Paper Review: Sunlight and Vitamin D: Necessary for Public Health
A GrassrootsHealth Paper
Published in Journal of American College Nutrition
June 22, 2015
This paper was created from the research knowledge presented at our Vitamin D for Public Health Seminar, December 2014. All presentations from this seminar were recorded and are available for viewing here.
There is a long cultural history of sun appreciation and heliotherapy
In the first half of the 20th century, heliotherapy was widely used in both Europe and North America, particularly for the treatment of cutaneous tuberculosis. However starting in the 1950s, we started treating tuberculosis with antibiotics and have never looked back. More details on this are included in the presentation by Alexander Wunsch, MD, on Why the Sun is Necessary for Optimal Health.
We have evolved with physiological adaptations to help protect the skin from the sun when we are mindful of our exposure and do not burn
When exposed to sunlight between 10 am and 3 pm, the stratum corneum (the outermost layer of the epidermis) thickens and increases skin pigmentation through the production of melanin. This response actually protects the skin and deeper tissues from the deeper penetrating and damaging UVA rays while retaining benefits from UVB exposure. Wunsch explains this process of solar acclimation in his presentation around minutes 36 – 44.
Increased sun exposure has been associated with protection from several different types of cancer, type 1 diabetes, multiple sclerosis, and other diseases
Several studies have shown a correlation between cancer mortality and latitude and that there is a 50% – 70% reduction in cancer with vitamin D sufficiency (> 40 ng/ml). Cedric Garland, DrPH, FACE, explains this in his presentation Vitamin D and Sunlight for Cancer Prevention.
Vitamin D supplementation and status have been associated with a lower risk of type 1 diabetes. A Finnish study found a 91% lower risk of type 1 diabetes by age 31 for individuals regularly given vitamin D supplements in infancy, versus those who were not given supplements. In a study of US service members, those with vitamin D blood levels < 14 ng/ml, had 4.5 times the risk of type 1 diabetes compared to those at 40 ng/ml or higher. Edward Gorham, Ph.D., explains this in his talk Prevention of Type 1 Diabetes with Vitamin D and Sunshine.
There is a preterm birth rate of 11% in the U.S. and an associated cost of $26 billion per year. Studies have shown that increasing 25(OH)D levels to 40 ng/ml have the potential to reduce preterm birth by as much as 50%. There are additional benefits to both the mother and child. Please watch Carol Wagner, MD, as she discusses meeting the vitamin D requirements of pregnant women – what is safe and what is effective.
What about optimal health?
Vitamin D is a necessary but not sufficient factor for key cell biologic processes. It is an enabler; it must be present for those processes to occur, but it does not, itself, stimulate or cause them. Low vitamin D status does not so much cause disease or dysfunction as it impairs cellular response to both internal and external signals. Vitamin D allows our body systems to work at their optimal potential. To hear more about how vitamin D and other nutrients affect the body system, watch Robert Heaney, MD, present Vitamin D, Sunshine, Optimal Health – Putting It All Together.
Sun has more benefit than just vitamin D
When the skin is stimulated with UVA radiation, nitric oxide is released, stimulating vasodilation and lowering blood pressure. During active exposure to UVA, diastolic blood pressure in one study fell by roughly 5 mmHg and remained lower for 30 minutes after exposure. Another study showed that reduction of diastolic blood pressure by 5 mmHg decreases risk for stroke by 34% and coronary heart disease by 21%.
Additionally, the human skin produces beta-endorphin in response to UVB exposure; these opioid peptides have the result of increasing a feeling of well-being, boosting the immune system, relieving pain, promoting relaxation, wound healing, and cellular differentiation. Light signals received through the eye regulate the production of melatonin and serotonin for circadian rhythm control and also play a role in seasonal affective disorder. Watch Michael F. Holick, Ph.D., MD, present SunLight and Your Health: An EnLIGHTening Perspective.
What is the cost, in dollars and lives, of vitamin D deficiency?
Raising 25(OH)D concentrations appears to be the most efficient and cost-effective way to reduce the burden of disease and increase life expectancy in the US. Of the 30 leading causes of death in the US in 2010, 19 have been linked to low vitamin D status. If the population of the US was to increase their vitamin D status to 40 ng/ml, we could expect to see a potential reduction of as much as 336,000 deaths each year (out of 2.1 million attributed to these diseases) and direct cost reduction of $130 billion each year. William B. Grant, Ph.D., discusses this in his talk Cost/Benefit of Optimal Health with Sunshine, Vitamin D.
Are there any concrete recommendations?
Three physiological criteria outlined in the paper converge on the need for a vitamin D blood concentration of around 48 ng/ml in order to achieve and maintain optimal health. Vitamin D may come from UV exposure, dietary intake, or supplements, but should total roughly 6000 IU/day. However, because of variations in individual ability to produce vitamin D from UV exposure or to absorb it from dietary sources, testing serum concentrations of 25(OH)D remains important. With regard to sun exposure, the key is to make sure that there is no burning of the skin. Further recommendations await measurement of skin types and many variables associated with such exposure.
Call for change in sun policy
GrassrootsHealth believes that moderate sun exposure (less than the time required to burn) to the arms, shoulders, trunk, and legs should be sought rather than avoided. Once that limited time has been achieved, it is important to cover the skin or seek shade, as appropriate.
The benefits of such exposure go beyond the production of vitamin D and include other physiological responses to sunlight, still inadequately explored, including the release of nitric oxide, production of beta-endorphin, and regulation of circadian rhythms – all important components of lifelong health and well-being. The current policy of sun avoidance is creating probable harm for the general population. Ignorance of the effects of portions of the solar spectrum at wavelengths longer than the ultraviolet is due mainly to lack of suitable measurement tools for cutaneous and systemic responses to those regions. We propose that the US Surgeon General’s office, the World Health Organization, the Institute of Medicine, and other health entities, together or separately, engage in an immediate effort both to define and quantify comprehensively the benefits and harms of sun exposure and to develop the measurement methods needed for their detection and quantification.