Sunbathing & Vitamin D Affect Cancer and Death Risk
A study was published this month in the Journal of Internal Medicine called ‘Avoidance of sun exposure is a risk factor for all cause mortality: results from Melanoma in Southern Sweden cohort’. Researchers (Lindqvist P.G. et al 2014) found that within a group of 25,500 women of various initial ages followed starting in 1992 those with the lowest sun exposure were approximately twice as likely to die for any reason than those with the highest sun exposure. In reporting these findings the researchers controlled for other factors including: martial status, income, education, smoking and alcohol habits, physical activity, number of pregnancies, body mass index and signs of chronic disease including diabetes and use of blood thinners.
This study correlated decreased risk of death in women with high sun exposure and went as far as to say it was a dose-dependent response. This means the more sun exposure the more the risk of death was decreased. Sun exposure was related to confounding variables like income, and one of this study’s limitations is its inability to clearly distinguish between sun exposure and healthy or unhealthy lifestyle habits.
Overall, this is a significant finding as it represents a large group of women followed for many years and since the most important source of vitamin D comes from sun exposure, this study may add to the growing body of research around how Vitamin D levels affect our health.
How does this relate to Skin Cancer?
Skin cancer is of three main types: basal cell carcinoma, squamous cell carcinoma and malignant melanoma. Basal cell is the least likely to spread away from the original site and cause death, but it could be locally invasive. Squamous cell carcinoma could spread but treatment options are excellent. Death from either of these cancers is unlikely. Basal cell and squamous cell carcinoma are the most common resulting from cumulative sun exposure and are generally found in older individuals in areas of high sun exposure (nose, ears, temples); areas of risk include sun spots and skin appearing aged.
Although malignant melanoma represents only 5% of all skin cancers it is the most likely to cause death and is difficult to treat if not found early. The article cited above states malignant melanoma risk is especially related to episodic sunburns and frequent tanning bed use in people with fair skin who do not use protection. Melanoma is related to family history with Northern Europeans who live in high intensity sun exposure areas at highest risk (think British citizens who moved to Australia). In addition there may be further complicating causes of melanoma that are unrelated to sun exposure but related to genetic tendencies.
Vitamin D, Sun Exposure and Risk of Cancer and Cardiovascular Disease.
In a healthy person sun exposure causes large amounts of the active form of vitamin D to be made in the body. Vitamin D deficiency is tentatively epidemiologically linked to all causes of death, death from cardiovascular disease, and to colorectal cancer risk. For example there is some evidence to suggest that people in the Navy have higher risk of basal cell carcinoma but are at lower risk for other causes of death. There is also seasonal variation in death from heart attack and stroke with winter and spring being the most risky time. There are a number of ways sun exposure may provide this protective effect including increased vitamin d synthesis, an endorphin effect (a feel-good-relaxation effect) and a vasodilatory effect thereby decreasing blood pressure. Importantly higher levels of vitamin d are associated with both the less severe forms and improved outcomes when diagnosed with malignant melanoma.
Like all health concerns there are many factors that affect us and a holistic approach is important for best outcomes, both at the individual and population level.
Take Home Points on Sunbathing and Health
-Always avoid burning; slowly building a tan protects vs sunburns.
-Avoid direct exposure during the highest intensity times.
-Common skin cancers appear in areas of high cumulative exposure so wear a hat and long sleeved collared shirt to protect ears, nose, cheeks and scalp.
-Know your family history and get frequent skin examines if you are at increased risk of melanoma.
-Take note of unusual moles or skin markings and have them periodically checked.
-Sun exposure increases vitamin d which is very protective overall including improving cancer outcomes.
-Sun exposure may decrease risk of heart attack and stroke.
-Know you vitamin d status and supplement as appropriate for you.
-Prevention of cancer and cardiovascular disease is most effective when approached holistically. Sun exposure is one (important) factor and Vitamin D supplementation won’t replace the benefits of time spent outdoors with moderate sun exposure. In opposite is also true - in chronic disease sun exposure may not be enough to get vitamin d to optimal levels.
-Talk to your naturopathic doctor, medical doctor or nurse practitioner about your risks for melanoma and your vitamin d status.
-Enjoy summer and the health benefits of the sun and fresh air and especially be sure to be active this summer!
References:
The Definite Guide to Cancer 3rd Edition – Lisa N Alschuler ND, FABNO, and Karolyn A. Gazella 2010.
‘Avoidance of sun exposure is a risk factor for all cause mortality: results from Melanoma in Southern Sweden cohort’. Lindqvist P.G. et al 2014. Journal of Internal Medicine.