamin D.
SACN says that it is important for those high-risk groups to be boosting their vitamin D intake with supplements. As there is no easy way to assess who is getting enough, the committee has proposed a blanket recommendation for everyone, because the risk of getting too much of the vitamin is considered to be extremely low.
“Before this, the general assumption was that adults were able to make all the vitamin D they needed from sunshine, and didn’t need to have any dietary or supplementary intake,” says Dr Adrian Martineau, an expert of vitamin D at the London School of Medicine and Dentistry.
“The action of sunlight on the skin in the UK is highly variable for different populations depending on the time of year and the latitude – you’ll get more UVB in Brighton than in John o’Groats – and finally how much skin is exposed and the colour of skin. SACN was right to say that we can’t rely on sunshine in the UK to meet the vitamin D requirements. That’s a major and important change. It’s a big step forward that this is now officially recognised.”
The National Institute for Health and Care Excellence (NICE) has also raised awareness of the need to counter hidden epidemics of vitamin D deficiency, calling for more free supplements and low-cost options in supermarkets.
Vitamin D deficiency has been linked to various health problems, but most notably causes rickets and brittle bones. Supplements to help you avoid these problems are widely available, and the NHS recommends that adults in need of supplementation take 10 micrograms a day.
Here are a few helpful facts about the vitamin and the best sources of it.
What Does Vitamin D Do?
Vitamin D has several important functions, but its main job is to help regulate the amount of calcium and phosphate in the body – nutrients which are needed to keep bones and teeth healthy.
The health benefits of Vitamin D
Vitamin D has multiple roles in the body including:
- Maintaining the health of bones and teeth
- Supporting the health of the immune system, brain and nervous system
- Regulating insulin levels and helping the management of diabetes
- Supporting lung function and cardiovascular health
- Influencing the genes involved in cancer development
The link between vitamin D and lowering the risk of cancer
Scientists have been conducting research into vitamin D for decades. In the 1980s Professor Cedric Garland and his late brother Frank from the University of California-San Diego School of Medicine, linked low levels of vitamin D with cancer.
They found that people who lived at higher latitudes where there was less sunshine, had lower levels of vitamin D and were more likely to develop bowel cancer. Further studies have found links between low levels of vitamin D and other cancers including cancers of the breast, lung and bladder.
In a new study, led again by Professor Garland, the aim was to determine what level of the vitamin was required to effectively reduce cancer risk. There has been much debate in recent years about what the recommended blood levels of vitamin D should be.
The study included all invasive cancers, excluding skin cancer and looked at two groups of women, totalling over 2,300 participants. The researchers found that cancer rates went down as vitamin D levels rose. They did not say what the optimum intake level should be or whether it should come from increased exposure to sunlight, dietary changes or supplements.
Professor Garland says their findings simply show that it is possible to see reduced cancer risk when blood levels of vitamin D reach 40ng/ml. At this level or higher, women had a 67% lower risk of developing cancer than women whose level was 20ng/ml or lower.
What are the Effects of a Vitamin D Deficiency?
A lack of vitamin D can cause of number of different bone problems. You may experience bone pain and muscle weakness, or develop rickets – a disease in which the bone tissue doesn’t properly mineralise. Research also suggests that a long-term lack of the vitamin has an impact on your general health, and may be associated with an increased risk of cardiovascular disease, cancer and cognitive impairment.
What are Good Sources of Vitamin D?
Our bodies make most of the vitamin D we need in reaction to sunlight on our skin so it’s important to regularly spend time outdoors. In the UK, however, our skin is only able to make vitamin D in the summer because the winter sunlight doesn’t have enough UVB radiation to aid the production of it.
The vitamin can also be found in a number of foods, including:
- Oily fish such as salmon, sardines and mackerel
- Fortified fat spreads
- Fortified breakfast cereals
- Some powdered milks
These foods, along with our body’s stores, were previously thought to provide us with the vitamin D we needed in the winter. Officials are now concerned that the recommended level of 10 micrograms a day may not be achievable by diet alone.
How Much Vitamin D Do You Need?
Previous thinking was that most people could get all of the vitamin D they needed by regularly spending time outdoors and eating a healthy balanced diet. Those most at risk of deficiency were thought to be:
- Pregnant and breastfeeding women
- Babies and children under the age of 5
- People over the age of 65
- People who are rarely exposed to the sun, such as those who are housebound
Now the change of advice suggests that everyone over the age of one needs to consume 10 micrograms of vitamin D each day. This advice is based on evidence looked at over the last five years. Public health officials now say that, in winter months, people should consider getting this from vitamin d supplements if their diet is unlikely to provide it.
NHS England says vitamin D supplements are available free of charge for low income families through the Healthy Start scheme.
Can You Have Too Much Vitamin D?
If you take vitamin D supplements, it’s important to take no more than 25 micrograms a day, as more than this can be harmful. Taking too much can cause the body to absorb more calcium than can be excreted, and the excess can then be deposited in and damage the kidneys. It can also encourage calcium to be removed from the bones, softening and weakening them.