For years now the message has been that if you want to avoid cancer, stay out of the sun.
The "SunSmart" and "Slip, Slop, Slap" campaigns were created in response to increasing incidences of skin cancer in Australia, and were soon adopted worldwide. However, there is a growing body of medical opinion that suggests that sunlight, which boosts the body's levels of vitamin D, is beneficial, not only in the prevention of osteoporosis and depression, but in helping to prevent certain forms of cancer, including breast cancer. In countries where the sun awareness campaigns have really taken hold, researchers have identified a correlating increase in the number of people who are vitamin D deficient.
Vitamin D has long been a neglected vitamin. It is the only vitamin that the body synthesises itself, and is largely created by the action of UV rays on the skin. A mere 10 per cent of our recommended daily dose of vitamin D can be obtained from sources other than the sun. Michelle Gelok, an Abu Dhabi-based nutritionist, explains: "There are three ways to get vitamin D - sun exposure, food sources and supplements. There are only a handful of food sources of vitamin D, including liver, egg yolks and fatty fish such as salmon. It's difficult to meet the daily requirement of vitamin D though food sources alone."
The chief health properties of vitamin D relate to bone health. People who are deficient in vitamin D are most likely to develop rickets as children or osteoporosis as they get older. In countries such as the UAE, where women cover their body and exposure to sunlight is reduced, problems relating to vitamin D deficiency are a matter of growing concern to health experts. The Dubai Bone and Joint Center estimate that 80 per cent of post-menopausal women suffer from a vitamin D deficiency, raising the risk of low bone mass, fracture and disability.
"Vitamin D is needed for calcium absorption," explains Dr Fatme al Anouti, an assistant professor in Natural Science and Public Health at Zayed University, Abu Dhabi. "So even if you take calcium supplements or eat calcium-rich foods, you cannot absorb it into your blood from the intestines without vitamin D. Indirect consequences we see of vitamin D deficiency are multiple sclerosis, Alzheimer's, diabetes and depression. It has been proved that if they supplemented children at an early stage [with vitamin D] they had a very low risk of developing diabetes as compared with other children who did not receive supplements."
Bone health isn't the only issue. Last year, Al Anouti and Dr Justin Thomas, a professor of psychology at Zayed University and columnist for The National, conducted a study looking at the correlation between vitamin D deficiency and depression in more than 200 students, male and female, in Abu Dhabi. Thomas explains the results: "We found a large amount of deficiency and severe deficiency among the student population. We also looked in tandem at the symptoms of depression and we found that the two things went hand in hand. As the severity of vitamin D deficiency increased, so too did the symptoms of depression."
Some research has also suggested that vitamin D could help the prevention of some cancers, including breast cancer. Findings presented to the American Association for Cancer Research Conference last week pointed to a link between vitamin D deficiency and certain types of breast cancer. The research found that 60 per cent of a group of 60 African-American women with the disease were found to have low levels of vitamin D, while only 15 per cent of white women with breast cancer in the study tested low for the vitamin. Susan Stock of the University of South Carolina, who carried out the study, said: "We know that darker skin pigmentation acts somewhat as a block to producing vitamin D when exposed to sunlight, which is the primary source of vitamin D in most people."
Similarly, in a paper in the journal Dermato-Endocrinology in January last year, William Grant, at the Sunlight, Nutrition and Health Research Center in California, analysed the results of several studies on the topic and stated that "the amount of vitamin D generated from casual solar UVB irradiance in summer… is sufficient to reduce the risk of many types of cancer by 10 per cent to 40 per cent." He concluded that "from a scientific point of view, vitamin D reduces the risk of developing many types of cancer and increases survival once cancer reaches the detectable stage".
Medical opinion on the subject of sunlight and cancer remains divided, however. Dr Safwan Khraisheh, an associate consultant and the head of the Dermatology Department at the Gulf Diagnostic Centre in Abu Dhabi, explains: "Normally we dermatologists don't like the sun, so we advise people to avoid it, because we know it may increase some forms of skin cancer and premature ageing. But now it has been found that not exposing yourself to the sun can lead to many problems. Vitamin D is a powerful antioxidant and anti-carcinogenic. It has been found that the deadly skin cancer, melanoma, is less common in people who regularly expose their skin to the sun than people who remain indoors then go out infrequently and burn. On the other hand, the non-melanomas, basal cell and squamous cell, are definitely related to the ageing of the skin and that is definitely related to the sun. But this is not deadly skin cancer."
The only way to ascertain whether you are deficient in vitamin D is to have a blood test, but as Khraisheh explains, there are symptoms that indicate your vitamin D levels are too low. "You might experience generalised things, such as dental decay, weakness of the bone, bone pain, fatigue and lack of energy. Some people may have trouble sleeping, or be anxious, stressed, or in severe cases, have diarrhoea. With the exclusion of other things, you have to check for vitamin D deficiency."
Dr Justin Thomas says that even though we live in a sun-soaked country like the UAE, our routines - driving our cars into underground car parks and spending the day in the office - might mean we are not getting enough sun. "Most of the time living in the city we are in the shade," he says. "You really have to go out of your way to get some sun." However it is difficult to say exactly how much sun each individual needs to generate sufficient vitamin D. Factors such as skin colour (darker skin needs greater exposure as melanin in the skin inhibits the production of vitamin D); cloud cover; the time of year; and distance from the equator will vary the exposure required.
According to the Cancer Council Australia, for most people, adequate vitamin D levels can be reached during incidental exposure to the sun. A few minutes of exposure to sunlight on the face, arms and hands or the equivalent area of skin on either side of the peak UV periods (10am to 3pm) should be sufficient. According to Dr Fatme al Anouti, a few minutes of regular direct exposure is also sufficient in the UAE.
"If you are light-skinned you might need five to 10 minutes every day of direct sun exposure. So if you are wearing long sleeves, sun block or makeup or are behind glass, the UVB rays will not get through to your skin." Dr Khraisheh agrees, but adds: "Exposure should be gradual, you shouldn't go out into the sun and burn. Sun exposure must be controlled."