Vitamin D is made in the skin with the help of sunlight. It has several important functions, including helping to regulate calcium and phosphate in the body to keep bones and teeth healthy. It is also important for good overall health and is an important factor in making sure your muscles, heart, lungs, brain and immune system work well. Vitamin D is particularly important in children, pregnant and breastfeeding women.In recent years, studies have linked vitamin D deficiency to a growing number of health concerns including heart disease, multiple sclerosis, Parkinson’s disease, stroke, diabetes, osteoporosis, prostate disease, some autoimmune conditions and depression.
Sunlight is our main source of vitamin D and requires bare skin and direct sunlight to work, however from October to April, 90% of the UK lies above the latitude that permits exposure to enough ultraviolet B light necessary for vitamin D synthesis. You can also get vitamin D from supplements and a small number of foods such as liver, oily fish and eggs are also good source of vitamin D, however, you would need to eat an enormous amount to keep your levels in the desired range. The farmed fish typically consumed in the UK may contain less vitamin D content than wild fish and in the UK, cows’ milk is generally not a good source of vitamin D because it isn’t fortified as it is in other countries. However, most people should be able to get all the vitamin D they need by eating a healthy balanced diet and by getting some summer sun. A simple blood test can be used to diagnose vitamin D deficiency and it can be treated with supplements. However the best and easiest way to increase your vitamin D level is to go out in the sun! Experts recommend we aim for 15 to 20 minutes of sun exposure a day, after which we should cover up or apply sunscreen. People with lighter skin may need less exposure than those with darker skin but everyone should be careful not to burn.
Vitamin D for cancer prevention?
In 2012 there were 14 million new cases of cancer worldwide and 8.2 million cancer related deaths with predictions of annual numbers of new cases rising to 22 million in the next two decades. With this in mind, prevention is key.
In a well publicised study published in April this year, researchers at the San Diego School of Medicine reported that higher levels of vitamin D (specifically serum 25-hydroxyvitamin D) were associated with a correspondingly reduced risk of cancer in women. The findings were published in PLOS ONE and can be read in full here. In 1980, 30 years earlier, one of the authors, Cedric Garland and his late brother, Frank, made the first connection between vitamin D deficiency and some cancers when they noted ‘populations at higher latitudes (with less available sunlight) were more likely to be deficient in vitamin D and experience higher rates of colon cancer.’ Subsequent studies by the Garlands and others found vitamin D links to other cancers such as breast, lung and bladder.
The new PLOS ONE study pooled analysis from two previous studies to obtain a larger sample size of over 2,300 women. The only accurate measure of vitamin D levels is a blood test and in this study, the researchers were looking for a greater range of blood serum levels of 25-hydroxyvitamin D or 25(OH)D. What they found was that women with 25(OH)D concentrations of 40 ng/ml (100nmol/L) or greater had a 67 percent lower risk of cancer than women with levels of 20 ng/ml (50nmol/L) or less.
What does this mean?
In the study, Garland and co. do not state whether the raised vitamin D levels should come from sunlight exposure, diet or supplements but they do state that an effort to increase vitamin D in the general population to a level of 40 ng/ml(100nmol/L) would likely and substantially reduce cancer incidence and associated mortality.
“Primary prevention of cancer, rather than expanding early detection or improving treatment, will be essential to reversing the current upward trend of cancer incidence worldwide,” the researchers wrote. “This analysis suggests that improving vitamin D status is a key prevention tool.”
We have to remember that this is just one study and that it has limitations but a 67% reduction in cancer risk is certainly interesting. Currently available data is not comprehensive enough to establish whether taking vitamin D can prevent cancer but several randomised trials need to be conducted. Several big scientific trials are underway including the Vitamin D/Calcium Polyp Prevention Study testing whether vitamin D supplements given alone or with calcium can prevent bowel polyps in patients who previously had a polyp removed. The Vitamin D and Omega 3 trial is looking at whether vitamin D can prevent the development of a variety of cancer types in healthy older men and women and should be reporting soon.
Recommended healthy blood serum levels of vitamin D have been a source of vigorous debate in recent years. In 2010, the Institute of Medicine (IOM) concluded that levels lower than 12 ng/ml (30nmol/L) represented a vitamin D deficiency and recommended a target of 20 ng/ml, (50mmol/L) which could be met in most healthy adults (ages 19 to 70) with the equivalent of 600 International Units of vitamin D each day.
As time goes on we may well see an increase in this recommended level as more research is published.
The National Institute for Health and Care Excellence (NICE) recommends that the following groups are particularly at risk of vitamin D deficiency:
- Infants and children aged under 5
- Pregnant and breastfeeding women, particularly teenagers and young women
- People over 65
- People who have low or no exposure to the sun, for example, those who cover their skin for cultural reasons, are housebound or confined indoors for long periods
- People with darker skin, for example, people of African, African-Caribbean or South Asian family origin.
We know from analysis of our blood results at Preventicum that vitamin D deficiency is very common in our clients who often work long hours indoors and many people are severely deficient particularly at this time of the year.
The advice from Public Health England is that adults and children over the age of one should consider taking a daily supplement containing 10mcg of vitamin D, particularly during autumn and winter.